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Add suggestion for impl_candidates with E0283

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Update compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

Co-authored-by: Esteban Kuber <estebank@users.noreply.github.com>
This commit is contained in:
Daiki Ihara 2021-01-15 22:33:38 +09:00
parent 86e0ff47a0
commit db95b5ca9b
4 changed files with 55 additions and 7 deletions
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40
compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
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@ -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