Make error message mention specific class

This commit modifies the error message to try and report the specific
name of the invalid class whenever possible.

Author: MichaelLeeDBX

mypy/semanal.py

@@ -770,7 +770,11 @@ def analyze_base_classes(self, defn: ClassDef) -> None:
                 base_types.append(base)
             elif isinstance(base, AnyType):
                 if self.options.disallow_subclassing_any:
-                    self.fail("Class cannot subclass value of type 'Any'", base_expr)
+                    if isinstance(base_expr, RefExpr):
+                        msg = "Class cannot subclass '{}' (has type 'Any')".format(base_expr.name)
+                    else:
+                        msg = "Class cannot subclass value of type 'Any'"
+                    self.fail(msg, base_expr)
                 info.fallback_to_any = True
             else:
                 self.fail('Invalid base class', base_expr)

test-data/unit/check-flags.test

@@ -41,15 +41,15 @@ main:2: error: Function is missing a type annotation
 # flags: --disallow-subclassing-any
 from typing import Any
 FakeClass = None  # type: Any
-class Foo(FakeClass): pass  # E: Class cannot subclass value of type 'Any'
+class Foo(FakeClass): pass  # E: Class cannot subclass 'FakeClass' (has type 'Any')
 [out]
 
 [case testSubclassingAnyMultipleBaseClasses]
 # flags: --disallow-subclassing-any
 from typing import Any
 FakeClass = None  # type: Any
 class ActualClass: pass
-class Foo(ActualClass, FakeClass): pass  # E: Class cannot subclass value of type 'Any'
+class Foo(ActualClass, FakeClass): pass  # E: Class cannot subclass 'FakeClass' (has type 'Any')
 [out]
 
 [case testSubclassingAnySilentImports]
@@ -64,4 +64,18 @@ class Foo(BaseClass): pass
 class BaseClass: pass
 
 [out]
-tmp/main.py:2: error: Class cannot subclass value of type 'Any'
+tmp/main.py:2: error: Class cannot subclass 'BaseClass' (has type 'Any')
+
+[case testSubclassingAnySilentImports2]
+# flags: --disallow-subclassing-any --silent-imports
+# cmd: mypy -m main
+
+[file main.py]
+import ignored_module
+class Foo(ignored_module.BaseClass): pass
+
+[file ignored_module.py]
+class BaseClass: pass
+
+[out]
+tmp/main.py:2: error: Class cannot subclass 'BaseClass' (has type 'Any')