libSyntax: add a C++ side read-only syntax visitor to facilitate verification. NFC (#13882)

Author: nkcsgexi

include/swift/Syntax/CMakeLists.txt

@@ -5,7 +5,8 @@ set(generated_include_sources
     SyntaxKind.h.gyb
     SyntaxNodes.h.gyb
     SyntaxBuilders.h.gyb
-    SyntaxFactory.h.gyb)
+    SyntaxFactory.h.gyb
+    SyntaxVisitor.h.gyb)
 
 add_gyb_target(swift-syntax-generated-headers
     "${generated_include_sources}")

include/swift/Syntax/Syntax.h

@@ -37,6 +37,8 @@ class SyntaxASTMap;
 
 namespace syntax {
 
+struct SyntaxVisitor;
+
 template <typename SyntaxNode>
 SyntaxNode make(RC<RawSyntax> Raw) {
   auto Data = SyntaxData::make(Raw);
@@ -172,6 +174,10 @@ class Syntax {
     // Trivially true.
     return true;
   }
+
+  /// Recursively visit this node.
+  void accept(SyntaxVisitor &Visitor);
+
   // TODO: hasSameStructureAs ?
 };
 

include/swift/Syntax/SyntaxVisitor.h.gyb

@@ -0,0 +1,53 @@
+%{
+  # -*- mode: C++ -*-
+  from gyb_syntax_support import *
+  NODE_MAP = create_node_map()
+  # Ignore the following admonition; it applies to the resulting .h file only
+}%
+//// Automatically Generated From SyntaxVisitor.h.gyb.
+//// Do Not Edit Directly!
+//===---------------- SyntaxVisitor.h - SyntaxVisitor definitions ---------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_SYNTAX_VISITOR_H
+#define SWIFT_SYNTAX_VISITOR_H
+
+#include "swift/Syntax/Syntax.h"
+#include "swift/Syntax/SyntaxCollection.h"
+#include "swift/Syntax/TokenSyntax.h"
+#include "swift/Syntax/UnknownSyntax.h"
+#include "swift/Syntax/SyntaxNodes.h"
+
+namespace swift {
+namespace syntax {
+struct SyntaxVisitor {
+  virtual ~SyntaxVisitor() {}
+
+% for node in SYNTAX_NODES:
+%   if is_visitable(node):
+  virtual void visit(${node.name} node);
+%   end
+% end
+
+  virtual void visit(TokenSyntax token) {}
+
+  void visit(Syntax node);
+
+  void visitChildren(Syntax node) {
+    for (auto C: node.getRaw()->Layout)
+      visit(make<Syntax>(C));
+  }
+};
+}
+}
+
+#endif // SWIFT_SYNTAX_VISITOR_H

lib/Syntax/CMakeLists.txt

@@ -6,6 +6,7 @@ add_swift_library(swiftSyntax STATIC
   SyntaxBuilders.cpp.gyb
   SyntaxKind.cpp.gyb
   SyntaxFactory.cpp.gyb
+  SyntaxVisitor.cpp.gyb
   Trivia.cpp
   RawSyntax.cpp
   RawTokenSyntax.cpp

lib/Syntax/SyntaxVisitor.cpp.gyb

@@ -0,0 +1,45 @@
+%{
+  # -*- mode: C++ -*-
+  from gyb_syntax_support import *
+  NODE_MAP = create_node_map()
+  # Ignore the following admonition; it applies to the resulting .cpp file only
+}%
+//// Automatically Generated From SyntaxVisitor.cpp.gyb.
+//// Do Not Edit Directly!
+//===------------- SyntaxVisitor.cpp - Syntax Visitor definitions ---------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include "swift/Syntax/SyntaxVisitor.h"
+
+% for node in SYNTAX_NODES:
+%   if is_visitable(node):
+void swift::syntax::SyntaxVisitor::visit(${node.name} node) {
+  visitChildren(node);
+}
+%   end
+% end
+
+void swift::syntax::SyntaxVisitor::visit(Syntax node) {
+  switch (node.getKind()) {
+  case SyntaxKind::Token: visit(make<TokenSyntax>(node.getRaw())); return;
+% for node in SYNTAX_NODES:
+%   if is_visitable(node):
+  case SyntaxKind::${node.syntax_kind}: visit(make<${node.name}>(node.getRaw())); return;
+%   end
+% end
+  default: visitChildren(node); return;
+  }
+}
+
+void swift::syntax::Syntax::accept(SyntaxVisitor &visitor) {
+  visitor.visit(*this);
+}

tools/SwiftSyntax/SyntaxRewriter.swift.gyb

@@ -2,8 +2,6 @@
   from gyb_syntax_support import *
   # -*- mode: Swift -*-
   # Ignore the following admonition it applies to the resulting .swift file only
-  def is_visitable(node):
-    return not node.is_base() and not node.collection_element
 }%
 //// Automatically Generated From SyntaxFactory.swift.gyb.
 //// Do Not Edit Directly!

utils/gyb_syntax_support/__init__.py

@@ -97,3 +97,7 @@ def create_node_map():
     Creates a lookup table to find nodes by their kind.
     """
     return {node.syntax_kind: node for node in SYNTAX_NODES}
+
+
+def is_visitable(node):
+    return not node.is_base() and not node.collection_element