Add more diagnostics on invalid custom derivative use. (#3309)

* Add more diagnostics on invalid custom derivative use.

* cleanup.

---------

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

1 files changed, 32 insertions, 0 deletions

diff --git a/tests/autodiff/custom-derivative-generic.slang b/tests/autodiff/custom-derivative-generic.slang
new file mode 100644
index 000000000..4ecde65cf
--- /dev/null
+++ b/tests/autodiff/custom-derivative-generic.slang
@@ -0,0 +1,32 @@
+//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
+
+struct Buggy<let N : int>
+{
+    float m(float x) { return N * x; }
+
+    [BackwardDerivativeOf(m)]
+    void mDiff(inout DifferentialPair<float> x, float dResult)
+    {
+        updateDiff(x, N * dResult);
+    }
+}
+
+[Differentiable]
+float test(float x)
+{
+    Buggy<2> b;
+    return b.m(x);
+}
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<float> outputBuffer;
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    var a = diffPair(3.0);
+    __bwd_diff(test)(a, 1.0);
+    outputBuffer[dispatchThreadID.x] = a.d;
+    // CHECK: 2.0
+}