Fix namedtuple crash in unannotated function

Fixes #11121.

Author: JukkaL

mypy/semanal_namedtuple.py

@@ -186,6 +186,8 @@ def check_namedtuple(self,
             # Error. Construct dummy return value.
             if var_name:
                 name = var_name
+                if is_func_scope:
+                    name += '@' + str(call.line)
             else:
                 name = 'namedtuple@' + str(call.line)
             info = self.build_namedtuple_typeinfo(name, [], [], {}, node.line)

test-data/unit/check-incremental.test

@@ -5711,3 +5711,24 @@ class C:
 [builtins fixtures/dict.pyi]
 [out2]
 tmp/a.py:2: error: "object" has no attribute "xyz"
+
+[case testIncrementalInvalidNamedTupleInUnannotatedFunction]
+import a
+
+[file a.py]
+import b
+
+[file a.py.2]
+import b # f
+
+[file b.py]
+from typing import NamedTuple
+
+def crash(fields):
+    TupleType = NamedTuple("TupleType", fields)
+    class InheritFromTuple(TupleType):
+        pass
+    NT2 = NamedTuple("bad", [('x', int)])
+    nt2: NT2 = NT2(x=1)
+
+[builtins fixtures/tuple.pyi]