rust-lang/rust
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

No more associated type bounds in dyn trait

Browse Source
This commit is contained in:
Michael Goulet
2024-02-06 19:35:57 +00:00
parent b5c46dc542
commit 973bbfbd23
22 changed files with 55 additions and 373 deletions
Download Patch File Download Diff File Expand all files Collapse all files

59
compiler/rustc_ast_lowering/src/lib.rs
View File

@@ -1085,33 +1085,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
AssocConstraintKind::Bound { bounds } => {
enum DesugarKind {
ImplTrait,
Error(ImplTraitPosition),
Error,
Bound,
}
// Piggy-back on the `impl Trait` context to figure out the correct behavior.
let desugar_kind = match itctx {
// in an argument, RPIT, or TAIT, if we are within a dyn type:
//
// fn foo(x: dyn Iterator<Item: Debug>)
//
// then desugar to:
//
// fn foo(x: dyn Iterator<Item = impl Debug>)
//
// This is because dyn traits must have all of their associated types specified.
ImplTraitContext::ReturnPositionOpaqueTy { .. }
| ImplTraitContext::TypeAliasesOpaqueTy { .. }
| ImplTraitContext::Universal
if self.is_in_dyn_type =>
{
DesugarKind::ImplTrait
}
ImplTraitContext::Disallowed(position) if self.is_in_dyn_type => {
DesugarKind::Error(position)
}
_ if self.is_in_dyn_type => DesugarKind::Error,
// We are in the parameter position, but not within a dyn type:
//
@@ -1124,32 +1104,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
};
match desugar_kind {
DesugarKind::ImplTrait => {
// Desugar `AssocTy: Bounds` into `AssocTy = impl Bounds`. We do this by
// constructing the HIR for `impl bounds...` and then lowering that.
let impl_trait_node_id = self.next_node_id();
// Shift `impl Trait` lifetime captures from the associated type bound's
// node id to the opaque node id, so that the opaque can actually use
// these lifetime bounds.
self.resolver
.remap_extra_lifetime_params(constraint.id, impl_trait_node_id);
self.with_dyn_type_scope(false, |this| {
let node_id = this.next_node_id();
let ty = this.lower_ty(
&Ty {
id: node_id,
kind: TyKind::ImplTrait(impl_trait_node_id, bounds.clone()),
span: this.lower_span(constraint.span),
tokens: None,
},
itctx,
);
hir::TypeBindingKind::Equality { term: ty.into() }
})
}
DesugarKind::Bound => {
// Desugar `AssocTy: Bounds` into a type binding where the
// later desugars into a trait predicate.
@@ -1157,11 +1111,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
hir::TypeBindingKind::Constraint { bounds }
}
DesugarKind::Error(position) => {
let guar = self.dcx().emit_err(errors::MisplacedAssocTyBinding {
span: constraint.span,
position: DiagnosticArgFromDisplay(&position),
});
DesugarKind::Error => {
let guar = self
.dcx()
.emit_err(errors::MisplacedAssocTyBinding { span: constraint.span });
let err_ty =
&*self.arena.alloc(self.ty(constraint.span, hir::TyKind::Err(guar)));
hir::TypeBindingKind::Equality { term: err_ty.into() }