enable analyzer scanner adapter generic method support

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

Index: pkg/analyzer/lib/src/dart/scanner/scanner.dart
diff --git a/pkg/analyzer/lib/src/dart/scanner/scanner.dart b/pkg/analyzer/lib/src/dart/scanner/scanner.dart
index 1a78ccfb4bbeaa183e99182fd1e6337cf7c76625..6d72b5ff945853185f891ea38663be7685ea93e0 100644
--- a/pkg/analyzer/lib/src/dart/scanner/scanner.dart
+++ b/pkg/analyzer/lib/src/dart/scanner/scanner.dart
@@ -48,7 +48,8 @@ class Scanner extends fe.Scanner {
   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)
@@ -75,6 +76,11 @@ class _Scanner2 implements Scanner {
   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.
    */
@@ -97,7 +103,8 @@ class _Scanner2 implements Scanner {
   @override
   bool scanLazyAssignmentOperators = false;
 
-  _Scanner2(this.source, this._contents, this._errorListener) {
+  _Scanner2(
+      this.source, this._contents, this._readerOffset, this._errorListener) {
     lineStarts.add(0);
   }
 
@@ -130,7 +137,15 @@ class _Scanner2 implements Scanner {
 
   @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
@@ -140,15 +155,9 @@ class _Scanner2 implements Scanner {
 
   @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
@@ -161,6 +170,14 @@ class _Scanner2 implements Scanner {
       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;
   }