Auto merge of #81042 - sasurau4:fix/unclear-error-with-trait, r=estebank
Add suggestion for impl_candidates with E0283
Fix #42226
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index aaab89a..bd43d3c 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -429,6 +429,7 @@
body_id: Option<hir::BodyId>,
span: Span,
arg: GenericArg<'tcx>,
+ impl_candidates: Vec<ty::TraitRef<'tcx>>,
error_code: TypeAnnotationNeeded,
) -> DiagnosticBuilder<'tcx> {
let arg = self.resolve_vars_if_possible(arg);
@@ -653,7 +654,44 @@
};
err.span_label(pattern.span, msg);
} else if let Some(e) = local_visitor.found_method_call {
- if let ExprKind::MethodCall(segment, ..) = &e.kind {
+ if let ExprKind::MethodCall(segment, _, exprs, _) = &e.kind {
+ // Suggest impl candidates:
+ //
+ // error[E0283]: type annotations needed
+ // --> $DIR/E0283.rs:35:24
+ // |
+ // LL | let bar = foo_impl.into() * 1u32;
+ // | ---------^^^^--
+ // | | |
+ // | | cannot infer type for type parameter `T` declared on the trait `Into`
+ // | this method call resolves to `T`
+ // | help: specify type like: `<Impl as Into<u32>>::into(foo_impl)`
+ // |
+ // = note: cannot satisfy `Impl: Into<_>`
+ if !impl_candidates.is_empty() && e.span.contains(span) {
+ if let Some(expr) = exprs.first() {
+ if let ExprKind::Path(hir::QPath::Resolved(_, path)) = expr.kind {
+ if let [path_segment] = &path.segments[..] {
+ let candidate_len = impl_candidates.len();
+ let suggestions = impl_candidates.iter().map(|candidate| {
+ format!(
+ "{}::{}({})",
+ candidate, segment.ident, path_segment.ident
+ )
+ });
+ err.span_suggestions(
+ e.span,
+ &format!(
+ "use the fully qualified path for the potential candidate{}",
+ pluralize!(candidate_len),
+ ),
+ suggestions,
+ Applicability::MaybeIncorrect,
+ );
+ }
+ }
+ };
+ }
// Suggest specifying type params or point out the return type of the call:
//
// error[E0282]: type annotations needed
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index 3eeb503..a42a05c 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -1498,11 +1498,18 @@
// check upstream for type errors and don't add the obligations to
// begin with in those cases.
if self.tcx.lang_items().sized_trait() == Some(trait_ref.def_id()) {
- self.emit_inference_failure_err(body_id, span, subst, ErrorCode::E0282).emit();
+ self.emit_inference_failure_err(body_id, span, subst, vec![], ErrorCode::E0282)
+ .emit();
return;
}
- let mut err =
- self.emit_inference_failure_err(body_id, span, subst, ErrorCode::E0283);
+ let impl_candidates = self.find_similar_impl_candidates(trait_ref);
+ let mut err = self.emit_inference_failure_err(
+ body_id,
+ span,
+ subst,
+ impl_candidates,
+ ErrorCode::E0283,
+ );
err.note(&format!("cannot satisfy `{}`", predicate));
if let ObligationCauseCode::ItemObligation(def_id) = obligation.cause.code {
self.suggest_fully_qualified_path(&mut err, def_id, span, trait_ref.def_id());
@@ -1566,7 +1573,7 @@
return;
}
- self.emit_inference_failure_err(body_id, span, arg, ErrorCode::E0282)
+ self.emit_inference_failure_err(body_id, span, arg, vec![], ErrorCode::E0282)
}
ty::PredicateKind::Subtype(data) => {
@@ -1577,7 +1584,7 @@
let SubtypePredicate { a_is_expected: _, a, b } = data;
// both must be type variables, or the other would've been instantiated
assert!(a.is_ty_var() && b.is_ty_var());
- self.emit_inference_failure_err(body_id, span, a.into(), ErrorCode::E0282)
+ self.emit_inference_failure_err(body_id, span, a.into(), vec![], ErrorCode::E0282)
}
ty::PredicateKind::Projection(data) => {
let trait_ref = bound_predicate.rebind(data).to_poly_trait_ref(self.tcx);
@@ -1592,6 +1599,7 @@
body_id,
span,
self_ty.into(),
+ vec![],
ErrorCode::E0284,
);
err.note(&format!("cannot satisfy `{}`", predicate));
diff --git a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
index 5a372c0..c491ba3 100644
--- a/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
+++ b/compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
@@ -1479,7 +1479,7 @@
ty
} else {
if !self.is_tainted_by_errors() {
- self.emit_inference_failure_err((**self).body_id, sp, ty.into(), E0282)
+ self.emit_inference_failure_err((**self).body_id, sp, ty.into(), vec![], E0282)
.note("type must be known at this point")
.emit();
}
diff --git a/compiler/rustc_typeck/src/check/writeback.rs b/compiler/rustc_typeck/src/check/writeback.rs
index 6edce62..9e6bf5c 100644
--- a/compiler/rustc_typeck/src/check/writeback.rs
+++ b/compiler/rustc_typeck/src/check/writeback.rs
@@ -694,6 +694,7 @@
Some(self.body.id()),
self.span.to_span(self.tcx),
t.into(),
+ vec![],
E0282,
)
.emit();
@@ -707,6 +708,7 @@
Some(self.body.id()),
self.span.to_span(self.tcx),
c.into(),
+ vec![],
E0282,
)
.emit();
diff --git a/src/test/ui/error-codes/E0283.rs b/src/test/ui/error-codes/E0283.rs
index 9bdcc9a..4d7c2f2 100644
--- a/src/test/ui/error-codes/E0283.rs
+++ b/src/test/ui/error-codes/E0283.rs
@@ -8,6 +8,18 @@
fn create() -> u32 { 1 }
}
+impl Impl {
+ fn new() -> Self {
+ Impl{}
+ }
+}
+
+impl Into<u32> for Impl {
+ fn into(self) -> u32 { 1 }
+}
+
+fn foo(bar: u32) {}
+
struct AnotherImpl;
impl Generator for AnotherImpl {
@@ -17,3 +29,9 @@
fn main() {
let cont: u32 = Generator::create(); //~ ERROR E0283
}
+
+fn buzz() {
+ let foo_impl = Impl::new();
+ let bar = foo_impl.into() * 1u32; //~ ERROR E0283
+ foo(bar);
+}
diff --git a/src/test/ui/error-codes/E0283.stderr b/src/test/ui/error-codes/E0283.stderr
index e95583c..2f0dfb6 100644
--- a/src/test/ui/error-codes/E0283.stderr
+++ b/src/test/ui/error-codes/E0283.stderr
@@ -1,5 +1,5 @@
error[E0283]: type annotations needed
- --> $DIR/E0283.rs:18:21
+ --> $DIR/E0283.rs:30:21
|
LL | fn create() -> u32;
| ------------------- required by `Generator::create`
@@ -9,6 +9,18 @@
|
= note: cannot satisfy `_: Generator`
-error: aborting due to previous error
+error[E0283]: type annotations needed
+ --> $DIR/E0283.rs:35:24
+ |
+LL | let bar = foo_impl.into() * 1u32;
+ | ---------^^^^--
+ | | |
+ | | cannot infer type for type parameter `T` declared on the trait `Into`
+ | this method call resolves to `T`
+ | help: use the fully qualified path for the potential candidate: `<Impl as Into<u32>>::into(foo_impl)`
+ |
+ = note: cannot satisfy `Impl: Into<_>`
+
+error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0283`.
