[WGSL] Packed struct should not assume every nested struct is also pa…

…cked

https://bugs.webkit.org/show_bug.cgi?id=264429
rdar://118129804

Reviewed by Mike Wyrzykowski.

A struct `S` might contain a field `x` whose type is another struct `T`. Currently,
if we pack `S`, during code generation we'll emit the type of `x` as `T::Packed`,
i.e. we just assume that all the structs referenced by `S` will also be packed.
Instead, we need to check before emitting code whether `T` was packed or not.

* Source/WebGPU/WGSL/Metal/MetalFunctionWriter.cpp:
(WGSL::Metal::FunctionDefinitionWriter::visit):
* Source/WebGPU/WGSL/tests/valid/packing.wgsl:

Canonical link: https://commits.webkit.org/270438@main

Source/WebGPU/WGSL/Metal/MetalFunctionWriter.cpp

@@ -764,7 +764,7 @@ void FunctionDefinitionWriter::visit(const Type* type)
         },
         [&](const Struct& structure) {
             m_stringBuilder.append(structure.structure.name());
-            if (m_structRole.has_value() && *m_structRole == AST::StructureRole::PackedResource)
+            if (m_structRole.has_value() && *m_structRole == AST::StructureRole::PackedResource && structure.structure.role() == AST::StructureRole::UserDefinedResource)
                 m_stringBuilder.append("::PackedType");
         },
         [&](const PrimitiveStruct& structure) {

Source/WebGPU/WGSL/tests/valid/packing.wgsl

@@ -1,6 +1,10 @@
 // RUN: %metal-compile main
 // RUN: %metal main 2>&1 | %check
 
+struct Unpacked {
+  x: i32,
+}
+
 struct T {
     v2f: vec2<f32>,
     v3f: vec3<f32>,
@@ -10,6 +14,7 @@ struct T {
     v4u: vec4<u32>,
     f: f32,
     u: u32,
+    unpacked: Unpacked,
 }
 
 struct U {