Fix redundant-expr for comprehensions

Author: A5rocks

mypy/checkexpr.py

@@ -5808,9 +5808,13 @@ def check_for_comp(self, e: GeneratorExpr | DictionaryComprehension) -> None:
                     self.chk.push_type_map(true_map)
 
                 if codes.REDUNDANT_EXPR in self.chk.options.enabled_error_codes:
-                    if true_map is None:
+                    if true_map is None or any(
+                        isinstance(get_proper_type(t), UninhabitedType) for t in true_map.values()
+                    ):
                         self.msg.redundant_condition_in_comprehension(False, condition)
-                    elif false_map is None:
+                    elif false_map is None or any(
+                        isinstance(get_proper_type(t), UninhabitedType) for t in false_map.values()
+                    ):
                         self.msg.redundant_condition_in_comprehension(True, condition)
 
     def visit_conditional_expr(self, e: ConditionalExpr, allow_none_return: bool = False) -> Type:

test-data/unit/check-errorcodes.test

@@ -805,7 +805,7 @@ g = 3 if True else 4                     # E: If condition is always true  [redu
 h = 3 if False else 4                    # E: If condition is always false  [redundant-expr]
 i = [x for x in lst if True]             # E: If condition in comprehension is always true  [redundant-expr]
 j = [x for x in lst if False]            # E: If condition in comprehension is always false  [redundant-expr]
-k = [x for x in lst if isinstance(x, int) or foo()]
+k = [x for x in lst if isinstance(x, int) or foo()]  # E: If condition in comprehension is always true  [redundant-expr]
 [builtins fixtures/isinstancelist.pyi]
 
 [case testRedundantExprTruthiness]

test-data/unit/check-isinstance.test

@@ -2522,8 +2522,6 @@ def f2(x: T2) -> T2:
     else:
         reveal_type(x)      # N: Revealed type is "__main__.C"
     return x
-
-
 [builtins fixtures/isinstance.pyi]
 
 [case testIsInstanceAdHocIntersectionGenericsWithValuesDirectReturn]
@@ -2537,7 +2535,6 @@ class B:
 class C:
     attr: str
 
-# TODO: these kinds of typevars play havoc with checking unreachable code
 T1 = TypeVar('T1', A, B)
 def f1(x: T1) -> T1:
     if isinstance(x, A):

test-data/unit/check-literal.test

@@ -2837,8 +2837,8 @@ w: Union[Truth, AlsoTruth]
 if w:
     reveal_type(w)  # N: Revealed type is "Union[__main__.Truth, __main__.AlsoTruth]"
 else:
-    _ = "unreachable"  # E: Statement is unreachable
-
+    reveal_type(w)  # E: Statement is unreachable \
+                    # N: Revealed type is "Never"
 [builtins fixtures/bool.pyi]
 
 [case testLiteralAndInstanceSubtyping]