From 8360a40a8a2ff2098eed561dd89c577349dbbb76 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Thu, 8 Sep 2022 22:28:00 +0300
Subject: [PATCH 01/16] Migrate named_anon_conflict.rs

---
 .../locales/en-US/infer.ftl                   | 11 ++++++
 compiler/rustc_infer/src/errors/mod.rs        | 24 +++++++++++-
 .../nice_region_error/named_anon_conflict.rs  | 38 +++++++------------
 3 files changed, 47 insertions(+), 26 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index c9d83746d5454..40ca2c1cd1626 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -172,3 +172,14 @@ infer_msl_unmet_req = because this has an unmet lifetime requirement
 infer_msl_trait_note = this has an implicit `'static` lifetime requirement
 infer_msl_trait_sugg = consider relaxing the implicit `'static` requirement
 infer_suggest_add_let_for_letchains = consider adding `let`
+
+infer_explicit_lifetime_required = explicit lifetime required in {$ident_kind ->
+    [ident] the type of `{$simple_ident}`
+    *[param_type] parameter type
+}
+    .label = lifetime `{$named}` required
+
+infer_explicit_lifetime_required_sugg = add explicit lifetime `{$named}` to {$ident_kind ->
+    [ident] the type of `{$simple_ident}`
+    *[param_type] type
+}
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index c4f11472d5548..99112397c7f68 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -357,8 +357,8 @@ impl AddToDiagnostic for LifetimeMismatchLabels {
 pub struct AddLifetimeParamsSuggestion<'a> {
     pub tcx: TyCtxt<'a>,
     pub sub: Region<'a>,
-    pub ty_sup: &'a Ty<'a>,
-    pub ty_sub: &'a Ty<'a>,
+    pub ty_sup: &'a hir::Ty<'a>,
+    pub ty_sub: &'a hir::Ty<'a>,
     pub add_note: bool,
 }
 
@@ -520,3 +520,23 @@ pub struct MismatchedStaticLifetime<'a> {
     #[subdiagnostic]
     pub implicit_static_lifetimes: Vec<ImplicitStaticLifetimeSubdiag>,
 }
+
+#[derive(SessionDiagnostic)]
+#[diag(infer::explicit_lifetime_required, code = "E0621")]
+pub struct ExplicitLifetimeRequired<'a> {
+    #[primary_span]
+    #[label]
+    pub span: Span,
+    pub ident_kind: &'static str,
+    pub simple_ident: String,
+    pub named: String,
+
+    #[suggestion(
+        infer::explicit_lifetime_required_sugg,
+        code = "{new_ty}",
+        applicability = "unspecified"
+    )]
+    pub new_ty_span: Span,
+    #[skip_arg]
+    pub new_ty: Ty<'a>,
+}
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
index 3fe7c1598fc3f..d7751158902b8 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
@@ -1,8 +1,11 @@
 //! Error Reporting for Anonymous Region Lifetime Errors
 //! where one region is named and the other is anonymous.
-use crate::infer::error_reporting::nice_region_error::find_anon_type::find_anon_type;
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
-use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder, ErrorGuaranteed};
+use crate::{
+    errors::ExplicitLifetimeRequired,
+    infer::error_reporting::nice_region_error::find_anon_type::find_anon_type,
+};
+use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
 use rustc_middle::ty;
 use rustc_span::symbol::kw;
 
@@ -87,30 +90,17 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             return None;
         }
 
-        let (error_var, span_label_var) = match param.pat.simple_ident() {
-            Some(simple_ident) => (
-                format!("the type of `{}`", simple_ident),
-                format!("the type of `{}`", simple_ident),
-            ),
-            None => ("parameter type".to_owned(), "type".to_owned()),
+        let simple_ident = param.pat.simple_ident();
+        let (ident_kind, simple_ident) = match simple_ident {
+            Some(ident) => ("ident", ident.to_string()),
+            None => ("param_type", String::new()),
         };
 
-        let mut diag = struct_span_err!(
-            self.tcx().sess,
-            span,
-            E0621,
-            "explicit lifetime required in {}",
-            error_var
-        );
-
-        diag.span_label(span, format!("lifetime `{}` required", named));
-        diag.span_suggestion(
-            new_ty_span,
-            &format!("add explicit lifetime `{}` to {}", named, span_label_var),
-            new_ty,
-            Applicability::Unspecified,
-        );
+        let named = named.to_string();
 
-        Some(diag)
+        let err =
+            ExplicitLifetimeRequired { span, ident_kind, simple_ident, named, new_ty_span, new_ty };
+        let err = self.tcx().sess.parse_sess.create_err(err);
+        Some(err)
     }
 }

From 2118ff401f64789b6a9e64134d6d2797efee4be9 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Sun, 11 Sep 2022 00:45:38 +0300
Subject: [PATCH 02/16] Migrate placeholder_error.rs

---
 .../locales/en-US/infer.ftl                   |  28 ++
 compiler/rustc_infer/src/errors/mod.rs        |  41 +++
 .../nice_region_error/placeholder_error.rs    | 243 +++++++++---------
 3 files changed, 186 insertions(+), 126 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index 40ca2c1cd1626..a52ac1339468c 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -183,3 +183,31 @@ infer_explicit_lifetime_required_sugg = add explicit lifetime `{$named}` to {$id
     [ident] the type of `{$simple_ident}`
     *[param_type] type
 }
+
+infer_actual_impl_expl_1 = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}{$kind ->
+    [signature] closure with signature `{$ty_or_sig}` must implement `{$trait_path}`
+    [passive] `{$trait_path}` would have to be implemented for the type `{$ty_or_sig}`
+    *[other] `{$ty_or_sig}` must implement `{$trait_path}`
+}{$lt_kind ->
+    [two] , for any two lifetimes `'{$lifetime_1}` and `'{$lifetime_2}`...
+    [any] , for any lifetime `'{$lifetime_1}`...
+    [some] , for some specific lifetime `'{lifetime_1}`...
+    *[nothing] {""}
+}
+
+infer_actual_impl_expl_2 = {$kind_2 ->
+    [implements_trait] ...but it actually implements `{$trait_path_2}`
+    [implemented_for_ty] ...but `{$trait_path_2}` is actually implemented for the type `{$ty}`
+    *[ty_implements] ...but `{$ty}` actually implements `{$trait_path_2}`
+}{$has_lifetime ->
+    [true] , for some specific lifetime `'{$lifetime}`
+    *[false] {""}
+}
+
+infer_trait_placeholder_mismatch = implementation of `{$trait_def_id}` is not general enough
+    .label_satisfy = doesn't satisfy where-clause
+    .label_where = due to a where-clause on `{$def_id}`...
+    .label_dup = implementation of `{$trait_def_id}` is not general enough
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 99112397c7f68..f694c5ca40978 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -540,3 +540,44 @@ pub struct ExplicitLifetimeRequired<'a> {
     #[skip_arg]
     pub new_ty: Ty<'a>,
 }
+
+#[derive(SessionSubdiagnostic)]
+pub enum ActualImplExplNotes {
+    // Field names have to be different across all variants
+    #[note(infer::actual_impl_expl_1)]
+    NoteOne {
+        leading_ellipsis: bool,
+        kind: &'static str,
+        ty_or_sig: String,
+        trait_path: String,
+        lt_kind: &'static str,
+        lifetime_1: usize,
+        lifetime_2: usize,
+    },
+    #[note(infer::actual_impl_expl_2)]
+    NoteTwo {
+        kind_2: &'static str,
+        trait_path_2: String,
+        has_lifetime: bool,
+        lifetime: usize,
+        ty: String,
+    },
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(infer::trait_placeholder_mismatch)]
+pub struct TraitPlaceholderMismatch {
+    #[primary_span]
+    pub span: Span,
+    #[label(infer::label_satisfy)]
+    pub satisfy_span: Option<Span>,
+    #[label(infer::label_where)]
+    pub where_span: Option<Span>,
+    #[label(infer::label_dup)]
+    pub dup_span: Option<Span>,
+    pub def_id: String,
+    pub trait_def_id: String,
+
+    #[subdiagnostic]
+    pub actual_impl_expl_notes: Vec<ActualImplExplNotes>,
+}
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index fed9fda74bfb3..d9fc2ec243f11 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -1,10 +1,11 @@
+use crate::errors::{ActualImplExplNotes, TraitPlaceholderMismatch};
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::ValuePairs;
 use crate::infer::{SubregionOrigin, TypeTrace};
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use rustc_data_structures::intern::Interned;
-use rustc_errors::{Diagnostic, DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::error::ExpectedFound;
@@ -12,7 +13,7 @@ use rustc_middle::ty::print::{FmtPrinter, Print, RegionHighlightMode};
 use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::{self, RePlaceholder, ReVar, Region, TyCtxt};
 
-use std::fmt::{self, Write};
+use std::fmt;
 
 impl<'tcx> NiceRegionError<'_, 'tcx> {
     /// When given a `ConcreteFailure` for a function with arguments containing a named region and
@@ -205,26 +206,21 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         actual_substs: SubstsRef<'tcx>,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
         let span = cause.span();
-        let msg = format!(
-            "implementation of `{}` is not general enough",
-            self.tcx().def_path_str(trait_def_id),
-        );
-        let mut err = self.tcx().sess.struct_span_err(span, &msg);
 
-        let leading_ellipsis = if let ObligationCauseCode::ItemObligation(def_id)
-        | ObligationCauseCode::ExprItemObligation(def_id, ..) =
-            *cause.code()
-        {
-            err.span_label(span, "doesn't satisfy where-clause");
-            err.span_label(
-                self.tcx().def_span(def_id),
-                &format!("due to a where-clause on `{}`...", self.tcx().def_path_str(def_id)),
-            );
-            true
-        } else {
-            err.span_label(span, &msg);
-            false
-        };
+        let (leading_ellipsis, satisfy_span, where_span, dup_span, def_id) =
+            if let ObligationCauseCode::ItemObligation(def_id)
+            | ObligationCauseCode::ExprItemObligation(def_id, ..) = *cause.code()
+            {
+                (
+                    true,
+                    Some(span),
+                    Some(self.tcx().def_span(def_id)),
+                    None,
+                    self.tcx().def_path_str(def_id),
+                )
+            } else {
+                (false, None, None, Some(span), String::new())
+            };
 
         let expected_trait_ref = self
             .cx
@@ -284,8 +280,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             ?expected_self_ty_has_vid,
         );
 
-        self.explain_actual_impl_that_was_found(
-            &mut err,
+        let actual_impl_expl_notes = self.explain_actual_impl_that_was_found(
             sub_placeholder,
             sup_placeholder,
             has_sub,
@@ -299,7 +294,17 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             leading_ellipsis,
         );
 
-        err
+        let diag = TraitPlaceholderMismatch {
+            span,
+            satisfy_span,
+            where_span,
+            dup_span,
+            def_id,
+            trait_def_id: self.tcx().def_path_str(trait_def_id),
+            actual_impl_expl_notes,
+        };
+
+        self.tcx().sess.create_err(diag)
     }
 
     /// Add notes with details about the expected and actual trait refs, with attention to cases
@@ -309,7 +314,6 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
     /// due to the number of combinations we have to deal with.
     fn explain_actual_impl_that_was_found(
         &self,
-        err: &mut Diagnostic,
         sub_placeholder: Option<Region<'tcx>>,
         sup_placeholder: Option<Region<'tcx>>,
         has_sub: Option<usize>,
@@ -321,7 +325,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         actual_has_vid: Option<usize>,
         any_self_ty_has_vid: bool,
         leading_ellipsis: bool,
-    ) {
+    ) -> Vec<ActualImplExplNotes> {
         // HACK(eddyb) maybe move this in a more central location.
         #[derive(Copy, Clone)]
         struct Highlighted<'tcx, T> {
@@ -380,120 +384,107 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         let mut expected_trait_ref = highlight_trait_ref(expected_trait_ref);
         expected_trait_ref.highlight.maybe_highlighting_region(sub_placeholder, has_sub);
         expected_trait_ref.highlight.maybe_highlighting_region(sup_placeholder, has_sup);
-        err.note(&{
-            let passive_voice = match (has_sub, has_sup) {
-                (Some(_), _) | (_, Some(_)) => any_self_ty_has_vid,
-                (None, None) => {
-                    expected_trait_ref.highlight.maybe_highlighting_region(vid, expected_has_vid);
-                    match expected_has_vid {
-                        Some(_) => true,
-                        None => any_self_ty_has_vid,
-                    }
-                }
-            };
 
