Give type annotation suggestion for incompatible **kwargs error

mypy/messages.py

@@ -817,6 +817,8 @@ def incompatible_argument(
                         quote_type_string(arg_type_str),
                         quote_type_string(expected_type_str),
                     )
+                    if isinstance(arg_type, Instance):
+                        notes = append_kwargs_notes(notes, arg_type, arg_kind)
                 expected_type = get_proper_type(expected_type)
                 if isinstance(expected_type, UnionType):
                     expected_types = list(expected_type.items)
@@ -3099,6 +3101,13 @@ def pretty_seq(args: Sequence[str], conjunction: str) -> str:
     return ", ".join(quoted[:-1]) + last_sep + quoted[-1]
 
 
+def append_kwargs_notes(notes: list[str], arg_type: Instance, arg_kind: ArgKind) -> list[str]:
+    """Explain that annotating keyword arguments may resolve incompatible type issues."""
+    if arg_kind == ARG_STAR2 and arg_type.type.fullname == "builtins.dict":
+        notes.append('Consider using a TypedDict type or "Dict[str, any]" for the ** argument')
+    return notes
+
+
 def append_invariance_notes(
     notes: list[str], arg_type: Instance, expected_type: Instance
 ) -> list[str]:

test-data/unit/check-columns.test

@@ -71,7 +71,8 @@ def g(**x: int) -> None: pass
 a = ['']
 f(*a)  # E:4: Argument 1 to "f" has incompatible type "*List[str]"; expected "int"
 b = {'x': 'y'}
-g(**b) # E:5: Argument 1 to "g" has incompatible type "**Dict[str, str]"; expected "int"
+g(**b) # E:5: Argument 1 to "g" has incompatible type "**Dict[str, str]"; expected "int" \
+       # N:5: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
 [builtins fixtures/dict.pyi]
 
 [case testColumnsMultipleStatementsPerLine]

test-data/unit/check-expressions.test

@@ -1712,7 +1712,8 @@ kw2 = {'x': ''}
 d2 = dict(it, **kw2)
 d2() # E: "Dict[str, object]" not callable
 
-d3 = dict(it, **kw2) # type: Dict[str, int] # E: Argument 2 to "dict" has incompatible type "**Dict[str, str]"; expected "int"
+d3 = dict(it, **kw2) # type: Dict[str, int] # E: Argument 2 to "dict" has incompatible type "**Dict[str, str]"; expected "int" \
+                                            # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
 [builtins fixtures/dict.pyi]
 
 [case testDictFromIterableAndStarStarArgs2]

test-data/unit/check-kwargs.test

@@ -75,6 +75,32 @@ def f(a: int): pass
 def g(): f(0, a=1)
 [out]
 
+[case testIncompatibleKeywordArgumentsClass]
+from typing import Dict
+
+class A:
+    def __init__(self, a: str, b: str, c: str, d: int = 2) -> None:
+        self.a: str = a
+        self.b: str = b
+        self.c: str = c
+        self.d: int = d
+
+argument_a: str = "argument_a"
+arguments_b_c: Dict[str, str] = {"b": "argument_b", "c": "argument_c"}
+object_a: A = A(a=argument_a, **arguments_b_c) # E: Argument 2 to "A" has incompatible type "**Dict[str, str]"; expected "int" \
+                                               # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
+[builtins fixtures/dict.pyi]
+
+[case testIncompatibleKeywordArgumentsJSON]
+import json
+json_kwargs = dict(indent=2)
+json.dumps({}, **json_kwargs) # E: Argument 2 to "dumps" has incompatible type "**Dict[str, int]"; expected "bool" \
+                              # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument \
+                              # E: Argument 2 to "dumps" has incompatible type "**Dict[str, int]"; expected "Optional[Type[JSONEncoder]]" \
+                              # E: Argument 2 to "dumps" has incompatible type "**Dict[str, int]"; expected "Optional[Tuple[str, str]]" \
+                              # E: Argument 2 to "dumps" has incompatible type "**Dict[str, int]"; expected "Optional[Callable[[Any], Any]]"
+[builtins fixtures/dict.pyi]
+
 [case testInvalidKeywordArgument]
 import typing
 def f(a: 'A') -> None: pass # N: "f" defined here
@@ -301,9 +327,12 @@ d: Dict[str, A]
 f(**d)
 f(x=A(), **d)
 d2: Dict[str, B]
-f(**d2)         # E: Argument 1 to "f" has incompatible type "**Dict[str, B]"; expected "A"
-f(x=A(), **d2)  # E: Argument 2 to "f" has incompatible type "**Dict[str, B]"; expected "A"
-f(**{'x': B()}) # E: Argument 1 to "f" has incompatible type "**Dict[str, B]"; expected "A"
+f(**d2)         # E: Argument 1 to "f" has incompatible type "**Dict[str, B]"; expected "A" \
+                # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
+f(x=A(), **d2)  # E: Argument 2 to "f" has incompatible type "**Dict[str, B]"; expected "A" \
+                # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
+f(**{'x': B()}) # E: Argument 1 to "f" has incompatible type "**Dict[str, B]"; expected "A" \
+                # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
 [builtins fixtures/dict.pyi]
 
