2 files changed, 54 insertions, 0 deletions
diff --git a/tests/language-feature/extensions/interface-extension.slang b/tests/language-feature/extensions/interface-extension.slang
new file mode 100644
index 000000000..824aa3450
--- /dev/null
+++ b/tests/language-feature/extensions/interface-extension.slang
@@ -0,0 +1,50 @@
+// interface-extension.slang
+
+// Test that an `extension` applied to an interface type works as users expect
+
+//TEST(compute):COMPARE_COMPUTE:
+
+interface ICounter
+{
+	[mutating] void add(int value);
+}
+
+struct MyCounter : ICounter
+{
+	int _state = 0;
+
+	[mutating] void add(int value) { _state += value; }
+}
+
+extension ICounter
+{
+	[mutating] void increment()
+	{
+	    this.add(1);
+	}
+}
+
+void helper<T : ICounter>(in out T counter)
+{
+	counter.increment();
+}
+
+int test(int value)
+{
+	MyCounter counter = { value };
+	counter.increment();
+	helper(counter);
+	return counter._state;
+}
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    uint tid = dispatchThreadID.x;
+    int inVal = tid;
+    int outVal = test(inVal);
+    outputBuffer[tid] = outVal;
+}
diff --git a/tests/language-feature/extensions/interface-extension.slang.expected.txt b/tests/language-feature/extensions/interface-extension.slang.expected.txt
new file mode 100644
index 000000000..f8affbc14
--- /dev/null
+++ b/tests/language-feature/extensions/interface-extension.slang.expected.txt
@@ -0,0 +1,4 @@
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+3
+4
+5