From 1006f910d3fbaa5d80039d94545a87a01626c0b8 Mon Sep 17 00:00:00 2001
From: John Zedlewski <jzedlewski@nvidia.com>
Date: Mon, 10 Aug 2026 20:54:34 +0000
Subject: [PATCH 1/3] Make is_supported_cast fail for variable-width inputs

---
 cpp/src/unary/cast_ops.cu      | 3 ++-
 cpp/tests/unary/cast_tests.cpp | 6 ++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/cpp/src/unary/cast_ops.cu b/cpp/src/unary/cast_ops.cu
index fcee2b368fcc..60f50eb8aa88 100644
--- a/cpp/src/unary/cast_ops.cu
+++ b/cpp/src/unary/cast_ops.cu
@@ -118,7 +118,8 @@ struct fixed_point_unary_cast {
 template <typename From, typename To>
 constexpr inline auto is_supported_non_fixed_point_cast()
 {
-  return cudf::is_fixed_width<To>() &&
+  return cudf::is_fixed_width<From>() &&
+         cudf::is_fixed_width<To>() &&
          // Disallow fixed_point here (requires different specialization)
          !(cudf::is_fixed_point<From>() || cudf::is_fixed_point<To>()) &&
          // Disallow conversions between timestamps and numeric
diff --git a/cpp/tests/unary/cast_tests.cpp b/cpp/tests/unary/cast_tests.cpp
index 5fcec956a8d9..fad01dee272d 100644
--- a/cpp/tests/unary/cast_tests.cpp
+++ b/cpp/tests/unary/cast_tests.cpp
@@ -201,6 +201,12 @@ inline auto make_data_type()
   return cudf::data_type{cudf::type_to_id<T>()};
 }
 
+TEST(IsSupportedCast, StringToInt32IsUnsupported)
+{
+  EXPECT_FALSE(cudf::is_supported_cast(cudf::data_type{cudf::type_id::STRING},
+                                       cudf::data_type{cudf::type_id::INT32}));
+}
+
 struct CastTimestampsSimple : public cudf::test::BaseFixture {};
 
 TEST_F(CastTimestampsSimple, IsIdempotent)

From 715e98ca39036f8c0304ffbd9aebff776e08e3eb Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 10 Aug 2026 21:46:50 +0000
Subject: [PATCH 2/3] [pre-commit.ci] auto code formatting

---
 cpp/src/unary/cast_ops.cu | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/cpp/src/unary/cast_ops.cu b/cpp/src/unary/cast_ops.cu
index 60f50eb8aa88..49fbbf76e663 100644
--- a/cpp/src/unary/cast_ops.cu
+++ b/cpp/src/unary/cast_ops.cu
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2019-2026, NVIDIA CORPORATION.
+ * SPDX-FileCopyrightText: Copyright (c) 2019-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
  * SPDX-License-Identifier: Apache-2.0
  */
 
@@ -118,8 +118,7 @@ struct fixed_point_unary_cast {
 template <typename From, typename To>
 constexpr inline auto is_supported_non_fixed_point_cast()
 {
-  return cudf::is_fixed_width<From>() &&
-         cudf::is_fixed_width<To>() &&
+  return cudf::is_fixed_width<From>() && cudf::is_fixed_width<To>() &&
          // Disallow fixed_point here (requires different specialization)
          !(cudf::is_fixed_point<From>() || cudf::is_fixed_point<To>()) &&
          // Disallow conversions between timestamps and numeric

From e8ca74d6bc39f033b1fae3fc686bcedccd867e1c Mon Sep 17 00:00:00 2001
From: John Zedlewski <jzedlewski@nvidia.com>
Date: Mon, 10 Aug 2026 22:12:26 +0000
Subject: [PATCH 3/3] Fix cast tests header comment

---
 cpp/tests/unary/cast_tests.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cpp/tests/unary/cast_tests.cpp b/cpp/tests/unary/cast_tests.cpp
index fad01dee272d..1fa8a825670d 100644
--- a/cpp/tests/unary/cast_tests.cpp
+++ b/cpp/tests/unary/cast_tests.cpp
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: Copyright (c) 2020-2026, NVIDIA CORPORATION.
+ * SPDX-FileCopyrightText: Copyright (c) 2020-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
  * SPDX-License-Identifier: Apache-2.0
  */