ProgramBuilder: Fixup last few uses of sem::Type*

With typ::Type.

Involves decoupling the use of named types as sub-types of other types,
otherwise ty.array("x", Structure(...)) produces an AST tree with
duplicated AST nodes.

Bug: tint:724
Change-Id: I2b4e904dc23bb554a75d4612f6543f1911f469bd
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/48693
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>

src/ast/type_name.cc

@@ -0,0 +1,47 @@
+// Copyright 2021 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "src/ast/type_name.h"
+
+#include "src/program_builder.h"
+
+TINT_INSTANTIATE_TYPEINFO(tint::ast::TypeName);
+
+namespace tint {
+namespace ast {
+
+TypeName::TypeName(ProgramID program_id, const Source& source, Symbol name)
+    : Base(program_id, source),
+      name_(name),
+      type_name_("__type_name_" + name.to_str()) {}
+
+TypeName::~TypeName() = default;
+
+TypeName::TypeName(TypeName&&) = default;
+
+std::string TypeName::type_name() const {
+  return type_name_;
+}
+
+std::string TypeName::FriendlyName(const SymbolTable& symbols) const {
+  return symbols.NameFor(name_);
+}
+
+TypeName* TypeName::Clone(CloneContext* ctx) const {
+  auto src = ctx->Clone(source());
+  return ctx->dst->create<TypeName>(src, name_);
+}
+
+}  // namespace ast
+}  // namespace tint

src/ast/type_name.h

@@ -0,0 +1,62 @@
+// Copyright 2021 The Tint Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef SRC_AST_TYPE_NAME_H_
+#define SRC_AST_TYPE_NAME_H_
+
+#include <string>
+
+#include "src/ast/type.h"
+
+namespace tint {
+namespace ast {
+
+/// A named type (i.e. struct or alias)
+class TypeName : public Castable<TypeName, Type> {
+ public:
+  /// Constructor
+  /// @param program_id the identifier of the program that owns this node
+  /// @param source the source of this node
+  /// @param name the type name
+  TypeName(ProgramID program_id, const Source& source, Symbol name);
+  /// Move constructor
+  TypeName(TypeName&&);
+  /// Destructor
+  ~TypeName() override;
+
+  /// @return the type name
+  const Symbol& name() const { return name_; }
+
+  /// @returns the name for th type
+  std::string type_name() const override;
+
+  /// @param symbols the program's symbol table
+  /// @returns the name for this type that closely resembles how it would be
+  /// declared in WGSL.
+  std::string FriendlyName(const SymbolTable& symbols) const override;
+
+  /// Clones this type and all transitive types using the `CloneContext` `ctx`.
+  /// @param ctx the clone context
+  /// @return the newly cloned type
+  TypeName* Clone(CloneContext* ctx) const override;
+
+ private:
+  Symbol name_;
+  std::string const type_name_;
+};
+
+}  // namespace ast
+}  // namespace tint
+
+#endif  // SRC_AST_TYPE_NAME_H_