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Allow declaring existential types inside blocks

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This commit is contained in:
Oliver Schneider 2018-07-23 14:56:36 +02:00
parent 3900bf8ae3
commit 2e33a557de
2 changed files with 28 additions and 0 deletions
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6
src/libsyntax/parse/parser.rs
View file

@ -4391,6 +4391,11 @@ impl<'a> Parser<'a> {
self.token.is_keyword(keywords::Extern) && self.look_ahead(1, |t| t != &token::ModSep)
}
fn is_existential_type_decl(&self) -> bool {
self.token.is_keyword(keywords::Existential) &&
self.look_ahead(1, |t| t.is_keyword(keywords::Type))
}
fn is_auto_trait_item(&mut self) -> bool {
// auto trait
(self.token.is_keyword(keywords::Auto)
@ -4495,6 +4500,7 @@ impl<'a> Parser<'a> {
!self.is_union_item() &&
!self.is_crate_vis() &&
!self.is_extern_non_path() &&
!self.is_existential_type_decl() &&
!self.is_auto_trait_item() {
let pth = self.parse_path(PathStyle::Expr)?;

22
src/test/ui/impl-trait/existential_type_in_fn_body.rs Normal file
View file

@ -0,0 +1,22 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// compile-pass
#![feature(existential_type)]
use std::fmt::Debug;
fn main() {
existential type Existential: Debug;
fn f() -> Existential {}
println!("{:?}", f());
}