Fix typemap handling for ternaries

Author: A5rocks

mypy/checker.py

@@ -8134,8 +8134,9 @@ def and_conditional_maps(m1: TypeMap, m2: TypeMap, use_meet: bool = False) -> Ty
     result = m2.copy()
     m2_keys = {literal_hash(n2) for n2 in m2}
     for n1 in m1:
-        # TODO: should this check for UninhabitedType as well as AnyType?
-        if literal_hash(n1) not in m2_keys or isinstance(get_proper_type(m1[n1]), AnyType):
+        if literal_hash(n1) not in m2_keys or isinstance(
+            get_proper_type(m1[n1]), (UninhabitedType, AnyType)
+        ):
             result[n1] = m1[n1]
     if use_meet:
         # For now, meet common keys only if specifically requested.

mypy/checkexpr.py

@@ -5836,9 +5836,13 @@ def visit_conditional_expr(self, e: ConditionalExpr, allow_none_return: bool = F
         # but only for the current expression
         if_map, else_map = self.chk.find_isinstance_check(e.cond)
         if codes.REDUNDANT_EXPR in self.chk.options.enabled_error_codes:
-            if if_map is None:
+            if if_map is None or any(
+                isinstance(get_proper_type(t), UninhabitedType) for t in if_map.values()
+            ):
                 self.msg.redundant_condition_in_if(False, e.cond)
-            elif else_map is None:
+            elif else_map is None or any(
+                isinstance(get_proper_type(t), UninhabitedType) for t in else_map.values()
+            ):
                 self.msg.redundant_condition_in_if(True, e.cond)
 
         if_type = self.analyze_cond_branch(
@@ -5915,17 +5919,28 @@ def analyze_cond_branch(
         node: Expression,
         context: Type | None,
         allow_none_return: bool = False,
-        suppress_unreachable_errors: bool = True,
+        suppress_unreachable_errors: bool | None = None,
     ) -> Type:
+        # TODO: default based on flag (default to `True` if flag is not passed)
+        unreachable_errors_suppressed = (
+            suppress_unreachable_errors
+            if suppress_unreachable_errors is not None
+            else self.chk.binder.is_unreachable_warning_suppressed()
+        )
         with self.chk.binder.frame_context(can_skip=True, fall_through=0):
-            if map is None:
+            self.chk.push_type_map(map)
+
+            if map is None or any(
+                isinstance(get_proper_type(t), UninhabitedType) for t in map.values()
+            ):
                 # We still need to type check node, in case we want to
                 # process it for isinstance checks later. Since the branch was
                 # determined to be unreachable, any errors should be suppressed.
-                with self.msg.filter_errors(filter_errors=suppress_unreachable_errors):
+
+                with self.msg.filter_errors(filter_errors=unreachable_errors_suppressed):
                     self.accept(node, type_context=context, allow_none_return=allow_none_return)
                 return UninhabitedType()
-            self.chk.push_type_map(map)
+
             return self.accept(node, type_context=context, allow_none_return=allow_none_return)
 
     #

test-data/unit/check-isinstance.test

@@ -1444,7 +1444,8 @@ if isinstance(x2, A) or isinstance(x2, C):  # E: Right operand of "or" is never
     f = x2.flag # E: "A" has no attribute "flag"
 else:
     # unreachable
-    _ = "unreachable"  # E: Statement is unreachable
+    reveal_type(x2)  # E: Statement is unreachable \
+                     # N: Revealed type is "Never"
 reveal_type(x2) # N: Revealed type is "__main__.A"
 [builtins fixtures/isinstance.pyi]
 

test-data/unit/check-unreachable-code.test

@@ -962,7 +962,8 @@ k = [x for x in lst if isinstance(x, int) or foo()]  # E: Right operand of "or"
 
 class Case1:
     def test1(self) -> bool:
-        return False and self.missing()  # E: Right operand of "and" is never evaluated
+        return False and self.missing()  # E: Right operand of "and" is never evaluated \
+                                         # E: "Case1" has no attribute "missing"
 
     def test2(self) -> bool:
         return not self.property_decorator_missing and self.missing()  # E: Function "property_decorator_missing" could always be true in boolean context \
@@ -1557,3 +1558,9 @@ if isinstance(x, int):
     reveal_type(y)  # N: Revealed type is "Never"
     reveal_type(ys)  # N: Revealed type is "builtins.list[Never]"
 [builtins fixtures/isinstancelist.pyi]
+
+[case testUnusedConditionalBranchesDoNotAffectType]
+# flags: --enable-error-code redundant-expr
+def foo(var: str) -> str:
+    return "aa" if isinstance(var, str) else 0  # E: If condition is always true
+[builtins fixtures/isinstancelist.pyi]