enable analyzer scanner adapter generic method support

pkg/analyzer/lib/src/dart/scanner/scanner.dart

 // Copyright (c) 2014, 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 analyzer.src.dart.scanner.scanner;
 
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/src/dart/error/syntactic_errors.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
@@ skipping 30 matching lines @@
 
   /**
    * Initialize a newly created scanner to scan characters from the given
    * [source]. The given character [reader] will be used to read the characters
    * in the source. The given [_errorListener] will be informed of any errors
    * that are found.
    */
   factory Scanner(Source source, CharacterReader reader,
           AnalysisErrorListener errorListener) =>
       fe.Scanner.useFasta
-          ? new _Scanner2(source, reader.getContents(), errorListener)
+          ? new _Scanner2(
+              source, reader.getContents(), reader.offset, errorListener)
           : new Scanner._(source, reader, errorListener);
 
   Scanner._(this.source, CharacterReader reader, this._errorListener)
       : super.create(reader);
 
   @override
   void reportError(
       ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     _errorListener
         .onError(new AnalysisError(source, offset, 1, errorCode, arguments));
   }
 }
 
 /**
  * Replacement scanner based on fasta.
  */
 class _Scanner2 implements Scanner {
   @override
   final Source source;
 
   /**
    * The text to be scanned.
    */
   final String _contents;
 
   /**
+   * The offset of the first character from the reader.
+   */
+  final int _readerOffset;
+
+  /**
    * The error listener that will be informed of any errors that are found
    * during the scan.
    */
   final AnalysisErrorListener _errorListener;
 
   /**
    * The flag specifying whether documentation comments should be parsed.
    */
   bool _preserveComments = true;
 
   @override
   final List<int> lineStarts = <int>[];
 
   @override
   Token firstToken;
 
   @override
   bool scanGenericMethodComments = false;
 
   @override
   bool scanLazyAssignmentOperators = false;
 
-  _Scanner2(this.source, this._contents, this._errorListener) {
+  _Scanner2(
+      this.source, this._contents, this._readerOffset, this._errorListener) {
     lineStarts.add(0);
   }
 
   @override
   void appendToken(Token token) {
     throw 'unsupported operation';
   }
 
   @override
   int bigSwitch(int next) {
@@ skipping 12 matching lines @@
 
   @override
   void reportError(
       ScannerErrorCode errorCode, int offset, List<Object> arguments) {
     _errorListener
         .onError(new AnalysisError(source, offset, 1, errorCode, arguments));
   }
 
   @override
   void setSourceStart(int line, int column) {
-    throw 'unsupported operation';
+    lineStarts.removeAt(0);
+    int offset = _readerOffset;
+    if (line < 1 || column < 1 || offset < 0 || (line + column - 2) >= offset) {
+      return;
+    }
+    for (int i = 2; i < line; i++) {
+      lineStarts.add(1);
+    }
+    lineStarts.add(offset - column + 1);
   }
 
   @override
   Token get tail {
     throw 'unsupported operation';
   }
 
   @override
   Token tokenize() {
-    // Note: Fasta always supports lazy assignment operators (`&&=` and `||=`),
-    // so we can ignore the `scanLazyAssignmentOperators` flag.
-    if (scanGenericMethodComments) {
-      // Fasta doesn't support generic method comments.
-      // TODO(danrubel): remove this once fasts support has been added.
-      throw 'No generic method comment support in Fasta';
-    }
     fasta.ScannerResult result = fasta.scanString(_contents,
         includeComments: _preserveComments,
+        scanGenericMethodComments: scanGenericMethodComments,
         scanLazyAssignmentOperators: scanLazyAssignmentOperators);
     // fasta pretends there is an additional line at EOF
     lineStarts
         .addAll(result.lineStarts.sublist(1, result.lineStarts.length - 1));
     fasta.Token token = result.tokens;
     // The default recovery strategy used by scanString
     // places all error tokens at the head of the stream.
     while (token.type == TokenType.BAD_INPUT) {
       translateErrorToken(token, reportError);
       token = token.next;
     }
     firstToken = token;
+    // Update all token offsets based upon the reader's starting offset
+    if (_readerOffset != -1) {
+      final int delta = _readerOffset + 1;
+      do {
+        token.offset += delta;
+        token = token.next;
+      } while (!token.isEof);
+    }
     return firstToken;
   }
 
   @override
   set preserveComments(bool preserveComments) {
     this._preserveComments = preserveComments;
   }
 }