-            let mut note = if same_self_type {
-                let mut self_ty = expected_trait_ref.map(|tr| tr.self_ty());
-                self_ty.highlight.maybe_highlighting_region(vid, actual_has_vid);
-
-                if self_ty.value.is_closure()
-                    && self.tcx().is_fn_trait(expected_trait_ref.value.def_id)
-                {
-                    let closure_sig = self_ty.map(|closure| {
-                        if let ty::Closure(_, substs) = closure.kind() {
-                            self.tcx().signature_unclosure(
-                                substs.as_closure().sig(),
-                                rustc_hir::Unsafety::Normal,
-                            )
-                        } else {
-                            bug!("type is not longer closure");
-                        }
-                    });
-
-                    format!(
-                        "{}closure with signature `{}` must implement `{}`",
-                        if leading_ellipsis { "..." } else { "" },
-                        closure_sig,
-                        expected_trait_ref.map(|tr| tr.print_only_trait_path()),
-                    )
-                } else {
-                    format!(
-                        "{}`{}` must implement `{}`",
-                        if leading_ellipsis { "..." } else { "" },
-                        self_ty,
-                        expected_trait_ref.map(|tr| tr.print_only_trait_path()),
-                    )
+        let passive_voice = match (has_sub, has_sup) {
+            (Some(_), _) | (_, Some(_)) => any_self_ty_has_vid,
+            (None, None) => {
+                expected_trait_ref.highlight.maybe_highlighting_region(vid, expected_has_vid);
+                match expected_has_vid {
+                    Some(_) => true,
+                    None => any_self_ty_has_vid,
                 }
-            } else if passive_voice {
-                format!(
-                    "{}`{}` would have to be implemented for the type `{}`",
-                    if leading_ellipsis { "..." } else { "" },
-                    expected_trait_ref.map(|tr| tr.print_only_trait_path()),
-                    expected_trait_ref.map(|tr| tr.self_ty()),
+            }
+        };
+
+        let (kind, ty_or_sig, trait_path) = if same_self_type {
+            let mut self_ty = expected_trait_ref.map(|tr| tr.self_ty());
+            self_ty.highlight.maybe_highlighting_region(vid, actual_has_vid);
+
+            if self_ty.value.is_closure()
+                && self.tcx().is_fn_trait(expected_trait_ref.value.def_id)
+            {
+                let closure_sig = self_ty.map(|closure| {
+                    if let ty::Closure(_, substs) = closure.kind() {
+                        self.tcx().signature_unclosure(
+                            substs.as_closure().sig(),
+                            rustc_hir::Unsafety::Normal,
+                        )
+                    } else {
+                        bug!("type is not longer closure");
+                    }
+                });
+                (
+                    "signature",
+                    closure_sig.to_string(),
+                    expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
                 )
             } else {
-                format!(
-                    "{}`{}` must implement `{}`",
-                    if leading_ellipsis { "..." } else { "" },
-                    expected_trait_ref.map(|tr| tr.self_ty()),
-                    expected_trait_ref.map(|tr| tr.print_only_trait_path()),
+                (
+                    "other",
+                    self_ty.to_string(),
+                    expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
                 )
-            };
+            }
+        } else if passive_voice {
+            (
+                "passive",
+                expected_trait_ref.map(|tr| tr.self_ty()).to_string(),
+                expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
+            )
+        } else {
+            (
+                "other",
+                expected_trait_ref.map(|tr| tr.self_ty()).to_string(),
+                expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
+            )
+        };
 
-            match (has_sub, has_sup) {
-                (Some(n1), Some(n2)) => {
-                    let _ = write!(
-                        note,
-                        ", for any two lifetimes `'{}` and `'{}`...",
-                        std::cmp::min(n1, n2),
-                        std::cmp::max(n1, n2),
-                    );
-                }
-                (Some(n), _) | (_, Some(n)) => {
-                    let _ = write!(note, ", for any lifetime `'{}`...", n,);
-                }
-                (None, None) => {
-                    if let Some(n) = expected_has_vid {
-                        let _ = write!(note, ", for some specific lifetime `'{}`...", n,);
-                    }
+        let (lt_kind, lifetime_1, lifetime_2) = match (has_sub, has_sup) {
+            (Some(n1), Some(n2)) => ("two", std::cmp::min(n1, n2), std::cmp::max(n1, n2)),
+            (Some(n), _) | (_, Some(n)) => ("any", n, 0),
+            (None, None) => {
+                if let Some(n) = expected_has_vid {
+                    ("some", n, 0)
+                } else {
+                    ("nothing", 0, 0)
                 }
             }
+        };
 
-            note
-        });
+        let note_1 = ActualImplExplNotes::NoteOne {
+            leading_ellipsis,
+            kind,
+            ty_or_sig,
+            trait_path,
+            lt_kind,
+            lifetime_1,
+            lifetime_2,
+        };
 
         let mut actual_trait_ref = highlight_trait_ref(actual_trait_ref);
         actual_trait_ref.highlight.maybe_highlighting_region(vid, actual_has_vid);
-        err.note(&{
-            let passive_voice = match actual_has_vid {
-                Some(_) => any_self_ty_has_vid,
-                None => true,
-            };
 
-            let mut note = if same_self_type {
-                format!(
-                    "...but it actually implements `{}`",
-                    actual_trait_ref.map(|tr| tr.print_only_trait_path()),
-                )
-            } else if passive_voice {
-                format!(
-                    "...but `{}` is actually implemented for the type `{}`",
-                    actual_trait_ref.map(|tr| tr.print_only_trait_path()),
-                    actual_trait_ref.map(|tr| tr.self_ty()),
-                )
-            } else {
-                format!(
-                    "...but `{}` actually implements `{}`",
-                    actual_trait_ref.map(|tr| tr.self_ty()),
-                    actual_trait_ref.map(|tr| tr.print_only_trait_path()),
-                )
-            };
+        let passive_voice = match actual_has_vid {
+            Some(_) => any_self_ty_has_vid,
+            None => true,
+        };
 
-            if let Some(n) = actual_has_vid {
-                let _ = write!(note, ", for some specific lifetime `'{}`", n);
-            }
+        let trait_path_2 = actual_trait_ref.map(|tr| tr.print_only_trait_path()).to_string();
+        let ty = actual_trait_ref.map(|tr| tr.self_ty()).to_string();
+        let kind_2 = if same_self_type {
+            "implements_trait"
+        } else if passive_voice {
+            "implemented_for_ty"
+        } else {
+            "ty_implements"
+        };
 
-            note
-        });
+        let has_lifetime = actual_has_vid.is_some();
+        let lifetime = actual_has_vid.unwrap_or_default();
+
+        let note_2 =
+            ActualImplExplNotes::NoteTwo { kind_2, trait_path_2, ty, has_lifetime, lifetime };
+
+        vec![note_1, note_2]
     }
 }

From 3935a81d473167387123f8d48087f5ee446f92c4 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Tue, 13 Sep 2022 20:11:42 +0300
Subject: [PATCH 03/16] Migrate trait_impl_difference.rs

---
 .../locales/en-US/infer.ftl                   | 10 +++++
 compiler/rustc_infer/src/errors/mod.rs        | 38 ++++++++++++++++++
 .../trait_impl_difference.rs                  | 40 ++++++-------------
 3 files changed, 61 insertions(+), 27 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index a52ac1339468c..d28608cf47de2 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -211,3 +211,13 @@ infer_trait_placeholder_mismatch = implementation of `{$trait_def_id}` is not ge
     .label_satisfy = doesn't satisfy where-clause
     .label_where = due to a where-clause on `{$def_id}`...
     .label_dup = implementation of `{$trait_def_id}` is not general enough
+
+infer_trait_impl_diff = `impl` item signature doesn't match `trait` item signature
+    .found = found `{$found}`
+    .expected = expected `{$expected}`
+    .expected_found = expected `{$expected}`
+               {"   "}found `{$found}`
+
+infer_tid_rel_help = verify the lifetime relationships in the `trait` and `impl` between the `self` argument, the other inputs and its output
+infer_tid_consider_borriwing = consider borrowing this type parameter in the trait
+infer_tid_param_help = the lifetime requirements from the `impl` do not correspond to the requirements in the `trait`
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index f694c5ca40978..e2579ab7b7ce0 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -581,3 +581,41 @@ pub struct TraitPlaceholderMismatch {
     #[subdiagnostic]
     pub actual_impl_expl_notes: Vec<ActualImplExplNotes>,
 }
+
+pub struct ConsiderBorrowingParamHelp {
+    pub spans: Vec<Span>,
+}
+
+impl AddSubdiagnostic for ConsiderBorrowingParamHelp {
+    fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
+        let mut type_param_span: MultiSpan = self.spans.clone().into();
+        for &span in &self.spans {
+            type_param_span.push_span_label(span, fluent::infer::tid_consider_borriwing);
+        }
+        diag.span_help(type_param_span, fluent::infer::tid_param_help);
+    }
+}
+
+#[derive(SessionSubdiagnostic)]
+#[help(infer::tid_rel_help)]
+pub struct RelationshipHelp;
+
+#[derive(SessionDiagnostic)]
+#[diag(infer::trait_impl_diff)]
+pub struct TraitImplDiff {
+    #[primary_span]
+    #[label(infer::found)]
+    pub sp: Span,
+    #[label(infer::expected)]
+    pub trait_sp: Span,
+    #[note(infer::expected_found)]
+    pub note: (),
+    #[subdiagnostic]
+    pub param_help: ConsiderBorrowingParamHelp,
+    #[subdiagnostic]
+    // Seems like subdiagnostics are always pushed to the end, so this one
+    // also has to be a subdiagnostic to maintain order.
+    pub rel_help: Option<RelationshipHelp>,
+    pub expected: String,
+    pub found: String,
+}
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs
index 5d536e982ed02..bacd8894a0fa3 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs
@@ -1,10 +1,11 @@
 //! Error Reporting for `impl` items that do not match the obligations from their `trait`.
 
+use crate::errors::{ConsiderBorrowingParamHelp, RelationshipHelp, TraitImplDiff};
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::Subtype;
 use crate::traits::ObligationCauseCode::CompareImplItemObligation;
-use rustc_errors::{ErrorGuaranteed, MultiSpan};
+use rustc_errors::ErrorGuaranteed;
 use rustc_hir as hir;
 use rustc_hir::def::Res;
 use rustc_hir::def_id::DefId;
@@ -51,10 +52,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         trait_def_id: DefId,
     ) -> ErrorGuaranteed {
         let trait_sp = self.tcx().def_span(trait_def_id);
-        let mut err = self
-            .tcx()
-            .sess
-            .struct_span_err(sp, "`impl` item signature doesn't match `trait` item signature");
 
         // Mark all unnamed regions in the type with a number.
         // This diagnostic is called in response to lifetime errors, so be informative.
@@ -91,9 +88,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let found =
             self.cx.extract_inference_diagnostics_data(found.into(), Some(found_highlight)).name;
 
-        err.span_label(sp, &format!("found `{}`", found));
-        err.span_label(trait_sp, &format!("expected `{}`", expected));
-
         // Get the span of all the used type parameters in the method.
         let assoc_item = self.tcx().associated_item(trait_def_id);
         let mut visitor = TypeParamSpanVisitor { tcx: self.tcx(), types: vec![] };
@@ -110,26 +104,18 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             }
             _ => {}
         }
-        let mut type_param_span: MultiSpan = visitor.types.to_vec().into();
-        for &span in &visitor.types {
-            type_param_span
-                .push_span_label(span, "consider borrowing this type parameter in the trait");
-        }
 
-        err.note(&format!("expected `{}`\n   found `{}`", expected, found));
-
-        err.span_help(
-            type_param_span,
-            "the lifetime requirements from the `impl` do not correspond to the requirements in \
-             the `trait`",
-        );
-        if visitor.types.is_empty() {
-            err.help(
-                "verify the lifetime relationships in the `trait` and `impl` between the `self` \
-                 argument, the other inputs and its output",
-            );
-        }
-        err.emit()
+        let diag = TraitImplDiff {
+            sp,
+            trait_sp,
+            note: (),
+            param_help: ConsiderBorrowingParamHelp { spans: visitor.types.to_vec() },
+            rel_help: visitor.types.is_empty().then_some(RelationshipHelp),
+            expected,
+            found,
+        };
+
+        self.tcx().sess.emit_err(diag)
     }
 }
 

From 0634b0119cadbf4fcc90d8a399b1c46e1442a5b5 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Sat, 17 Sep 2022 02:54:59 +0300
Subject: [PATCH 04/16] Partial work on static_impl_trait.rs

---
 .../locales/en-US/infer.ftl                   |  52 +++++
 compiler/rustc_infer/src/errors/mod.rs        |  97 ++++++++++
 .../nice_region_error/static_impl_trait.rs    | 183 +++++++-----------
 3 files changed, 221 insertions(+), 111 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index d28608cf47de2..7a10f4b7bc549 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -221,3 +221,55 @@ infer_trait_impl_diff = `impl` item signature doesn't match `trait` item signatu
 infer_tid_rel_help = verify the lifetime relationships in the `trait` and `impl` between the `self` argument, the other inputs and its output
 infer_tid_consider_borriwing = consider borrowing this type parameter in the trait
 infer_tid_param_help = the lifetime requirements from the `impl` do not correspond to the requirements in the `trait`
+
+infer_dtcs_has_lifetime_req_label = this has an implicit `'static` lifetime requirement
+infer_dtcs_introduces_requirement = calling this method introduces the `impl`'s 'static` requirement
+infer_dtcs_has_req_note = the used `impl` has a `'static` requirement
+infer_dtcs_suggestion = consider relaxing the implicit `'static` requirement
+
+infer_but_calling_introduces = {$has_param_name ->
+    [true] `{$param_name}`
+    *[false] `fn` parameter
+} has {$lifetime_kind ->
+    [named] lifetime `{lifetime}`
+    *[anon] an anonymous lifetime `'_`
+} but calling `{assoc_item}` introduces an implicit `'static` lifetime requirement
+    .label1 = {$has_lifetime ->
+        [named] lifetime `{lifetime}`
+        *[anon] an anonymous lifetime `'_`
+    }
+    .label2 = ...is used and required to live as long as `'static` here because of an implicit lifetime bound on the {$has_impl_path ->
+        [named] `impl` of `{$impl_path}`
+        *[anon] inherent `impl`
+    }
+
+infer_but_needs_to_satisfy = {$has_param_name ->
+    [true] `{$param_name}`
+    *[false] `fn` parameter
+} has {$has_lifetime ->
+    [named] lifetime `{lifetime}`
+    *[anon] an anonymous lifetime `'_`
+} but it needs to satisfy a `'static` lifetime requirement
+    .influencer = this data with {$has_lifetime ->
+        [named] lifetime `{lifetime}`
+        *[anon] an anonymous lifetime `'_`
+    }...
+    .require = {$spans_empty ->
+        *[true] ...is used and required to live as long as `'static` here
+        [false] ...and is required to live as long as `'static` here
+    }
+    .used_here = ...is used here...
+    .introduced_by_bound = 'static` lifetime requirement introduced by this bound
+
+infer_more_targeted = {$has_param_name ->
+    [true] `{$param_name}`
+    *[false] `fn` parameter
+} has {$has_lifetime ->
+    [named] lifetime `{lifetime}`
+    *[anon] an anonymous lifetime `'_`
+} but calling `{$ident}` introduces an implicit `'static` lifetime requirement
+
+infer_ril_introduced_here = `'static` requirement introduced here
+infer_ril_introduced_by = requirement introduced by this return type
+infer_ril_because_of = because of this returned expression
+infer_ril_static_introduced_by = "`'static` lifetime requirement introduced by the return type
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index e2579ab7b7ce0..dc79c725951b3 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -8,6 +8,7 @@ use rustc_hir::{FnRetTy, Ty};
 use rustc_macros::{Diagnostic, Subdiagnostic};
 use rustc_middle::ty::{Region, TyCtxt};
 use rustc_span::symbol::kw;
+use rustc_span::Symbol;
 use rustc_span::{symbol::Ident, BytePos, Span};
 
