Auto merge of #98816 - estebank:implicit-sized, r=oli-obk

Track implicit `Sized` obligations in type params

When we evaluate `ty::GenericPredicates` we introduce the implicit
`Sized` predicate of type params, but we do so with only the `Predicate`
its `Span` as context, we don't have an `Obligation` or
`ObligationCauseCode` we could influence. To try and carry this
information through, we add a new field to `ty::GenericPredicates` that
tracks both which predicates come from a type param and whether that
param has any bounds already (to use in suggestions).

We also suggest adding a `?Sized` bound if appropriate on E0599.

Address part of #98539.

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -270,7 +270,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
     }
 
     fn normalize(mut self) -> Vec<traits::PredicateObligation<'tcx>> {
-        let cause = self.cause(traits::MiscObligation);
+        let cause = self.cause(traits::WellFormed(None));
         let infcx = &mut self.infcx;
         let param_env = self.param_env;
         let mut obligations = Vec::with_capacity(self.out.len());
@@ -384,7 +384,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         self.out.extend(obligations);
 
         let tcx = self.tcx();
-        let cause = self.cause(traits::MiscObligation);
+        let cause = self.cause(traits::WellFormed(None));
         let param_env = self.param_env;
         let depth = self.recursion_depth;
 
@@ -444,7 +444,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                             let predicate =
                                 ty::Binder::dummy(ty::PredicateKind::ConstEvaluatable(uv.shrink()))
                                     .to_predicate(self.tcx());
-                            let cause = self.cause(traits::MiscObligation);
+                            let cause = self.cause(traits::WellFormed(None));
                             self.out.push(traits::Obligation::with_depth(
                                 cause,
                                 self.recursion_depth,
@@ -456,7 +456,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                             let resolved = self.infcx.shallow_resolve(infer);
                             // the `InferConst` changed, meaning that we made progress.
                             if resolved != infer {
-                                let cause = self.cause(traits::MiscObligation);
+                                let cause = self.cause(traits::WellFormed(None));
 
                                 let resolved_constant = self.infcx.tcx.mk_const(ty::ConstS {
                                     kind: ty::ConstKind::Infer(resolved),
@@ -647,7 +647,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     let defer_to_coercion = self.tcx().features().object_safe_for_dispatch;
 
                     if !defer_to_coercion {
-                        let cause = self.cause(traits::MiscObligation);
+                        let cause = self.cause(traits::WellFormed(None));
                         let component_traits = data.auto_traits().chain(data.principal_def_id());
                         let tcx = self.tcx();
                         self.out.extend(component_traits.map(|did| {
@@ -678,7 +678,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     let ty = self.infcx.shallow_resolve(ty);
                     if let ty::Infer(ty::TyVar(_)) = ty.kind() {
                         // Not yet resolved, but we've made progress.
-                        let cause = self.cause(traits::MiscObligation);
+                        let cause = self.cause(traits::WellFormed(None));
                         self.out.push(traits::Obligation::with_depth(
                             cause,
                             self.recursion_depth,

compiler/rustc_typeck/src/check/callee.rs

@@ -117,7 +117,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         // we must check that return type of called functions is WF:
-        self.register_wf_obligation(output.into(), call_expr.span, traits::MiscObligation);
+        self.register_wf_obligation(output.into(), call_expr.span, traits::WellFormed(None));
 
         output
     }

compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs

@@ -496,7 +496,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     pub fn to_ty(&self, ast_t: &hir::Ty<'_>) -> Ty<'tcx> {
         let t = <dyn AstConv<'_>>::ast_ty_to_ty(self, ast_t);
-        self.register_wf_obligation(t.into(), ast_t.span, traits::MiscObligation);
+        self.register_wf_obligation(t.into(), ast_t.span, traits::WellFormed(None));
         t
     }
 
@@ -526,7 +526,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.register_wf_obligation(
             c.into(),
             self.tcx.hir().span(ast_c.hir_id),
-            ObligationCauseCode::MiscObligation,
+            ObligationCauseCode::WellFormed(None),
         );
         c
     }
@@ -544,7 +544,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self.register_wf_obligation(
             c.into(),
             self.tcx.hir().span(ast_c.hir_id),
-            ObligationCauseCode::MiscObligation,
+            ObligationCauseCode::WellFormed(None),
         );
         c
     }
@@ -607,7 +607,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         for arg in substs.iter().filter(|arg| {
             matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..))
         }) {
-            self.register_wf_obligation(arg, expr.span, traits::MiscObligation);
+            self.register_wf_obligation(arg, expr.span, traits::WellFormed(None));
         }
     }
 

compiler/rustc_typeck/src/check/method/confirm.rs

@@ -501,7 +501,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // the function type must also be well-formed (this is not
         // implied by the substs being well-formed because of inherent
         // impls and late-bound regions - see issue #28609).
-        self.register_wf_obligation(fty.into(), self.span, traits::MiscObligation);
+        self.register_wf_obligation(fty.into(), self.span, traits::WellFormed(None));
     }
 
