Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/polymer_expressions/parser.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library polymer_expressions.parser;
+
+import 'tokenizer.dart';
+export 'tokenizer.dart' show ParseException;
+import 'expression.dart';
+
+const _UNARY_OPERATORS = const <String>['+', '-', '!'];
+const _BINARY_OPERATORS = const <String>['+', '-', '*', '/', '%', '^', '==',
+    '!=', '>', '<', '>=', '<=', '||', '&&', '&', '===', '!==', '|'];
+
+Expression parse(String expr) => new Parser(expr).parse();
+
+class Parser {
+  final AstFactory _astFactory;
+  final Tokenizer _tokenizer;
+  List<Token> _tokens;
+  Iterator _iterator;
+  Token get _token => _iterator.current;
+
+  Parser(String input, {AstFactory astFactory})
+      : _tokenizer = new Tokenizer(input),
+        _astFactory = (astFactory == null) ? new AstFactory() : astFactory;
+
+  Expression parse() {
+    _tokens = _tokenizer.tokenize();
+    _iterator = _tokens.iterator;
+    _advance();
+    return _parseExpression();
+  }
+
+  _advance([int kind, String value]) {
+    if ((kind != null && (_token == null || _token.kind != kind))
+        || (value != null && (_token == null || _token.value != value))) {
+      throw new ParseException("Expected kind $kind ($value): $_token");
+    }
+    _iterator.moveNext();
+  }
+
+  Expression _parseExpression() {
+    if (_token == null) return _astFactory.empty();
+    var expr = _parseUnary();
+    return (expr == null) ? null : _parsePrecedence(expr, 0);
+  }
+
+  // _parsePrecedence and _parseBinary implement the precedence climbing
+  // algorithm as described in:
+  // http://en.wikipedia.org/wiki/Operator-precedence_parser#Precedence_climbing_method
+  Expression _parsePrecedence(Expression left, int precedence) {
+    assert(left != null);
+    while (_token != null) {
+      if (_token.kind == GROUPER_TOKEN) {
+        if (_token.value == '(') {
+          var args = _parseArguments();
+          assert(args != null);
+          left = _astFactory.invoke(left, null, args);
+        } else if (_token.value == '[') {
+          var indexExpr = _parseIndex();
+          left = _astFactory.index(left, indexExpr);
+        } else {
+          break;
+        }
+      } else if (_token.kind == DOT_TOKEN) {
+        _advance();
+        var right = _parseUnary();
+        left = _makeInvokeOrGetter(left, right);
+      } else if (_token.kind == KEYWORD_TOKEN) {
+        if (_token.value == 'in') {
+          left = _parseInExpression(left);
+        } else if (_token.value == 'as') {
+          left = _parseAsExpression(left);
+        } else {
+          break;
+        }
+      } else if (_token.kind == OPERATOR_TOKEN
+          && _token.precedence >= precedence) {
+        left = _token.value == '?' ? _parseTernary(left) : _parseBinary(left);
+      } else {
+        break;
+      }
+    }
+    return left;
+  }
+
+  // invoke or getter
+  Expression _makeInvokeOrGetter(left, right) {
+    if (right is Identifier) {
+      return _astFactory.getter(left, right.value);
+    } else if (right is Invoke && right.receiver is Identifier) {
+      Identifier method = right.receiver;
+      return _astFactory.invoke(left, method.value, right.arguments);
+    } else {
+      throw new ParseException("expected identifier: $right");
+    }
+  }
+
+  Expression _parseBinary(left) {
+    var op = _token;
+    if (!_BINARY_OPERATORS.contains(op.value)) {
+      throw new ParseException("unknown operator: ${op.value}");
+    }
+    _advance();
+    var right = _parseUnary();
+    while (_token != null
+        && (_token.kind == OPERATOR_TOKEN
+        || _token.kind == DOT_TOKEN
+        || _token.kind == GROUPER_TOKEN)
+        && _token.precedence > op.precedence) {
+      right = _parsePrecedence(right, _token.precedence);
+    }
+    return _astFactory.binary(left, op.value, right);
+  }
+
+  Expression _parseUnary() {
+    if (_token.kind == OPERATOR_TOKEN) {
+      var value = _token.value;
+      if (value == '+' || value == '-') {
+        _advance();
+        if (_token.kind == INTEGER_TOKEN) {
+          return _parseInteger(value);
+        } else if (_token.kind == DECIMAL_TOKEN) {
+          return _parseDecimal(value);
+        } else {
+          var expr = _parsePrecedence(_parsePrimary(), POSTFIX_PRECEDENCE);
+          return _astFactory.unary(value, expr);
+        }
+      } else if (value == '!') {
+        _advance();
+        var expr = _parsePrecedence(_parsePrimary(), POSTFIX_PRECEDENCE);
+        return _astFactory.unary(value, expr);
+      } else {
+        throw new ParseException("unexpected token: $value");
+      }
+    }
+    return _parsePrimary();
+  }
+
+  Expression _parseTernary(condition) {
+    _advance(OPERATOR_TOKEN, '?');
+    var trueExpr = _parseExpression();
+    _advance(COLON_TOKEN);
+    var falseExpr = _parseExpression();
+    return _astFactory.ternary(condition, trueExpr, falseExpr);
+  }
+
