Support async gen fn

1 files changed, 23 insertions, 16 deletions

diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index 2816386cbad..7a306823ed4 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1125,23 +1125,30 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses asyncness: `async` or nothing.
-    fn parse_asyncness(&mut self, case: Case) -> Option<CoroutineKind> {
+    fn parse_coroutine_kind(&mut self, case: Case) -> Option<CoroutineKind> {
+        let span = self.token.uninterpolated_span();
         if self.eat_keyword_case(kw::Async, case) {
-            let span = self.prev_token.uninterpolated_span();
-            Some(CoroutineKind::Async {
-                span,
-                closure_id: DUMMY_NODE_ID,
-                return_impl_trait_id: DUMMY_NODE_ID,
-            })
-        } else {
-            None
-        }
-    }
-
-    /// Parses genness: `gen` or nothing.
-    fn parse_genness(&mut self, case: Case) -> Option<CoroutineKind> {
-        if self.token.span.at_least_rust_2024() && self.eat_keyword_case(kw::Gen, case) {
-            let span = self.prev_token.uninterpolated_span();
+            // FIXME(gen_blocks): Do we want to unconditionally parse `gen` and then
+            // error if edition <= 2024, like we do with async and edition <= 2018?
+            if self.token.uninterpolated_span().at_least_rust_2024()
+                && self.eat_keyword_case(kw::Gen, case)
+            {
+                let gen_span = self.prev_token.uninterpolated_span();
+                Some(CoroutineKind::AsyncGen {
+                    span: span.to(gen_span),
+                    closure_id: DUMMY_NODE_ID,
+                    return_impl_trait_id: DUMMY_NODE_ID,
+                })
+            } else {
+                Some(CoroutineKind::Async {
+                    span,
+                    closure_id: DUMMY_NODE_ID,
+                    return_impl_trait_id: DUMMY_NODE_ID,
+                })
+            }
+        } else if self.token.uninterpolated_span().at_least_rust_2024()
+            && self.eat_keyword_case(kw::Gen, case)
+        {
             Some(CoroutineKind::Gen {
                 span,
                 closure_id: DUMMY_NODE_ID,