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Do not discard ?Sized type params and suggest their removal

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This commit is contained in:
Esteban Küber
2021-07-23 18:47:53 -07:00
parent 5fb3394cbd
commit 15a40c7ee8
32 changed files with 615 additions and 19 deletions
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23
compiler/rustc_ast_lowering/src/item.rs
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@@ -1443,16 +1443,19 @@ impl<'hir> LoweringContext<'_, 'hir> {
ImplTraitContext::disallowed(),
),
bounded_ty: this.lower_ty(bounded_ty, ImplTraitContext::disallowed()),
bounds: this.arena.alloc_from_iter(bounds.iter().filter_map(|bound| {
match *bound {
// Ignore `?Trait` bounds.
// They were copied into type parameters already.
GenericBound::Trait(_, TraitBoundModifier::Maybe) => None,
_ => Some(
this.lower_param_bound(bound, ImplTraitContext::disallowed()),
),
}
})),
bounds: this.arena.alloc_from_iter(bounds.iter().map(
|bound| match bound {
// We used to ignore `?Trait` bounds, as they were copied into type
// parameters already, but we need to keep them around only for
// diagnostics when we suggest removal of `?Sized` bounds. See
// `suggest_constraining_type_param`. This will need to change if
// we ever allow something *other* than `?Sized`.
GenericBound::Trait(p, TraitBoundModifier::Maybe) => {
hir::GenericBound::Unsized(p.span)
}
_ => this.lower_param_bound(bound, ImplTraitContext::disallowed()),
},
)),
span,
})
})