Handle missing type_params on AST Function/Class/TypeAlias nodes (#6512)

Copilot · youknowone · github-actions[bot] · web-flow · commit 61ddd98b8930 · 2025-12-25T19:08:23.000+09:00
Co-authored-by: copilot-swe-agent[bot] &lt;198982749+Copilot@users.noreply.github.com&gt;
Co-authored-by: youknowone &lt;69878+youknowone@users.noreply.github.com&gt;
Co-authored-by: github-actions[bot] &lt;github-actions[bot]@users.noreply.github.com&gt;
diff --git a/crates/vm/src/stdlib/ast/statement.rs b/crates/vm/src/stdlib/ast/statement.rs
@@ -257,7 +257,7 @@ impl Node for ruff::StmtFunctionDef {
             type_params: Node::ast_from_object(
                 _vm,
                 source_file,
-                get_node_field(_vm, &_object, "type_params", "FunctionDef")?,
+                get_node_field_opt(_vm, &_object, "type_params")?.unwrap_or_else(|| _vm.ctx.none()),
             )?,
             range: range_from_object(_vm, source_file, _object, "FunctionDef")?,
             is_async,
@@ -341,7 +341,7 @@ impl Node for ruff::StmtClassDef {
             type_params: Node::ast_from_object(
                 _vm,
                 source_file,
-                get_node_field(_vm, &_object, "type_params", "ClassDef")?,
+                get_node_field_opt(_vm, &_object, "type_params")?.unwrap_or_else(|| _vm.ctx.none()),
             )?,
             range: range_from_object(_vm, source_file, _object, "ClassDef")?,
         })
@@ -503,7 +503,7 @@ impl Node for ruff::StmtTypeAlias {
             type_params: Node::ast_from_object(
                 _vm,
                 source_file,
-                get_node_field(_vm, &_object, "type_params", "TypeAlias")?,
+                get_node_field_opt(_vm, &_object, "type_params")?.unwrap_or_else(|| _vm.ctx.none()),
             )?,
             value: Node::ast_from_object(
                 _vm,
diff --git a/extra_tests/snippets/stdlib_types.py b/extra_tests/snippets/stdlib_types.py
@@ -1,3 +1,5 @@
+import _ast
+import platform
 import types
 
 from testutils import assert_raises
@@ -8,3 +10,31 @@
 assert ns.b == "Rust"
 with assert_raises(AttributeError):
     _ = ns.c
+
+
+def _run_missing_type_params_regression():
+    args = _ast.arguments(
+        posonlyargs=[],
+        args=[],
+        vararg=None,
+        kwonlyargs=[],
+        kw_defaults=[],
+        kwarg=None,
+        defaults=[],
+    )
+    fn = _ast.FunctionDef("f", args, [], [], None, None)
+    fn.lineno = 1
+    fn.col_offset = 0
+    fn.end_lineno = 1
+    fn.end_col_offset = 0
+    mod = _ast.Module([fn], [])
+    mod.lineno = 1
+    mod.col_offset = 0
+    mod.end_lineno = 1
+    mod.end_col_offset = 0
+    compiled = compile(mod, "<stdlib_types_missing_type_params>", "exec")
+    exec(compiled, {})
+
+
+if platform.python_implementation() == "RustPython":
+    _run_missing_type_params_regression()
