TypedDict get tweaks

Some of the tests are adapted from #2620 by @rowillia.

mypy/checkexpr.py

@@ -1848,13 +1848,14 @@ def visit_dict_expr(self, e: DictExpr) -> Type:
         # an error, but returns the TypedDict type that matches the literal it found
         # that would cause a second error when that TypedDict type is returned upstream
         # to avoid the second error, we always return TypedDict type that was requested
-        if isinstance(self.type_context[-1], TypedDictType):
+        typeddict_context = self.find_typeddict_context(self.type_context[-1])
+        if typeddict_context:
             self.check_typeddict_call_with_dict(
-                callee=self.type_context[-1],
+                callee=typeddict_context,
                 kwargs=e,
                 context=e
             )
-            return self.type_context[-1].copy_modified()
+            return typeddict_context.copy_modified()
 
         # Collect function arguments, watching out for **expr.
         args = []  # type: List[Expression]  # Regular "key: value"
@@ -1905,6 +1906,19 @@ def visit_dict_expr(self, e: DictExpr) -> Type:
                     self.check_call(method, [arg], [nodes.ARG_POS], arg)
         return rv
 
+    def find_typeddict_context(self, context: Type) -> Optional[TypedDictType]:
+        if isinstance(context, TypedDictType):
+            return context
+        elif isinstance(context, UnionType):
+            items = []
+            for item in context.items:
+                item_context = self.find_typeddict_context(item)
+                if item_context:
+                    items.append(item_context)
+            if len(items) == 1:
+                return items[0]
+        return None
+
     def visit_lambda_expr(self, e: LambdaExpr) -> Type:
         """Type check lambda expression."""
         inferred_type, type_override = self.infer_lambda_type_using_context(e)

mypy/plugin.py

@@ -224,9 +224,6 @@ def typed_dict_get_callback(
             else:
                 context.msg.typeddict_item_name_not_found(object_type, key, context.context)
                 return AnyType()
-        else:
-            context.msg.typeddict_item_name_must_be_string_literal(object_type, context.context)
-            return AnyType()
     return inferred_return_type
 
 

test-data/unit/check-typeddict.test

@@ -784,8 +784,8 @@ d.get('x', 1, 2) # E: No overload variant of "get" of "Mapping" matches argument
 x = d.get('z') # E: 'z' is not a valid item name; expected one of ['x', 'y']
 reveal_type(x) # E: Revealed type is 'Any'
 s = ''
-y = d.get(s) # E: Cannot prove expression is a valid item name; expected one of ['x', 'y']
-reveal_type(y) # E: Revealed type is 'Any'
+y = d.get(s)
+reveal_type(y) # E: Revealed type is 'builtins.object*'
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-full.pyi]
 
@@ -795,3 +795,21 @@ D = TypedDict('D', {'x': int, 'y': str})
 d: D
 d.bad(1) # E: "D" has no attribute "bad"
 [builtins fixtures/dict.pyi]
+
+[case testTypedDictChainedGetMethodWithDictFallback]
+from mypy_extensions import TypedDict
+D = TypedDict('D', {'x': int, 'y': str})
+E = TypedDict('E', {'d': D})
+p = E(d=D(x=0, y=''))
+reveal_type(p.get('d', {'x': 1, 'y': ''})) # E: Revealed type is 'TypedDict(x=builtins.int, y=builtins.str, _fallback=__main__.D)'
+p.get('d', {}) # E: Expected items ['x', 'y'] but found [].
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-full.pyi]
+
+[case testTypedDictGetDefaultParameterStillTypeChecked]
+from mypy_extensions import TypedDict
+TaggedPoint = TypedDict('TaggedPoint', {'type': str, 'x': int, 'y': int})
+p = TaggedPoint(type='2d', x=42, y=1337)
+p.get('x', 1 + 'y')     # E: Unsupported operand types for + ("int" and "str")
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-full.pyi]