Fix a bug on default initialization of interface typed value. (#4249)

* Fix a bug on default initialization of interface typed value.

* Fix.

source/slang/slang-lower-to-ir.cpp

@@ -4413,6 +4413,10 @@ struct ExprLoweringVisitorBase : public ExprVisitor<Derived, LoweredValInfo>
  {
  return LoweredValInfo::simple(getBuilder()->getIntValue(irType, 0));
  }
+ else if (declRef.as<InterfaceDecl>())
+ {
+ return LoweredValInfo::simple(getBuilder()->emitDefaultConstruct(irType));
+ }
  else if (auto aggTypeDeclRef = declRef.as<AggTypeDecl>())
  {
  List<IRInst*> args;

tests/language-feature/interfaces/zero-init-interface.slang

@@ -0,0 +1,32 @@
+// Test that we can zero-init a struct with interface typed member.
+
+//TEST(compute):COMPARE_COMPUTE(filecheck-buffer=BUFFER): -shaderobj
+
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):out,name=outputBuffer
+RWStructuredBuffer<int> outputBuffer;
+
+interface IFoo
+{
+ int method();
+}
+
+//TEST_INPUT: type_conformance Impl1:IFoo = 0
+struct Impl1 : IFoo
+{
+ int data;
+ int method() { return data + 1; }
+}
+
+struct MyType
+{
+ IFoo foo;
+}
+
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+ MyType t = {};
+ // BUFFER: 1
+ outputBuffer[0] = t.foo.method();
+}