Add initial prototype for the GN meta-buildsystem.

tools/gn/parse_tree.h

Index: tools/gn/parse_tree.h
diff --git a/tools/gn/parse_tree.h b/tools/gn/parse_tree.h
new file mode 100644
index 0000000000000000000000000000000000000000..09646e51ac4c4b2366ef1b549f1f3ef304819d2c
--- /dev/null
+++ b/tools/gn/parse_tree.h
@@ -0,0 +1,366 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TOOLS_GN_PARSE_TREE_H_
+#define TOOLS_GN_PARSE_TREE_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
+#include "tools/gn/err.h"
+#include "tools/gn/token.h"
+#include "tools/gn/value.h"
+
+class AccessorNode;
+class BinaryOpNode;
+class BlockNode;
+class ConditionNode;
+class FunctionCallNode;
+class IdentifierNode;
+class ListNode;
+class LiteralNode;
+class Scope;
+class UnaryOpNode;
+
+// ParseNode -------------------------------------------------------------------
+
+// A node in the AST.
+class ParseNode {
+ public:
+  ParseNode();
+  virtual ~ParseNode();
+
+  virtual const AccessorNode* AsAccessor() const;
+  virtual const BinaryOpNode* AsBinaryOp() const;
+  virtual const BlockNode* AsBlock() const;
+  virtual const ConditionNode* AsConditionNode() const;
+  virtual const FunctionCallNode* AsFunctionCall() const;
+  virtual const IdentifierNode* AsIdentifier() const;
+  virtual const ListNode* AsList() const;
+  virtual const LiteralNode* AsLiteral() const;
+  virtual const UnaryOpNode* AsUnaryOp() const;
+
+  virtual Value Execute(Scope* scope, Err* err) const = 0;
+
+  virtual LocationRange GetRange() const = 0;
+
+  // Returns an error with the given messages and the range set to something
+  // that indicates this node.
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const = 0;
+
+  // Prints a representation of this node to the given string, indenting
+  // by the given number of spaces.
+  virtual void Print(std::ostream& out, int indent) const = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ParseNode);
+};
+
+// AccessorNode ----------------------------------------------------------------
+
+// Access an array element.
+//
+// If we need to add support for member variables like "variable.len" I was
+// thinking this would also handle that case.
+class AccessorNode : public ParseNode {
+ public:
+  AccessorNode();
+  virtual ~AccessorNode();
+
+  virtual const AccessorNode* AsAccessor() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  // Base is the thing on the left of the [], currently always required to be
+  // an identifier token.
+  const Token& base() const { return base_; }
+  void set_base(const Token& b) { base_ = b; }
+
+  // Index is the expression inside the [].
+  const ParseNode* index() const { return index_.get(); }
+  void set_index(scoped_ptr<ParseNode> i) { index_ = i.Pass(); }
+
+ private:
+  Token base_;
+  scoped_ptr<ParseNode> index_;
+
+  DISALLOW_COPY_AND_ASSIGN(AccessorNode);
+};
+
+// BinaryOpNode ----------------------------------------------------------------
+
+class BinaryOpNode : public ParseNode {
+ public:
+  BinaryOpNode();
+  virtual ~BinaryOpNode();
+
+  virtual const BinaryOpNode* AsBinaryOp() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  const Token& op() const { return op_; }
+  void set_op(const Token& t) { op_ = t; }
+
+  const ParseNode* left() const { return left_.get(); }
+  void set_left(scoped_ptr<ParseNode> left) {
+    left_ = left.Pass();
+  }
+
+  const ParseNode* right() const { return right_.get(); }
+  void set_right(scoped_ptr<ParseNode> right) {
+    right_ = right.Pass();
+  }
+
+ private:
+  scoped_ptr<ParseNode> left_;
+  Token op_;
+  scoped_ptr<ParseNode> right_;
+
+  DISALLOW_COPY_AND_ASSIGN(BinaryOpNode);
+};
+
+// BlockNode -------------------------------------------------------------------
+
+class BlockNode : public ParseNode {
+ public:
+  // Set has_scope if this block introduces a nested scope.
+  BlockNode(bool has_scope);
+  virtual ~BlockNode();
+
+  virtual const BlockNode* AsBlock() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  void set_begin_token(const Token* t) { begin_token_ = t; }
+  void set_end_token(const Token* t) { end_token_ = t; }
+
+  const std::vector<ParseNode*>& statements() const { return statements_; }
+  void append_statement(scoped_ptr<ParseNode> s) {
+    statements_.push_back(s.release());
+  }
+
+  // Doesn't create a nested scope.
+  Value ExecuteBlockInScope(Scope* our_scope, Err* err) const;
+
+ private:
+  bool has_scope_;
+
+  // Tokens corresponding to { and }, if any (may be NULL).
+  const Token* begin_token_;
+  const Token* end_token_;
+
+  // Owning pointers, use unique_ptr when we can use C++11.
