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, 9 insertions, 8 deletions

diff --git a/src/libsyntax/visit.rs b/src/libsyntax/visit.rs
index 613f1a4f113..41e3ad9d4f4 100644
--- a/src/libsyntax/visit.rs
+++ b/src/libsyntax/visit.rs
@@ -23,17 +23,15 @@
 //! instance, a walker looking for item names in a module will miss all of
 //! those that are created by the expansion of a macro.
 
-use rustc_target::spec::abi::Abi;
 use ast::*;
 use syntax_pos::Span;
-use codemap::Spanned;
 use parse::token::Token;
 use tokenstream::{TokenTree, TokenStream};
 
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum FnKind<'a> {
     /// fn foo() or extern "Abi" fn foo()
-    ItemFn(Ident, Unsafety, Spanned<Constness>, Abi, &'a Visibility, &'a Block),
+    ItemFn(Ident, FnHeader, &'a Visibility, &'a Block),
 
     /// fn foo(&self)
     Method(Ident, &'a MethodSig, Option<&'a Visibility>, &'a Block),
@@ -235,10 +233,10 @@ pub fn walk_item<'a, V: Visitor<'a>>(visitor: &mut V, item: &'a Item) {
             visitor.visit_ty(typ);
             visitor.visit_expr(expr);
         }
-        ItemKind::Fn(ref declaration, unsafety, constness, abi, ref generics, ref body) => {
+        ItemKind::Fn(ref declaration, header, ref generics, ref body) => {
             visitor.visit_generics(generics);
-            visitor.visit_fn(FnKind::ItemFn(item.ident, unsafety,
-                                            constness, abi, &item.vis, body),
+            visitor.visit_fn(FnKind::ItemFn(item.ident, header,
+                                            &item.vis, body),
                              declaration,
                              item.span,
                              item.id)
@@ -544,7 +542,7 @@ pub fn walk_fn<'a, V>(visitor: &mut V, kind: FnKind<'a>, declaration: &'a FnDecl
     where V: Visitor<'a>,
 {
     match kind {
-        FnKind::ItemFn(_, _, _, _, _, body) => {
+        FnKind::ItemFn(_, _, _, body) => {
             walk_fn_decl(visitor, declaration);
             visitor.visit_block(body);
         }
@@ -737,7 +735,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             visitor.visit_expr(subexpression);
             walk_list!(visitor, visit_arm, arms);
         }
-        ExprKind::Closure(_, _, ref function_declaration, ref body, _decl_span) => {
+        ExprKind::Closure(_, _, _, ref function_declaration, ref body, _decl_span) => {
             visitor.visit_fn(FnKind::Closure(body),
                              function_declaration,
                              expression.span,
@@ -747,6 +745,9 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             walk_list!(visitor, visit_label, opt_label);
             visitor.visit_block(block);
         }
+        ExprKind::Async(_, _, ref body) => {
+            visitor.visit_block(body);
+        }
         ExprKind::Assign(ref left_hand_expression, ref right_hand_expression) => {
             visitor.visit_expr(left_hand_expression);
             visitor.visit_expr(right_hand_expression);