Resolver: Track storage class usages of structures

This will be used to validate layout rules, as well as preventing
illegal types from being used in a uniform / storage buffer.

Also: Cleanup logic around VariableDeclStatement
This was spread across 3 places, entirely unnecessarily.

Bug: tint:643
Change-Id: I9d309c3a5dfb5676984f49ce51763a97bcac93bb
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/45125
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>
Reviewed-by: David Neto <dneto@google.com>

src/semantic/sem_struct.cc

@@ -24,12 +24,14 @@ Struct::Struct(type::Struct* type,
                StructMemberList members,
                uint32_t align,
                uint32_t size,
-               uint32_t size_no_padding)
+               uint32_t size_no_padding,
+               std::unordered_set<ast::StorageClass> storage_class_usage)
     : type_(type),
       members_(std::move(members)),
       align_(align),
       size_(size),
-      size_no_padding_(size_no_padding) {}
+      size_no_padding_(size_no_padding),
+      storage_class_usage_(std::move(storage_class_usage)) {}
 
 Struct::~Struct() = default;
 

src/semantic/struct.h

@@ -17,8 +17,10 @@
 
 #include <stdint.h>
 
+#include <unordered_set>
 #include <vector>
 
+#include "src/ast/storage_class.h"
 #include "src/semantic/node.h"
 
 namespace tint {
@@ -48,11 +50,13 @@ class Struct : public Castable<Struct, Node> {
   /// @param size the byte size of the structure
   /// @param size_no_padding size of the members without the end of structure
   /// alignment padding
+  /// @param storage_class_usage a set of all the storage class usages
   Struct(type::Struct* type,
          StructMemberList members,
          uint32_t align,
          uint32_t size,
-         uint32_t size_no_padding);
+         uint32_t size_no_padding,
+         std::unordered_set<ast::StorageClass> storage_class_usage);
 
   /// Destructor
   ~Struct() override;
@@ -79,12 +83,24 @@ class Struct : public Castable<Struct, Node> {
   /// alignment padding
   uint32_t SizeNoPadding() const { return size_no_padding_; }
 
+  /// @returns the set of storage class uses of this structure
+  const std::unordered_set<ast::StorageClass>& StorageClassUsage() const {
+    return storage_class_usage_;
+  }
+
+  /// @param usage the ast::StorageClass usage type to query
+  /// @returns true iff this structure has been used as the given storage class
+  bool UsedAs(ast::StorageClass usage) const {
+    return storage_class_usage_.count(usage) > 0;
+  }
+
  private:
   type::Struct* const type_;
   StructMemberList const members_;
   uint32_t const align_;
   uint32_t const size_;
   uint32_t const size_no_padding_;
+  std::unordered_set<ast::StorageClass> const storage_class_usage_;
 };
 
 /// StructMember holds the semantic information for structure members.