Auto merge of #51580 - cramertj:async-await, r=eddyb

async/await

This PR implements `async`/`await` syntax for `async fn` in Rust 2015 and `async` closures and `async` blocks in Rust 2018 (tracking issue: https://github.com/rust-lang/rust/issues/50547). Limitations: non-`move` async closures with arguments are currently not supported, nor are `async fn` with multiple different input lifetimes. These limitations are not fundamental and will be removed in the future, however I'd like to go ahead and get this PR merged so we can start experimenting with this in combination with futures 0.3.

Based on https://github.com/rust-lang/rust/pull/51414.
cc @petrochenkov for parsing changes.
r? @eddyb

1 files changed, 8 insertions, 3 deletions

diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 9044cab05d6..61356507665 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -915,6 +915,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
                       fn_decl_span: Span) // span of the `|...|` part
                       -> P<ast::Expr> {
         self.expr(span, ast::ExprKind::Closure(ast::CaptureBy::Ref,
+                                               ast::IsAsync::NotAsync,
                                                ast::Movability::Movable,
                                                fn_decl,
                                                body,
@@ -935,6 +936,7 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         // the entire lambda body. Probably we should extend the API
         // here, but that's not entirely clear.
         self.expr(span, ast::ExprKind::Closure(ast::CaptureBy::Ref,
+                                               ast::IsAsync::NotAsync,
                                                ast::Movability::Movable,
                                                fn_decl,
                                                body,
@@ -1008,9 +1010,12 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
                   name,
                   Vec::new(),
                   ast::ItemKind::Fn(self.fn_decl(inputs, ast::FunctionRetTy::Ty(output)),
-                              ast::Unsafety::Normal,
-                              dummy_spanned(ast::Constness::NotConst),
-                              Abi::Rust,
+                              ast::FnHeader {
+                                  unsafety: ast::Unsafety::Normal,
+                                  asyncness: ast::IsAsync::NotAsync,
+                                  constness: dummy_spanned(ast::Constness::NotConst),
+                                  abi: Abi::Rust,
+                              },
                               generics,
                               body))
     }