pkg/front_end/lib/src/scanner/errors.dart

// Copyright (c) 2016, 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.

import '../base/errors.dart';
import '../fasta/fasta_codes.dart';
import '../fasta/scanner/error_token.dart';
import 'token.dart' show Token, TokenType;
import '../fasta/scanner/token_constants.dart';

/**
 * The error codes used for errors detected by the scanner.
 */
class ScannerErrorCode extends ErrorCode {
  /**
   * Parameters:
   * 0: the token that was expected but not found
   */
  static const ScannerErrorCode EXPECTED_TOKEN =
      const ScannerErrorCode('EXPECTED_TOKEN', "Expected to find '{0}'.");

  /**
   * Parameters:
   * 0: the illegal character
   */
  static const ScannerErrorCode ILLEGAL_CHARACTER =
      const ScannerErrorCode('ILLEGAL_CHARACTER', "Illegal character '{0}'.");

  static const ScannerErrorCode MISSING_DIGIT =
      const ScannerErrorCode('MISSING_DIGIT', "Decimal digit expected.");

  static const ScannerErrorCode MISSING_HEX_DIGIT = const ScannerErrorCode(
      'MISSING_HEX_DIGIT', "Hexidecimal digit expected.");

  static const ScannerErrorCode MISSING_IDENTIFIER =
      const ScannerErrorCode('MISSING_IDENTIFIER', "Expected an identifier.");

  static const ScannerErrorCode MISSING_QUOTE =
      const ScannerErrorCode('MISSING_QUOTE', "Expected quote (' or \").");

  /**
   * Parameters:
   * 0: the path of the file that cannot be read
   */
  static const ScannerErrorCode UNABLE_GET_CONTENT = const ScannerErrorCode(
      'UNABLE_GET_CONTENT', "Unable to get content of '{0}'.");

  static const ScannerErrorCode UNEXPECTED_DOLLAR_IN_STRING =
      const ScannerErrorCode(
          'UNEXPECTED_DOLLAR_IN_STRING',
          "A '\$' has special meaning inside a string, and must be followed by "
          "an identifier or an expression in curly braces ({}).",
          correction: "Try adding a backslash (\\) to escape the '\$'.");

  /**
   * Parameters:
   * 0: the unsupported operator
   */
  static const ScannerErrorCode UNSUPPORTED_OPERATOR = const ScannerErrorCode(
      'UNSUPPORTED_OPERATOR', "The '{0}' operator is not supported.");

  static const ScannerErrorCode UNTERMINATED_MULTI_LINE_COMMENT =
      const ScannerErrorCode(
          'UNTERMINATED_MULTI_LINE_COMMENT', "Unterminated multi-line comment.",
          correction: "Try terminating the comment with '*/', or "
              "removing any unbalanced occurances of '/*'"
              " (because comments nest in Dart).");

  static const ScannerErrorCode UNTERMINATED_STRING_LITERAL =
      const ScannerErrorCode(
          'UNTERMINATED_STRING_LITERAL', "Unterminated string literal.");

  /**
   * Initialize a newly created error code to have the given [name]. The message
   * associated with the error will be created from the given [message]
   * template. The correction associated with the error will be created from the
   * given [correction] template.
   */
  const ScannerErrorCode(String name, String message, {String correction})
      : super.temporary(name, message, correction: correction);

  @override
  ErrorSeverity get errorSeverity => ErrorSeverity.ERROR;

  @override
  ErrorType get type => ErrorType.SYNTACTIC_ERROR;
}

/**
 * Used to report a scan error at the given offset.
 * The [errorCode] is the error code indicating the nature of the error.
 * The [arguments] are any arguments needed to complete the error message.
 */
typedef ReportError(
    ScannerErrorCode errorCode, int offset, List<Object> arguments);