     ///////////////////////////////////////////////////////////////////////////

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -348,9 +348,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let type_param = generics.type_param(param_type, self.tcx);
                         Some(self.tcx.def_span(type_param.def_id))
                     }
-                    ty::Adt(def, _) if def.did().is_local() => {
-                        tcx.def_ident_span(def.did()).map(|span| span)
-                    }
+                    ty::Adt(def, _) if def.did().is_local() => Some(tcx.def_span(def.did())),
                     _ => None,
                 };
 
@@ -621,12 +619,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // Find all the requirements that come from a local `impl` block.
                     let mut skip_list: FxHashSet<_> = Default::default();
                     let mut spanned_predicates: FxHashMap<MultiSpan, _> = Default::default();
-                    for (data, p, parent_p, impl_def_id, cause_span) in unsatisfied_predicates
+                    for (data, p, parent_p, impl_def_id, cause) in unsatisfied_predicates
                         .iter()
                         .filter_map(|(p, parent, c)| c.as_ref().map(|c| (p, parent, c)))
                         .filter_map(|(p, parent, c)| match c.code() {
                             ObligationCauseCode::ImplDerivedObligation(ref data) => {
-                                Some((&data.derived, p, parent, data.impl_def_id, data.span))
+                                Some((&data.derived, p, parent, data.impl_def_id, data))
                             }
                             _ => None,
                         })
@@ -695,9 +693,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                     let _ = format_pred(*pred);
                                 }
                                 skip_list.insert(p);
-                                let mut spans = if cause_span != *item_span {
-                                    let mut spans: MultiSpan = cause_span.into();
-                                    spans.push_span_label(cause_span, unsatisfied_msg);
+                                let mut spans = if cause.span != *item_span {
+                                    let mut spans: MultiSpan = cause.span.into();
+                                    spans.push_span_label(cause.span, unsatisfied_msg);
                                     spans
                                 } else {
                                     ident.span.into()
@@ -709,7 +707,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                             // Unmet obligation coming from an `impl`.
                             Some(Node::Item(hir::Item {
-                                kind: hir::ItemKind::Impl(hir::Impl { of_trait, self_ty, .. }),
+                                kind:
+                                    hir::ItemKind::Impl(hir::Impl {
+                                        of_trait, self_ty, generics, ..
+                                    }),
                                 span: item_span,
                                 ..
                             })) if !matches!(
@@ -725,14 +726,40 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 Some(ExpnKind::Macro(MacroKind::Derive, _))
                             ) =>
                             {
+                                let sized_pred =
+                                    unsatisfied_predicates.iter().any(|(pred, _, _)| {
+                                        match pred.kind().skip_binder() {
+                                            ty::PredicateKind::Trait(pred) => {
+                                                Some(pred.def_id())
+                                                    == self.tcx.lang_items().sized_trait()
+                                                    && pred.polarity == ty::ImplPolarity::Positive
+                                            }
+                                            _ => false,
+                                        }
+                                    });
+                                for param in generics.params {
+                                    if param.span == cause.span && sized_pred {
+                                        let (sp, sugg) = match param.colon_span {
+                                            Some(sp) => (sp.shrink_to_hi(), " ?Sized +"),
+                                            None => (param.span.shrink_to_hi(), ": ?Sized"),
+                                        };
+                                        err.span_suggestion_verbose(
+                                            sp,
+                                            "consider relaxing the type parameter's implicit \
+                                             `Sized` bound",
+                                            sugg,
+                                            Applicability::MachineApplicable,
+                                        );
+                                    }
+                                }
                                 if let Some(pred) = parent_p {
                                     // Done to add the "doesn't satisfy" `span_label`.
                                     let _ = format_pred(*pred);
                                 }
                                 skip_list.insert(p);
-                                let mut spans = if cause_span != *item_span {
-                                    let mut spans: MultiSpan = cause_span.into();
-                                    spans.push_span_label(cause_span, unsatisfied_msg);
+                                let mut spans = if cause.span != *item_span {
+                                    let mut spans: MultiSpan = cause.span.into();
+                                    spans.push_span_label(cause.span, unsatisfied_msg);
                                     spans
                                 } else {
                                     let mut spans = Vec::with_capacity(2);