 use crate::infer::error_reporting::{
@@ -619,3 +620,99 @@ pub struct TraitImplDiff {
     pub expected: String,
     pub found: String,
 }
+
+pub struct DynTraitConstraintSuggestion {
+    pub span: Span,
+    pub ident: Ident,
+}
+
+impl AddSubdiagnostic for DynTraitConstraintSuggestion {
+    fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
+        let mut multi_span: MultiSpan = vec![self.span].into();
+        multi_span.push_span_label(self.span, fluent::infer::dtcs_has_lifetime_req_label);
+        multi_span.push_span_label(self.ident.span, fluent::infer::dtcs_introduces_requirement);
+        diag.span_note(multi_span, fluent::infer::dtcs_has_req_note);
+        diag.span_suggestion_verbose(
+            self.span.shrink_to_hi(),
+            fluent::infer::dtcs_suggestion,
+            " + '_",
+            Applicability::MaybeIncorrect,
+        );
+    }
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(infer::but_calling_introduces, code = "E0772")]
+pub struct ButCallingIntroduces {
+    #[label(infer::label1)]
+    pub param_ty_span: Span,
+    #[primary_span]
+    #[label(infer::label2)]
+    pub cause_span: Span,
+
+    pub has_param_name: bool,
+    pub param_name: String,
+    pub has_lifetime: bool,
+    pub lifetime: String,
+    pub assoc_item: Symbol,
+    pub has_impl_path: bool,
+    pub impl_path: String,
+}
+
+pub struct ReqIntroducedLocations {
+    pub span: MultiSpan,
+    pub spans: Vec<Span>,
+    pub fn_decl_span: Span,
+    pub cause_span: Span,
+    pub add_label: bool,
+}
+
+impl AddSubdiagnostic for ReqIntroducedLocations {
+    fn add_to_diagnostic(mut self, diag: &mut rustc_errors::Diagnostic) {
+        for sp in self.spans {
+            self.span.push_span_label(sp, fluent::infer::ril_introduced_here);
+        }
+
+        if self.add_label {
+            self.span.push_span_label(self.fn_decl_span, fluent::infer::ril_introduced_by);
+        }
+        self.span.push_span_label(self.cause_span, fluent::infer::ril_because_of);
+        diag.span_note(self.span, fluent::infer::ril_static_introduced_by);
+    }
+}
+
+pub struct MoreTargeted {
+    pub ident: Symbol,
+}
+
+impl AddSubdiagnostic for MoreTargeted {
+    fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
+        diag.code(rustc_errors::error_code!(E0772));
+        diag.set_primary_message(fluent::infer::more_targeted);
+        diag.set_arg("ident", self.ident);
+    }
+}
+
+#[derive(SessionDiagnostic)]
+#[diag(infer::but_needs_to_satisfy, code = "E0759")]
+pub struct ButNeedsToSatisfy {
+    #[primary_span]
+    pub sp: Span,
+    #[label(infer::influencer)]
+    pub influencer_point: Span,
+    #[label(infer::used_here)]
+    pub spans: Vec<Span>,
+    #[label(infer::require)]
+    pub require_span_as_label: Option<Span>,
+    #[note(infer::require)]
+    pub require_span_as_note: Option<Span>,
+    #[note(infer::introduced_by_bound)]
+    pub bound: Option<Span>,
+
+    #[subdiagnostic]
+    pub req_introduces_loc: Option<ReqIntroducedLocations>,
+
+    pub spans_empty: bool,
+    pub has_lifetime: bool,
+    pub lifetime: String,
+}
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
index 9bd2202d2601e..b76f7e7689ff9 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
@@ -1,11 +1,15 @@
 //! Error Reporting for static impl Traits.
 
+use crate::errors::{
+    ButCallingIntroduces, ButNeedsToSatisfy, DynTraitConstraintSuggestion, MoreTargeted,
+    ReqIntroducedLocations,
+};
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::{SubregionOrigin, TypeTrace};
 use crate::traits::{ObligationCauseCode, UnifyReceiverContext};
-use rustc_data_structures::fx::FxIndexSet;
-use rustc_errors::{struct_span_err, Applicability, Diagnostic, ErrorGuaranteed, MultiSpan};
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::{AddSubdiagnostic, Applicability, Diagnostic, ErrorGuaranteed, MultiSpan};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_ty, Visitor};
 use rustc_hir::{self as hir, GenericBound, Item, ItemKind, Lifetime, LifetimeName, Node, TyKind};
@@ -49,46 +53,33 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                     }
 
                     let param = self.find_param_with_region(*sup_r, *sub_r)?;
-                    let lifetime = if sup_r.has_name() {
-                        format!("lifetime `{}`", sup_r)
-                    } else {
-                        "an anonymous lifetime `'_`".to_string()
+                    let simple_ident = param.param.pat.simple_ident();
+
+                    let (has_impl_path, impl_path) = match ctxt.assoc_item.container {
+                        AssocItemContainer::TraitContainer => {
+                            let id = ctxt.assoc_item.container_id(tcx);
+                            (true, tcx.def_path_str(id))
+                        }
+                        AssocItemContainer::ImplContainer => (false, String::new()),
                     };
-                    let mut err = struct_span_err!(
-                        tcx.sess,
-                        cause.span,
-                        E0772,
-                        "{} has {} but calling `{}` introduces an implicit `'static` lifetime \
-                         requirement",
-                        param
-                            .param
-                            .pat
-                            .simple_ident()
-                            .map(|s| format!("`{}`", s))
-                            .unwrap_or_else(|| "`fn` parameter".to_string()),
-                        lifetime,
-                        ctxt.assoc_item.name,
-                    );
-                    err.span_label(param.param_ty_span, &format!("this data with {}...", lifetime));
-                    err.span_label(
-                        cause.span,
-                        &format!(
-                            "...is used and required to live as long as `'static` here \
-                             because of an implicit lifetime bound on the {}",
-                            match ctxt.assoc_item.container {
-                                AssocItemContainer::TraitContainer => {
-                                    let id = ctxt.assoc_item.container_id(tcx);
-                                    format!("`impl` of `{}`", tcx.def_path_str(id))
-                                }
-                                AssocItemContainer::ImplContainer => "inherent `impl`".to_string(),
-                            },
-                        ),
-                    );
+
+                    let diag = ButCallingIntroduces {
+                        param_ty_span: param.param_ty_span,
+                        cause_span: cause.span,
+                        has_param_name: simple_ident.is_some(),
+                        param_name: simple_ident.map(|x| x.to_string()).unwrap_or_default(),
+                        has_lifetime: sup_r.has_name(),
+                        lifetime: sup_r.to_string(),
+                        assoc_item: ctxt.assoc_item.name,
+                        has_impl_path,
+                        impl_path,
+                    };
+                    let mut err = self.tcx().sess.create_err(diag);
                     if self.find_impl_on_dyn_trait(&mut err, param.param_ty, &ctxt) {
                         let reported = err.emit();
                         return Some(reported);
                     } else {
-                        err.cancel();
+                        err.cancel()
                     }
                 }
                 return None;
@@ -104,25 +95,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         let sp = var_origin.span();
         let return_sp = sub_origin.span();
         let param = self.find_param_with_region(*sup_r, *sub_r)?;
-        let (lifetime_name, lifetime) = if sup_r.has_name() {
-            (sup_r.to_string(), format!("lifetime `{}`", sup_r))
-        } else {
-            ("'_".to_owned(), "an anonymous lifetime `'_`".to_string())
-        };
-        let param_name = param
-            .param
-            .pat
-            .simple_ident()
-            .map(|s| format!("`{}`", s))
-            .unwrap_or_else(|| "`fn` parameter".to_string());
-        let mut err = struct_span_err!(
-            tcx.sess,
-            sp,
-            E0759,
-            "{} has {} but it needs to satisfy a `'static` lifetime requirement",
-            param_name,
-            lifetime,
-        );
+        let lifetime_name = if sup_r.has_name() { sup_r.to_string() } else { "'_".to_owned() };
 
         let (mention_influencer, influencer_point) =
             if sup_origin.span().overlaps(param.param_ty_span) {
@@ -141,7 +114,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             } else {
                 (!sup_origin.span().overlaps(return_sp), param.param_ty_span)
             };
-        err.span_label(influencer_point, &format!("this data with {}...", lifetime));
 
         debug!("try_report_static_impl_trait: param_info={:?}", param);
 
@@ -155,31 +127,19 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         spans.dedup_by_key(|span| (span.lo(), span.hi()));
 
         // We try to make the output have fewer overlapping spans if possible.
-        let require_msg = if spans.is_empty() {
-            "...is used and required to live as long as `'static` here"
-        } else {
-            "...and is required to live as long as `'static` here"
-        };
         let require_span =
             if sup_origin.span().overlaps(return_sp) { sup_origin.span() } else { return_sp };
 
-        for span in &spans {
-            err.span_label(*span, "...is used here...");
-        }
-
-        if spans.iter().any(|sp| sp.overlaps(return_sp) || *sp > return_sp) {
-            // If any of the "captured here" labels appears on the same line or after
-            // `require_span`, we put it on a note to ensure the text flows by appearing
-            // always at the end.
-            err.span_note(require_span, require_msg);
+        let spans_empty = spans.is_empty();
+        let require_as_note = spans.iter().any(|sp| sp.overlaps(return_sp) || *sp > return_sp);
+        let bound = if let SubregionOrigin::RelateParamBound(_, _, Some(bound)) = sub_origin {
+            Some(*bound)
         } else {
-            // We don't need a note, it's already at the end, it can be shown as a `span_label`.
-            err.span_label(require_span, require_msg);
-        }
+            None
+        };
+
+        let mut subdiag = None;
 
-        if let SubregionOrigin::RelateParamBound(_, _, Some(bound)) = sub_origin {
-            err.span_note(*bound, "`'static` lifetime requirement introduced by this bound");
-        }
         if let SubregionOrigin::Subtype(box TypeTrace { cause, .. }) = sub_origin {
             if let ObligationCauseCode::ReturnValue(hir_id)
             | ObligationCauseCode::BlockTailExpression(hir_id) = cause.code()
@@ -187,33 +147,50 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                 let parent_id = tcx.hir().get_parent_item(*hir_id);
                 if let Some(fn_decl) = tcx.hir().fn_decl_by_hir_id(parent_id.into()) {
                     let mut span: MultiSpan = fn_decl.output.span().into();
+                    let mut spans = Vec::new();
                     let mut add_label = true;
                     if let hir::FnRetTy::Return(ty) = fn_decl.output {
                         let mut v = StaticLifetimeVisitor(vec![], tcx.hir());
                         v.visit_ty(ty);
                         if !v.0.is_empty() {
                             span = v.0.clone().into();
-                            for sp in v.0 {
-                                span.push_span_label(sp, "`'static` requirement introduced here");
-                            }
+                            spans = v.0;
                             add_label = false;
                         }
                     }
-                    if add_label {
-                        span.push_span_label(
-                            fn_decl.output.span(),
-                            "requirement introduced by this return type",
-                        );
-                    }
-                    span.push_span_label(cause.span, "because of this returned expression");
-                    err.span_note(
+                    let fn_decl_span = fn_decl.output.span();
+
+                    subdiag = Some(ReqIntroducedLocations {
                         span,
-                        "`'static` lifetime requirement introduced by the return type",
-                    );
+                        spans,
+                        fn_decl_span,
+                        cause_span: cause.span,
+                        add_label,
+                    });
                 }
             }
         }
 
