Fix crash when using wrong type for inout parameter with WGSL target (#7588)

* Initial plan

* Fix crash in WGSL L-value cast lowering with type mismatches

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

* Apply formatting to fix

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

* Update test to verify successful compilation instead of error checking

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>
Co-authored-by: Yong He <yonghe@outlook.com>

2 files changed, 40 insertions, 2 deletions

diff --git a/source/slang/slang-ir-lower-l-value-cast.cpp b/source/slang/slang-ir-lower-l-value-cast.cpp
index 3d3c15132..058589862 100644
--- a/source/slang/slang-ir-lower-l-value-cast.cpp
+++ b/source/slang/slang-ir-lower-l-value-cast.cpp
@@ -175,8 +175,17 @@ struct LValueCastLoweringContext
 
         IRBuilder builder(m_module);
 
-        IRType* toValueType = as<IRPtrType>(toType)->getValueType();
-        IRType* fromValueType = as<IRPtrType>(fromType)->getValueType();
+        auto toPtrType = as<IRPtrTypeBase>(toType);
+        auto fromPtrType = as<IRPtrTypeBase>(fromType);
+
+        if (!toPtrType || !fromPtrType)
+        {
+            // If either type is not a pointer type, we cannot process this L-value cast
+            return;
+        }
+
+        IRType* toValueType = toPtrType->getValueType();
+        IRType* fromValueType = fromPtrType->getValueType();
 
         for (auto useSite : useSites)
         {
diff --git a/tests/wgsl/inout-type-mismatch.slang b/tests/wgsl/inout-type-mismatch.slang
new file mode 100644
index 000000000..939727ba8
--- /dev/null
+++ b/tests/wgsl/inout-type-mismatch.slang
@@ -0,0 +1,29 @@
+//TEST:SIMPLE(filecheck=CHECK): -target wgsl -entry main -stage compute
+
+// Test for issue #7362: Crash when using wrong type for inout parameter with WGSL target
+// This test verifies that the shader compiles successfully without crashing.
+// The fix changed IRPtrType to IRPtrTypeBase in slang-ir-lower-l-value-cast.cpp
+// to handle implicit l-value casts properly.
+
+void B(inout uint param)
+{
+    param = param + 10;
+}
+
+void A(inout int param)
+{
+    // This should work with implicit l-value cast from int to uint
+    // Previously this would cause a segfault due to null pointer dereference
+    B(param);
+}
+
+[numthreads(1, 1, 1)]
+void main(uint3 DTid : SV_DispatchThreadID)
+{
+    int param = 5;
+    A(param);
+}
+
+// The test passes if compilation succeeds and generates valid WGSL
+// CHECK: @compute
+// CHECK: fn main
\ No newline at end of file