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Avoid GenFuture shim when compiling async constructs

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Previously, async constructs would be lowered to "normal" generators,
with an additional `from_generator` / `GenFuture` shim in between to
convert from `Generator` to `Future`.

The compiler will now special-case these generators internally so that
async constructs will *directly* implement `Future` without the need
to go through the `from_generator` / `GenFuture` shim.

The primary motivation for this change was hiding this implementation
detail in stack traces and debuginfo, but it can in theory also help
the optimizer as there is less abstractions to see through.
This commit is contained in:
Arpad Borsos 2022-11-18 22:56:22 +01:00
parent 91d2ce3020
commit 1ebdcca8b9
3 changed files with 3 additions and 5 deletions
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4
clippy_lints/src/doc.rs
View File

@ -427,9 +427,7 @@ fn lint_for_missing_headers(
let body = cx.tcx.hir().body(body_id);
let ret_ty = typeck.expr_ty(body.value);
if implements_trait(cx, ret_ty, future, &[]);
if let ty::Opaque(_, subs) = ret_ty.kind();
if let Some(gen) = subs.types().next();
if let ty::Generator(_, subs, _) = gen.kind();
if let ty::Generator(_, subs, _) = ret_ty.kind();
if is_type_diagnostic_item(cx, subs.as_generator().return_ty(), sym::Result);
then {
span_lint(

2
clippy_lints/src/manual_async_fn.rs
View File

@ -177,7 +177,7 @@ fn desugared_async_block<'tcx>(cx: &LateContext<'tcx>, block: &'tcx Block<'tcx>)
if let Some(args) = cx
.tcx
.lang_items()
.from_generator_fn()
.identity_future_fn()
.and_then(|def_id| match_function_call_with_def_id(cx, block_expr, def_id));
if args.len() == 1;
if let Expr {

2
tests/ui/author/blocks.stdout
View File

@ -45,7 +45,7 @@ if let ExprKind::Closure(CaptureBy::Value, fn_decl, body_id, _, None) = expr.kin
&& expr1 = &cx.tcx.hir().body(body_id).value
&& let ExprKind::Call(func, args) = expr1.kind
&& let ExprKind::Path(ref qpath) = func.kind
&& matches!(qpath, QPath::LangItem(LangItem::FromGenerator, _))
&& matches!(qpath, QPath::LangItem(LangItem::IdentityFuture, _))
&& args.len() == 1
&& let ExprKind::Closure(CaptureBy::Value, fn_decl1, body_id1, _, Some(Movability::Static)) = args[0].kind
&& let FnRetTy::DefaultReturn(_) = fn_decl1.output