+        let diag = ButNeedsToSatisfy {
+            sp,
+            influencer_point,
+            spans: spans.clone(),
+            // If any of the "captured here" labels appears on the same line or after
+            // `require_span`, we put it on a note to ensure the text flows by appearing
+            // always at the end.
+            require_span_as_note: require_as_note.then_some(require_span),
+            // We don't need a note, it's already at the end, it can be shown as a `span_label`.
+            require_span_as_label: (!require_as_note).then_some(require_span),
+            req_introduces_loc: subdiag,
+
+            has_lifetime: sup_r.has_name(),
+            lifetime: sup_r.to_string(),
+            spans_empty,
+            bound,
+        };
+
+        let mut err = self.tcx().sess.create_err(diag);
+
         let fn_returns = tcx.return_type_impl_or_dyn_traits(anon_reg_sup.def_id);
 
         let mut override_error_code = None;
@@ -247,12 +224,8 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         }
         if let (Some(ident), true) = (override_error_code, fn_returns.is_empty()) {
             // Provide a more targeted error code and description.
-            err.code(rustc_errors::error_code!(E0772));
-            err.set_primary_message(&format!(
-                "{} has {} but calling `{}` introduces an implicit `'static` lifetime \
-                requirement",
-                param_name, lifetime, ident,
-            ));
+            let retarget_subdiag = MoreTargeted { ident };
+            retarget_subdiag.add_to_diagnostic(&mut err);
         }
 
         let arg = match param.param.pat.simple_ident() {
@@ -513,21 +486,9 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             let mut traits = vec![];
             let mut hir_v = HirTraitObjectVisitor(&mut traits, *found_did);
             hir_v.visit_ty(&self_ty);
-            for span in &traits {
-                let mut multi_span: MultiSpan = vec![*span].into();
-                multi_span
-                    .push_span_label(*span, "this has an implicit `'static` lifetime requirement");
-                multi_span.push_span_label(
-                    ident.span,
-                    "calling this method introduces the `impl`'s 'static` requirement",
-                );
-                err.span_note(multi_span, "the used `impl` has a `'static` requirement");
-                err.span_suggestion_verbose(
-                    span.shrink_to_hi(),
-                    "consider relaxing the implicit `'static` requirement",
-                    " + '_",
-                    Applicability::MaybeIncorrect,
-                );
+            for &span in &traits {
+                let subdiag = DynTraitConstraintSuggestion { span, ident };
+                subdiag.add_to_diagnostic(err);
                 suggested = true;
             }
         }

From 57fdd196aeda1e0fa5829248bd4afb8e6f06d7e5 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Thu, 22 Sep 2022 17:29:21 +0300
Subject: [PATCH 05/16] Rebase and fix

---
 compiler/rustc_infer/src/errors/mod.rs        | 26 +++++++++----------
 .../nice_region_error/static_impl_trait.rs    |  2 +-
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index dc79c725951b3..55df63075d22f 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -4,9 +4,9 @@ use rustc_errors::{
     MultiSpan, SubdiagnosticMessage,
 };
 use rustc_hir as hir;
-use rustc_hir::{FnRetTy, Ty};
+use rustc_hir::FnRetTy;
 use rustc_macros::{Diagnostic, Subdiagnostic};
-use rustc_middle::ty::{Region, TyCtxt};
+use rustc_middle::ty::{Region, Ty, TyCtxt};
 use rustc_span::symbol::kw;
 use rustc_span::Symbol;
 use rustc_span::{symbol::Ident, BytePos, Span};
@@ -522,7 +522,7 @@ pub struct MismatchedStaticLifetime<'a> {
     pub implicit_static_lifetimes: Vec<ImplicitStaticLifetimeSubdiag>,
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(infer::explicit_lifetime_required, code = "E0621")]
 pub struct ExplicitLifetimeRequired<'a> {
     #[primary_span]
@@ -542,7 +542,7 @@ pub struct ExplicitLifetimeRequired<'a> {
     pub new_ty: Ty<'a>,
 }
 
-#[derive(SessionSubdiagnostic)]
+#[derive(Subdiagnostic)]
 pub enum ActualImplExplNotes {
     // Field names have to be different across all variants
     #[note(infer::actual_impl_expl_1)]
@@ -565,7 +565,7 @@ pub enum ActualImplExplNotes {
     },
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(infer::trait_placeholder_mismatch)]
 pub struct TraitPlaceholderMismatch {
     #[primary_span]
@@ -587,7 +587,7 @@ pub struct ConsiderBorrowingParamHelp {
     pub spans: Vec<Span>,
 }
 
-impl AddSubdiagnostic for ConsiderBorrowingParamHelp {
+impl AddToDiagnostic for ConsiderBorrowingParamHelp {
     fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
         let mut type_param_span: MultiSpan = self.spans.clone().into();
         for &span in &self.spans {
@@ -597,11 +597,11 @@ impl AddSubdiagnostic for ConsiderBorrowingParamHelp {
     }
 }
 
-#[derive(SessionSubdiagnostic)]
+#[derive(Subdiagnostic)]
 #[help(infer::tid_rel_help)]
 pub struct RelationshipHelp;
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(infer::trait_impl_diff)]
 pub struct TraitImplDiff {
     #[primary_span]
@@ -626,7 +626,7 @@ pub struct DynTraitConstraintSuggestion {
     pub ident: Ident,
 }
 
-impl AddSubdiagnostic for DynTraitConstraintSuggestion {
+impl AddToDiagnostic for DynTraitConstraintSuggestion {
     fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
         let mut multi_span: MultiSpan = vec![self.span].into();
         multi_span.push_span_label(self.span, fluent::infer::dtcs_has_lifetime_req_label);
@@ -641,7 +641,7 @@ impl AddSubdiagnostic for DynTraitConstraintSuggestion {
     }
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(infer::but_calling_introduces, code = "E0772")]
 pub struct ButCallingIntroduces {
     #[label(infer::label1)]
@@ -667,7 +667,7 @@ pub struct ReqIntroducedLocations {
     pub add_label: bool,
 }
 
-impl AddSubdiagnostic for ReqIntroducedLocations {
+impl AddToDiagnostic for ReqIntroducedLocations {
     fn add_to_diagnostic(mut self, diag: &mut rustc_errors::Diagnostic) {
         for sp in self.spans {
             self.span.push_span_label(sp, fluent::infer::ril_introduced_here);
@@ -685,7 +685,7 @@ pub struct MoreTargeted {
     pub ident: Symbol,
 }
 
-impl AddSubdiagnostic for MoreTargeted {
+impl AddToDiagnostic for MoreTargeted {
     fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
         diag.code(rustc_errors::error_code!(E0772));
         diag.set_primary_message(fluent::infer::more_targeted);
@@ -693,7 +693,7 @@ impl AddSubdiagnostic for MoreTargeted {
     }
 }
 
-#[derive(SessionDiagnostic)]
+#[derive(Diagnostic)]
 #[diag(infer::but_needs_to_satisfy, code = "E0759")]
 pub struct ButNeedsToSatisfy {
     #[primary_span]
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
index b76f7e7689ff9..fbc71bd7e0196 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
@@ -9,7 +9,7 @@ use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::{SubregionOrigin, TypeTrace};
 use crate::traits::{ObligationCauseCode, UnifyReceiverContext};
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{AddSubdiagnostic, Applicability, Diagnostic, ErrorGuaranteed, MultiSpan};
+use rustc_errors::{AddToDiagnostic, Applicability, Diagnostic, ErrorGuaranteed, MultiSpan};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_ty, Visitor};
 use rustc_hir::{self as hir, GenericBound, Item, ItemKind, Lifetime, LifetimeName, Node, TyKind};

From 6c19c08140b7c0c5a9f9f9a434036b460167c87d Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Sun, 25 Sep 2022 10:55:42 +0300
Subject: [PATCH 06/16] More descriptive names for ActualImplExplNotes variants

---
 compiler/rustc_error_messages/locales/en-US/infer.ftl     | 4 ++--
 compiler/rustc_infer/src/errors/mod.rs                    | 8 ++++----
 .../nice_region_error/placeholder_error.rs                | 4 ++--
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index 7a10f4b7bc549..8cfd20c6eda24 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -184,7 +184,7 @@ infer_explicit_lifetime_required_sugg = add explicit lifetime `{$named}` to {$id
     *[param_type] type
 }
 
-infer_actual_impl_expl_1 = {$leading_ellipsis ->
+infer_actual_impl_expl_expected = {$leading_ellipsis ->
     [true] ...
     *[false] {""}
 }{$kind ->
@@ -198,7 +198,7 @@ infer_actual_impl_expl_1 = {$leading_ellipsis ->
     *[nothing] {""}
 }
 
-infer_actual_impl_expl_2 = {$kind_2 ->
+infer_actual_impl_expl_but_actually = {$kind_2 ->
     [implements_trait] ...but it actually implements `{$trait_path_2}`
     [implemented_for_ty] ...but `{$trait_path_2}` is actually implemented for the type `{$ty}`
     *[ty_implements] ...but `{$ty}` actually implements `{$trait_path_2}`
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 55df63075d22f..edd9eca24cb99 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -545,8 +545,8 @@ pub struct ExplicitLifetimeRequired<'a> {
 #[derive(Subdiagnostic)]
 pub enum ActualImplExplNotes {
     // Field names have to be different across all variants
-    #[note(infer::actual_impl_expl_1)]
-    NoteOne {
+    #[note(infer::actual_impl_expl_expected)]
+    Expected {
         leading_ellipsis: bool,
         kind: &'static str,
         ty_or_sig: String,
@@ -555,8 +555,8 @@ pub enum ActualImplExplNotes {
         lifetime_1: usize,
         lifetime_2: usize,
     },
-    #[note(infer::actual_impl_expl_2)]
-    NoteTwo {
+    #[note(infer::actual_impl_expl_but_actually)]
+    ButActually {
         kind_2: &'static str,
         trait_path_2: String,
         has_lifetime: bool,
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index d9fc2ec243f11..cf1032f70063f 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -451,7 +451,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             }
         };
 
-        let note_1 = ActualImplExplNotes::NoteOne {
+        let note_1 = ActualImplExplNotes::Expected {
             leading_ellipsis,
             kind,
             ty_or_sig,
@@ -483,7 +483,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         let lifetime = actual_has_vid.unwrap_or_default();
 
         let note_2 =
-            ActualImplExplNotes::NoteTwo { kind_2, trait_path_2, ty, has_lifetime, lifetime };
+            ActualImplExplNotes::ButActually { kind_2, trait_path_2, ty, has_lifetime, lifetime };
 
         vec![note_1, note_2]
     }

From 71d24da665c122fe885d0f62917c01b7f8e8d77f Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Thu, 29 Sep 2022 17:10:43 +0300
Subject: [PATCH 07/16] Split into several messages

---
 .../locales/en-US/infer.ftl                   |  71 ++++++--
 compiler/rustc_infer/src/errors/mod.rs        | 168 +++++++++++++++++-
 .../nice_region_error/placeholder_error.rs    |  58 +++---
 3 files changed, 250 insertions(+), 47 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index 8cfd20c6eda24..4a43d150968f8 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -184,25 +184,64 @@ infer_explicit_lifetime_required_sugg = add explicit lifetime `{$named}` to {$id
     *[param_type] type
 }
 
-infer_actual_impl_expl_expected = {$leading_ellipsis ->
+infer_actual_impl_expl_expected_signature_two = {$leading_ellipsis ->
     [true] ...
     *[false] {""}
-}{$kind ->
-    [signature] closure with signature `{$ty_or_sig}` must implement `{$trait_path}`
-    [passive] `{$trait_path}` would have to be implemented for the type `{$ty_or_sig}`
-    *[other] `{$ty_or_sig}` must implement `{$trait_path}`
-}{$lt_kind ->
-    [two] , for any two lifetimes `'{$lifetime_1}` and `'{$lifetime_2}`...
-    [any] , for any lifetime `'{$lifetime_1}`...
-    [some] , for some specific lifetime `'{lifetime_1}`...
-    *[nothing] {""}
-}
+}closure with signature `{$ty_or_sig}` must implement `{$trait_path}`, for any two lifetimes `'{$lifetime_1}` and `'{$lifetime_2}`...
+infer_actual_impl_expl_expected_signature_any = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}closure with signature `{$ty_or_sig}` must implement `{$trait_path}`, for any lifetime `'{$lifetime_1}`...
+infer_actual_impl_expl_expected_signature_some = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}closure with signature `{$ty_or_sig}` must implement `{$trait_path}`, for some specific lifetime `'{lifetime_1}`...
+infer_actual_impl_expl_expected_signature_nothing = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}closure with signature `{$ty_or_sig}` must implement `{$trait_path}`
+infer_actual_impl_expl_expected_passive_two = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}`{$trait_path}` would have to be implemented for the type `{$ty_or_sig}`, for any two lifetimes `'{$lifetime_1}` and `'{$lifetime_2}`...
+infer_actual_impl_expl_expected_passive_any = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}`{$trait_path}` would have to be implemented for the type `{$ty_or_sig}`, for any lifetime `'{$lifetime_1}`...
+infer_actual_impl_expl_expected_passive_some = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}`{$trait_path}` would have to be implemented for the type `{$ty_or_sig}`, for some specific lifetime `'{lifetime_1}`...
+infer_actual_impl_expl_expected_passive_nothing = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}`{$trait_path}` would have to be implemented for the type `{$ty_or_sig}`
+infer_actual_impl_expl_expected_other_two = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}`{$ty_or_sig}` must implement `{$trait_path}`, for any two lifetimes `'{$lifetime_1}` and `'{$lifetime_2}`...
+infer_actual_impl_expl_expected_other_any = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}`{$ty_or_sig}` must implement `{$trait_path}`, for any lifetime `'{$lifetime_1}`...
+infer_actual_impl_expl_expected_other_some = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}`{$ty_or_sig}` must implement `{$trait_path}`, for some specific lifetime `'{lifetime_1}`...
+infer_actual_impl_expl_expected_other_nothing = {$leading_ellipsis ->
+    [true] ...
+    *[false] {""}
+}`{$ty_or_sig}` must implement `{$trait_path}`
 