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -1180,7 +1180,7 @@ fn check_item_type(tcx: TyCtxt<'_>, item_id: LocalDefId, ty_span: Span, allow_fo
             fcx.register_bound(
                 item_ty,
                 tcx.require_lang_item(LangItem::Sized, None),
-                traits::ObligationCause::new(ty_span, fcx.body_id, traits::MiscObligation),
+                traits::ObligationCause::new(ty_span, fcx.body_id, traits::WellFormed(None)),
             );
         }
 

compiler/rustc_typeck/src/hir_wf_check.rs

@@ -72,7 +72,7 @@ fn diagnostic_hir_wf_check<'tcx>(
                 let cause = traits::ObligationCause::new(
                     ty.span,
                     self.hir_id,
-                    traits::ObligationCauseCode::MiscObligation,
+                    traits::ObligationCauseCode::WellFormed(None),
                 );
                 fulfill.register_predicate_obligation(
                     &infcx,

src/test/ui/associated-item/associated-item-enum.stderr

@@ -2,7 +2,7 @@ error[E0599]: no variant or associated item named `mispellable` found for enum `
   --> $DIR/associated-item-enum.rs:17:11
    |
 LL | enum Enum { Variant }
-   |      ---- variant or associated item `mispellable` not found for this enum
+   | --------- variant or associated item `mispellable` not found for this enum
 ...
 LL |     Enum::mispellable();
    |           ^^^^^^^^^^^
@@ -14,7 +14,7 @@ error[E0599]: no variant or associated item named `mispellable_trait` found for
   --> $DIR/associated-item-enum.rs:18:11
    |
 LL | enum Enum { Variant }
-   |      ---- variant or associated item `mispellable_trait` not found for this enum
+   | --------- variant or associated item `mispellable_trait` not found for this enum
 ...
 LL |     Enum::mispellable_trait();
    |           ^^^^^^^^^^^^^^^^^
@@ -26,7 +26,7 @@ error[E0599]: no variant or associated item named `MISPELLABLE` found for enum `
   --> $DIR/associated-item-enum.rs:19:11
    |
 LL | enum Enum { Variant }
-   |      ---- variant or associated item `MISPELLABLE` not found for this enum
+   | --------- variant or associated item `MISPELLABLE` not found for this enum
 ...
 LL |     Enum::MISPELLABLE;
    |           ^^^^^^^^^^^

src/test/ui/async-await/pin-needed-to-poll.stderr

@@ -2,7 +2,7 @@ error[E0599]: no method named `poll` found for struct `Sleep` in the current sco
   --> $DIR/pin-needed-to-poll.rs:42:20
    |
 LL | struct Sleep;
-   |        ----- method `poll` not found for this struct
+   | ------------ method `poll` not found for this struct
 ...
 LL |         self.sleep.poll(cx)
    |                    ^^^^ method not found in `Sleep`

src/test/ui/bogus-tag.stderr

@@ -2,7 +2,7 @@ error[E0599]: no variant or associated item named `Hsl` found for enum `Color` i
   --> $DIR/bogus-tag.rs:7:16
    |
 LL | enum Color { Rgb(isize, isize, isize), Rgba(isize, isize, isize, isize), }
-   |      ----- variant or associated item `Hsl` not found for this enum
+   | ---------- variant or associated item `Hsl` not found for this enum
 ...
 LL |         Color::Hsl(h, s, l) => { println!("hsl"); }
    |                ^^^ variant or associated item not found in `Color`

src/test/ui/confuse-field-and-method/issue-18343.stderr

@@ -2,7 +2,7 @@ error[E0599]: no method named `closure` found for struct `Obj` in the current sc
   --> $DIR/issue-18343.rs:7:7
    |
 LL | struct Obj<F> where F: FnMut() -> u32 {
-   |        --- method `closure` not found for this struct
+   | ------------- method `closure` not found for this struct
 ...
 LL |     o.closure();
    |       ^^^^^^^ field, not a method

