Accept more labels per switch case.

lib/compiler/implementation/scanner/parser.dart

Index: lib/compiler/implementation/scanner/parser.dart
diff --git a/lib/compiler/implementation/scanner/parser.dart b/lib/compiler/implementation/scanner/parser.dart
index c24ed64610a41cc6d9f619825bef173ec89626dd..debe508636c87cc45f25396eac87b468e05b2da7 100644
--- a/lib/compiler/implementation/scanner/parser.dart
+++ b/lib/compiler/implementation/scanner/parser.dart
@@ -1573,48 +1573,68 @@ class Parser {
   Token parseSwitchCase(Token token) {
     Token begin = token;
     Token defaultKeyword = null;
-    Token label = null;
-    // First an optional label.
-    if (isIdentifier(token)) {
-      label = token;
-      token = parseLabel(token);
+
+    /**
+     * Peek ahead in the token stream to see what's after a sequence
+     * of labels. We don't parse the labels before we know whether we
+     * need to call [listener.beginLabeledStatement].
+     */
+    Token peekAfterLabels(Token token) {
+      while (isIdentifier(token) && optional(':', token.next)) {
+        token = token.next.next;
+      }
+      return token;
     }
-    // Then one or more case expressions, the last of which may be
-    // 'default' instead.
+
     int expressionCount = 0;
-    {
-      String value = token.stringValue;
-      do {
-        if (value === 'default') {
-          defaultKeyword = token;
-          token = expect(':', token.next);
-          break;
-        }
-        token = expect('case', token);
-        token = parseExpression(token);
+    int labelCount = 0;
+
+    Token parseLabelsUntil(Token token, Token limit) {
+      while (token !== limit) {
+        token = parseLabel(token);
+        labelCount++;
+      }
+      return token;
+    }
+
+    while (true) {
+      // Look-ahead to after a sequence of labels. The labels can belong to
+      // either a case or a following statement.
+      Token peek = peekAfterLabels(token);
+      // Loop until we find something that can't be part of a switch case.
+      String value = peek.stringValue;
+      if (value === 'default') {
+        token = parseLabelsUntil(token, peek);
+        defaultKeyword = token;
+        token = expect(':', token.next);
+        break;
+      } else if (value === 'case') {
+        token = parseLabelsUntil(token, peek);
+        Token caseKeyword = token;
+        token = parseExpression(token.next);
+        Token colon = token;
         token = expect(':', token);
+        listener.handleCaseMatch(caseKeyword, colon);
         expressionCount++;
-        value = token.stringValue;
-      } while (value === 'case' || value === 'default');
+      } else {
+        break;
+      }
     }
     // Finally zero or more statements.
     int statementCount = 0;
     while (token.kind !== EOF_TOKEN) {
-      String value;
-      if (isIdentifier(token) && optional(':', token.next)) {
-        // Skip label.
-        value = token.next.next.stringValue;
-      } else {
-        value = token.stringValue;
-      }
-      if (value === 'case' || value === 'default' || value === '}') {
+      Token peek = peekAfterLabels(token);
+      String value = peek.stringValue;
+      if (value === 'case' || value === 'default' ||
+          (value === '}' && peek === token)) {
+        // A label just before "}" will be handled as a statement error.
         break;
       } else {
         token = parseStatement(token);
         ++statementCount;
       }
     }
-    listener.handleSwitchCase(label, expressionCount, defaultKeyword,
+    listener.handleSwitchCase(labelCount, expressionCount, defaultKeyword,
                               statementCount, begin, token);
     return token;
   }