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‎compiler/rustc_ast_lowering/messages.ftl

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@@ -10,6 +10,7 @@ ast_lowering_argument = argument
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ast_lowering_assoc_ty_binding_in_dyn =
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associated type bounds are not allowed in `dyn` types
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.suggestion = use `impl Trait` to introduce a type instead
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ast_lowering_assoc_ty_parentheses =
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parenthesized generic arguments cannot be used in associated type constraints

‎compiler/rustc_ast_lowering/src/errors.rs

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@@ -98,6 +98,8 @@ pub struct MisplacedImplTrait<'a> {
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pub struct MisplacedAssocTyBinding {
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#[primary_span]
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pub span: Span,
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#[suggestion(code = " = impl", applicability = "maybe-incorrect", style = "verbose")]
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pub suggestion: Option<Span>,
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}
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#[derive(Diagnostic, Clone, Copy)]

‎compiler/rustc_ast_lowering/src/lib.rs

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@@ -1088,32 +1088,50 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
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AssocConstraintKind::Bound { bounds } => {
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enum DesugarKind {
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ImplTrait,
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Error,
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Error(Option<Span>),
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Bound,
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}
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// Piggy-back on the `impl Trait` context to figure out the correct behavior.
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let desugar_kind = match itctx {
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_ if self.is_in_dyn_type => DesugarKind::Error,
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// We are in the return position:
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//
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// fn foo() -> impl Iterator<Item: Debug>
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//
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// so desugar to
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//
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// fn foo() -> impl Iterator<Item = impl Debug>
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ImplTraitContext::ReturnPositionOpaqueTy { .. }
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| ImplTraitContext::TypeAliasesOpaqueTy { .. } => DesugarKind::ImplTrait,
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// We are in the parameter position, but not within a dyn type:
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//
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// fn foo(x: impl Iterator<Item: Debug>)
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//
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// so we leave it as is and this gets expanded in astconv to a bound like
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// `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
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// `impl Iterator`.
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_ => DesugarKind::Bound,
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let desugar_kind = if self.is_in_dyn_type {
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match itctx {
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ImplTraitContext::ReturnPositionOpaqueTy { .. }
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| ImplTraitContext::TypeAliasesOpaqueTy { .. }
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| ImplTraitContext::Universal => {
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let bound_end_span = constraint
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.gen_args
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.as_ref()
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.map_or(constraint.ident.span, |args| args.span());
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let colon_span = if bound_end_span.eq_ctxt(constraint.span) {
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Some(self.tcx.sess.source_map().next_point(bound_end_span))
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} else {
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None
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};
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DesugarKind::Error(colon_span)
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}
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_ => DesugarKind::Error(None),
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}
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} else {
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match itctx {
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// We are in the return position:
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//
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// fn foo() -> impl Iterator<Item: Debug>
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//
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// so desugar to
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//
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// fn foo() -> impl Iterator<Item = impl Debug>
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ImplTraitContext::ReturnPositionOpaqueTy { .. }
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| ImplTraitContext::TypeAliasesOpaqueTy { .. } => DesugarKind::ImplTrait,
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// We are in the parameter position, but not within a dyn type:
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//
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// fn foo(x: impl Iterator<Item: Debug>)
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//
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// so we leave it as is and this gets expanded in astconv to a bound like
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// `<T as Iterator>::Item: Debug` where `T` is the type parameter for the
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// `impl Iterator`.
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_ => DesugarKind::Bound,
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}
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};
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match desugar_kind {
@@ -1150,10 +1168,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
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hir::TypeBindingKind::Constraint { bounds }
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}
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DesugarKind::Error => {
1154-
let guar = self
1155-
.dcx()
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.emit_err(errors::MisplacedAssocTyBinding { span: constraint.span });
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DesugarKind::Error(suggestion) => {
1172+
let guar = self.dcx().emit_err(errors::MisplacedAssocTyBinding {
1173+
span: constraint.span,
1174+
suggestion,
1175+
});
11571176
let err_ty =
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&*self.arena.alloc(self.ty(constraint.span, hir::TyKind::Err(guar)));
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hir::TypeBindingKind::Equality { term: err_ty.into() }

‎tests/ui/associated-type-bounds/assoc-type-eq-with-dyn-atb-fail.stderr

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@@ -3,6 +3,11 @@ error: associated type bounds are not allowed in `dyn` types
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|
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LL | type Out = Box<dyn Bar<Assoc: Copy>>;
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| ^^^^^^^^^^^
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|
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help: use `impl Trait` to introduce a type instead
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|
9+
LL | type Out = Box<dyn Bar<Assoc = impl Copy>>;
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| ~~~~~~
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712
error: aborting due to 1 previous error
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‎tests/ui/associated-type-bounds/dyn-impl-trait-type.stderr

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This file was deleted.

‎tests/ui/associated-type-bounds/dyn-rpit-and-let.stderr

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This file was deleted.

‎tests/ui/associated-type-bounds/elision.stderr

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Original file line numberDiff line numberDiff line change
@@ -15,6 +15,11 @@ error: associated type bounds are not allowed in `dyn` types
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|
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LL | fn f(x: &mut dyn Iterator<Item: Iterator<Item = &'_ ()>>) -> Option<&'_ ()> { x.next() }
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
18+
|
19+
help: use `impl Trait` to introduce a type instead
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|
21+
LL | fn f(x: &mut dyn Iterator<Item = impl Iterator<Item = &'_ ()>>) -> Option<&'_ ()> { x.next() }
22+
| ~~~~~~
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error: aborting due to 2 previous errors
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