Yield in non-generator function is compile-time error

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index a8fc76ad3a71ae0f5dbf94083c425e14cffb157e..6cc8e5421676438b17b07fdde16c095f27fbaeca 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -9599,14 +9599,17 @@ AstNode* Parser::ParseYieldStatement() {
   bool is_yield_each = false;
   const intptr_t yield_pos = TokenPos();
   ConsumeToken();  // yield reserved word.
-  ASSERT(innermost_function().IsGenerator() ||
-         innermost_function().IsSyncGenClosure() ||
-         innermost_function().IsAsyncGenerator() ||
-         innermost_function().IsAsyncGenClosure());
   if (CurrentToken() == Token::kMUL) {
     is_yield_each = true;
     ConsumeToken();
   }
+  if (!innermost_function().IsGenerator() &&
+      !innermost_function().IsGeneratorClosure()) {
+    ReportError(yield_pos,
+                "yield%s statement only allowed in generator functions",
+                is_yield_each ? "*" : "");
+  }
+
   AstNode* expr = ParseAwaitableExpr(kAllowConst, kConsumeCascades, NULL);
 
   LetNode* yield = new(Z) LetNode(yield_pos);