+  std::vector<ParseNode*> statements_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlockNode);
+};
+
+// ConditionNode ---------------------------------------------------------------
+
+class ConditionNode : public ParseNode {
+ public:
+  ConditionNode();
+  virtual ~ConditionNode();
+
+  virtual const ConditionNode* AsConditionNode() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  void set_if_token(const Token& token) { if_token_ = token; }
+
+  const ParseNode* condition() const { return condition_.get(); }
+  void set_condition(scoped_ptr<ParseNode> c) {
+    condition_ = c.Pass();
+  }
+
+  const BlockNode* if_true() const { return if_true_.get(); }
+  void set_if_true(scoped_ptr<BlockNode> t) {
+    if_true_ = t.Pass();
+  }
+
+  // This is either empty, a block (for the else clause), or another
+  // condition.
+  const ParseNode* if_false() const { return if_false_.get(); }
+  void set_if_false(scoped_ptr<ParseNode> f) {
+    if_false_ = f.Pass();
+  }
+
+ private:
+  // Token corresponding to the "if" string.
+  Token if_token_;
+
+  scoped_ptr<ParseNode> condition_;  // Always non-null.
+  scoped_ptr<BlockNode> if_true_;  // Always non-null.
+  scoped_ptr<ParseNode> if_false_;  // May be null.
+
+  DISALLOW_COPY_AND_ASSIGN(ConditionNode);
+};
+
+// FunctionCallNode ------------------------------------------------------------
+
+class FunctionCallNode : public ParseNode {
+ public:
+  FunctionCallNode();
+  virtual ~FunctionCallNode();
+
+  virtual const FunctionCallNode* AsFunctionCall() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  const Token& function() const { return function_; }
+  void set_function(Token t) { function_ = t; }
+
+  const ListNode* args() const { return args_.get(); }
+  void set_args(scoped_ptr<ListNode> a) { args_ = a.Pass(); }
+
+  const BlockNode* block() const { return block_.get(); }
+  void set_block(scoped_ptr<BlockNode> b) { block_ = b.Pass(); }
+
+ private:
+  Token function_;
+  scoped_ptr<ListNode> args_;
+  scoped_ptr<BlockNode> block_;  // May be null.
+
+  DISALLOW_COPY_AND_ASSIGN(FunctionCallNode);
+};
+
+// IdentifierNode --------------------------------------------------------------
+
+class IdentifierNode : public ParseNode {
+ public:
+  IdentifierNode();
+  IdentifierNode(const Token& token);
+  virtual ~IdentifierNode();
+
+  virtual const IdentifierNode* AsIdentifier() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  const Token& value() const { return value_; }
+  void set_value(const Token& t) { value_ = t; }
+
+ private:
+  Token value_;
+
+  DISALLOW_COPY_AND_ASSIGN(IdentifierNode);
+};
+
+// ListNode --------------------------------------------------------------------
+
+class ListNode : public ParseNode {
+ public:
+  ListNode();
+  virtual ~ListNode();
+
+  virtual const ListNode* AsList() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  void set_begin_token(const Token& t) { begin_token_ = t; }
+  void set_end_token(const Token& t) { end_token_ = t; }
+
+  void append_item(scoped_ptr<ParseNode> s) {
+    contents_.push_back(s.release());
+  }
+  const std::vector<ParseNode*>& contents() const { return contents_; }
+
+ private:
+  // Tokens corresponding to the [ and ].
+  Token begin_token_;
+  Token end_token_;
+
+  // Owning pointers, use unique_ptr when we can use C++11.
+  std::vector<ParseNode*> contents_;
+
+  DISALLOW_COPY_AND_ASSIGN(ListNode);
+};
+
+// LiteralNode -----------------------------------------------------------------
+
+class LiteralNode : public ParseNode {
+ public:
+  LiteralNode();
+  LiteralNode(const Token& token);
+  virtual ~LiteralNode();
+
+  virtual const LiteralNode* AsLiteral() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  const Token& value() const { return value_; }
+  void set_value(const Token& t) { value_ = t; }
+
+ private:
+  Token value_;
+
+  DISALLOW_COPY_AND_ASSIGN(LiteralNode);
+};
+
+// UnaryOpNode -----------------------------------------------------------------
+
+class UnaryOpNode : public ParseNode {
+ public:
+  UnaryOpNode();
+  virtual ~UnaryOpNode();
+
+  virtual const UnaryOpNode* AsUnaryOp() const OVERRIDE;
+  virtual Value Execute(Scope* scope, Err* err) const OVERRIDE;
+  virtual LocationRange GetRange() const OVERRIDE;
+  virtual Err MakeErrorDescribing(
+      const std::string& msg,
+      const std::string& help = std::string()) const OVERRIDE;
+  virtual void Print(std::ostream& out, int indent) const OVERRIDE;
+
+  const Token& op() const { return op_; }
+  void set_op(const Token& t) { op_ = t; }
+
+  const ParseNode* operand() const { return operand_.get(); }
+  void set_operand(scoped_ptr<ParseNode> operand) {
+    operand_ = operand.Pass();
+  }
+
+ private:
+  Token op_;
+  scoped_ptr<ParseNode> operand_;
+
+  DISALLOW_COPY_AND_ASSIGN(UnaryOpNode);
+};
+
+#endif  // TOOLS_GN_PARSE_TREE_H_