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Auto merge of #81042 - sasurau4:fix/unclear-error-with-trait, r=estebank

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Add suggestion for impl_candidates with E0283

Fix #42226
This commit is contained in:
bors 2021-01-19 00:00:21 +00:00
commit 4ba1aaf35f
6 changed files with 87 additions and 9 deletions
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40
compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
View File

@ -429,6 +429,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
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 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
};
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

18
compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
View File

@ -1498,11 +1498,18 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
// 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 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
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 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
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 @@ impl<'a, 'tcx> InferCtxtPrivExt<'tcx> for InferCtxt<'a, 'tcx> {
body_id,
span,
self_ty.into(),
vec![],
ErrorCode::E0284,
);
err.note(&format!("cannot satisfy `{}`", predicate));

2
compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs
View File

@ -1479,7 +1479,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
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();
}

2
compiler/rustc_typeck/src/check/writeback.rs
View File

@ -694,6 +694,7 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
Some(self.body.id()),
self.span.to_span(self.tcx),
t.into(),
vec![],
E0282,
)
.emit();
@ -707,6 +708,7 @@ impl<'cx, 'tcx> Resolver<'cx, 'tcx> {
Some(self.body.id()),
self.span.to_span(self.tcx),
c.into(),
vec![],
E0282,
)
.emit();

18
src/test/ui/error-codes/E0283.rs
View File

@ -8,6 +8,18 @@ impl Generator for Impl {
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 @@ impl Generator for AnotherImpl {
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);
}

16
src/test/ui/error-codes/E0283.stderr
View File

@ -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 @@ LL | let cont: u32 = Generator::create();
|
= 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`.