Factor out two checks

Author: huonw

mypy/checker.py

@@ -5689,7 +5689,7 @@ def _format_expr_type(self, t: Type, expr: Expression) -> str:
         else:
             return f"Expression has type {typ}"
 
-    def check_for_truthy_type(self, t: Type, expr: Expression) -> None:
+    def _check_for_truthy_type(self, t: Type, expr: Expression) -> None:
         """
         Check if a type can have a truthy value.
 
@@ -5731,7 +5731,7 @@ def get_expr_name() -> str:
         else:
             self.fail(message_registry.TYPE_ALWAYS_TRUE.format(format_expr_type()), expr)
 
-    def check_for_optional_non_truthy_type(self, t: Type, expr: Expression) -> None:
+    def _check_for_optional_non_truthy_type(self, t: Type, expr: Expression) -> None:
         """Check if a type involves both None and types that aren't always true, catching
         suspicious cases of falsy values being lumped together with None.
 
@@ -5766,6 +5766,21 @@ def check_for_optional_non_truthy_type(self, t: Type, expr: Expression) -> None:
             expr,
         )
 
+    def check_for_appropriate_truthiness_in_boolean_context(
+        self, t: Type, expr: Expression
+    ) -> None:
+        """Check if a type is truthy or potentially-falsy when it shouldn't be.
+
+        Used in checks like::
+
+            if x: # <---
+
+            not x  # <---
+
+        """
+        self._check_for_truthy_type(t, expr)
+        self._check_for_optional_non_truthy_type(t, expr)
+
     def find_type_equals_check(
         self, node: ComparisonExpr, expr_indices: list[int]
     ) -> tuple[TypeMap, TypeMap]:
@@ -6212,9 +6227,7 @@ def has_no_custom_eq_checks(t: Type) -> bool:
         if in_boolean_context:
             # We don't check `:=` values in expressions like `(a := A())`,
             # because they produce two error messages.
-            # FIXME: make this a single call again
-            self.check_for_truthy_type(original_vartype, node)
-            self.check_for_optional_non_truthy_type(original_vartype, node)
+            self.check_for_appropriate_truthiness_in_boolean_context(original_vartype, node)
         vartype = try_expanding_sum_type_to_union(original_vartype, "builtins.bool")
 
         if_type = true_only(vartype)

mypy/checkexpr.py

@@ -4296,9 +4296,7 @@ def visit_unary_expr(self, e: UnaryExpr) -> Type:
         op = e.op
         if op == "not":
             result: Type = self.bool_type()
-            # FIXME: make this a single call again
-            self.chk.check_for_truthy_type(operand_type, e.expr)
-            self.chk.check_for_optional_non_truthy_type(operand_type, e.expr)
+            self.chk.check_for_appropriate_truthiness_in_boolean_context(operand_type, e.expr)
         else:
             method = operators.unary_op_methods[op]
             result, method_type = self.check_method_call_by_name(method, operand_type, [], [], e)