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| author | Jonas Schievink <jonasschievink@gmail.com> | 2020-03-04 14:53:47 +0100 |
|---|---|---|
| committer | Jonas Schievink <jonasschievink@gmail.com> | 2020-03-17 22:17:31 +0100 |
| commit | 78274bc17c671655aaadba2096490fad59de2133 (patch) | |
| tree | f95b995d62ecb4890f39e93040d5b46d1432d303 | |
| parent | e419168bb8256444ab98f220c03545b8824037d4 (diff) | |
| download | rust-78274bc17c671655aaadba2096490fad59de2133.tar.gz rust-78274bc17c671655aaadba2096490fad59de2133.zip | |
Don't create AST fragments when lowering to HIR
| -rw-r--r-- | src/librustc_ast_lowering/expr.rs | 62 | ||||
| -rw-r--r-- | src/librustc_ast_lowering/item.rs | 2 |
2 files changed, 34 insertions, 30 deletions
diff --git a/src/librustc_ast_lowering/expr.rs b/src/librustc_ast_lowering/expr.rs index f84efe2ba76..a212f0a7107 100644 --- a/src/librustc_ast_lowering/expr.rs +++ b/src/librustc_ast_lowering/expr.rs @@ -10,7 +10,6 @@ use rustc_hir as hir; use rustc_hir::def::Res; use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned}; use rustc_span::symbol::{sym, Symbol}; -use rustc_span::DUMMY_SP; impl<'hir> LoweringContext<'_, 'hir> { fn lower_exprs(&mut self, exprs: &[AstP<Expr>]) -> &'hir [hir::Expr<'hir>] { @@ -471,6 +470,15 @@ impl<'hir> LoweringContext<'_, 'hir> { } } + /// Lower an `async` construct to a generator that is then wrapped so it implements `Future`. + /// + /// This results in: + /// + /// ```text + /// std::future::from_generator(static move? |_task_context| -> <ret_ty> { + /// <body> + /// }) + /// ``` pub(super) fn make_async_expr( &mut self, capture_clause: CaptureBy, @@ -481,46 +489,42 @@ impl<'hir> LoweringContext<'_, 'hir> { body: impl FnOnce(&mut Self) -> hir::Expr<'hir>, ) -> hir::ExprKind<'hir> { let output = match ret_ty { - Some(ty) => FnRetTy::Ty(ty), - None => FnRetTy::Default(span), + Some(ty) => hir::FnRetTy::Return(self.lower_ty(&ty, ImplTraitContext::disallowed())), + None => hir::FnRetTy::DefaultReturn(span), }; - let task_context_id = self.resolver.next_node_id(); - let task_context_hid = self.lower_node_id(task_context_id); + // Resume argument type. We let the compiler infer this to simplify the lowering. It is + // fully constrained by `future::from_generator`. + let input_ty = hir::Ty { hir_id: self.next_id(), kind: hir::TyKind::Infer, span }; - let arg_ty = Ty { id: self.resolver.next_node_id(), kind: TyKind::Infer, span: DUMMY_SP }; - let arg_pat = Pat { - id: task_context_id, - kind: PatKind::Ident( - BindingMode::ByValue(Mutability::Mut), - Ident::with_dummy_span(sym::_task_context), - None, - ), - span: DUMMY_SP, - }; - let ast_decl = FnDecl { - inputs: vec![Param { - attrs: AttrVec::new(), - ty: AstP(arg_ty), - pat: AstP(arg_pat), - id: self.resolver.next_node_id(), - span: DUMMY_SP, - is_placeholder: false, - }], + // The closure/generator `FnDecl` takes a single (resume) argument of type `input_ty`. + let decl = self.arena.alloc(hir::FnDecl { + inputs: arena_vec![self; input_ty], output, - }; - let decl = self.lower_fn_decl(&ast_decl, None, /* impl trait allowed */ false, None); - let body_id = self.lower_fn_body(&ast_decl, |this| { + c_variadic: false, + implicit_self: hir::ImplicitSelfKind::None, + }); + + // Lower the argument pattern/ident. The ident is used again in the `.await` lowering. + let (pat, task_context_hid) = self.pat_ident_binding_mode( + span, + Ident::with_dummy_span(sym::_task_context), + hir::BindingAnnotation::Mutable, + ); + let param = hir::Param { attrs: &[], hir_id: self.next_id(), pat, span }; + let params = arena_vec![self; param]; + + let body_id = self.lower_body(move |this| { this.generator_kind = Some(hir::GeneratorKind::Async(async_gen_kind)); let old_ctx = this.task_context; this.task_context = Some(task_context_hid); let res = body(this); this.task_context = old_ctx; - res + (params, res) }); - // `static |task_context| -> <ret_ty> { body }`: + // `static |_task_context| -> <ret_ty> { body }`: let generator_kind = hir::ExprKind::Closure( capture_clause, decl, diff --git a/src/librustc_ast_lowering/item.rs b/src/librustc_ast_lowering/item.rs index b1fd3da99ce..5f056ef6a4d 100644 --- a/src/librustc_ast_lowering/item.rs +++ b/src/librustc_ast_lowering/item.rs @@ -955,7 +955,7 @@ impl<'hir> LoweringContext<'_, 'hir> { id } - fn lower_body( + pub(super) fn lower_body( &mut self, f: impl FnOnce(&mut Self) -> (&'hir [hir::Param<'hir>], hir::Expr<'hir>), ) -> hir::BodyId { |