Deprecate --strict-boolean

(Putting this in a separate commit since it's more controversial --
since it did work, some people might still be using it, even though
it's been deprecated since May 2017.  See discussion in
python#3195.)

mypy/checker.py

@@ -2693,11 +2693,6 @@ def visit_if_stmt(self, s: IfStmt) -> None:
                 if isinstance(t, DeletedType):
                     self.msg.deleted_as_rvalue(t, s)
 
-                if self.options.strict_boolean:
-                    is_bool = isinstance(t, Instance) and t.type.fullname() == 'builtins.bool'
-                    if not (is_bool or isinstance(t, AnyType)):
-                        self.fail(messages.NON_BOOLEAN_IN_CONDITIONAL, e)
-
                 if_map, else_map = self.find_isinstance_check(e)
 
                 # XXX Issue a warning if condition is always False?

mypy/checkexpr.py

@@ -2930,11 +2930,6 @@ def check_for_comp(self, e: Union[GeneratorExpr, DictionaryComprehension]) -> No
 
     def visit_conditional_expr(self, e: ConditionalExpr) -> Type:
         cond_type = self.accept(e.cond)
-        if self.chk.options.strict_boolean:
-            is_bool = (isinstance(cond_type, Instance)
-                and cond_type.type.fullname() == 'builtins.bool')
-            if not (is_bool or isinstance(cond_type, AnyType)):
-                self.chk.fail(messages.NON_BOOLEAN_IN_CONDITIONAL, e)
         ctx = self.type_context[-1]
 
         # Gain type information from isinstance if it is there

mypy/main.py

@@ -689,11 +689,10 @@ def add_invertible_flag(flag: str,
                         help=argparse.SUPPRESS)
 
     # deprecated options
-    add_invertible_flag('--strict-boolean', default=False,
-                        help=argparse.SUPPRESS)
     parser.add_argument('--quick-and-dirty', action='store_true',
                         help=argparse.SUPPRESS)
 
+    # options specifying code to check
     code_group = parser.add_argument_group(
         title="Running code",
         description="Specify the code you want to type check. For more details, see "
@@ -739,9 +738,6 @@ def add_invertible_flag(flag: str,
     parser.parse_args(args, SplitNamespace(options, special_opts, 'special-opts:'))
 
     # Process deprecated options
-    if options.strict_boolean:
-        print("Warning: --strict-boolean is deprecated; "
-              "see https://github.com/python/mypy/issues/3195", file=sys.stderr)
     if options.quick_and_dirty:
         print("Warning: --quick-and-dirty is deprecated.  It will disappear in the next release.",
               file=sys.stderr)

mypy/messages.py

@@ -101,7 +101,6 @@
 TYPEDDICT_KEY_MUST_BE_STRING_LITERAL = \
     'Expected TypedDict key to be string literal'  # type: Final
 MALFORMED_ASSERT = 'Assertion is always true, perhaps remove parentheses?'  # type: Final
-NON_BOOLEAN_IN_CONDITIONAL = 'Condition must be a boolean'  # type: Final
 DUPLICATE_TYPE_SIGNATURES = 'Function has duplicate type signatures'  # type: Final
 GENERIC_INSTANCE_VAR_CLASS_ACCESS = \
     'Access to generic instance variables via class is ambiguous'  # type: Final

mypy/options.py

@@ -43,7 +43,6 @@ class BuildType:
     "mypyc",
     "no_implicit_optional",
     "show_none_errors",
-    "strict_boolean",
     "strict_optional",
     "strict_optional_whitelist",
     "warn_no_return",
@@ -131,9 +130,6 @@ def __init__(self) -> None:
         # Files in which to ignore all non-fatal errors
         self.ignore_errors = False
 
-        # Only allow booleans in conditions
-        self.strict_boolean = False
-
         # Apply strict None checking
         self.strict_optional = True