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lowering: extract lower_expr_async_closure

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This commit is contained in:
Mazdak Farrokhzad 2019-08-10 14:47:23 +02:00
parent 309bf2fcad
commit ca19e326a6
1 changed files with 67 additions and 49 deletions
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116
src/librustc/hir/lowering/expr.rs
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@ -268,55 +268,13 @@ impl LoweringContext<'_> {
capture_clause, asyncness, movability, ref decl, ref body, fn_decl_span
) => {
if let IsAsync::Async { closure_id, .. } = asyncness {
let outer_decl = FnDecl {
inputs: decl.inputs.clone(),
output: FunctionRetTy::Default(fn_decl_span),
c_variadic: false,
};
// We need to lower the declaration outside the new scope, because we
// have to conserve the state of being inside a loop condition for the
// closure argument types.
let fn_decl = self.lower_fn_decl(&outer_decl, None, false, None);
self.with_new_scopes(|this| {
// FIXME(cramertj): allow `async` non-`move` closures with arguments.
if capture_clause == CaptureBy::Ref &&
!decl.inputs.is_empty()
{
struct_span_err!(
this.sess,
fn_decl_span,
E0708,
"`async` non-`move` closures with arguments \
are not currently supported",
)
.help("consider using `let` statements to manually capture \
variables by reference before entering an \
`async move` closure")
.emit();
}
// Transform `async |x: u8| -> X { ... }` into
// `|x: u8| future_from_generator(|| -> X { ... })`.
let body_id = this.lower_fn_body(&outer_decl, |this| {
let async_ret_ty = if let FunctionRetTy::Ty(ty) = &decl.output {
Some(ty.clone())
} else { None };
let async_body = this.make_async_expr(
capture_clause, closure_id, async_ret_ty, body.span,
|this| {
this.with_new_scopes(|this| this.lower_expr(body))
});
this.expr(fn_decl_span, async_body, ThinVec::new())
});
hir::ExprKind::Closure(
this.lower_capture_clause(capture_clause),
fn_decl,
body_id,
fn_decl_span,
None,
)
})
self.lower_expr_async_closure(
capture_clause,
closure_id,
decl,
body,
fn_decl_span,
)
} else {
// Lower outside new scope to preserve `is_in_loop_condition`.
let fn_decl = self.lower_fn_decl(decl, None, false, None);
@ -449,6 +407,66 @@ impl LoweringContext<'_> {
}
}
fn lower_expr_async_closure(
&mut self,
capture_clause: CaptureBy,
closure_id: NodeId,
decl: &FnDecl,
body: &Expr,
fn_decl_span: Span,
) -> hir::ExprKind {
let outer_decl = FnDecl {
inputs: decl.inputs.clone(),
output: FunctionRetTy::Default(fn_decl_span),
c_variadic: false,
};
// We need to lower the declaration outside the new scope, because we
// have to conserve the state of being inside a loop condition for the
// closure argument types.
let fn_decl = self.lower_fn_decl(&outer_decl, None, false, None);
self.with_new_scopes(|this| {
// FIXME(cramertj): allow `async` non-`move` closures with arguments.
if capture_clause == CaptureBy::Ref && !decl.inputs.is_empty() {
struct_span_err!(
this.sess,
fn_decl_span,
E0708,
"`async` non-`move` closures with arguments are not currently supported",
)
.help(
"consider using `let` statements to manually capture \
variables by reference before entering an `async move` closure"
)
.emit();
}
// Transform `async |x: u8| -> X { ... }` into
// `|x: u8| future_from_generator(|| -> X { ... })`.
let body_id = this.lower_fn_body(&outer_decl, |this| {
let async_ret_ty = if let FunctionRetTy::Ty(ty) = &decl.output {
Some(ty.clone())
} else {
None
};
let async_body = this.make_async_expr(
capture_clause, closure_id, async_ret_ty, body.span,
|this| {
this.with_new_scopes(|this| this.lower_expr(body))
}
);
this.expr(fn_decl_span, async_body, ThinVec::new())
});
hir::ExprKind::Closure(
this.lower_capture_clause(capture_clause),
fn_decl,
body_id,
fn_decl_span,
None,
)
})
}
/// Desugar `<start>..=<end>` into `std::ops::RangeInclusive::new(<start>, <end>)`.
fn lower_expr_range_closed(&mut self, span: Span, e1: &Expr, e2: &Expr) -> hir::ExprKind {
let id = self.next_id();