bjoernager/rust
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Account for incorrect where T::Assoc = Ty bound

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Provide suggestoin to constrain trait bound for associated type.
Revert incorrect changes to `missing-bounds` test.

Address part of #20041.
This commit is contained in:
Esteban Kuber 2021-11-25 01:38:05 +00:00
parent 311fa1f14d
commit 4954389a9d
7 changed files with 142 additions and 6 deletions
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49
compiler/rustc_ast_passes/src/ast_validation.rs
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@ -23,7 +23,7 @@ use rustc_span::symbol::{kw, sym, Ident};
use rustc_span::Span;
use rustc_target::spec::abi;
use std::mem;
use std::ops::DerefMut;
use std::ops::{Deref, DerefMut};
const MORE_EXTERN: &str =
"for more information, visit https://doc.rust-lang.org/std/keyword.extern.html";
@ -1714,6 +1714,53 @@ fn deny_equality_constraints(
}
}
}
// Given `A: Foo, A::Bar = RhsTy`, suggest `A: Foo<Bar = RhsTy>`.
if let TyKind::Path(None, full_path) = &predicate.lhs_ty.kind {
if let [potential_param, potential_assoc] = &full_path.segments[..] {
for param in &generics.params {
if param.ident == potential_param.ident {
for bound in &param.bounds {
if let ast::GenericBound::Trait(trait_ref, TraitBoundModifier::None) = bound
{
if let [trait_segment] = &trait_ref.trait_ref.path.segments[..] {
let assoc = pprust::path_to_string(&ast::Path::from_ident(
potential_assoc.ident,
));
let ty = pprust::ty_to_string(&predicate.rhs_ty);
let (args, span) = match &trait_segment.args {
Some(args) => match args.deref() {
ast::GenericArgs::AngleBracketed(args) => {
let Some(arg) = args.args.last() else {
continue;
};
(
format!(", {} = {}", assoc, ty),
arg.span().shrink_to_hi(),
)
}
_ => continue,
},
None => (
format!("<{} = {}>", assoc, ty),
trait_segment.span().shrink_to_hi(),
),
};
err.multipart_suggestion(
&format!(
"if `{}::{}` is an associated type you're trying to set, \
use the associated type binding syntax",
trait_segment.ident, potential_assoc.ident,
),
vec![(span, args), (predicate.span, String::new())],
Applicability::MaybeIncorrect,
);
}
}
}
}
}
}
}
err.note(
"see issue #20041 <https://github.com/rust-lang/rust/issues/20041> for more information",
);