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Make async fn in traits work

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This commit is contained in:
Michael Goulet
2022-09-02 15:57:31 +00:00
parent ed2a32f22c
commit 5be30f9d79
10 changed files with 46 additions and 41 deletions
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21
compiler/rustc_ast_lowering/src/lib.rs
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@@ -42,7 +42,7 @@
#[macro_use]
extern crate tracing;
use crate::errors::{AssocTyParentheses, AssocTyParenthesesSub, MisplacedImplTrait};
use crate::errors::{AssocTyParentheses, AssocTyParenthesesSub, MisplacedImplTrait, TraitFnAsync};
use rustc_arena::declare_arena;
use rustc_ast::ptr::P;
@@ -1274,7 +1274,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
generic_params,
unsafety: lctx.lower_unsafety(f.unsafety),
abi: lctx.lower_extern(f.ext),
decl: lctx.lower_fn_decl(&f.decl, None, FnDeclKind::Pointer, None),
decl: lctx.lower_fn_decl(&f.decl, None, t.span, FnDeclKind::Pointer, None),
param_names: lctx.lower_fn_params_to_names(&f.decl),
}))
})
@@ -1677,19 +1677,17 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
// `fn_def_id`: if `Some`, impl Trait arguments are lowered into generic parameters on the
// given DefId, otherwise impl Trait is disallowed. Must be `Some` if
// `make_ret_async` is also `Some`.
// `impl_trait_return_allow`: determines whether `impl Trait` can be used in return position.
// This guards against trait declarations and implementations where `impl Trait` is
// disallowed.
// `make_ret_async`: if `Some`, converts `-> T` into `-> impl Future<Output = T>` in the
// return type. This is used for `async fn` declarations. The `NodeId` is the ID of the
// return type `impl Trait` item.
// return type `impl Trait` item, and the `Span` points to the `async` keyword.
#[instrument(level = "debug", skip(self))]
fn lower_fn_decl(
&mut self,
decl: &FnDecl,
fn_node_id: Option<NodeId>,
fn_span: Span,
kind: FnDeclKind,
make_ret_async: Option<NodeId>,
make_ret_async: Option<(NodeId, Span)>,
) -> &'hir hir::FnDecl<'hir> {
let c_variadic = decl.c_variadic();
@@ -1720,7 +1718,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
}
}));
let output = if let Some(ret_id) = make_ret_async {
let output = if let Some((ret_id, span)) = make_ret_async {
if !self.tcx.features().return_position_impl_trait_in_trait {
self.tcx.sess.emit_feature_err(
TraitFnAsync { fn_span, span },
sym::return_position_impl_trait_in_trait,
);
}
self.lower_async_fn_ret_ty(
&decl.output,
fn_node_id.expect("`make_ret_async` but no `fn_def_id`"),