[WGSL] Add typing for indexed access on vectors

https://bugs.webkit.org/show_bug.cgi?id=255598
rdar://108197306

Reviewed by Myles C. Maxfield.

So far we only supported field access on vectors (e.g. vec2.x) but not indexed
access (e.g. vec2[0]). This extends the typing to add support for that. Just
like our current support for indexed access on arrays, we still don't validate
if the access is out-of-bounds when the index is a constant.

* Source/WebGPU/WGSL/TypeCheck.cpp:
(WGSL::TypeChecker::visit):
* Source/WebGPU/WGSL/tests/invalid/vector.wgsl: Added.

Canonical link: https://commits.webkit.org/263122@main

Source/WebGPU/WGSL/TypeCheck.cpp

@@ -302,7 +302,7 @@ void TypeChecker::visit(AST::IndexAccessExpression& access)
         return;
     }
 
-    if (!unify(index, m_types.i32Type()) && !unify(index, m_types.u32Type()) && !unify(index, m_types.abstractIntType())) {
+    if (!unify(m_types.i32Type(), index) && !unify(m_types.u32Type(), index) && !unify(m_types.abstractIntType(), index)) {
         typeError(access.span(), "index must be of type 'i32' or 'u32', found: '", *index, "'");
         return;
     }
@@ -314,6 +314,13 @@ void TypeChecker::visit(AST::IndexAccessExpression& access)
         return;
     }
 
+    if (std::holds_alternative<Types::Vector>(*base)) {
+        // FIXME: check bounds if index is constant
+        auto& vector = std::get<Types::Vector>(*base);
+        inferred(vector.element);
+        return;
+    }
+
     // FIXME: Implement reference and matrix accesses
     typeError(access.span(), "cannot index type '", *base, "'");
 }

Source/WebGPU/WGSL/tests/invalid/vector.wgsl

@@ -0,0 +1,4 @@
+fn testIndexAccess() {
+  // CHECK-L: index must be of type 'i32' or 'u32', found: 'f32'
+  let x1 = vec2(0)[1f];
+}