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Don't create AST fragments when lowering to HIR

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This commit is contained in:
Jonas Schievink 2020-03-04 14:53:47 +01:00
parent e419168bb8
commit 78274bc17c
2 changed files with 34 additions and 30 deletions
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62
src/librustc_ast_lowering/expr.rs
View file

@ -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,

2
src/librustc_ast_lowering/item.rs
View file

@ -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 {