[libSyntax] Remove the C++ SyntaxClassifier

The recommended way forward is to use the SyntaxClassifier on the Swift
side.

By removing the C++ SyntaxClassifier, we can also eliminate the
-force-libsyntax-based-processing option that was used to bootstrap
incremental parsing and would generate the syntax map from a syntax
tree.

include/swift/Syntax/CMakeLists.txt

@@ -8,7 +8,6 @@ set(generated_include_sources
     SyntaxKind.h.gyb
     SyntaxNodes.h.gyb
     SyntaxBuilders.h.gyb
-    SyntaxClassifier.h.gyb
     SyntaxFactory.h.gyb
     SyntaxVisitor.h.gyb
     Trivia.h.gyb)

include/swift/Syntax/SyntaxClassifier.h.gyb

@@ -1,118 +0,0 @@
-%{
-  # -*- 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 SyntaxClassifier.h.gyb.
-//// Do Not Edit Directly!
-//===----------- SyntaxClassifier.h - SyntaxClassifier definitions --------===//
-//
-// This source file is part of the Swift.org open source project
-//
-// Copyright (c) 2014 - 2018 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_CLASSIFIER_H
-#define SWIFT_SYNTAX_CLASSIFIER_H
-
-#include "swift/Syntax/SyntaxVisitor.h"
-#include <stack>
-
-namespace swift {
-namespace syntax {
-
-
-/// A classification that determines which color a token should be colored in
-/// for syntax coloring.
-enum class SyntaxClassification {
-  None,
-  Keyword,
-  Identifier,
-  DollarIdentifier,
-  IntegerLiteral,
-  FloatingLiteral,
-  StringLiteral,
-  /// Marks the parens for a string interpolation.
-  StringInterpolationAnchor,
-  TypeIdentifier,
-  /// #if/#else/#endif occurrence.
-  BuildConfigKeyword,
-  /// An identifier in a #if condition.
-  BuildConfigId,
-  /// #-keywords like #warning, #sourceLocation
-  PoundDirectiveKeyword,
-  /// Any occurrence of '@<attribute-name>' anywhere.
-  Attribute,
-  /// An editor placeholder string <#like this#>.
-  EditorPlaceholder,
-  ObjectLiteral
-};
-
-
-class SyntaxClassifier: public SyntaxVisitor {
-  struct ContextStackEntry {
-    /// The classification all identifiers shall inherit
-    SyntaxClassification Classification;
-    /// If set to \c true, all tokens will be forced to receive the above
-    /// classification, overriding their context-free classification
-    bool ForceClassification;
-
-    ContextStackEntry(SyntaxClassification Classification,
-                      bool ForceClassification)
-      : Classification(Classification),
-        ForceClassification(ForceClassification) {}
-  };
-
-  std::map<SyntaxNodeId, SyntaxClassification> ClassifiedTokens;
-  /// The top classification of this stack determines the color of identifiers
-  std::stack<ContextStackEntry, llvm::SmallVector<ContextStackEntry, 16>> ContextStack;
-
-  template<typename T>
-  void visit(T Node, SyntaxClassification Classification,
-             bool ForceClassification) {
-    ContextStack.emplace(Classification, ForceClassification);
-    visit(Node);
-    ContextStack.pop();
-  }
-
-  template<typename T>
-  void visit(llvm::Optional<T> OptNode) {
-    if (OptNode.hasValue()) {
-      static_cast<SyntaxVisitor *>(this)->visit(OptNode.getValue());
-    }
-  }
-
-  virtual void visit(TokenSyntax TokenNode) override;
-
-  virtual void visit(Syntax Node) override {
-    SyntaxVisitor::visit(Node);
-  }
-
-% for node in SYNTAX_NODES:
-%   if is_visitable(node):
-  virtual void visit(${node.name} Node) override;
-%   end
-% end
-
-public:
-  std::map<SyntaxNodeId, SyntaxClassification> classify(Syntax Node) {
-    // Clean up the environment
-    ContextStack = std::stack<ContextStackEntry, llvm::SmallVector<ContextStackEntry, 16>>();
-    ContextStack.push({SyntaxClassification::None, false});
-    ClassifiedTokens.clear();
-
-    Node.accept(*this);
-
-    return ClassifiedTokens;
-  }
-};
-} // namespace syntax
-} // namespace swift
-
-#endif // SWIFT_SYNTAX_CLASSIFIER_H