| // Copyright (c) 2017, 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 '../scanner/error_token.dart' show UnmatchedToken; |
| |
| import '../../scanner/token.dart' |
| show |
| BeginToken, |
| SimpleToken, |
| SyntheticBeginToken, |
| SyntheticStringToken, |
| SyntheticToken, |
| Token, |
| TokenType; |
| |
| /// Provides the capability of inserting tokens into a token stream. This |
| /// implementation does this by rewriting the previous token to point to the |
| /// inserted token. |
| class TokenStreamRewriter { |
| // TODO(brianwilkerson): |
| // |
| // When we get to the point of removing `token.previous`, the plan is to |
| // convert this into an interface and provide two implementations. |
| // |
| // One, used by Fasta, will connect the inserted tokens to the following token |
| // without modifying the previous token. |
| // |
| // The other, used by 'analyzer', will be created with the first token in the |
| // stream (actually with the BOF marker at the beginning of the stream). It |
| // will be created only when invoking 'analyzer' specific parse methods (in |
| // `Parser`), such as |
| // |
| // Token parseUnitWithRewrite(Token bof) { |
| // rewriter = AnalyzerTokenStreamRewriter(bof); |
| // return parseUnit(bof.next); |
| // } |
| // |
| |
| /// Initialize a newly created re-writer. |
| TokenStreamRewriter(); |
| |
| /// Insert a synthetic open and close parenthesis and return the new synthetic |
| /// open parenthesis. If [insertIdentifier] is true, then a synthetic |
| /// identifier is included between the open and close parenthesis. |
| Token insertParens(Token token, bool includeIdentifier) { |
| Token next = token.next; |
| int offset = next.charOffset; |
| BeginToken leftParen = |
| next = new SyntheticBeginToken(TokenType.OPEN_PAREN, offset); |
| if (includeIdentifier) { |
| next = next.setNext( |
| new SyntheticStringToken(TokenType.IDENTIFIER, '', offset, 0)); |
| } |
| next = next.setNext(new SyntheticToken(TokenType.CLOSE_PAREN, offset)); |
| leftParen.endGroup = next; |
| next.setNext(token.next); |
| |
| // A no-op rewriter could skip this step. |
| token.setNext(leftParen); |
| |
| return leftParen; |
| } |
| |
| /// Insert a synthetic identifier after [token] and return the new identifier. |
| Token insertSyntheticIdentifier(Token token) { |
| return insertToken( |
| token, |
| new SyntheticStringToken( |
| TokenType.IDENTIFIER, '', token.next.charOffset, 0)); |
| } |
| |
| /// Insert [newToken] after [token] and return [newToken]. |
| Token insertToken(Token token, Token newToken) { |
| newToken.setNext(token.next); |
| |
| // A no-op rewriter could skip this step. |
| token.setNext(newToken); |
| |
| return newToken; |
| } |
| |
| /// Move [endGroup] (a synthetic `)`, `]`, or `}` token) and associated |
| /// error token after [token] in the token stream and return [endGroup]. |
| Token moveSynthetic(Token token, Token endGroup) { |
| assert(endGroup.beforeSynthetic != null); |
| Token errorToken; |
| if (endGroup.next is UnmatchedToken) { |
| errorToken = endGroup.next; |
| } |
| |
| // Remove endGroup from its current location |
| endGroup.beforeSynthetic.setNext((errorToken ?? endGroup).next); |
| |
| // Insert endGroup into its new location |
| Token next = token.next; |
| token.setNext(endGroup); |
| (errorToken ?? endGroup).setNext(next); |
| endGroup.offset = next.offset; |
| if (errorToken != null) { |
| errorToken.offset = next.offset; |
| } |
| |
| return endGroup; |
| } |
| |
| /// Replace the single token immediately following the [previousToken] with |
| /// the chain of tokens starting at the [replacementToken]. Return the |
| /// [replacementToken]. |
| Token replaceTokenFollowing(Token previousToken, Token replacementToken) { |
| Token replacedToken = previousToken.next; |
| previousToken.setNext(replacementToken); |
| |
| (replacementToken as SimpleToken).precedingComments = |
| replacedToken.precedingComments; |
| |
| _lastTokenInChain(replacementToken).setNext(replacedToken.next); |
| |
| return replacementToken; |
| } |
| |
| /// Given the [firstToken] in a chain of tokens to be inserted, return the |
| /// last token in the chain. |
| /// |
| /// As a side-effect, this method also ensures that the tokens in the chain |
| /// have their `previous` pointers set correctly. |
| Token _lastTokenInChain(Token firstToken) { |
| Token previous; |
| Token current = firstToken; |
| while (current.next != null && current.next.type != TokenType.EOF) { |
| if (previous != null) { |
| current.previous = previous; |
| } |
| previous = current; |
| current = current.next; |
| } |
| if (previous != null) { |
| current.previous = previous; |
| } |
| return current; |
| } |
| } |