-infer_actual_impl_expl_but_actually = {$kind_2 ->
-    [implements_trait] ...but it actually implements `{$trait_path_2}`
-    [implemented_for_ty] ...but `{$trait_path_2}` is actually implemented for the type `{$ty}`
-    *[ty_implements] ...but `{$ty}` actually implements `{$trait_path_2}`
-}{$has_lifetime ->
+infer_actual_impl_expl_but_actually_implements_trait = ...but it actually implements `{$trait_path_2}`{$has_lifetime ->
+    [true] , for some specific lifetime `'{$lifetime}`
+    *[false] {""}
+}
+infer_actual_impl_expl_but_actually_implemented_for_ty = ...but `{$trait_path_2}` is actually implemented for the type `{$ty}`{$has_lifetime ->
+    [true] , for some specific lifetime `'{$lifetime}`
+    *[false] {""}
+}
+infer_actual_impl_expl_but_actually_ty_implements = ...but `{$ty}` actually implements `{$trait_path_2}`{$has_lifetime ->
     [true] , for some specific lifetime `'{$lifetime}`
     *[false] {""}
 }
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index edd9eca24cb99..69fc3be2bc3a7 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -544,20 +544,90 @@ pub struct ExplicitLifetimeRequired<'a> {
 
 #[derive(Subdiagnostic)]
 pub enum ActualImplExplNotes {
-    // Field names have to be different across all variants
-    #[note(infer::actual_impl_expl_expected)]
-    Expected {
+    // Field names have to be different across Expected* and ButActually variants
+    #[note(infer::actual_impl_expl_expected_signature_two)]
+    ExpectedSignatureTwo {
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+        lifetime_2: usize,
+    },
+    #[note(infer::actual_impl_expl_expected_signature_any)]
+    ExpectedSignatureAny {
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+    },
+    #[note(infer::actual_impl_expl_expected_signature_some)]
+    ExpectedSignatureSome {
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+    },
+    #[note(infer::actual_impl_expl_expected_signature_nothing)]
+    ExpectedSignatureNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
+    #[note(infer::actual_impl_expl_expected_passive_two)]
+    ExpectedPassiveTwo {
         leading_ellipsis: bool,
-        kind: &'static str,
         ty_or_sig: String,
         trait_path: String,
-        lt_kind: &'static str,
         lifetime_1: usize,
         lifetime_2: usize,
     },
-    #[note(infer::actual_impl_expl_but_actually)]
-    ButActually {
-        kind_2: &'static str,
+    #[note(infer::actual_impl_expl_expected_passive_any)]
+    ExpectedPassiveAny {
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+    },
+    #[note(infer::actual_impl_expl_expected_passive_some)]
+    ExpectedPassiveSome {
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+    },
+    #[note(infer::actual_impl_expl_expected_passive_nothing)]
+    ExpectedPassiveNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
+    #[note(infer::actual_impl_expl_expected_other_two)]
+    ExpectedOtherTwo {
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+        lifetime_2: usize,
+    },
+    #[note(infer::actual_impl_expl_expected_other_any)]
+    ExpectedOtherAny {
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+    },
+    #[note(infer::actual_impl_expl_expected_other_some)]
+    ExpectedOtherSome {
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+    },
+    #[note(infer::actual_impl_expl_expected_other_nothing)]
+    ExpectedOtherNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
+    #[note(infer::actual_impl_expl_but_actually_implements_trait)]
+    ButActuallyImplementsTrait { trait_path_2: String, has_lifetime: bool, lifetime: usize },
+    #[note(infer::actual_impl_expl_but_actually_implemented_for_ty)]
+    ButActuallyImplementedForTy {
+        trait_path_2: String,
+        has_lifetime: bool,
+        lifetime: usize,
+        ty: String,
+    },
+    #[note(infer::actual_impl_expl_but_actually_ty_implements)]
+    ButActuallyTyImplements {
         trait_path_2: String,
         has_lifetime: bool,
         lifetime: usize,
@@ -565,6 +635,88 @@ pub enum ActualImplExplNotes {
     },
 }
 
+pub enum ActualImplExpectedKind {
+    Signature,
+    Passive,
+    Other,
+}
+
+pub enum ActualImplExpectedLifetimeKind {
+    Two,
+    Any,
+    Some,
+    Nothing,
+}
+
+impl ActualImplExplNotes {
+    pub fn new_expected(
+        kind: ActualImplExpectedKind,
+        lt_kind: ActualImplExpectedLifetimeKind,
+        leading_ellipsis: bool,
+        ty_or_sig: String,
+        trait_path: String,
+        lifetime_1: usize,
+        lifetime_2: usize,
+    ) -> Self {
+        match (kind, lt_kind) {
+            (ActualImplExpectedKind::Signature, ActualImplExpectedLifetimeKind::Two) => {
+                Self::ExpectedSignatureTwo {
+                    leading_ellipsis,
+                    ty_or_sig,
+                    trait_path,
+                    lifetime_1,
+                    lifetime_2,
+                }
+            }
+            (ActualImplExpectedKind::Signature, ActualImplExpectedLifetimeKind::Any) => {
+                Self::ExpectedSignatureAny { leading_ellipsis, ty_or_sig, trait_path, lifetime_1 }
+            }
+            (ActualImplExpectedKind::Signature, ActualImplExpectedLifetimeKind::Some) => {
+                Self::ExpectedSignatureSome { leading_ellipsis, ty_or_sig, trait_path, lifetime_1 }
+            }
+            (ActualImplExpectedKind::Signature, ActualImplExpectedLifetimeKind::Nothing) => {
+                Self::ExpectedSignatureNothing { leading_ellipsis, ty_or_sig, trait_path }
+            }
+            (ActualImplExpectedKind::Passive, ActualImplExpectedLifetimeKind::Two) => {
+                Self::ExpectedPassiveTwo {
+                    leading_ellipsis,
+                    ty_or_sig,
+                    trait_path,
+                    lifetime_1,
+                    lifetime_2,
+                }
+            }
+            (ActualImplExpectedKind::Passive, ActualImplExpectedLifetimeKind::Any) => {
+                Self::ExpectedPassiveAny { leading_ellipsis, ty_or_sig, trait_path, lifetime_1 }
+            }
+            (ActualImplExpectedKind::Passive, ActualImplExpectedLifetimeKind::Some) => {
+                Self::ExpectedPassiveSome { leading_ellipsis, ty_or_sig, trait_path, lifetime_1 }
+            }
+            (ActualImplExpectedKind::Passive, ActualImplExpectedLifetimeKind::Nothing) => {
+                Self::ExpectedPassiveNothing { leading_ellipsis, ty_or_sig, trait_path }
+            }
+            (ActualImplExpectedKind::Other, ActualImplExpectedLifetimeKind::Two) => {
+                Self::ExpectedOtherTwo {
+                    leading_ellipsis,
+                    ty_or_sig,
+                    trait_path,
+                    lifetime_1,
+                    lifetime_2,
+                }
+            }
+            (ActualImplExpectedKind::Other, ActualImplExpectedLifetimeKind::Any) => {
+                Self::ExpectedOtherAny { leading_ellipsis, ty_or_sig, trait_path, lifetime_1 }
+            }
+            (ActualImplExpectedKind::Other, ActualImplExpectedLifetimeKind::Some) => {
+                Self::ExpectedOtherSome { leading_ellipsis, ty_or_sig, trait_path, lifetime_1 }
+            }
+            (ActualImplExpectedKind::Other, ActualImplExpectedLifetimeKind::Nothing) => {
+                Self::ExpectedOtherNothing { leading_ellipsis, ty_or_sig, trait_path }
+            }
+        }
+    }
+}
+
 #[derive(Diagnostic)]
 #[diag(infer::trait_placeholder_mismatch)]
 pub struct TraitPlaceholderMismatch {
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index cf1032f70063f..d2fd4f6cd7cab 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -1,4 +1,7 @@
-use crate::errors::{ActualImplExplNotes, TraitPlaceholderMismatch};
+use crate::errors::{
+    ActualImplExpectedKind, ActualImplExpectedLifetimeKind, ActualImplExplNotes,
+    TraitPlaceholderMismatch,
+};
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::ValuePairs;
@@ -414,52 +417,54 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
                     }
                 });
                 (
-                    "signature",
+                    ActualImplExpectedKind::Signature,
                     closure_sig.to_string(),
                     expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
                 )
             } else {
                 (
-                    "other",
+                    ActualImplExpectedKind::Other,
                     self_ty.to_string(),
                     expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
                 )
             }
         } else if passive_voice {
             (
-                "passive",
+                ActualImplExpectedKind::Passive,
                 expected_trait_ref.map(|tr| tr.self_ty()).to_string(),
                 expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
             )
         } else {
             (
-                "other",
+                ActualImplExpectedKind::Other,
                 expected_trait_ref.map(|tr| tr.self_ty()).to_string(),
                 expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
             )
         };
 
         let (lt_kind, lifetime_1, lifetime_2) = match (has_sub, has_sup) {
-            (Some(n1), Some(n2)) => ("two", std::cmp::min(n1, n2), std::cmp::max(n1, n2)),
-            (Some(n), _) | (_, Some(n)) => ("any", n, 0),
+            (Some(n1), Some(n2)) => {
+                (ActualImplExpectedLifetimeKind::Two, std::cmp::min(n1, n2), std::cmp::max(n1, n2))
+            }
+            (Some(n), _) | (_, Some(n)) => (ActualImplExpectedLifetimeKind::Any, n, 0),
             (None, None) => {
                 if let Some(n) = expected_has_vid {
-                    ("some", n, 0)
+                    (ActualImplExpectedLifetimeKind::Some, n, 0)
                 } else {
-                    ("nothing", 0, 0)
+                    (ActualImplExpectedLifetimeKind::Nothing, 0, 0)
                 }
             }
         };
 
-        let note_1 = ActualImplExplNotes::Expected {
-            leading_ellipsis,
+        let note_1 = ActualImplExplNotes::new_expected(
             kind,
+            lt_kind,
+            leading_ellipsis,
             ty_or_sig,
             trait_path,
-            lt_kind,
             lifetime_1,
             lifetime_2,
-        };
+        );
 
         let mut actual_trait_ref = highlight_trait_ref(actual_trait_ref);
         actual_trait_ref.highlight.maybe_highlighting_region(vid, actual_has_vid);
@@ -471,19 +476,26 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
 
         let trait_path_2 = actual_trait_ref.map(|tr| tr.print_only_trait_path()).to_string();
         let ty = actual_trait_ref.map(|tr| tr.self_ty()).to_string();
-        let kind_2 = if same_self_type {
-            "implements_trait"
-        } else if passive_voice {
-            "implemented_for_ty"
-        } else {
-            "ty_implements"
-        };
-
         let has_lifetime = actual_has_vid.is_some();
         let lifetime = actual_has_vid.unwrap_or_default();
 
-        let note_2 =
-            ActualImplExplNotes::ButActually { kind_2, trait_path_2, ty, has_lifetime, lifetime };
+        let note_2 = if same_self_type {
+            ActualImplExplNotes::ButActuallyImplementsTrait { trait_path_2, has_lifetime, lifetime }
+        } else if passive_voice {
+            ActualImplExplNotes::ButActuallyImplementedForTy {
+                trait_path_2,
+                ty,
+                has_lifetime,
+                lifetime,
+            }
+        } else {
+            ActualImplExplNotes::ButActuallyTyImplements {
+                trait_path_2,
+                ty,
+                has_lifetime,
+                lifetime,
+            }
+        };
 
         vec![note_1, note_2]
     }

From eb7ce1703bb719c1d038be6572a349a3e70f7ca2 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Fri, 14 Oct 2022 21:50:06 +0300
Subject: [PATCH 08/16] Use eager translation

---
 .../locales/en-US/infer.ftl                   |  2 +-
 compiler/rustc_infer/src/errors/mod.rs        | 38 +++++++++++++------
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index 4a43d150968f8..4219964a87739 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -258,7 +258,7 @@ infer_trait_impl_diff = `impl` item signature doesn't match `trait` item signatu
                {"   "}found `{$found}`
 
 infer_tid_rel_help = verify the lifetime relationships in the `trait` and `impl` between the `self` argument, the other inputs and its output
-infer_tid_consider_borriwing = consider borrowing this type parameter in the trait
+infer_tid_consider_borrowing = consider borrowing this type parameter in the trait
 infer_tid_param_help = the lifetime requirements from the `impl` do not correspond to the requirements in the `trait`
 
 infer_dtcs_has_lifetime_req_label = this has an implicit `'static` lifetime requirement
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 69fc3be2bc3a7..9092874dfae78 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -544,7 +544,6 @@ pub struct ExplicitLifetimeRequired<'a> {
 
 #[derive(Subdiagnostic)]
 pub enum ActualImplExplNotes {
-    // Field names have to be different across Expected* and ButActually variants
     #[note(infer::actual_impl_expl_expected_signature_two)]
     ExpectedSignatureTwo {
         leading_ellipsis: bool,
@@ -731,7 +730,7 @@ pub struct TraitPlaceholderMismatch {
     pub def_id: String,
     pub trait_def_id: String,
 
-    #[subdiagnostic]
+    #[subdiagnostic(eager)]
     pub actual_impl_expl_notes: Vec<ActualImplExplNotes>,
 }
 
