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Auto merge of #81149 - Aaron1011:feature/better-no-method-found-err, r=estebank

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Avoid describing a method as 'not found' when bounds are unsatisfied

Fixes #76267

When there is a single applicable method candidate, but its trait bounds
are not satisfied, we avoid saying that the method is "not found".
Insted, we update the error message to directly mention which bounds are
not satisfied, rather than mentioning them in a note.
This commit is contained in:
bors 2021-01-28 12:09:50 +00:00
commit 643a79af3d
47 changed files with 144 additions and 128 deletions
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53
compiler/rustc_typeck/src/check/method/suggest.rs
View file

@ -446,6 +446,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
}
let mut label_span_not_found = || {
if unsatisfied_predicates.is_empty() {
err.span_label(span, format!("{item_kind} not found in `{ty_str}`"));
} else {
err.span_label(span, format!("{item_kind} cannot be called on `{ty_str}` due to unsatisfied trait bounds"));
}
self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span);
};
// If the method name is the name of a field with a function or closure type,
// give a helping note that it has to be called as `(x.f)(...)`.
if let SelfSource::MethodCall(expr) = source {
@ -501,12 +510,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
let field_kind = if is_accessible { "field" } else { "private field" };
err.span_label(item_name.span, format!("{}, not a method", field_kind));
} else if lev_candidate.is_none() && static_sources.is_empty() {
err.span_label(span, format!("{} not found in `{}`", item_kind, ty_str));
self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span);
label_span_not_found();
}
} else {
err.span_label(span, format!("{} not found in `{}`", item_kind, ty_str));
self.tcx.sess.trait_methods_not_found.borrow_mut().insert(orig_span);
label_span_not_found();
}
if self.is_fn_ty(&rcvr_ty, span) {
@ -721,10 +728,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
.map(|(_, path)| path)
.collect::<Vec<_>>()
.join("\n");
let actual_prefix = actual.prefix_string();
err.set_primary_message(&format!(
"the {item_kind} `{item_name}` exists for {actual_prefix} `{ty_str}`, but its trait bounds were not satisfied"
));
err.note(&format!(
"the method `{}` exists but the following trait bounds were not \
satisfied:\n{}",
item_name, bound_list
"the following trait bounds were not satisfied:\n{bound_list}"
));
}
}
@ -742,7 +751,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
);
}
if actual.is_enum() {
// Don't emit a suggestion if we found an actual method
// that had unsatisfied trait bounds
if unsatisfied_predicates.is_empty() && actual.is_enum() {
let adt_def = actual.ty_adt_def().expect("enum is not an ADT");
if let Some(suggestion) = lev_distance::find_best_match_for_name(
&adt_def.variants.iter().map(|s| s.ident.name).collect::<Vec<_>>(),
@ -778,17 +789,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
err.span_label(span, msg);
}
} else if let Some(lev_candidate) = lev_candidate {
let def_kind = lev_candidate.kind.as_def_kind();
err.span_suggestion(
span,
&format!(
"there is {} {} with a similar name",
def_kind.article(),
def_kind.descr(lev_candidate.def_id),
),
lev_candidate.ident.to_string(),
Applicability::MaybeIncorrect,
);
// Don't emit a suggestion if we found an actual method
// that had unsatisfied trait bounds
if unsatisfied_predicates.is_empty() {
let def_kind = lev_candidate.kind.as_def_kind();
err.span_suggestion(
span,
&format!(
"there is {} {} with a similar name",
def_kind.article(),
def_kind.descr(lev_candidate.def_id),
),
lev_candidate.ident.to_string(),
Applicability::MaybeIncorrect,
);
}
}
return Some(err);

1
compiler/rustc_typeck/src/lib.rs
View file

@ -60,6 +60,7 @@ This API is completely unstable and subject to change.
#![feature(bool_to_option)]
#![feature(box_syntax)]
#![feature(crate_visibility_modifier)]
#![feature(format_args_capture)]
#![feature(in_band_lifetimes)]
#![feature(is_sorted)]
#![feature(nll)]