fix: ensure await check recurses into generator conditions

crates/pyrefly_python/src/ast.rs

@@ -330,12 +330,16 @@ impl Ast {
     }
 
     pub fn contains_await(expr: &Expr) -> bool {
-        let mut found = false;
-        expr.visit(&mut |node: &Expr| {
+        // Iterative DFS to safely visit all nodes, including the root and nested children.
+        let mut stack = vec![expr];
+
+        while let Some(node) = stack.pop() {
             if matches!(node, Expr::Await(_)) {
-                found = true;
+                return true;
             }
-        });
-        found
+            node.recurse(&mut |child| stack.push(child));
+        }
+
+        false
     }
 }

pyrefly/lib/test/yields.rs

@@ -483,3 +483,19 @@ def f(start, iterable: Iterable[_T], step) ->  Iterator[_T]:
 
     "#,
 );
+
+testcase!(
+    test_async_generator_nested_await_in_condition,
+    r#"
+from typing import AsyncGenerator, assert_type
+
+async def some_async_func(x: int) -> bool:
+    return True
+
+async def main() -> None:
+    # Regression test for Issue #1611
+    # Previously inferred as Generator (sync) because await was nested in comparison
+    generator = (x for x in [1, 2, 3] if await some_async_func(x) == True)
+    assert_type(generator, AsyncGenerator[int, None])
+"#,
+);