Auto merge of #91019 - JohnTitor:rollup-q95ra7r, r=JohnTitor

Rollup of 8 pull requests

Successful merges:

 - #90386 (Add `-Zassert-incr-state` to assert state of incremental cache)
 - #90438 (Clean up mess for --show-coverage documentation)
 - #90480 (Mention `Vec::remove` in `Vec::swap_remove`'s docs)
 - #90607 (Make slice->str conversion and related functions `const`)
 - #90750 (rustdoc: Replace where-bounded Clean impl with simple function)
 - #90895 (require full validity when determining the discriminant of a value)
 - #90989 (Avoid suggesting literal formatting that turns into member access)
 - #91002 (rustc: Remove `#[rustc_synthetic]`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_ast_lowering/src/lib.rs

@@ -1338,10 +1338,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             pure_wrt_drop: false,
                             bounds: hir_bounds,
                             span: self.lower_span(span),
-                            kind: hir::GenericParamKind::Type {
-                                default: None,
-                                synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
-                            },
+                            kind: hir::GenericParamKind::Type { default: None, synthetic: true },
                         });
 
                         hir::TyKind::Path(hir::QPath::Resolved(
@@ -1954,12 +1951,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     default: default.as_ref().map(|x| {
                         self.lower_ty(x, ImplTraitContext::Disallowed(ImplTraitPosition::Other))
                     }),
-                    synthetic: param
-                        .attrs
-                        .iter()
-                        .filter(|attr| attr.has_name(sym::rustc_synthetic))
-                        .map(|_| hir::SyntheticTyParamKind::FromAttr)
-                        .next(),
+                    synthetic: false,
                 };
 
                 (hir::ParamName::Plain(self.lower_ident(param.ident)), kind)

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -265,6 +265,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
             sym::discriminant_value => {
                 let place = self.deref_operand(&args[0])?;
+                if M::enforce_validity(self) {
+                    // This is 'using' the value, so make sure the validity invariant is satisfied.
+                    // (Also see https://github.com/rust-lang/rust/pull/89764.)
+                    self.validate_operand(&place.into())?;
+                }
+
                 let discr_val = self.read_discriminant(&place.into())?.0;
                 self.write_scalar(discr_val, dest)?;
             }

compiler/rustc_const_eval/src/interpret/step.rs

@@ -304,6 +304,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
             Discriminant(place) => {
                 let op = self.eval_place_to_op(place, None)?;
+                if M::enforce_validity(self) {
+                    // This is 'using' the value, so make sure the validity invariant is satisfied.
+                    // (Also see https://github.com/rust-lang/rust/pull/89764.)
+                    self.validate_operand(&op)?;
+                }
+
                 let discr_val = self.read_discriminant(&op)?.0;
                 self.write_scalar(discr_val, &dest)?;
             }

compiler/rustc_feature/src/builtin_attrs.rs

@@ -601,7 +601,6 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         TEST, rustc_expected_cgu_reuse, Normal,
         template!(List: r#"cfg = "...", module = "...", kind = "...""#),
     ),
-    rustc_attr!(TEST, rustc_synthetic, Normal, template!(Word)),
     rustc_attr!(TEST, rustc_symbol_name, Normal, template!(Word)),
     rustc_attr!(TEST, rustc_polymorphize_error, Normal, template!(Word)),
     rustc_attr!(TEST, rustc_def_path, Normal, template!(Word)),

compiler/rustc_hir/src/hir.rs

@@ -504,7 +504,7 @@ pub enum GenericParamKind<'hir> {
     },
     Type {
         default: Option<&'hir Ty<'hir>>,
-        synthetic: Option<SyntheticTyParamKind>,
+        synthetic: bool,
     },
     Const {
         ty: &'hir Ty<'hir>,
@@ -577,16 +577,6 @@ impl Generics<'hir> {
     }
 }
 
