From 26bfc631c1cd25a874cce21c0b08df5e7d939edb Mon Sep 17 00:00:00 2001
From: Purna Chandra Mansingh <42216008+purna135@users.noreply.github.com>
Date: Wed, 2 Mar 2022 07:42:56 +0530
Subject: [PATCH] Improve the "Argument must be a mapping" error message
 (#12222)

Fixes #12070
---
 mypy/messages.py                 | 5 +----
 test-data/unit/check-kwargs.test | 7 +++++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/mypy/messages.py b/mypy/messages.py
index 96cb2f3ae371..bb6977190105 100644
--- a/mypy/messages.py
+++ b/mypy/messages.py
@@ -954,11 +954,8 @@ def invalid_keyword_var_arg(self, typ: Type, is_mapping: bool, context: Context)
         if isinstance(typ, Instance) and is_mapping:
             self.fail('Keywords must be strings', context)
         else:
-            suffix = ''
-            if isinstance(typ, Instance):
-                suffix = ', not {}'.format(format_type(typ))
             self.fail(
-                'Argument after ** must be a mapping{}'.format(suffix),
+                'Argument after ** must be a mapping, not {}'.format(format_type(typ)),
                 context, code=codes.ARG_TYPE)
 
     def undefined_in_superclass(self, member: str, context: Context) -> None:
diff --git a/test-data/unit/check-kwargs.test b/test-data/unit/check-kwargs.test
index 7f0b8af3ba0e..9f8de1265ee7 100644
--- a/test-data/unit/check-kwargs.test
+++ b/test-data/unit/check-kwargs.test
@@ -350,12 +350,15 @@ class A: pass
 [builtins fixtures/dict.pyi]
 
 [case testInvalidTypeForKeywordVarArg]
-from typing import Dict
+# flags: --strict-optional
+from typing import Dict, Any, Optional
 def f(**kwargs: 'A') -> None: pass
-d = None # type: Dict[A, A]
+d = {} # type: Dict[A, A]
 f(**d)         # E: Keywords must be strings
 f(**A())       # E: Argument after ** must be a mapping, not "A"
 class A: pass
+kwargs: Optional[Any]
+f(**kwargs)    # E: Argument after ** must be a mapping, not "Optional[Any]"
 [builtins fixtures/dict.pyi]
 
 [case testPassingKeywordVarArgsToNonVarArgsFunction]