From d930c65e7fef6414af363e1f8d4fff52beb448af Mon Sep 17 00:00:00 2001
From: Yong He <yonghe@outlook.com>
Date: Mon, 5 Oct 2020 10:30:27 -0700
Subject: Update the type of a call inst during specialization. (#1569)

---
 source/slang/slang-ir-specialize.cpp               |  6 +++
 tests/compute/interface-assoc-type-param.slang     | 60 ++++++++++++++++++++++
 .../interface-assoc-type-param.slang.expected.txt  |  4 ++
 3 files changed, 70 insertions(+)
 create mode 100644 tests/compute/interface-assoc-type-param.slang
 create mode 100644 tests/compute/interface-assoc-type-param.slang.expected.txt

diff --git a/source/slang/slang-ir-specialize.cpp b/source/slang/slang-ir-specialize.cpp
index ceba4b03c..caaa700a0 100644
--- a/source/slang/slang-ir-specialize.cpp
+++ b/source/slang/slang-ir-specialize.cpp
@@ -901,6 +901,12 @@ struct SpecializationContext
         if(!calleeFunc)
             return;
 
+        // Update result type since the callee may have been changed.
+        if (inst->getDataType() != calleeFunc->getResultType())
+        {
+            inst->setFullType(calleeFunc->getResultType());
+        }
+
         // We can only specialize if we have access to a body for the callee.
         //
         if(!calleeFunc->isDefinition())
diff --git a/tests/compute/interface-assoc-type-param.slang b/tests/compute/interface-assoc-type-param.slang
new file mode 100644
index 000000000..d43a43fc9
--- /dev/null
+++ b/tests/compute/interface-assoc-type-param.slang
@@ -0,0 +1,60 @@
+// Tests using associated types through an existential-struct-typed param.
+
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -cuda
+//TEST(compute):COMPARE_COMPUTE_EX:-slang -compute -cpu
+
+[anyValueSize(8)]
+interface IInterface
+{
+    associatedtype TEval:IEval;
+    TEval getEval();
+}
+
+[anyValueSize(8)]
+interface IEval
+{
+    uint eval();
+}
+
+struct Impl : IInterface
+{
+    uint val;
+    struct TEval : IEval
+    {
+        uint val;
+        uint eval()
+        {
+            return val;
+        }
+    };
+    TEval getEval()
+    {
+        TEval rs;
+        rs.val = val;
+        return rs;
+    }
+};
+
+struct Params
+{
+    StructuredBuffer<IInterface> obj;
+};
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=gOutputBuffer
+RWStructuredBuffer<uint> gOutputBuffer;
+
+void compute(uint tid, Params p)
+{
+    gOutputBuffer[tid] = p.obj[0].getEval().eval();
+}
+
+//TEST_INPUT: entryPointExistentialType Impl
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID,
+//TEST_INPUT:ubuffer(data=[0 0 0 0 1 0], stride=4):name=params.obj
+    uniform Params params)
+{
+	uint tid = dispatchThreadID.x;
+	compute(tid, params);
+}
\ No newline at end of file
diff --git a/tests/compute/interface-assoc-type-param.slang.expected.txt b/tests/compute/interface-assoc-type-param.slang.expected.txt
new file mode 100644
index 000000000..98fb6a686
--- /dev/null
+++ b/tests/compute/interface-assoc-type-param.slang.expected.txt
@@ -0,0 +1,4 @@
+1
+1
+1
+1
-- 
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