-/// Synthetic type parameters are converted to another form during lowering; this allows
-/// us to track the original form they had, and is useful for error messages.
-#[derive(Copy, Clone, PartialEq, Eq, Encodable, Decodable, Hash, Debug)]
-#[derive(HashStable_Generic)]
-pub enum SyntheticTyParamKind {
-    ImplTrait,
-    // Created by the `#[rustc_synthetic]` attribute.
-    FromAttr,
-}
-
 /// A where-clause in a definition.
 #[derive(Debug, HashStable_Generic)]
 pub struct WhereClause<'hir> {

compiler/rustc_incremental/src/persist/load.rs

@@ -6,6 +6,7 @@ use rustc_middle::dep_graph::{SerializedDepGraph, WorkProduct, WorkProductId};
 use rustc_middle::ty::OnDiskCache;
 use rustc_serialize::opaque::Decoder;
 use rustc_serialize::Decodable;
+use rustc_session::config::IncrementalStateAssertion;
 use rustc_session::Session;
 use std::path::Path;
 
@@ -16,6 +17,7 @@ use super::work_product;
 
 type WorkProductMap = FxHashMap<WorkProductId, WorkProduct>;
 
+#[derive(Debug)]
 pub enum LoadResult<T> {
     Ok { data: T },
     DataOutOfDate,
@@ -24,6 +26,26 @@ pub enum LoadResult<T> {
 
 impl<T: Default> LoadResult<T> {
     pub fn open(self, sess: &Session) -> T {
+        // Check for errors when using `-Zassert-incremental-state`
+        match (sess.opts.assert_incr_state, &self) {
+            (Some(IncrementalStateAssertion::NotLoaded), LoadResult::Ok { .. }) => {
+                sess.fatal(
+                    "We asserted that the incremental cache should not be loaded, \
+                         but it was loaded.",
+                );
+            }
+            (
+                Some(IncrementalStateAssertion::Loaded),
+                LoadResult::Error { .. } | LoadResult::DataOutOfDate,
+            ) => {
+                sess.fatal(
+                    "We asserted that an existing incremental cache directory should \
+                         be successfully loaded, but it was not.",
+                );
+            }
+            _ => {}
+        };
+
         match self {
             LoadResult::Error { message } => {
                 sess.warn(&message);
@@ -33,7 +55,7 @@ impl<T: Default> LoadResult<T> {
                 if let Err(err) = delete_all_session_dir_contents(sess) {
                     sess.err(&format!(
                         "Failed to delete invalidated or incompatible \
-                                      incremental compilation session directory contents `{}`: {}.",
+                         incremental compilation session directory contents `{}`: {}.",
                         dep_graph_path(sess).display(),
                         err
                     ));

compiler/rustc_interface/src/tests.rs

@@ -636,6 +636,7 @@ fn test_debugging_options_tracking_hash() {
 
     // Make sure that changing an [UNTRACKED] option leaves the hash unchanged.
     // This list is in alphabetical order.
+    untracked!(assert_incr_state, Some(String::from("loaded")));
     untracked!(ast_json, true);
     untracked!(ast_json_noexpand, true);
     untracked!(borrowck, String::from("other"));

compiler/rustc_middle/src/ty/generics.rs

@@ -3,7 +3,6 @@ use crate::ty;
 use crate::ty::subst::{Subst, SubstsRef};
 use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_span::symbol::Symbol;
 use rustc_span::Span;
@@ -13,14 +12,8 @@ use super::{EarlyBoundRegion, InstantiatedPredicates, ParamConst, ParamTy, Predi
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub enum GenericParamDefKind {
     Lifetime,
-    Type {
-        has_default: bool,
-        object_lifetime_default: ObjectLifetimeDefault,
-        synthetic: Option<hir::SyntheticTyParamKind>,
-    },
-    Const {
-        has_default: bool,
-    },
+    Type { has_default: bool, object_lifetime_default: ObjectLifetimeDefault, synthetic: bool },
+    Const { has_default: bool },
 }
 
 impl GenericParamDefKind {
@@ -202,15 +195,7 @@ impl<'tcx> Generics {
     /// Returns `true` if `params` has `impl Trait`.
     pub fn has_impl_trait(&'tcx self) -> bool {
         self.params.iter().any(|param| {
-            matches!(
-                param.kind,
-                ty::GenericParamDefKind::Type {
-                    synthetic: Some(
-                        hir::SyntheticTyParamKind::ImplTrait | hir::SyntheticTyParamKind::FromAttr,
-                    ),
-                    ..
-                }
-            )
+            matches!(param.kind, ty::GenericParamDefKind::Type { synthetic: true, .. })
         })
     }
 }

