Fix ICE when lowering an associatedtype declref from an derived interface. (#3312)

* Fix ICE when lowering an associatedtype declref from an derived interface.

* Fixes.

* Fix test.

* Fix GLSL/SPIRV image subscript swizzle store regression.

* Fix.

---------

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 55 insertions, 0 deletions

diff --git a/tests/autodiff/derived-interface.slang b/tests/autodiff/derived-interface.slang
new file mode 100644
index 000000000..68e84ebad
--- /dev/null
+++ b/tests/autodiff/derived-interface.slang
@@ -0,0 +1,55 @@
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHECK):-slang -compute -shaderobj -output-using-type
+//TEST(compute, vulkan):COMPARE_COMPUTE_EX(filecheck-buffer=CHECK):-vk -compute -shaderobj -output-using-type
+
+//TEST_INPUT:ubuffer(data=[0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+interface IFoo : IDifferentiable
+{
+    [Differentiable]
+    __init<T:IFoo>(T d); 
+    
+    [Differentiable]
+    static This create(Differential d);
+
+    [Differentiable]
+    float getVal();
+}
+
+struct Impl : IFoo
+{
+    float x;
+    [Differentiable]
+    __init<T : IFoo>(T d)
+    {
+        this = (Impl)d;
+    }
+    
+    [Differentiable]
+    static This create(Differential d)
+    {
+        This v;
+        v.x = d.x * d.x;
+        return v;
+    }
+
+    [Differentiable]
+    float getVal() { return x; }
+}
+
+[Differentiable]
+float test<T:IFoo>(T.Differential d)
+{
+    return T.create(d).getVal();
+}
+
+[numthreads(1,1,1)]
+void computeMain(uint threadId: SV_DispatchThreadID)
+{
+    Impl.Differential d;
+    d.x = 3.0;
+    Impl.Differential dd;
+    dd.x = 1.0;
+    outputBuffer[0] = fwd_diff(test<Impl>)(diffPair(d, dd)).d;
+    // CHECK: 6.0
+}