 [case testKwargsAllowedInDunderCall]
@@ -366,7 +395,8 @@ def f(a: 'A', b: 'B') -> None: pass
 d: Dict[str, Any]
 f(**d)
 d2: Dict[str, A]
-f(**d2) # E: Argument 1 to "f" has incompatible type "**Dict[str, A]"; expected "B"
+f(**d2) # E: Argument 1 to "f" has incompatible type "**Dict[str, A]"; expected "B" \
+        # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
 class A: pass
 class B: pass
 [builtins fixtures/dict.pyi]
@@ -443,7 +473,8 @@ f(**a) # okay
 
 b = {'': ''}
 f(b) # E: Argument 1 to "f" has incompatible type "Dict[str, str]"; expected "int"
-f(**b) # E: Argument 1 to "f" has incompatible type "**Dict[str, str]"; expected "int"
+f(**b) # E: Argument 1 to "f" has incompatible type "**Dict[str, str]"; expected "int" \
+       # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
 
 c = {0: 0}
 f(**c) # E: Keywords must be strings
@@ -488,7 +519,8 @@ def g(arg: int = 0, **kwargs: object) -> None:
 
 d = {} # type: Dict[str, object]
 f(**d)
-g(**d)  # E: Argument 1 to "g" has incompatible type "**Dict[str, object]"; expected "int"
+g(**d)  # E: Argument 1 to "g" has incompatible type "**Dict[str, object]"; expected "int" \
+        # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
 
 m = {} # type: Mapping[str, object]
 f(**m)
@@ -563,4 +595,5 @@ main:37: error: Argument 1 to "foo" has incompatible type "**B[str, str]"; expec
 main:38: error: Argument after ** must be a mapping, not "C[str, float]"
 main:39: error: Argument after ** must be a mapping, not "D"
 main:41: error: Argument 1 to "foo" has incompatible type "**Dict[str, str]"; expected "float"
+main:41: note: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
 [builtins fixtures/dict.pyi]

test-data/unit/check-parameter-specification.test

@@ -1257,7 +1257,8 @@ def c3(f: Callable[P, int], *args, **kwargs) -> int: ...
 def c4(f: Callable[P, int], *args: int, **kwargs: str) -> int:
     # but not ok to call:
     f(*args, **kwargs)  # E: Argument 1 has incompatible type "*Tuple[int, ...]"; expected "P.args" \
-                        # E: Argument 2 has incompatible type "**Dict[str, str]"; expected "P.kwargs"
+                        # E: Argument 2 has incompatible type "**Dict[str, str]"; expected "P.kwargs" \
+                        # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
     return 1
 
 def f1(f: Callable[P, int], *args, **kwargs: P.kwargs) -> int: ...  # E: ParamSpec must have "*args" typed as "P.args" and "**kwargs" typed as "P.kwargs"
@@ -1287,7 +1288,8 @@ def c3(f: Callable[Concatenate[int, P], int], *args, **kwargs) -> int: ...
 def c4(f: Callable[Concatenate[int, P], int], *args: int, **kwargs: str) -> int:
     # but not ok to call:
     f(1, *args, **kwargs)  # E: Argument 2 has incompatible type "*Tuple[int, ...]"; expected "P.args" \
-                           # E: Argument 3 has incompatible type "**Dict[str, str]"; expected "P.kwargs"
+                           # E: Argument 3 has incompatible type "**Dict[str, str]"; expected "P.kwargs" \
+                           # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
     return 1
 
 def f1(f: Callable[Concatenate[int, P], int], *args, **kwargs: P.kwargs) -> int: ...  # E: ParamSpec must have "*args" typed as "P.args" and "**kwargs" typed as "P.kwargs"

test-data/unit/check-varargs.test

@@ -804,7 +804,8 @@ Weird = TypedDict("Weird", {"@": int})
 def foo(**kwargs: Unpack[Weird]) -> None:
     reveal_type(kwargs["@"])  # N: Revealed type is "builtins.int"
 foo(**{"@": 42})
-foo(**{"no": "way"})  # E: Argument 1 to "foo" has incompatible type "**Dict[str, str]"; expected "int"
+foo(**{"no": "way"})  # E: Argument 1 to "foo" has incompatible type "**Dict[str, str]"; expected "int" \
+                      # N: Consider using a TypedDict type or "Dict[str, any]" for the ** argument
 [builtins fixtures/dict.pyi]
 
 [case testUnpackKwargsEmpty]