[WGSL] Function parameters have incorrect scope

https://bugs.webkit.org/show_bug.cgi?id=274602
rdar://128625182

Reviewed by Mike Wyrzykowski.

The parameters were being placed in a separate scope from the function local variables,
allowing a local variable to shadow a parameter, which shouldn't be valid according to
the spec.

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

Canonical link: https://commits.webkit.org/279262@main

Source/WebGPU/WGSL/TypeCheck.cpp

@@ -722,7 +722,7 @@ void TypeChecker::visit(AST::Function& function)
         ContextScope functionContext(this);
         for (unsigned i = 0; i < parameters.size(); ++i)
             introduceValue(function.parameters()[i].name(), parameters[i]);
-        Base::visit(function.body());
+        AST::Visitor::visit(function.body());
 
         auto behaviors = analyze(function.body());
         if (behaviors.contains(Behavior::Next) && function.maybeReturnType())

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

@@ -0,0 +1,7 @@
+// RUN: %not %wgslc | %check
+
+fn testParameterScope(x: f32) -> i32
+{
+    // CHECK-L: redeclaration of 'x'
+    let x: i32 = 1;
+}