src/test/ui/confuse-field-and-method/issue-2392.stderr

@@ -2,7 +2,7 @@ error[E0599]: no method named `closure` found for struct `Obj` in the current sc
   --> $DIR/issue-2392.rs:36:15
    |
 LL | struct Obj<F> where F: FnOnce() -> u32 {
-   |        --- method `closure` not found for this struct
+   | ------------- method `closure` not found for this struct
 ...
 LL |     o_closure.closure();
    |               ^^^^^^^ field, not a method
@@ -16,7 +16,7 @@ error[E0599]: no method named `not_closure` found for struct `Obj` in the curren
   --> $DIR/issue-2392.rs:38:15
    |
 LL | struct Obj<F> where F: FnOnce() -> u32 {
-   |        --- method `not_closure` not found for this struct
+   | ------------- method `not_closure` not found for this struct
 ...
 LL |     o_closure.not_closure();
    |               ^^^^^^^^^^^-- help: remove the arguments
@@ -27,7 +27,7 @@ error[E0599]: no method named `closure` found for struct `Obj` in the current sc
   --> $DIR/issue-2392.rs:42:12
    |
 LL | struct Obj<F> where F: FnOnce() -> u32 {
-   |        --- method `closure` not found for this struct
+   | ------------- method `closure` not found for this struct
 ...
 LL |     o_func.closure();
    |            ^^^^^^^ field, not a method
@@ -41,7 +41,7 @@ error[E0599]: no method named `boxed_closure` found for struct `BoxedObj` in the
   --> $DIR/issue-2392.rs:45:14
    |
 LL | struct BoxedObj {
-   |        -------- method `boxed_closure` not found for this struct
+   | --------------- method `boxed_closure` not found for this struct
 ...
 LL |     boxed_fn.boxed_closure();
    |              ^^^^^^^^^^^^^ field, not a method
@@ -55,7 +55,7 @@ error[E0599]: no method named `boxed_closure` found for struct `BoxedObj` in the
   --> $DIR/issue-2392.rs:48:19
    |
 LL | struct BoxedObj {
-   |        -------- method `boxed_closure` not found for this struct
+   | --------------- method `boxed_closure` not found for this struct
 ...
 LL |     boxed_closure.boxed_closure();
    |                   ^^^^^^^^^^^^^ field, not a method
@@ -69,7 +69,7 @@ error[E0599]: no method named `closure` found for struct `Obj` in the current sc
   --> $DIR/issue-2392.rs:53:12
    |
 LL | struct Obj<F> where F: FnOnce() -> u32 {
-   |        --- method `closure` not found for this struct
+   | ------------- method `closure` not found for this struct
 ...
 LL |     w.wrap.closure();
    |            ^^^^^^^ field, not a method
@@ -83,7 +83,7 @@ error[E0599]: no method named `not_closure` found for struct `Obj` in the curren
   --> $DIR/issue-2392.rs:55:12
    |
 LL | struct Obj<F> where F: FnOnce() -> u32 {
-   |        --- method `not_closure` not found for this struct
+   | ------------- method `not_closure` not found for this struct
 ...
 LL |     w.wrap.not_closure();
    |            ^^^^^^^^^^^-- help: remove the arguments
@@ -94,7 +94,7 @@ error[E0599]: no method named `closure` found for struct `Obj` in the current sc
   --> $DIR/issue-2392.rs:58:24
    |
 LL | struct Obj<F> where F: FnOnce() -> u32 {
-   |        --- method `closure` not found for this struct
+   | ------------- method `closure` not found for this struct
 ...
 LL |     check_expression().closure();
    |                        ^^^^^^^ field, not a method
@@ -108,7 +108,7 @@ error[E0599]: no method named `f1` found for struct `FuncContainer` in the curre
   --> $DIR/issue-2392.rs:64:31
    |
 LL | struct FuncContainer {
-   |        ------------- method `f1` not found for this struct
+   | -------------------- method `f1` not found for this struct
 ...
 LL |             (*self.container).f1(1);
    |                               ^^ field, not a method
@@ -122,7 +122,7 @@ error[E0599]: no method named `f2` found for struct `FuncContainer` in the curre
   --> $DIR/issue-2392.rs:65:31
    |
 LL | struct FuncContainer {
-   |        ------------- method `f2` not found for this struct
+   | -------------------- method `f2` not found for this struct
 ...
 LL |             (*self.container).f2(1);
    |                               ^^ field, not a method
@@ -136,7 +136,7 @@ error[E0599]: no method named `f3` found for struct `FuncContainer` in the curre
   --> $DIR/issue-2392.rs:66:31
    |
 LL | struct FuncContainer {
-   |        ------------- method `f3` not found for this struct
+   | -------------------- method `f3` not found for this struct
 ...
 LL |             (*self.container).f3(1);
    |                               ^^ field, not a method

src/test/ui/confuse-field-and-method/issue-32128.stderr

@@ -2,7 +2,7 @@ error[E0599]: no method named `example` found for struct `Example` in the curren
   --> $DIR/issue-32128.rs:12:10
    |
 LL | struct Example {
-   |        ------- method `example` not found for this struct
+   | -------------- method `example` not found for this struct
 ...
 LL |     demo.example(1);
    |          ^^^^^^^ field, not a method

src/test/ui/confuse-field-and-method/private-field.stderr

@@ -2,7 +2,7 @@ error[E0599]: no method named `dog_age` found for struct `Dog` in the current sc
   --> $DIR/private-field.rs:16:23
    |
 LL |     pub struct Dog {
-   |                --- method `dog_age` not found for this struct
+   |     -------------- method `dog_age` not found for this struct
 ...
 LL |     let dog_age = dog.dog_age();
    |                       ^^^^^^^ private field, not a method