Now unpacking kwargs does not include args with default values

mypy/argmap.py

@@ -89,12 +89,17 @@ def map_actuals_to_formals(actual_kinds: List[nodes.ArgKind],
         #
         # TODO: If there are also tuple varargs, we might be missing some potential
         #       matches if the tuple was short enough to not match everything.
-        unmatched_formals = [fi for fi in range(nformals)
-                             if (formal_names[fi]
-                                 and (not formal_to_actual[fi]
-                                      or actual_kinds[formal_to_actual[fi][0]] == nodes.ARG_STAR)
-                                 and formal_kinds[fi] != nodes.ARG_STAR)
-                             or formal_kinds[fi] == nodes.ARG_STAR2]
+        unmatched_formals = []
+        for fi in range(nformals):
+            if (formal_names[fi]
+                    and formal_kinds[fi] != nodes.ARG_STAR
+                    and (not formal_to_actual[fi]
+                         or actual_kinds[formal_to_actual[fi][0]] == nodes.ARG_STAR)
+                    # Arguments with default values should not be matched:
+                    and not formal_kinds[fi].is_optional()
+                    or formal_kinds[fi] == nodes.ARG_STAR2):
+                unmatched_formals.append(fi)
+
         for ai in ambiguous_actual_kwargs:
             for fi in unmatched_formals:
                 formal_to_actual[fi].append(ai)

mypy/test/testcheck.py

@@ -96,7 +96,7 @@
     'check-functools.test',
     'check-singledispatch.test',
     'check-slots.test',
-    'check-formatting.test'
+    'check-formatting.test',
 ]
 
 # Tests that use Python 3.8-only AST features (like expression-scoped ignores):

test-data/unit/check-dataclasses.test

@@ -1346,14 +1346,7 @@ from dataclasses import dataclass, field
 
 @dataclass
 class Foo:
-    bar: float = field(**{"repr": False})
-[out]
-main:7: error: Unpacking **kwargs in "field()" is not supported
-main:7: error: No overload variant of "field" matches argument type "Dict[str, bool]"
-main:7: note: Possible overload variants:
-main:7: note:     def [_T] field(*, default: _T, init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> _T
-main:7: note:     def [_T] field(*, default_factory: Callable[[], _T], init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> _T
-main:7: note:     def field(*, init: bool = ..., repr: bool = ..., hash: Optional[bool] = ..., compare: bool = ..., metadata: Optional[Mapping[str, Any]] = ..., kw_only: bool = ...) -> Any
+    bar: float = field(**{"repr": False})  # E: Unpacking **kwargs in "field()" is not supported
 [builtins fixtures/dataclasses.pyi]
 
 [case testDataclassFieldWithPositionalArguments]

test-data/unit/check-kwargs.test

@@ -484,13 +484,50 @@ def f(*vargs: int, **kwargs: object) -> None:
 def g(arg: int = 0, **kwargs: object) -> None:
 	pass
 
+def h(*, arg: int = 0, **kwargs: object) -> None:
+  pass
+
+def j(arg: int, **kwargs: object) -> None:
+  pass
+
+def k(*, arg: int, **kwargs: object) -> None:
+  pass
+
 d = {} # type: Dict[str, object]
+f()
 f(**d)
-g(**d)  # E: Argument 1 to "g" has incompatible type "**Dict[str, object]"; expected "int"
+g()
+g(**d)
+g(1, **d)
+g(arg=1, **d)
+h()
+h(**d)
+h(arg=1, **d)
+j(1)
+j(1, **d)
+j(arg=1, **d)
+j(**d)  # E: Argument 1 to "j" has incompatible type "**Dict[str, object]"; expected "int"
+k(arg=1)
+k(arg=1, **d)
+k(**d)  # E: Argument 1 to "k" has incompatible type "**Dict[str, object]"; expected "int"
 
 m = {} # type: Mapping[str, object]
+f()
 f(**m)
-g(**m)  # E: Argument 1 to "g" has incompatible type "**Mapping[str, object]"; expected "int"
+g()
+g(**m)
+g(1, **d)
+g(arg=1, **d)
+h()
+h(**m)
+h(arg=1, **d)
+j(1)
+j(1, **d)
+j(arg=1, **d)
+j(**m)  # E: Argument 1 to "j" has incompatible type "**Mapping[str, object]"; expected "int"
+k(arg=1)
+k(arg=1, **d)
+k(**m)  # E: Argument 1 to "k" has incompatible type "**Mapping[str, object]"; expected "int"
 [builtins fixtures/dict.pyi]
 
 [case testPassingEmptyDictWithStars]