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1810,12 +1810,10 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                     let (span, sugg) = if let Some(param) = generics.params.iter().find(|p| {
                         !matches!(
                             p.kind,
-                            hir::GenericParamKind::Type {
-                                synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
-                                ..
-                            } | hir::GenericParamKind::Lifetime {
-                                kind: hir::LifetimeParamKind::Elided,
-                            }
+                            hir::GenericParamKind::Type { synthetic: true, .. }
+                                | hir::GenericParamKind::Lifetime {
+                                    kind: hir::LifetimeParamKind::Elided,
+                                }
                         )
                     }) {
                         (param.span.shrink_to_lo(), format!("{}, ", lifetime_ref))
@@ -2042,12 +2040,10 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
                         if let Some(param) = generics.params.iter().find(|p| {
                             !matches!(
                                 p.kind,
-                                hir::GenericParamKind::Type {
-                                    synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
-                                    ..
-                                } | hir::GenericParamKind::Lifetime {
-                                    kind: hir::LifetimeParamKind::Elided
-                                }
+                                hir::GenericParamKind::Type { synthetic: true, .. }
+                                    | hir::GenericParamKind::Lifetime {
+                                        kind: hir::LifetimeParamKind::Elided
+                                    }
                             )
                         }) {
                             (param.span.shrink_to_lo(), "'a, ".to_string())

compiler/rustc_session/src/config.rs

@@ -165,6 +165,18 @@ pub enum LinkerPluginLto {
     Disabled,
 }
 
+/// Used with `-Z assert-incr-state`.
+#[derive(Clone, Copy, PartialEq, Hash, Debug)]
+pub enum IncrementalStateAssertion {
+    /// Found and loaded an existing session directory.
+    ///
+    /// Note that this says nothing about whether any particular query
+    /// will be found to be red or green.
+    Loaded,
+    /// Did not load an existing session directory.
+    NotLoaded,
+}
+
 impl LinkerPluginLto {
     pub fn enabled(&self) -> bool {
         match *self {
@@ -704,6 +716,7 @@ pub fn host_triple() -> &'static str {
 impl Default for Options {
     fn default() -> Options {
         Options {
+            assert_incr_state: None,
             crate_types: Vec::new(),
             optimize: OptLevel::No,
             debuginfo: DebugInfo::None,
@@ -1626,6 +1639,21 @@ fn select_debuginfo(
     }
 }
 
+crate fn parse_assert_incr_state(
+    opt_assertion: &Option<String>,
+    error_format: ErrorOutputType,
+) -> Option<IncrementalStateAssertion> {
+    match opt_assertion {
+        Some(s) if s.as_str() == "loaded" => Some(IncrementalStateAssertion::Loaded),
+        Some(s) if s.as_str() == "not-loaded" => Some(IncrementalStateAssertion::NotLoaded),
+        Some(s) => early_error(
+            error_format,
+            &format!("unexpected incremental state assertion value: {}", s),
+        ),
+        None => None,
+    }
+}
+
 fn parse_native_lib_kind(
     matches: &getopts::Matches,
     kind: &str,
@@ -2015,6 +2043,9 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
 
     let incremental = cg.incremental.as_ref().map(PathBuf::from);
 
+    let assert_incr_state =
+        parse_assert_incr_state(&debugging_opts.assert_incr_state, error_format);
+
     if debugging_opts.profile && incremental.is_some() {
         early_error(
             error_format,
@@ -2179,6 +2210,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
     };
 
     Options {
+        assert_incr_state,
         crate_types,
         optimize: opt_level,
         debuginfo,

compiler/rustc_session/src/options.rs

@@ -4,7 +4,6 @@ use crate::early_error;
 use crate::lint;
 use crate::search_paths::SearchPath;
 use crate::utils::NativeLib;
-
 use rustc_target::spec::{CodeModel, LinkerFlavor, MergeFunctions, PanicStrategy, SanitizerSet};
 use rustc_target::spec::{RelocModel, RelroLevel, SplitDebuginfo, TargetTriple, TlsModel};
 