@@ -740,12 +739,17 @@ pub struct ConsiderBorrowingParamHelp {
 }
 
 impl AddToDiagnostic for ConsiderBorrowingParamHelp {
-    fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
+    fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, f: F)
+    where
+        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
+    {
         let mut type_param_span: MultiSpan = self.spans.clone().into();
         for &span in &self.spans {
-            type_param_span.push_span_label(span, fluent::infer::tid_consider_borriwing);
+            // Seems like we can't call f() here as Into<DiagnosticMessage> is required
+            type_param_span.push_span_label(span, fluent::infer::tid_consider_borrowing);
         }
-        diag.span_help(type_param_span, fluent::infer::tid_param_help);
+        let msg = f(diag, fluent::infer::tid_param_help.into());
+        diag.span_help(type_param_span, msg);
     }
 }
 
@@ -779,14 +783,19 @@ pub struct DynTraitConstraintSuggestion {
 }
 
 impl AddToDiagnostic for DynTraitConstraintSuggestion {
-    fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
+    fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, f: F)
+    where
+        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
+    {
         let mut multi_span: MultiSpan = vec![self.span].into();
         multi_span.push_span_label(self.span, fluent::infer::dtcs_has_lifetime_req_label);
         multi_span.push_span_label(self.ident.span, fluent::infer::dtcs_introduces_requirement);
-        diag.span_note(multi_span, fluent::infer::dtcs_has_req_note);
+        let msg = f(diag, fluent::infer::dtcs_has_req_note.into());
+        diag.span_note(multi_span, msg);
+        let msg = f(diag, fluent::infer::dtcs_suggestion.into());
         diag.span_suggestion_verbose(
             self.span.shrink_to_hi(),
-            fluent::infer::dtcs_suggestion,
+            msg,
             " + '_",
             Applicability::MaybeIncorrect,
         );
@@ -820,7 +829,10 @@ pub struct ReqIntroducedLocations {
 }
 
 impl AddToDiagnostic for ReqIntroducedLocations {
-    fn add_to_diagnostic(mut self, diag: &mut rustc_errors::Diagnostic) {
+    fn add_to_diagnostic_with<F>(mut self, diag: &mut Diagnostic, f: F)
+    where
+        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
+    {
         for sp in self.spans {
             self.span.push_span_label(sp, fluent::infer::ril_introduced_here);
         }
@@ -829,7 +841,8 @@ impl AddToDiagnostic for ReqIntroducedLocations {
             self.span.push_span_label(self.fn_decl_span, fluent::infer::ril_introduced_by);
         }
         self.span.push_span_label(self.cause_span, fluent::infer::ril_because_of);
-        diag.span_note(self.span, fluent::infer::ril_static_introduced_by);
+        let msg = f(diag, fluent::infer::ril_static_introduced_by.into());
+        diag.span_note(self.span, msg);
     }
 }
 
@@ -838,7 +851,10 @@ pub struct MoreTargeted {
 }
 
 impl AddToDiagnostic for MoreTargeted {
-    fn add_to_diagnostic(self, diag: &mut rustc_errors::Diagnostic) {
+    fn add_to_diagnostic_with<F>(self, diag: &mut Diagnostic, _f: F)
+    where
+        F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
+    {
         diag.code(rustc_errors::error_code!(E0772));
         diag.set_primary_message(fluent::infer::more_targeted);
         diag.set_arg("ident", self.ident);

From 40b221814ea00a9d279474188d81b9a063eb3f68 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Sat, 15 Oct 2022 13:16:51 +0300
Subject: [PATCH 09/16] Rename subdiagnostic fields that do not need to be
 unique now

---
 .../rustc_error_messages/locales/en-US/infer.ftl    |  6 +++---
 compiler/rustc_infer/src/errors/mod.rs              | 11 +++--------
 .../nice_region_error/placeholder_error.rs          | 13 ++++---------
 3 files changed, 10 insertions(+), 20 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index 4219964a87739..f74af62702e99 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -233,15 +233,15 @@ infer_actual_impl_expl_expected_other_nothing = {$leading_ellipsis ->
     *[false] {""}
 }`{$ty_or_sig}` must implement `{$trait_path}`
 
-infer_actual_impl_expl_but_actually_implements_trait = ...but it actually implements `{$trait_path_2}`{$has_lifetime ->
+infer_actual_impl_expl_but_actually_implements_trait = ...but it actually implements `{$trait_path}`{$has_lifetime ->
     [true] , for some specific lifetime `'{$lifetime}`
     *[false] {""}
 }
-infer_actual_impl_expl_but_actually_implemented_for_ty = ...but `{$trait_path_2}` is actually implemented for the type `{$ty}`{$has_lifetime ->
+infer_actual_impl_expl_but_actually_implemented_for_ty = ...but `{$trait_path}` is actually implemented for the type `{$ty}`{$has_lifetime ->
     [true] , for some specific lifetime `'{$lifetime}`
     *[false] {""}
 }
-infer_actual_impl_expl_but_actually_ty_implements = ...but `{$ty}` actually implements `{$trait_path_2}`{$has_lifetime ->
+infer_actual_impl_expl_but_actually_ty_implements = ...but `{$ty}` actually implements `{$trait_path}`{$has_lifetime ->
     [true] , for some specific lifetime `'{$lifetime}`
     *[false] {""}
 }
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 9092874dfae78..1733b6e148fd2 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -617,21 +617,16 @@ pub enum ActualImplExplNotes {
     #[note(infer::actual_impl_expl_expected_other_nothing)]
     ExpectedOtherNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
     #[note(infer::actual_impl_expl_but_actually_implements_trait)]
-    ButActuallyImplementsTrait { trait_path_2: String, has_lifetime: bool, lifetime: usize },
+    ButActuallyImplementsTrait { trait_path: String, has_lifetime: bool, lifetime: usize },
     #[note(infer::actual_impl_expl_but_actually_implemented_for_ty)]
     ButActuallyImplementedForTy {
-        trait_path_2: String,
+        trait_path: String,
         has_lifetime: bool,
         lifetime: usize,
         ty: String,
     },
     #[note(infer::actual_impl_expl_but_actually_ty_implements)]
-    ButActuallyTyImplements {
-        trait_path_2: String,
-        has_lifetime: bool,
-        lifetime: usize,
-        ty: String,
-    },
+    ButActuallyTyImplements { trait_path: String, has_lifetime: bool, lifetime: usize, ty: String },
 }
 
 pub enum ActualImplExpectedKind {
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index d2fd4f6cd7cab..904723c4da9d7 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -474,27 +474,22 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             None => true,
         };
 
-        let trait_path_2 = actual_trait_ref.map(|tr| tr.print_only_trait_path()).to_string();
+        let trait_path = actual_trait_ref.map(|tr| tr.print_only_trait_path()).to_string();
         let ty = actual_trait_ref.map(|tr| tr.self_ty()).to_string();
         let has_lifetime = actual_has_vid.is_some();
         let lifetime = actual_has_vid.unwrap_or_default();
 
         let note_2 = if same_self_type {
-            ActualImplExplNotes::ButActuallyImplementsTrait { trait_path_2, has_lifetime, lifetime }
+            ActualImplExplNotes::ButActuallyImplementsTrait { trait_path, has_lifetime, lifetime }
         } else if passive_voice {
             ActualImplExplNotes::ButActuallyImplementedForTy {
-                trait_path_2,
+                trait_path,
                 ty,
                 has_lifetime,
                 lifetime,
             }
         } else {
-            ActualImplExplNotes::ButActuallyTyImplements {
-                trait_path_2,
-                ty,
-                has_lifetime,
-                lifetime,
-            }
+            ActualImplExplNotes::ButActuallyTyImplements { trait_path, ty, has_lifetime, lifetime }
         };
 
         vec![note_1, note_2]

From 19b8579803979dd3b1e83f7aa9655920eef14b98 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Mon, 24 Oct 2022 19:06:45 +0300
Subject: [PATCH 10/16] Address changes of pr 103345

---
 compiler/rustc_infer/src/errors/mod.rs | 92 +++++++++++++-------------
 1 file changed, 46 insertions(+), 46 deletions(-)

diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 1733b6e148fd2..51b04eb0df011 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -523,7 +523,7 @@ pub struct MismatchedStaticLifetime<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(infer::explicit_lifetime_required, code = "E0621")]
+#[diag(infer_explicit_lifetime_required, code = "E0621")]
 pub struct ExplicitLifetimeRequired<'a> {
     #[primary_span]
     #[label]
@@ -533,7 +533,7 @@ pub struct ExplicitLifetimeRequired<'a> {
     pub named: String,
 
     #[suggestion(
-        infer::explicit_lifetime_required_sugg,
+        infer_explicit_lifetime_required_sugg,
         code = "{new_ty}",
         applicability = "unspecified"
     )]
@@ -544,7 +544,7 @@ pub struct ExplicitLifetimeRequired<'a> {
 
 #[derive(Subdiagnostic)]
 pub enum ActualImplExplNotes {
-    #[note(infer::actual_impl_expl_expected_signature_two)]
+    #[note(infer_actual_impl_expl_expected_signature_two)]
     ExpectedSignatureTwo {
         leading_ellipsis: bool,
         ty_or_sig: String,
@@ -552,23 +552,23 @@ pub enum ActualImplExplNotes {
         lifetime_1: usize,
         lifetime_2: usize,
     },
-    #[note(infer::actual_impl_expl_expected_signature_any)]
+    #[note(infer_actual_impl_expl_expected_signature_any)]
     ExpectedSignatureAny {
         leading_ellipsis: bool,
         ty_or_sig: String,
         trait_path: String,
         lifetime_1: usize,
     },
-    #[note(infer::actual_impl_expl_expected_signature_some)]
+    #[note(infer_actual_impl_expl_expected_signature_some)]
     ExpectedSignatureSome {
         leading_ellipsis: bool,
         ty_or_sig: String,
         trait_path: String,
         lifetime_1: usize,
     },
-    #[note(infer::actual_impl_expl_expected_signature_nothing)]
+    #[note(infer_actual_impl_expl_expected_signature_nothing)]
     ExpectedSignatureNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
-    #[note(infer::actual_impl_expl_expected_passive_two)]
+    #[note(infer_actual_impl_expl_expected_passive_two)]
     ExpectedPassiveTwo {
         leading_ellipsis: bool,
         ty_or_sig: String,
@@ -576,23 +576,23 @@ pub enum ActualImplExplNotes {
         lifetime_1: usize,
         lifetime_2: usize,
     },
-    #[note(infer::actual_impl_expl_expected_passive_any)]
+    #[note(infer_actual_impl_expl_expected_passive_any)]
     ExpectedPassiveAny {
         leading_ellipsis: bool,
         ty_or_sig: String,
         trait_path: String,
         lifetime_1: usize,
     },
-    #[note(infer::actual_impl_expl_expected_passive_some)]
+    #[note(infer_actual_impl_expl_expected_passive_some)]
     ExpectedPassiveSome {
         leading_ellipsis: bool,
         ty_or_sig: String,
         trait_path: String,
         lifetime_1: usize,
     },
-    #[note(infer::actual_impl_expl_expected_passive_nothing)]
+    #[note(infer_actual_impl_expl_expected_passive_nothing)]
     ExpectedPassiveNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
-    #[note(infer::actual_impl_expl_expected_other_two)]
+    #[note(infer_actual_impl_expl_expected_other_two)]
     ExpectedOtherTwo {
         leading_ellipsis: bool,
         ty_or_sig: String,
@@ -600,32 +600,32 @@ pub enum ActualImplExplNotes {
         lifetime_1: usize,
         lifetime_2: usize,
     },
-    #[note(infer::actual_impl_expl_expected_other_any)]
+    #[note(infer_actual_impl_expl_expected_other_any)]
     ExpectedOtherAny {
         leading_ellipsis: bool,
         ty_or_sig: String,
         trait_path: String,
         lifetime_1: usize,
     },
-    #[note(infer::actual_impl_expl_expected_other_some)]
+    #[note(infer_actual_impl_expl_expected_other_some)]
     ExpectedOtherSome {
         leading_ellipsis: bool,
         ty_or_sig: String,
         trait_path: String,
         lifetime_1: usize,
     },
-    #[note(infer::actual_impl_expl_expected_other_nothing)]
+    #[note(infer_actual_impl_expl_expected_other_nothing)]
     ExpectedOtherNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
-    #[note(infer::actual_impl_expl_but_actually_implements_trait)]
+    #[note(infer_actual_impl_expl_but_actually_implements_trait)]
     ButActuallyImplementsTrait { trait_path: String, has_lifetime: bool, lifetime: usize },
-    #[note(infer::actual_impl_expl_but_actually_implemented_for_ty)]
+    #[note(infer_actual_impl_expl_but_actually_implemented_for_ty)]
     ButActuallyImplementedForTy {
         trait_path: String,
         has_lifetime: bool,
         lifetime: usize,
         ty: String,
     },
-    #[note(infer::actual_impl_expl_but_actually_ty_implements)]
+    #[note(infer_actual_impl_expl_but_actually_ty_implements)]
     ButActuallyTyImplements { trait_path: String, has_lifetime: bool, lifetime: usize, ty: String },
 }
 
@@ -712,15 +712,15 @@ impl ActualImplExplNotes {
 }
 
 #[derive(Diagnostic)]
-#[diag(infer::trait_placeholder_mismatch)]
+#[diag(infer_trait_placeholder_mismatch)]
 pub struct TraitPlaceholderMismatch {
     #[primary_span]
     pub span: Span,
-    #[label(infer::label_satisfy)]
+    #[label(label_satisfy)]
     pub satisfy_span: Option<Span>,
-    #[label(infer::label_where)]
+    #[label(label_where)]
     pub where_span: Option<Span>,
-    #[label(infer::label_dup)]
+    #[label(label_dup)]
     pub dup_span: Option<Span>,
     pub def_id: String,
     pub trait_def_id: String,
@@ -741,26 +741,26 @@ impl AddToDiagnostic for ConsiderBorrowingParamHelp {
         let mut type_param_span: MultiSpan = self.spans.clone().into();
         for &span in &self.spans {
             // Seems like we can't call f() here as Into<DiagnosticMessage> is required
-            type_param_span.push_span_label(span, fluent::infer::tid_consider_borrowing);
+            type_param_span.push_span_label(span, fluent::infer_tid_consider_borrowing);
         }
-        let msg = f(diag, fluent::infer::tid_param_help.into());
+        let msg = f(diag, fluent::infer_tid_param_help.into());
         diag.span_help(type_param_span, msg);
     }
 }
 
