Revert "Add support for the new function-type syntax."

pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart

 // Copyright (c) 2012, 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 fasta.scanner.abstract_scanner;
 
 import '../scanner.dart' show
     ErrorToken,
     Scanner,
     buildUnexpectedCharacterToken;
@@ skipping 223 matching lines @@
     if ($a <= next && next <= $z) {
       if (identical($r, next)) {
         return tokenizeRawStringKeywordOrIdentifier(next);
       }
       return tokenizeKeywordOrIdentifier(next, true);
     }
 
     if (($A <= next && next <= $Z) ||
         identical(next, $_) ||
         identical(next, $$)) {
-      return tokenizeKeywordOrIdentifier(next, true);
+      return tokenizeIdentifier(next, scanOffset, true);
     }
 
     if (identical(next, $LT)) {
       return tokenizeLessThan(next);
     }
 
     if (identical(next, $GT)) {
       return tokenizeGreaterThan(next);
     }
 
@@ skipping 546 matching lines @@
       int start = scanOffset;
       next = advance();
       return tokenizeString(next, start, true);
     }
     return tokenizeKeywordOrIdentifier(next, true);
   }
 
   int tokenizeKeywordOrIdentifier(int next, bool allowDollar) {
     KeywordState state = KeywordState.KEYWORD_STATE;
     int start = scanOffset;
-    // We allow a leading capital character.
-    if ($A <= next && next <= $Z) {
-      state = state.nextCapital(next);
-      next = advance();
-    } else if ($a <= next && next <= $z){
-      // Do the first next call outside the loop to avoid an additional test
-      // and to make the loop monomorphic.
-      state = state.next(next);
-      next = advance();
-    }
     while (state != null && $a <= next && next <= $z) {
       state = state.next(next);
       next = advance();
     }
     if (state == null || state.keyword == null) {
       return tokenizeIdentifier(next, start, allowDollar);
     }
     if (($A <= next && next <= $Z) ||
         ($0 <= next && next <= $9) ||
         identical(next, $_) ||
@@ skipping 117 matching lines @@
     }
     if (identical(next, $EOF)) return next;
     next = advance(); // Move past the $STX.
     beginToken(); // The string interpolation suffix starts here.
     return next;
   }
 
   int tokenizeInterpolatedIdentifier(int next) {
     appendPrecedenceToken(STRING_INTERPOLATION_IDENTIFIER_INFO);
 
-    if ($a <= next && next <= $z ||
-        $A <= next && next <= $Z ||
-        identical(next, $_)) {
+    if ($a <= next && next <= $z) {
       beginToken(); // The identifier starts here.
       next = tokenizeKeywordOrIdentifier(next, false);
+    } else if (($A <= next && next <= $Z) || identical(next, $_)) {
+      beginToken(); // The identifier starts here.
+      next = tokenizeIdentifier(next, scanOffset, false);
     } else {
       unterminated(r'$', shouldAdvance: false);
     }
     beginToken(); // The string interpolation suffix starts here.
     return next;
   }
 
   int tokenizeSingleLineRawString(int next, int quoteChar, int start) {
     bool asciiOnly = true;
     while (next != $EOF) {
@@ skipping 194 matching lines @@
 
 PrecedenceInfo closeBraceInfoFor(BeginGroupToken begin) {
   return const {
     '(': CLOSE_PAREN_INFO,
     '[': CLOSE_SQUARE_BRACKET_INFO,
     '{': CLOSE_CURLY_BRACKET_INFO,
     '<': GT_INFO,
     r'${': CLOSE_CURLY_BRACKET_INFO,
   }[begin.value];
 }