From 6a23949f07f4eba38086b656e7073ce3bf8cd2fe Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Fri, 13 Jun 2025 22:13:00 -0700
Subject: Allow interface methods to have default implementations. (#7439)

---
 .../interfaces/default-method-differentiable.slang | 42 ++++++++++++++++++++++
 1 file changed, 42 insertions(+)
 create mode 100644 tests/language-feature/interfaces/default-method-differentiable.slang

(limited to 'tests/language-feature/interfaces/default-method-differentiable.slang')

diff --git a/tests/language-feature/interfaces/default-method-differentiable.slang b/tests/language-feature/interfaces/default-method-differentiable.slang
new file mode 100644
index 000000000..4cd5dc1ed
--- /dev/null
+++ b/tests/language-feature/interfaces/default-method-differentiable.slang
@@ -0,0 +1,42 @@
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=CHECK): -shaderobj -output-using-type
+
+// Test that a default interface method can be differentiable.
+
+interface IFoo<int v>
+{
+    [Differentiable]
+    float getVal(float x);
+
+    [Differentiable]
+    float getGreaterVal<int y>(float x)
+    {
+        return getVal(x) + y + v;
+    }
+}
+
+struct Impl : IFoo<2>
+{
+    [Differentiable]
+    float getVal(float x)
+    {
+        return x*x;
+    }
+    
+    // Using the default implementation for getGreaterVal.
+}
+
+[Differentiable]
+float test<int y, T:IFoo<y>>(T v, float x) { return v.getGreaterVal<1>(x); }
+
+//TEST_INPUT: set resultBuffer = out ubuffer(data=[0 0 0 0], stride=4)
+RWStructuredBuffer<float> resultBuffer;
+
+[numthreads(1,1,1)]
+void computeMain()
+{
+    Impl impl = {};
+    var dpx = diffPair(3.0);
+    bwd_diff(test)(impl, dpx, 1.0f);
+    resultBuffer[0] = dpx.d;
+    // CHECK: 6.0
+}
-- 
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