 #[derive(Subdiagnostic)]
-#[help(infer::tid_rel_help)]
+#[help(infer_tid_rel_help)]
 pub struct RelationshipHelp;
 
 #[derive(Diagnostic)]
-#[diag(infer::trait_impl_diff)]
+#[diag(infer_trait_impl_diff)]
 pub struct TraitImplDiff {
     #[primary_span]
-    #[label(infer::found)]
+    #[label(found)]
     pub sp: Span,
-    #[label(infer::expected)]
+    #[label(expected)]
     pub trait_sp: Span,
-    #[note(infer::expected_found)]
+    #[note(expected_found)]
     pub note: (),
     #[subdiagnostic]
     pub param_help: ConsiderBorrowingParamHelp,
@@ -783,11 +783,11 @@ impl AddToDiagnostic for DynTraitConstraintSuggestion {
         F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
     {
         let mut multi_span: MultiSpan = vec![self.span].into();
-        multi_span.push_span_label(self.span, fluent::infer::dtcs_has_lifetime_req_label);
-        multi_span.push_span_label(self.ident.span, fluent::infer::dtcs_introduces_requirement);
-        let msg = f(diag, fluent::infer::dtcs_has_req_note.into());
+        multi_span.push_span_label(self.span, fluent::infer_dtcs_has_lifetime_req_label);
+        multi_span.push_span_label(self.ident.span, fluent::infer_dtcs_introduces_requirement);
+        let msg = f(diag, fluent::infer_dtcs_has_req_note.into());
         diag.span_note(multi_span, msg);
-        let msg = f(diag, fluent::infer::dtcs_suggestion.into());
+        let msg = f(diag, fluent::infer_dtcs_suggestion.into());
         diag.span_suggestion_verbose(
             self.span.shrink_to_hi(),
             msg,
@@ -798,12 +798,12 @@ impl AddToDiagnostic for DynTraitConstraintSuggestion {
 }
 
 #[derive(Diagnostic)]
-#[diag(infer::but_calling_introduces, code = "E0772")]
+#[diag(infer_but_calling_introduces, code = "E0772")]
 pub struct ButCallingIntroduces {
-    #[label(infer::label1)]
+    #[label(label1)]
     pub param_ty_span: Span,
     #[primary_span]
-    #[label(infer::label2)]
+    #[label(label2)]
     pub cause_span: Span,
 
     pub has_param_name: bool,
@@ -829,14 +829,14 @@ impl AddToDiagnostic for ReqIntroducedLocations {
         F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
     {
         for sp in self.spans {
-            self.span.push_span_label(sp, fluent::infer::ril_introduced_here);
+            self.span.push_span_label(sp, fluent::infer_ril_introduced_here);
         }
 
         if self.add_label {
-            self.span.push_span_label(self.fn_decl_span, fluent::infer::ril_introduced_by);
+            self.span.push_span_label(self.fn_decl_span, fluent::infer_ril_introduced_by);
         }
-        self.span.push_span_label(self.cause_span, fluent::infer::ril_because_of);
-        let msg = f(diag, fluent::infer::ril_static_introduced_by.into());
+        self.span.push_span_label(self.cause_span, fluent::infer_ril_because_of);
+        let msg = f(diag, fluent::infer_ril_static_introduced_by.into());
         diag.span_note(self.span, msg);
     }
 }
@@ -851,25 +851,25 @@ impl AddToDiagnostic for MoreTargeted {
         F: Fn(&mut Diagnostic, SubdiagnosticMessage) -> SubdiagnosticMessage,
     {
         diag.code(rustc_errors::error_code!(E0772));
-        diag.set_primary_message(fluent::infer::more_targeted);
+        diag.set_primary_message(fluent::infer_more_targeted);
         diag.set_arg("ident", self.ident);
     }
 }
 
 #[derive(Diagnostic)]
-#[diag(infer::but_needs_to_satisfy, code = "E0759")]
+#[diag(infer_but_needs_to_satisfy, code = "E0759")]
 pub struct ButNeedsToSatisfy {
     #[primary_span]
     pub sp: Span,
-    #[label(infer::influencer)]
+    #[label(influencer)]
     pub influencer_point: Span,
-    #[label(infer::used_here)]
+    #[label(used_here)]
     pub spans: Vec<Span>,
-    #[label(infer::require)]
+    #[label(require)]
     pub require_span_as_label: Option<Span>,
-    #[note(infer::require)]
+    #[note(require)]
     pub require_span_as_note: Option<Span>,
-    #[note(infer::introduced_by_bound)]
+    #[note(introduced_by_bound)]
     pub bound: Option<Span>,
 
     #[subdiagnostic]

From 7ecd064bbe32419eb473b28cdc8e41dd34f20aa9 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Thu, 3 Nov 2022 20:45:14 +0300
Subject: [PATCH 11/16] Split infer_explicit_lifetime_required into several
 diags

---
 .../locales/en-US/infer.ftl                   | 15 +++---
 compiler/rustc_infer/src/errors/mod.rs        | 49 ++++++++++++-------
 .../nice_region_error/named_anon_conflict.rs  | 23 +++++----
 3 files changed, 50 insertions(+), 37 deletions(-)

diff --git a/compiler/rustc_error_messages/locales/en-US/infer.ftl b/compiler/rustc_error_messages/locales/en-US/infer.ftl
index f74af62702e99..52babec4f9ea7 100644
--- a/compiler/rustc_error_messages/locales/en-US/infer.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/infer.ftl
@@ -173,16 +173,15 @@ infer_msl_trait_note = this has an implicit `'static` lifetime requirement
 infer_msl_trait_sugg = consider relaxing the implicit `'static` requirement
 infer_suggest_add_let_for_letchains = consider adding `let`
 
-infer_explicit_lifetime_required = explicit lifetime required in {$ident_kind ->
-    [ident] the type of `{$simple_ident}`
-    *[param_type] parameter type
-}
+infer_explicit_lifetime_required_with_ident = explicit lifetime required in the type of `{$simple_ident}`
     .label = lifetime `{$named}` required
 
-infer_explicit_lifetime_required_sugg = add explicit lifetime `{$named}` to {$ident_kind ->
-    [ident] the type of `{$simple_ident}`
-    *[param_type] type
-}
+infer_explicit_lifetime_required_with_param_type = explicit lifetime required in parameter type
+    .label = lifetime `{$named}` required
+
+infer_explicit_lifetime_required_sugg_with_ident = add explicit lifetime `{$named}` to the type of `{$simple_ident}`
+
+infer_explicit_lifetime_required_sugg_with_param_type = add explicit lifetime `{$named}` to type
 
 infer_actual_impl_expl_expected_signature_two = {$leading_ellipsis ->
     [true] ...
diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 51b04eb0df011..9e3def93a6d3d 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -523,23 +523,38 @@ pub struct MismatchedStaticLifetime<'a> {
 }
 
 #[derive(Diagnostic)]
-#[diag(infer_explicit_lifetime_required, code = "E0621")]
-pub struct ExplicitLifetimeRequired<'a> {
-    #[primary_span]
-    #[label]
-    pub span: Span,
-    pub ident_kind: &'static str,
-    pub simple_ident: String,
-    pub named: String,
-
-    #[suggestion(
-        infer_explicit_lifetime_required_sugg,
-        code = "{new_ty}",
-        applicability = "unspecified"
-    )]
-    pub new_ty_span: Span,
-    #[skip_arg]
-    pub new_ty: Ty<'a>,
+pub enum ExplicitLifetimeRequired<'a> {
+    #[diag(infer_explicit_lifetime_required_with_ident, code = "E0621")]
+    WithIdent {
+        #[primary_span]
+        #[label]
+        span: Span,
+        simple_ident: Ident,
+        named: String,
+        #[suggestion(
+            infer_explicit_lifetime_required_sugg_with_ident,
+            code = "{new_ty}",
+            applicability = "unspecified"
+        )]
+        new_ty_span: Span,
+        #[skip_arg]
+        new_ty: Ty<'a>,
+    },
+    #[diag(infer_explicit_lifetime_required_with_param_type, code = "E0621")]
+    WithParamType {
+        #[primary_span]
+        #[label]
+        span: Span,
+        named: String,
+        #[suggestion(
+            infer_explicit_lifetime_required_sugg_with_param_type,
+            code = "{new_ty}",
+            applicability = "unspecified"
+        )]
+        new_ty_span: Span,
+        #[skip_arg]
+        new_ty: Ty<'a>,
+    },
 }
 
 #[derive(Subdiagnostic)]
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
index d7751158902b8..4e13ec90228d6 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/named_anon_conflict.rs
@@ -89,18 +89,17 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         {
             return None;
         }
-
-        let simple_ident = param.pat.simple_ident();
-        let (ident_kind, simple_ident) = match simple_ident {
-            Some(ident) => ("ident", ident.to_string()),
-            None => ("param_type", String::new()),
-        };
-
         let named = named.to_string();
-
-        let err =
-            ExplicitLifetimeRequired { span, ident_kind, simple_ident, named, new_ty_span, new_ty };
-        let err = self.tcx().sess.parse_sess.create_err(err);
-        Some(err)
+        let err = match param.pat.simple_ident() {
+            Some(simple_ident) => ExplicitLifetimeRequired::WithIdent {
+                span,
+                simple_ident,
+                named,
+                new_ty_span,
+                new_ty,
+            },
+            None => ExplicitLifetimeRequired::WithParamType { span, named, new_ty_span, new_ty },
+        };
+        Some(self.tcx().sess.parse_sess.create_err(err))
     }
 }

From 62f9962eafbf4cf1196d256cf6c559ac397261e1 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Thu, 3 Nov 2022 21:50:52 +0300
Subject: [PATCH 12/16] Made ty_or_sig and trait_path use their actual types
 instead of String

---
 compiler/rustc_infer/src/errors/mod.rs        | 101 ++++++++++++------
 .../error_reporting/nice_region_error/mod.rs  |   2 +-
 .../nice_region_error/placeholder_error.rs    |  92 ++++++++--------
 3 files changed, 118 insertions(+), 77 deletions(-)

diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 9e3def93a6d3d..388ddd09905ac 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -1,16 +1,18 @@
 use hir::GenericParamKind;
 use rustc_errors::{
     fluent, AddToDiagnostic, Applicability, Diagnostic, DiagnosticMessage, DiagnosticStyledString,
-    MultiSpan, SubdiagnosticMessage,
+    IntoDiagnosticArg, MultiSpan, SubdiagnosticMessage,
 };
 use rustc_hir as hir;
 use rustc_hir::FnRetTy;
 use rustc_macros::{Diagnostic, Subdiagnostic};
-use rustc_middle::ty::{Region, Ty, TyCtxt};
+use rustc_middle::ty::print::TraitRefPrintOnlyTraitPath;
+use rustc_middle::ty::{Binder, FnSig, Region, Ty, TyCtxt};
 use rustc_span::symbol::kw;
 use rustc_span::Symbol;
 use rustc_span::{symbol::Ident, BytePos, Span};
 
+use crate::infer::error_reporting::nice_region_error::placeholder_error::Highlighted;
 use crate::infer::error_reporting::{
     need_type_info::{GeneratorKindAsDiagArg, UnderspecifiedArgKind},
     ObligationCauseAsDiagArg,
@@ -557,91 +559,126 @@ pub enum ExplicitLifetimeRequired<'a> {
     },
 }
 
