Lookup refactor (#8467)

Close #8201.

This PR unify the lowering logic for LookupDeclRef of an interface
requirement. We will always lower this AST node to a
LookupWitness IR. The key of this IR is the special witnessTableType
`ThisTypeWitness`, this witness Table is simply a wrapper for an
interface type. Our current specialization pass doesn't handle this kind
of LookupWitness IR at all, so we will also add the specialization of
this_type IR as well.

1 files changed, 42 insertions, 0 deletions

diff --git a/tests/autodiff/differential-ptr-pair-with-associate-type.slang b/tests/autodiff/differential-ptr-pair-with-associate-type.slang
new file mode 100644
index 000000000..870660b84
--- /dev/null
+++ b/tests/autodiff/differential-ptr-pair-with-associate-type.slang
@@ -0,0 +1,42 @@
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHECK):-vk -compute -shaderobj -output-using-type
+//TEST(compute):COMPARE_COMPUTE_EX(filecheck-buffer=CHECK):-cuda -compute -shaderobj -output-using-type
+interface IFoo<T>
+{
+    associatedtype Parameters : IDifferentiablePtrType;
+    property DifferentialPtrPair<Parameters> parametersDual { get; }
+}
+
+extension<T: __BuiltinFloatingPointType> T: IDifferentiablePtrType
+{
+    typealias Differential = T;
+}
+
+struct Foo<T:__BuiltinFloatingPointType> : IFoo<T>
+{
+    typealias Parameters = Array<T, 1>;
+    property DifferentialPtrPair<Parameters> parametersDual
+    {
+        get
+        {
+            Parameters primal = {T(1)};
+            Parameters diff   = {T(2)};
+            return DifferentialPtrPair<Parameters>(primal, diff);
+        }
+    }
+}
+
+//TEST_INPUT:ubuffer(data=[0 0], stride=4):out,name=output
+RWStructuredBuffer<float> output;
+
+[shader("compute")]
+[numthreads(1, 1, 1)]
+void computeMain()
+{
+    Foo<float> foo;
+    let res = foo.parametersDual;
+    output[0] = res.p[0];
+    output[1] = res.d[0];
+
+    // CHECK: 1.0
+    // CHECK: 2.0
+}