From 1ebdcca8b97feca67ce077a2bad87e7655bc774a Mon Sep 17 00:00:00 2001 From: Arpad Borsos Date: Fri, 18 Nov 2022 22:56:22 +0100 Subject: [PATCH] Avoid `GenFuture` shim when compiling async constructs 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. --- clippy_lints/src/doc.rs | 4 +--- clippy_lints/src/manual_async_fn.rs | 2 +- tests/ui/author/blocks.stdout | 2 +- 3 files changed, 3 insertions(+), 5 deletions(-) diff --git a/clippy_lints/src/doc.rs b/clippy_lints/src/doc.rs index 4557e432885..ae5f9424b23 100644 --- a/clippy_lints/src/doc.rs +++ b/clippy_lints/src/doc.rs @@ -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( diff --git a/clippy_lints/src/manual_async_fn.rs b/clippy_lints/src/manual_async_fn.rs index 5c6a342b3d0..6a98df49912 100644 --- a/clippy_lints/src/manual_async_fn.rs +++ b/clippy_lints/src/manual_async_fn.rs @@ -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 { diff --git a/tests/ui/author/blocks.stdout b/tests/ui/author/blocks.stdout index 9de0550d81d..c6acf24c21e 100644 --- a/tests/ui/author/blocks.stdout +++ b/tests/ui/author/blocks.stdout @@ -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