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Handle desugaring in impl trait bound suggestion

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This commit is contained in:
William Bain 2020-12-19 16:52:19 -05:00
parent 1b6b06a03a
commit b76c9be7f5
5 changed files with 95 additions and 13 deletions
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18
compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
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@ -254,27 +254,21 @@ fn suggest_restriction(
let pred = trait_ref.without_const().to_predicate(tcx).to_string();
let pred = pred.replace(&impl_trait_str, &type_param_name);
let mut sugg = vec![
// Find the last of the generic parameters contained within the span of
// the generics
match generics
.params
.iter()
.filter(|p| match p.kind {
hir::GenericParamKind::Type {
synthetic: Some(hir::SyntheticTyParamKind::ImplTrait),
..
} => false,
_ => true,
})
.last()
.map(|p| p.bounds_span().unwrap_or(p.span))
.filter(|&span| generics.span.contains(span) && span.desugaring_kind().is_none())
.max_by_key(|span| span.hi())
{
// `fn foo(t: impl Trait)`
// ^ suggest `<T: Trait>` here
None => (generics.span, format!("<{}>", type_param)),
// `fn foo<A>(t: impl Trait)`
// ^^^ suggest `<A, T: Trait>` here
Some(param) => (
param.bounds_span().unwrap_or(param.span).shrink_to_hi(),
format!(", {}", type_param),
),
Some(span) => (span.shrink_to_hi(), format!(", {}", type_param)),
},
// `fn foo(t: impl Trait)`
// ^ suggest `where <T as Trait>::A: Bound`