Fix issue of missing scope for 'Differential' type

source/slang/slang-check-expr.cpp

@@ -674,6 +674,9 @@ Expr* SemanticsVisitor::maybeUseSynthesizedDeclForLookupResult(
                 conformanceDecl->base.type = m_astBuilder->getDiffInterfaceType();
                 structDecl->addMember(conformanceDecl);
                 structDecl->parentDecl = parent;
+                structDecl->ownedScope = m_astBuilder->create<Scope>();
+                structDecl->ownedScope->containerDecl = structDecl;
+                structDecl->ownedScope->parent = getScope(parent);
 
                 synthesizedDecl = structDecl;
                 auto typeDef = m_astBuilder->create<TypeAliasDecl>();

tests/bugs/gh-6756.slang

@@ -0,0 +1,31 @@
+//TEST:SIMPLE(filecheck=CHECK):-target spirv -emit-spirv-via-glsl
+
+// This test is to test that PartlyDiffable.Differential is synthesized
+// with correct scope. If not, the constructor for it will be wrong, and
+// slang will generate wrong code, the downstream compiler will fail to
+// compile.
+
+// CHECK: OpEntryPoint Fragment
+
+struct PartlyDiffable : IDifferentiable
+{
+    int i;
+    float q;
+}
+
+
+func breaker(x:PartlyDiffable.Differential) {
+    return;
+}
+
+
+[shader("fragment")]
+float4 fragment(float4 in: SV_Position)
+    : SV_Target
+{
+    if (PartlyDiffable.Differential(0).q == 0) {
+        return float4(0);
+    } else {
+        return float4(1);
+    }
+}