@@ -150,6 +149,7 @@ top_level_options!(
         /// If `Some`, enable incremental compilation, using the given
         /// directory to store intermediate results.
         incremental: Option<PathBuf> [UNTRACKED],
+        assert_incr_state: Option<IncrementalStateAssertion> [UNTRACKED],
 
         debugging_opts: DebuggingOptions [SUBSTRUCT],
         prints: Vec<PrintRequest> [UNTRACKED],
@@ -1046,6 +1046,9 @@ options! {
         "make cfg(version) treat the current version as incomplete (default: no)"),
     asm_comments: bool = (false, parse_bool, [TRACKED],
         "generate comments into the assembly (may change behavior) (default: no)"),
+    assert_incr_state: Option<String> = (None, parse_opt_string, [UNTRACKED],
+        "assert that the incremental cache is in given state: \
+         either `loaded` or `not-loaded`."),
     ast_json: bool = (false, parse_bool, [UNTRACKED],
         "print the AST as JSON and halt (default: no)"),
     ast_json_noexpand: bool = (false, parse_bool, [UNTRACKED],

compiler/rustc_span/src/symbol.rs

@@ -1148,7 +1148,6 @@ symbols! {
         rustc_std_internal_symbol,
         rustc_strict_coherence,
         rustc_symbol_name,
-        rustc_synthetic,
         rustc_test_marker,
         rustc_then_this_would_need,
         rustc_trivial_field_reads,

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -290,9 +290,10 @@ fn suggest_restriction(
     } else {
         // Trivial case: `T` needs an extra bound: `T: Bound`.
         let (sp, suggestion) = match (
-            generics.params.iter().find(|p| {
-                !matches!(p.kind, hir::GenericParamKind::Type { synthetic: Some(_), .. })
-            }),
+            generics
+                .params
+                .iter()
+                .find(|p| !matches!(p.kind, hir::GenericParamKind::Type { synthetic: true, .. })),
             super_traits,
         ) {
             (_, None) => predicate_constraint(

compiler/rustc_typeck/src/astconv/generics.rs

@@ -464,16 +464,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 .params
                 .iter()
                 .filter(|param| {
-                    matches!(
-                        param.kind,
-                        ty::GenericParamDefKind::Type {
-                            synthetic: Some(
-                                hir::SyntheticTyParamKind::ImplTrait
-                                    | hir::SyntheticTyParamKind::FromAttr
-                            ),
-                            ..
-                        }
-                    )
+                    matches!(param.kind, ty::GenericParamDefKind::Type { synthetic: true, .. })
                 })
                 .count()
         } else {

compiler/rustc_typeck/src/check/compare_method.rs

@@ -607,10 +607,7 @@ fn compare_number_of_generics<'tcx>(
                         .params
                         .iter()
                         .filter_map(|p| match p.kind {
-                            GenericParamKind::Type {
-                                synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
-                                ..
-                            } => Some(p.span),
+                            GenericParamKind::Type { synthetic: true, .. } => Some(p.span),
                             _ => None,
                         })
                         .collect();
@@ -627,10 +624,7 @@ fn compare_number_of_generics<'tcx>(
                 .params
                 .iter()
                 .filter_map(|p| match p.kind {
-                    GenericParamKind::Type {
-                        synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
-                        ..
-                    } => Some(p.span),
+                    GenericParamKind::Type { synthetic: true, .. } => Some(p.span),
                     _ => None,
                 })
                 .collect();
@@ -823,7 +817,7 @@ fn compare_synthetic_generics<'tcx>(
             match (impl_synthetic, trait_synthetic) {
                 // The case where the impl method uses `impl Trait` but the trait method uses
                 // explicit generics
-                (Some(hir::SyntheticTyParamKind::ImplTrait), None) => {
+                (true, false) => {
                     err.span_label(impl_span, "expected generic parameter, found `impl Trait`");
                     (|| {
                         // try taking the name from the trait impl
@@ -864,7 +858,7 @@ fn compare_synthetic_generics<'tcx>(
                 }
                 // The case where the trait method uses `impl Trait`, but the impl method uses
                 // explicit generics.
-                (None, Some(hir::SyntheticTyParamKind::ImplTrait)) => {
+                (false, true) => {
                     err.span_label(impl_span, "expected `impl Trait`, found generic parameter");
                     (|| {
                         let impl_m = impl_m.def_id.as_local()?;