+pub enum TyOrSig<'tcx> {
+    Ty(Highlighted<'tcx, Ty<'tcx>>),
+    ClosureSig(Highlighted<'tcx, Binder<'tcx, FnSig<'tcx>>>),
+}
+
+impl IntoDiagnosticArg for TyOrSig<'_> {
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+        match self {
+            TyOrSig::Ty(ty) => ty.into_diagnostic_arg(),
+            TyOrSig::ClosureSig(sig) => sig.into_diagnostic_arg(),
+        }
+    }
+}
+
 #[derive(Subdiagnostic)]
-pub enum ActualImplExplNotes {
+pub enum ActualImplExplNotes<'tcx> {
     #[note(infer_actual_impl_expl_expected_signature_two)]
     ExpectedSignatureTwo {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
         lifetime_2: usize,
     },
     #[note(infer_actual_impl_expl_expected_signature_any)]
     ExpectedSignatureAny {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
     },
     #[note(infer_actual_impl_expl_expected_signature_some)]
     ExpectedSignatureSome {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
     },
     #[note(infer_actual_impl_expl_expected_signature_nothing)]
-    ExpectedSignatureNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
+    ExpectedSignatureNothing {
+        leading_ellipsis: bool,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
+    },
     #[note(infer_actual_impl_expl_expected_passive_two)]
     ExpectedPassiveTwo {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
         lifetime_2: usize,
     },
     #[note(infer_actual_impl_expl_expected_passive_any)]
     ExpectedPassiveAny {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
     },
     #[note(infer_actual_impl_expl_expected_passive_some)]
     ExpectedPassiveSome {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
     },
     #[note(infer_actual_impl_expl_expected_passive_nothing)]
-    ExpectedPassiveNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
+    ExpectedPassiveNothing {
+        leading_ellipsis: bool,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
+    },
     #[note(infer_actual_impl_expl_expected_other_two)]
     ExpectedOtherTwo {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
         lifetime_2: usize,
     },
     #[note(infer_actual_impl_expl_expected_other_any)]
     ExpectedOtherAny {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
     },
     #[note(infer_actual_impl_expl_expected_other_some)]
     ExpectedOtherSome {
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
     },
     #[note(infer_actual_impl_expl_expected_other_nothing)]
-    ExpectedOtherNothing { leading_ellipsis: bool, ty_or_sig: String, trait_path: String },
+    ExpectedOtherNothing {
+        leading_ellipsis: bool,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
+    },
     #[note(infer_actual_impl_expl_but_actually_implements_trait)]
-    ButActuallyImplementsTrait { trait_path: String, has_lifetime: bool, lifetime: usize },
+    ButActuallyImplementsTrait {
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
+        has_lifetime: bool,
+        lifetime: usize,
+    },
     #[note(infer_actual_impl_expl_but_actually_implemented_for_ty)]
     ButActuallyImplementedForTy {
-        trait_path: String,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         has_lifetime: bool,
         lifetime: usize,
         ty: String,
     },
     #[note(infer_actual_impl_expl_but_actually_ty_implements)]
-    ButActuallyTyImplements { trait_path: String, has_lifetime: bool, lifetime: usize, ty: String },
+    ButActuallyTyImplements {
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
+        has_lifetime: bool,
+        lifetime: usize,
+        ty: String,
+    },
 }
 
 pub enum ActualImplExpectedKind {
@@ -657,13 +694,13 @@ pub enum ActualImplExpectedLifetimeKind {
     Nothing,
 }
 
-impl ActualImplExplNotes {
+impl<'tcx> ActualImplExplNotes<'tcx> {
     pub fn new_expected(
         kind: ActualImplExpectedKind,
         lt_kind: ActualImplExpectedLifetimeKind,
         leading_ellipsis: bool,
-        ty_or_sig: String,
-        trait_path: String,
+        ty_or_sig: TyOrSig<'tcx>,
+        trait_path: Highlighted<'tcx, TraitRefPrintOnlyTraitPath<'tcx>>,
         lifetime_1: usize,
         lifetime_2: usize,
     ) -> Self {
@@ -728,7 +765,7 @@ impl ActualImplExplNotes {
 
 #[derive(Diagnostic)]
 #[diag(infer_trait_placeholder_mismatch)]
-pub struct TraitPlaceholderMismatch {
+pub struct TraitPlaceholderMismatch<'tcx> {
     #[primary_span]
     pub span: Span,
     #[label(label_satisfy)]
@@ -741,7 +778,7 @@ pub struct TraitPlaceholderMismatch {
     pub trait_def_id: String,
 
     #[subdiagnostic(eager)]
-    pub actual_impl_expl_notes: Vec<ActualImplExplNotes>,
+    pub actual_impl_expl_notes: Vec<ActualImplExplNotes<'tcx>>,
 }
 
 pub struct ConsiderBorrowingParamHelp {
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs
index 8a0e332f9c704..59fb74eb54378 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mod.rs
@@ -9,7 +9,7 @@ mod different_lifetimes;
 pub mod find_anon_type;
 mod mismatched_static_lifetime;
 mod named_anon_conflict;
-mod placeholder_error;
+pub(crate) mod placeholder_error;
 mod placeholder_relation;
 mod static_impl_trait;
 mod trait_impl_difference;
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index 904723c4da9d7..2ff2d1926a260 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -1,6 +1,6 @@
 use crate::errors::{
     ActualImplExpectedKind, ActualImplExpectedLifetimeKind, ActualImplExplNotes,
-    TraitPlaceholderMismatch,
+    TraitPlaceholderMismatch, TyOrSig,
 };
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
@@ -8,7 +8,7 @@ use crate::infer::ValuePairs;
 use crate::infer::{SubregionOrigin, TypeTrace};
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use rustc_data_structures::intern::Interned;
-use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
+use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed, IntoDiagnosticArg};
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::error::ExpectedFound;
@@ -18,6 +18,42 @@ use rustc_middle::ty::{self, RePlaceholder, ReVar, Region, TyCtxt};
 
 use std::fmt;
 
+// HACK(eddyb) maybe move this in a more central location.
+#[derive(Copy, Clone)]
+pub struct Highlighted<'tcx, T> {
+    tcx: TyCtxt<'tcx>,
+    highlight: RegionHighlightMode<'tcx>,
+    value: T,
+}
+
+impl<'tcx, T> IntoDiagnosticArg for Highlighted<'tcx, T>
+where
+    T: for<'a> Print<'tcx, FmtPrinter<'a, 'tcx>, Error = fmt::Error, Output = FmtPrinter<'a, 'tcx>>,
+{
+    fn into_diagnostic_arg(self) -> rustc_errors::DiagnosticArgValue<'static> {
+        rustc_errors::DiagnosticArgValue::Str(self.to_string().into())
+    }
+}
+
+impl<'tcx, T> Highlighted<'tcx, T> {
+    fn map<U>(self, f: impl FnOnce(T) -> U) -> Highlighted<'tcx, U> {
+        Highlighted { tcx: self.tcx, highlight: self.highlight, value: f(self.value) }
+    }
+}
+
+impl<'tcx, T> fmt::Display for Highlighted<'tcx, T>
+where
+    T: for<'a> Print<'tcx, FmtPrinter<'a, 'tcx>, Error = fmt::Error, Output = FmtPrinter<'a, 'tcx>>,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS);
+        printer.region_highlight_mode = self.highlight;
+
+        let s = self.value.print(printer)?.into_buffer();
+        f.write_str(&s)
+    }
+}
+
 impl<'tcx> NiceRegionError<'_, 'tcx> {
     /// When given a `ConcreteFailure` for a function with arguments containing a named region and
     /// an anonymous region, emit a descriptive diagnostic error.
@@ -328,39 +364,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         actual_has_vid: Option<usize>,
         any_self_ty_has_vid: bool,
         leading_ellipsis: bool,
-    ) -> Vec<ActualImplExplNotes> {
-        // HACK(eddyb) maybe move this in a more central location.
-        #[derive(Copy, Clone)]
-        struct Highlighted<'tcx, T> {
-            tcx: TyCtxt<'tcx>,
-            highlight: RegionHighlightMode<'tcx>,
-            value: T,
-        }
-
-        impl<'tcx, T> Highlighted<'tcx, T> {
-            fn map<U>(self, f: impl FnOnce(T) -> U) -> Highlighted<'tcx, U> {
-                Highlighted { tcx: self.tcx, highlight: self.highlight, value: f(self.value) }
-            }
-        }
-
-        impl<'tcx, T> fmt::Display for Highlighted<'tcx, T>
-        where
-            T: for<'a> Print<
-                'tcx,
-                FmtPrinter<'a, 'tcx>,
-                Error = fmt::Error,
-                Output = FmtPrinter<'a, 'tcx>,
-            >,
-        {
-            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-                let mut printer = ty::print::FmtPrinter::new(self.tcx, Namespace::TypeNS);
-                printer.region_highlight_mode = self.highlight;
-
-                let s = self.value.print(printer)?.into_buffer();
-                f.write_str(&s)
-            }
-        }
-
+    ) -> Vec<ActualImplExplNotes<'tcx>> {
         // The weird thing here with the `maybe_highlighting_region` calls and the
         // the match inside is meant to be like this:
         //
@@ -418,27 +422,27 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
                 });
                 (
                     ActualImplExpectedKind::Signature,
-                    closure_sig.to_string(),
-                    expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
+                    TyOrSig::ClosureSig(closure_sig),
+                    expected_trait_ref.map(|tr| tr.print_only_trait_path()),
                 )
             } else {
                 (
                     ActualImplExpectedKind::Other,
-                    self_ty.to_string(),
-                    expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
+                    TyOrSig::Ty(self_ty),
+                    expected_trait_ref.map(|tr| tr.print_only_trait_path()),
                 )
             }
         } else if passive_voice {
             (
                 ActualImplExpectedKind::Passive,
-                expected_trait_ref.map(|tr| tr.self_ty()).to_string(),
-                expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
+                TyOrSig::Ty(expected_trait_ref.map(|tr| tr.self_ty())),
+                expected_trait_ref.map(|tr| tr.print_only_trait_path()),
             )
         } else {
             (
                 ActualImplExpectedKind::Other,
-                expected_trait_ref.map(|tr| tr.self_ty()).to_string(),
-                expected_trait_ref.map(|tr| tr.print_only_trait_path()).to_string(),
+                TyOrSig::Ty(expected_trait_ref.map(|tr| tr.self_ty())),
+                expected_trait_ref.map(|tr| tr.print_only_trait_path()),
             )
         };
 
@@ -474,7 +478,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             None => true,
         };
 
-        let trait_path = actual_trait_ref.map(|tr| tr.print_only_trait_path()).to_string();
+        let trait_path = actual_trait_ref.map(|tr| tr.print_only_trait_path());
         let ty = actual_trait_ref.map(|tr| tr.self_ty()).to_string();
         let has_lifetime = actual_has_vid.is_some();
         let lifetime = actual_has_vid.unwrap_or_default();

From a86173766c113fdde95c2510de5909d4f9469833 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Thu, 3 Nov 2022 21:56:15 +0300
Subject: [PATCH 13/16] Fix nits

---
 .../error_reporting/nice_region_error/placeholder_error.rs  | 6 ++----
 .../error_reporting/nice_region_error/static_impl_trait.rs  | 5 ++---
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index 2ff2d1926a260..a5e5f9538565b 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -333,7 +333,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             leading_ellipsis,
         );
 
-        let diag = TraitPlaceholderMismatch {
+        self.tcx().sess.create_err(TraitPlaceholderMismatch {
             span,
             satisfy_span,
             where_span,
@@ -341,9 +341,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             def_id,
             trait_def_id: self.tcx().def_path_str(trait_def_id),
             actual_impl_expl_notes,
-        };
-
-        self.tcx().sess.create_err(diag)
+        })
     }
 
     /// Add notes with details about the expected and actual trait refs, with attention to cases
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
index fbc71bd7e0196..ae3f174c72e64 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
@@ -63,7 +63,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                         AssocItemContainer::ImplContainer => (false, String::new()),
                     };
 
-                    let diag = ButCallingIntroduces {
+                    let mut err = self.tcx().sess.create_err(ButCallingIntroduces {
                         param_ty_span: param.param_ty_span,
                         cause_span: cause.span,
                         has_param_name: simple_ident.is_some(),
@@ -73,8 +73,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                         assoc_item: ctxt.assoc_item.name,
                         has_impl_path,
                         impl_path,
-                    };
-                    let mut err = self.tcx().sess.create_err(diag);
+                    });
                     if self.find_impl_on_dyn_trait(&mut err, param.param_ty, &ctxt) {
                         let reported = err.emit();
                         return Some(reported);

From dda3ebad0a2b26ee35e2f4f3d26f529b092edfc4 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Mon, 7 Nov 2022 15:56:52 +0300
Subject: [PATCH 14/16] Fix broken rebase

---
 .../error_reporting/nice_region_error/static_impl_trait.rs      | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
index ae3f174c72e64..8a6dadf935f42 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
@@ -8,7 +8,7 @@ use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::infer::{SubregionOrigin, TypeTrace};
 use crate::traits::{ObligationCauseCode, UnifyReceiverContext};
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{AddToDiagnostic, Applicability, Diagnostic, ErrorGuaranteed, MultiSpan};
 use rustc_hir::def_id::DefId;
 use rustc_hir::intravisit::{walk_ty, Visitor};

From 2a8b17dbc5489ee085cf1587cf3c63a3fd2746aa Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Tue, 29 Nov 2022 19:19:26 +0300
Subject: [PATCH 15/16] Fix formatting

---
 .../error_reporting/nice_region_error/placeholder_error.rs     | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index a5e5f9538565b..202f39521e967 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -405,8 +405,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             let mut self_ty = expected_trait_ref.map(|tr| tr.self_ty());
             self_ty.highlight.maybe_highlighting_region(vid, actual_has_vid);
 
-            if self_ty.value.is_closure()
-                && self.tcx().is_fn_trait(expected_trait_ref.value.def_id)
+            if self_ty.value.is_closure() && self.tcx().is_fn_trait(expected_trait_ref.value.def_id)
             {
                 let closure_sig = self_ty.map(|closure| {
                     if let ty::Closure(_, substs) = closure.kind() {

From 0c50e1f146efc594eb84146c598d577c9f8a27d2 Mon Sep 17 00:00:00 2001
From: Nikita Tomashevich <quant3234@gmail.com>
Date: Wed, 28 Dec 2022 15:24:18 +0300
Subject: [PATCH 16/16] eager is the default now

---
 compiler/rustc_infer/src/errors/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/rustc_infer/src/errors/mod.rs b/compiler/rustc_infer/src/errors/mod.rs
index 388ddd09905ac..9cd053694fe45 100644
--- a/compiler/rustc_infer/src/errors/mod.rs
+++ b/compiler/rustc_infer/src/errors/mod.rs
@@ -777,7 +777,7 @@ pub struct TraitPlaceholderMismatch<'tcx> {
     pub def_id: String,
     pub trait_def_id: String,
 
-    #[subdiagnostic(eager)]
+    #[subdiagnostic]
     pub actual_impl_expl_notes: Vec<ActualImplExplNotes<'tcx>>,
 }