+  Expression _parsePrimary() {
+    var kind = _token.kind;
+    switch (kind) {
+      case KEYWORD_TOKEN:
+        var keyword = _token.value;
+        if (keyword == 'this') {
+          _advance();
+          // TODO(justin): return keyword node
+          return _astFactory.identifier('this');
+        } else if (KEYWORDS.contains(keyword)) {
+          throw new ParseException('unexpected keyword: $keyword');
+        }
+        throw new ParseException('unrecognized keyword: $keyword');
+      case IDENTIFIER_TOKEN:
+        return _parseInvokeOrIdentifier();
+      case STRING_TOKEN:
+        return _parseString();
+      case INTEGER_TOKEN:
+        return _parseInteger();
+      case DECIMAL_TOKEN:
+        return _parseDecimal();
+      case GROUPER_TOKEN:
+        if (_token.value == '(') {
+          return _parseParenthesized();
+        } else if (_token.value == '{') {
+          return _parseMapLiteral();
+        } else if (_token.value == '[') {
+          return _parseListLiteral();
+        }
+        return null;
+      case COLON_TOKEN:
+        throw new ParseException('unexpected token ":"');
+      default:
+        return null;
+    }
+  }
+
+  ListLiteral _parseListLiteral() {
+    var items = [];
+    do {
+      _advance();
+      if (_token.kind == GROUPER_TOKEN && _token.value == ']') {
+        break;
+      }
+      items.add(_parseExpression());
+    } while(_token != null && _token.value == ',');
+    _advance(GROUPER_TOKEN, ']');
+    return new ListLiteral(items);
+  }
+
+  MapLiteral _parseMapLiteral() {
+    var entries = [];
+    do {
+      _advance();
+      if (_token.kind == GROUPER_TOKEN && _token.value == '}') {
+        break;
+      }
+      entries.add(_parseMapLiteralEntry());
+    } while(_token != null && _token.value == ',');
+    _advance(GROUPER_TOKEN, '}');
+    return new MapLiteral(entries);
+  }
+
+  MapLiteralEntry _parseMapLiteralEntry() {
+    var key = _parseString();
+    _advance(COLON_TOKEN, ':');
+    var value = _parseExpression();
+    return _astFactory.mapLiteralEntry(key, value);
+  }
+
+  InExpression _parseInExpression(Expression left) {
+    assert(_token.value == 'in');
+    if (left is! Identifier) {
+      throw new ParseException(
+          "in... statements must start with an identifier");
+    }
+    _advance();
+    var right = _parseExpression();
+    return _astFactory.inExpr(left, right);
+  }
+
+  AsExpression _parseAsExpression(Expression left) {
+    assert(_token.value == 'as');
+    _advance();
+    var right = _parseExpression();
+    if (right is! Identifier) {
+      throw new ParseException(
+          "'as' statements must end with an identifier");
+    }
+    return _astFactory.asExpr(left, right);
+  }
+
+  Expression _parseInvokeOrIdentifier() {
+    if (_token.value == 'true') {
+      _advance();
+      return _astFactory.literal(true);
+    }
+    if (_token.value == 'false') {
+      _advance();
+      return _astFactory.literal(false);
+    }
+    if (_token.value == 'null') {
+      _advance();
+      return _astFactory.literal(null);
+    }
+    var identifier = _parseIdentifier();
+    var args = _parseArguments();
+    if (args == null) {
+      return identifier;
+    } else {
+      return _astFactory.invoke(identifier, null, args);
+    }
+  }
+
+  Identifier _parseIdentifier() {
+    if (_token.kind != IDENTIFIER_TOKEN) {
+      throw new ParseException("expected identifier: $_token.value");
+    }
+    var value = _token.value;
+    _advance();
+    return _astFactory.identifier(value);
+  }
+
+  List<Expression> _parseArguments() {
+    if (_token != null && _token.kind == GROUPER_TOKEN && _token.value == '(') {
+      var args = [];
+      do {
+        _advance();
+        if (_token.kind == GROUPER_TOKEN && _token.value == ')') {
+          break;
+        }
+        var expr = _parseExpression();
+        args.add(expr);
+      } while(_token != null && _token.value == ',');
+      _advance(GROUPER_TOKEN, ')');
+      return args;
+    }
+    return null;
+  }
+
+  Expression _parseIndex() {
+    if (_token != null && _token.kind == GROUPER_TOKEN && _token.value == '[') {
+      _advance();
+      var expr = _parseExpression();
+      _advance(GROUPER_TOKEN, ']');
+      return expr;
+    }
+    return null;
+  }
+
+  ParenthesizedExpression _parseParenthesized() {
+    _advance();
+    var expr = _parseExpression();
+    _advance(GROUPER_TOKEN, ')');
+    return _astFactory.parenthesized(expr);
+  }
+
+  Literal<String> _parseString() {
+    var value = _astFactory.literal(_token.value);
+    _advance();
+    return value;
+  }
+
+  Literal<int> _parseInteger([String prefix = '']) {
+    var value = _astFactory.literal(int.parse('$prefix${_token.value}'));
+    _advance();
+    return value;
+  }
+
+  Literal<double> _parseDecimal([String prefix = '']) {
+    var value = _astFactory.literal(double.parse('$prefix${_token.value}'));
+    _advance();
+    return value;
+  }
+
+}