From cda7cb1c7722b37dd2f727a4b107c6aafb637f20 Mon Sep 17 00:00:00 2001
From: Piyush Bhakuni <bhakunipiyush23@gmail.com>
Date: Fri, 26 Jun 2026 16:43:48 +0530
Subject: [PATCH 1/2] Suppress redundant-expr for validation guards that always
 terminate

---
 mypy/checker.py                      |  9 +++++++++
 mypy/checkexpr.py                    |  1 +
 mypy/nodes.py                        |  4 ++++
 test-data/unit/check-errorcodes.test | 23 +++++++++++++++++++++++
 4 files changed, 37 insertions(+)

diff --git a/mypy/checker.py b/mypy/checker.py
index 33705c98e10c3..1fff2e2a0e369 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -5345,6 +5345,15 @@ def visit_if_stmt(self, s: IfStmt) -> None:
         # Fall-through to the original frame is handled explicitly in each block.
         with self.binder.frame_context(can_skip=False, conditional_frame=True, fall_through=0):
             for e, b in zip(s.expr, s.body):
+                # Suppress redundant-expr warnings for validation code
+                # that only terminates execution (raise,assert false, no return ,etc)
+                if (
+                    isinstance(e, OpExpr)
+                    and e.op == "and"
+                    and b.body
+                    and all(self.is_noop_for_reachability(stmt) for stmt in b.body) 
+                ):
+                    e.suppress_redundant_expr = True
                 t = get_proper_type(self.expr_checker.accept(e))
 
                 if isinstance(t, DeletedType):
diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
index 44855f49afaf9..2af0c9027510e 100644
--- a/mypy/checkexpr.py
+++ b/mypy/checkexpr.py
@@ -4446,6 +4446,7 @@ def check_boolean_op(self, e: OpExpr) -> Type:
             codes.REDUNDANT_EXPR in self.chk.options.enabled_error_codes
             and left_unreachable
             # don't report an error if it's intentional
+            and not e.suppress_redundant_expr
             and not e.right_always
         ):
             self.msg.redundant_left_operand(e.op, e.left)
diff --git a/mypy/nodes.py b/mypy/nodes.py
index e2ea348d2df11..a3ae182dc5cd1 100644
--- a/mypy/nodes.py
+++ b/mypy/nodes.py
@@ -2662,6 +2662,7 @@ class OpExpr(Expression):
         "right_unreachable",
         "analyzed",
         "as_type",
+        "suppress_redundant_expr",
     )
 
     __match_args__ = ("left", "op", "right")
@@ -2675,6 +2676,8 @@ class OpExpr(Expression):
     right_always: bool
     # Per static analysis only: Is the right side unreachable?
     right_unreachable: bool
+    # Suppress redundant-expr warnings for this expression.
+    suppress_redundant_expr: bool
     # Used for expressions that represent a type "X | Y" in some contexts
     analyzed: TypeAliasExpr | None
     # If this value expression can also be parsed as a valid type expression,
@@ -2693,6 +2696,7 @@ def __init__(
         self.right_always = False
         self.right_unreachable = False
         self.analyzed = analyzed
+        self.suppress_redundant_expr = False
         self.as_type = NotParsed.VALUE
 
     def accept(self, visitor: ExpressionVisitor[T]) -> T:
diff --git a/test-data/unit/check-errorcodes.test b/test-data/unit/check-errorcodes.test
index 5296d813334e4..10e7194d6ccf2 100644
--- a/test-data/unit/check-errorcodes.test
+++ b/test-data/unit/check-errorcodes.test
@@ -964,6 +964,29 @@ for y in bad_list:
 [builtins fixtures/isinstancelist.pyi]
 [typing fixtures/typing-full.pyi]
 
+[case testNoRedundantExprForTypeIsAndRaise]
+# flags: --enable-error-code redundant-expr
+from typing import TypeVar, Sequence, Any
+from typing_extensions import TypeIs, Self
+
+class Cat:
+    def foo(self) -> Self:  # type: ignore[empty-body]
+        ...
+
+MyType = TypeVar('MyType', int, str, Cat)
+T = TypeVar('T')
+
+def _is_seq_of(seq: Sequence[Any], tp: type[T]) -> TypeIs[Sequence[T]]:  # type: ignore[empty-body]
+    ...
+
+def main(a: Sequence[MyType]) -> MyType:
+    if not _is_seq_of(a, Cat) and not _is_seq_of(a, int):
+        assert False
+    return a[0]
+
+[typing fixtures/typing-full.pyi]
+[builtins fixtures/tuple.pyi]
+
 
 [case testNamedTupleNameMismatch]
 from typing import NamedTuple

From 8310f1d54dd67cb144465561ac965f808f0571a1 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Fri, 26 Jun 2026 11:22:30 +0000
Subject: [PATCH 2/2] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 mypy/checker.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mypy/checker.py b/mypy/checker.py
index 1fff2e2a0e369..98bce9d504ad7 100644
--- a/mypy/checker.py
+++ b/mypy/checker.py
@@ -5351,7 +5351,7 @@ def visit_if_stmt(self, s: IfStmt) -> None:
                     isinstance(e, OpExpr)
                     and e.op == "and"
                     and b.body
-                    and all(self.is_noop_for_reachability(stmt) for stmt in b.body) 
+                    and all(self.is_noop_for_reachability(stmt) for stmt in b.body)
                 ):
                     e.suppress_redundant_expr = True
                 t = get_proper_type(self.expr_checker.accept(e))