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Auto merge of #60586 - cramertj:await, r=oli-obk

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Implement built-in await syntax

Adds support for .await under the existing async_await feature gate.
Moves macro-like await! syntax to the await_macro feature gate.
Removes support for `await` as a non-keyword under the `async_await`
feature.

This new syntax is not final, but is the consensus solution proposed by the lang team, as explained in https://boats.gitlab.io/blog/post/await-decision/

Fix https://github.com/rust-lang/rust/issues/51719
Fix https://github.com/rust-lang/rust/issues/51751
Fix https://github.com/rust-lang/rust/issues/60016
This commit is contained in:
bors 2019-05-07 22:33:12 +00:00
commit 33cde4aac2
37 changed files with 932 additions and 166 deletions
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17
src/libsyntax/parse/parser.rs
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@ -2752,6 +2752,14 @@ impl<'a> Parser<'a> {
db.span_label(self.span, "expected expression");
db.note("variable declaration using `let` is a statement");
return Err(db);
} else if self.span.rust_2018() && self.eat_keyword(keywords::Await) {
// FIXME: remove this branch when `await!` is no longer supported
// https://github.com/rust-lang/rust/issues/60610
self.expect(&token::Not)?;
self.expect(&token::OpenDelim(token::Paren))?;
let expr = self.parse_expr()?;
self.expect(&token::CloseDelim(token::Paren))?;
ex = ExprKind::Await(ast::AwaitOrigin::MacroLike, expr);
} else if self.token.is_path_start() {
let path = self.parse_path(PathStyle::Expr)?;
@ -3015,6 +3023,15 @@ impl<'a> Parser<'a> {
// Assuming we have just parsed `.`, continue parsing into an expression.
fn parse_dot_suffix(&mut self, self_arg: P<Expr>, lo: Span) -> PResult<'a, P<Expr>> {
if self.span.rust_2018() && self.eat_keyword(keywords::Await) {
let span = lo.to(self.prev_span);
let await_expr = self.mk_expr(
span,
ExprKind::Await(ast::AwaitOrigin::FieldLike, self_arg),
ThinVec::new(),
);
return Ok(await_expr);
}
let segment = self.parse_path_segment(PathStyle::Expr)?;
self.check_trailing_angle_brackets(&segment, token::OpenDelim(token::Paren));