Fix and store fallbacks for incomplete namedtuples (#5429)

Author: ilevkivskyi

mypy/semanal_namedtuple.py

@@ -151,7 +151,13 @@ def check_namedtuple(self,
         items, types, defaults, ok = self.parse_namedtuple_args(call, fullname)
         if not ok:
             # Error. Construct dummy return value.
-            return self.build_namedtuple_typeinfo('namedtuple', [], [], {})
+            if var_name:
+                name = var_name
+            else:
+                name = 'namedtuple@' + str(call.line)
+            info = self.build_namedtuple_typeinfo(name, [], [], {})
+            self.store_namedtuple_info(info, name, call, is_typed)
+            return info
         name = cast(StrExpr, call.args[0]).value
         if name != var_name or is_func_scope:
             # Give it a unique name derived from the line number.
@@ -166,11 +172,15 @@ def check_namedtuple(self,
         info = self.build_namedtuple_typeinfo(name, items, types, default_items)
         # Store it as a global just in case it would remain anonymous.
         # (Or in the nearest class if there is one.)
+        self.store_namedtuple_info(info, name, call, is_typed)
+        return info
+
+    def store_namedtuple_info(self, info: TypeInfo, name: str,
+                              call: CallExpr, is_typed: bool) -> None:
         stnode = SymbolTableNode(GDEF, info)
         self.api.add_symbol_table_node(name, stnode)
         call.analyzed = NamedTupleExpr(info, is_typed=is_typed)
         call.analyzed.set_line(call.line, call.column)
-        return info
 
     def parse_namedtuple_args(self, call: CallExpr, fullname: str
                               ) -> Tuple[List[str], List[Type], List[Expression], bool]:

test-data/unit/fine-grained.test

@@ -7260,6 +7260,26 @@ x = []  # type: List
 [out]
 ==
 
+[case testNamedTupleFallbackModule]
+import b
+[file b.py]
+from a import A
+def f(a: A):
+    pass
+[file b.py.2]
+from a import A
+def f(a: A):
+    reveal_type(a)
+[file a.py]
+from typing import NamedTuple
+
+F = [('x', int)]
+A = NamedTuple('A', F)  # type: ignore
+[builtins fixtures/list.pyi]
+[out]
+==
+b.py:3: error: Revealed type is 'Tuple[, fallback=a.A]'
+
 [case testImportOnTopOfAlias1]
 from a import A
 x: A