Improve typing.TypedDict inference

ChangeLog

@@ -11,6 +11,9 @@ Release Date: TBA
 
   Closes #895 #899
 
+* Improve typing.TypedDict inference
+
+
 What's New in astroid 2.5?
 ============================
 Release Date: 2021-02-15

astroid/brain/brain_typing.py

@@ -4,6 +4,7 @@
 # Copyright (c) 2018 Bryce Guinta <bryce.paul.guinta@gmail.com>
 
 """Astroid hooks for typing.py support."""
+import sys
 import typing
 
 from astroid import (
@@ -12,9 +13,11 @@
     extract_node,
     inference_tip,
     nodes,
+    context,
     InferenceError,
 )
 
+PY39 = sys.version_info[:2] >= (3, 9)
 
 TYPING_NAMEDTUPLE_BASENAMES = {"NamedTuple", "typing.NamedTuple"}
 TYPING_TYPEVARS = {"TypeVar", "NewType"}
@@ -85,6 +88,28 @@ def infer_typing_attr(node, context=None):
     return node.infer(context=context)
 
 
+def _looks_like_typedDict(  # pylint: disable=invalid-name
+    node: nodes.FunctionDef,
+) -> bool:
+    """Check if node is TypedDict FunctionDef."""
+    return isinstance(node, nodes.FunctionDef) and node.name == "TypedDict"
+
+
+def infer_typedDict(  # pylint: disable=invalid-name
+    node: nodes.FunctionDef, ctx: context.InferenceContext = None
+) -> None:
+    """Replace TypedDict FunctionDef with ClassDef."""
+    class_def = nodes.ClassDef(
+        name="TypedDict",
+        doc=node.doc,
+        lineno=node.lineno,
+        col_offset=node.col_offset,
+        parent=node.parent,
+    )
+    class_def.postinit(bases=[], body=[], decorators=None)
+    node.root().locals["TypedDict"] = [class_def]
+
+
 MANAGER.register_transform(
     nodes.Call,
     inference_tip(infer_typing_typevar_or_newtype),
@@ -93,3 +118,8 @@ def infer_typing_attr(node, context=None):
 MANAGER.register_transform(
     nodes.Subscript, inference_tip(infer_typing_attr), _looks_like_typing_subscript
 )
+
+if PY39:
+    MANAGER.register_transform(
+        nodes.FunctionDef, infer_typedDict, _looks_like_typedDict
+    )

tests/unittest_brain.py

@@ -1188,6 +1188,22 @@ def test_typing_namedtuple_dont_crash_on_no_fields(self):
         inferred = next(node.infer())
         self.assertIsInstance(inferred, astroid.Instance)
 
+    @test_utils.require_version("3.8")
+    def test_typedDict(self):
+        node = builder.extract_node(
+            """
+        from typing import TypedDict
+        class CustomTD(TypedDict):
+            var: int
+        """
+        )
+        assert len(node.bases) == 1
+        inferred_base = next(node.bases[0].infer())
+        self.assertIsInstance(inferred_base, nodes.ClassDef, node.as_string())
+        typing_module = inferred_base.root()
+        assert len(typing_module.locals["TypedDict"]) == 1
+        assert inferred_base == typing_module.locals["TypedDict"][0]
+
 
 class ReBrainTest(unittest.TestCase):
     def test_regex_flags(self):