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check for non-defining uses of RPIT

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This commit is contained in:
lcnr 2023-07-21 12:27:41 +02:00
parent 3071e0aef6
commit 95fddbc501
8 changed files with 112 additions and 37 deletions
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44
compiler/rustc_borrowck/src/region_infer/opaque_types.rs
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@ -371,39 +371,29 @@ fn check_opaque_type_parameter_valid(
span: Span,
) -> Result<(), ErrorGuaranteed> {
let opaque_ty_hir = tcx.hir().expect_item(opaque_type_key.def_id);
match opaque_ty_hir.expect_opaque_ty().origin {
// No need to check return position impl trait (RPIT)
// because for type and const parameters they are correct
// by construction: we convert
//
// fn foo<P0..Pn>() -> impl Trait
//
// into
//
// type Foo<P0...Pn>
// fn foo<P0..Pn>() -> Foo<P0...Pn>.
//
// For lifetime parameters we convert
//
// fn foo<'l0..'ln>() -> impl Trait<'l0..'lm>
//
// into
//
// type foo::<'p0..'pn>::Foo<'q0..'qm>
// fn foo<l0..'ln>() -> foo::<'static..'static>::Foo<'l0..'lm>.
//
// which would error here on all of the `'static` args.
OpaqueTyOrigin::FnReturn(..) | OpaqueTyOrigin::AsyncFn(..) => return Ok(()),
// Check these
OpaqueTyOrigin::TyAlias { .. } => {}
}
let is_ty_alias = match opaque_ty_hir.expect_opaque_ty().origin {
OpaqueTyOrigin::TyAlias { .. } => true,
OpaqueTyOrigin::AsyncFn(..) | OpaqueTyOrigin::FnReturn(..) => false,
};
let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
let mut seen_params: FxIndexMap<_, Vec<_>> = FxIndexMap::default();
for (i, arg) in opaque_type_key.args.iter().enumerate() {
if let Err(guar) = arg.error_reported() {
return Err(guar);
}
let arg_is_param = match arg.unpack() {
GenericArgKind::Type(ty) => matches!(ty.kind(), ty::Param(_)),
GenericArgKind::Lifetime(lt) => {
matches!(*lt, ty::ReEarlyBound(_) | ty::ReFree(_))
if is_ty_alias {
matches!(*lt, ty::ReEarlyBound(_) | ty::ReFree(_))
} else {
// FIXME(#113916): we can't currently check for unique lifetime params,
// see that issue for more. We will also have to ignore bivariant lifetime
// params for RPIT, but that's comparatively trivial ✨
continue;
}
}
GenericArgKind::Const(ct) => matches!(ct.kind(), ty::ConstKind::Param(_)),
};