/**
 *  Translates the given error [token] into an analyzer error and reports it
 *  using [reportError].
 */
void translateErrorToken(ErrorToken token, ReportError reportError) {
  int charOffset = token.charOffset;
  // TODO(paulberry,ahe): why is endOffset sometimes null?
  int endOffset = token.endOffset ?? charOffset;
  void _makeError(ScannerErrorCode errorCode, List<Object> arguments) {
    if (_isAtEnd(token, charOffset)) {
      // Analyzer never generates an error message past the end of the input,
      // since such an error would not be visible in an editor.
      // TODO(paulberry,ahe): would it make sense to replicate this behavior
      // in fasta, or move it elsewhere in analyzer?
      charOffset--;
    }
    reportError(errorCode, charOffset, arguments);
  }

  var errorCode = token.errorCode;
  switch (errorCode.analyzerCode) {
    case "UNTERMINATED_STRING_LITERAL":
      // TODO(paulberry,ahe): Fasta reports the error location as the entire
      // string; analyzer expects the end of the string.
      charOffset = endOffset - 1;
      return _makeError(ScannerErrorCode.UNTERMINATED_STRING_LITERAL, null);

    case "UNTERMINATED_MULTI_LINE_COMMENT":
      // TODO(paulberry,ahe): Fasta reports the error location as the entire
      // comment; analyzer expects the end of the comment.
      charOffset = endOffset;
      return _makeError(ScannerErrorCode.UNTERMINATED_MULTI_LINE_COMMENT, null);

    case "MISSING_DIGIT":
      // TODO(paulberry,ahe): Fasta reports the error location as the entire
      // number; analyzer expects the end of the number.
      charOffset = endOffset - 1;
      return _makeError(ScannerErrorCode.MISSING_DIGIT, null);

    case "MISSING_HEX_DIGIT":
      // TODO(paulberry,ahe): Fasta reports the error location as the entire
      // number; analyzer expects the end of the number.
      charOffset = endOffset - 1;
      return _makeError(ScannerErrorCode.MISSING_HEX_DIGIT, null);

    case "ILLEGAL_CHARACTER":
      return _makeError(ScannerErrorCode.ILLEGAL_CHARACTER, [token.character]);

    case "UNSUPPORTED_OPERATOR":
      return _makeError(ScannerErrorCode.UNSUPPORTED_OPERATOR,
          [(token as UnsupportedOperator).token.lexeme]);

    default:
      if (errorCode == codeUnmatchedToken) {
        charOffset = token.begin.endToken.charOffset;
        TokenType type = token.begin?.type;
        if (type == TokenType.OPEN_CURLY_BRACKET ||
            type == TokenType.STRING_INTERPOLATION_EXPRESSION) {
          return _makeError(ScannerErrorCode.EXPECTED_TOKEN, ['}']);
        }
        if (type == TokenType.OPEN_SQUARE_BRACKET) {
          return _makeError(ScannerErrorCode.EXPECTED_TOKEN, [']']);
        }
        if (type == TokenType.OPEN_PAREN) {
          return _makeError(ScannerErrorCode.EXPECTED_TOKEN, [')']);
        }
        if (type == TokenType.LT) {
          return _makeError(ScannerErrorCode.EXPECTED_TOKEN, ['>']);
        }
      } else if (errorCode == codeUnexpectedDollarInString) {
        return _makeError(ScannerErrorCode.MISSING_IDENTIFIER, null);
      }
      throw new UnimplementedError('$errorCode "${errorCode.analyzerCode}"');
  }
}

/**
 * Determines whether the given [charOffset], which came from the non-EOF token
 * [token], represents the end of the input.
 */
bool _isAtEnd(Token token, int charOffset) {
  while (true) {
    // Skip to the next token.
    token = token.next;
    // If we've found an EOF token, its charOffset indicates where the end of
    // the input is.
    if (token.isEof) return token.charOffset == charOffset;
    // If we've found a non-error token, then we know there is additional input
    // text after [charOffset].
    if (token.type.kind != BAD_INPUT_TOKEN) return false;
    // Otherwise keep looking.
  }
}