Switch-implementation.

frog/leg/scanner/parser.dart

 // Copyright (c) 2011, 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.
 
 /**
  * An event generating parser of Dart programs. This parser expects
  * all tokens in a linked list.
  */
 class Parser {
   final Listener listener;
@@ skipping 1491 matching lines @@
     listener.beginSwitchStatement(switchKeyword);
     token = parseParenthesizedExpression(token.next);
     token = parseSwitchBlock(token);
     listener.endSwitchStatement(switchKeyword, token);
     return token.next;
   }
 
   Token parseSwitchBlock(Token token) {
     Token begin = token;
     listener.beginSwitchBlock(begin);
+    token = expect('{', token);
     int caseCount = 0;
-    token = expect('{', token);
     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') {
-        token = parseSwitchCase(token);
-        ++caseCount;
-      } else if (value === 'default') {
-        token = parseDefaultCase(token);
-        ++caseCount;
-      } else {
+      if (optional('}', token)) {
         break;
       }
+      token = parseSwitchCase(token);
+      ++caseCount;
     }
     listener.endSwitchBlock(caseCount, begin, token);
     expect('}', token);
     return token;
   }
 
   Token parseSwitchCase(Token token) {
     Token begin = token;
-    Token colon;
+    Token defaultKeyword = null;
+    Token label = null;
+    // First an optional label.
     if (isIdentifier(token)) {
       token = parseIdentifier(token);
-      colon = token;
+      label = token;
       token = expect(':', token);
     }
-    Token caseKeyword = token;
-    token = expect('case', token);
-    token = parseExpression(token);
-    token = expect(':', token);
+    // Then one or more case expressions, the last of which may be
+    // 'default' instead.
+    int expressionCount = 0;
+    String tokenValue = token.stringValue;
+    do {
+      if (tokenValue === 'default') {
+        defaultKeyword = token;
+        token = expect(':', token.next);
+        break;
+      }
+      token = expect('case', token);

[ahe, 2012/03/09 13:58:32]

Where do you store the case token?

[Lasse Reichstein Nielsen, 2012/03/12 13:05:23]

I don't.
You can find it, if you need it, from the begin Token, by iterating forward. We
know it's just before the 
I'll add a function that returns the case keywords if anyone needs them.

+      token = parseExpression(token);
+      token = expect(':', token);
+      expressionCount++;
+      tokenValue = token.stringValue;
+    } while (tokenValue === 'case' || tokenValue === 'default');

[ahe, 2012/03/09 13:58:32]

What happens if I write:

switch (expr) {
default:
default:
case foo:
  print('fisk'); break;
case bar:
  print('hest'); break;
}

[Lasse Reichstein Nielsen, 2012/03/12 13:05:23]

The "default:" always ends the case, so this is equivalent to
  default: {}
  default: {}
  case foo: ...
  case bar: ...
I.e., two default cases with fallthrough, and both default keywords will be
considered errors, since only the last case may have one.

+    // 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 === '}') {
-        break;
-      } else {
-        token = parseStatement(token);
-        ++statementCount;
-      }
-    }
-    listener.handleSwitchCase(colon, caseKeyword, statementCount, token);
-    return token;
-  }
-
-  Token parseDefaultCase(Token token) {
-    Token begin = token;
-    Token colon;
-    if (isIdentifier(token)) {
-      token = parseIdentifier(token);
-      colon = token;
-      token = expect(':', token);
-    }
-    Token defaultKeyword = token;
-    token = expect('default', token);
-    token = expect(':', token);
-    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 === '}') {
-        break;
-      } else if (value === 'case' || value === 'default') {
-        // The default case should be the last case in a switch.
-        listener.recoverableError("expected '}'", token: token);
+      if (value === 'case' || value === 'default' || value === '}') {
         break;
       } else {
         token = parseStatement(token);
         ++statementCount;
       }
     }
-    listener.handleDefaultCase(colon, defaultKeyword, statementCount, token);
+    listener.handleSwitchCase(label, expressionCount, defaultKeyword,
+                              statementCount, begin, token);
     return token;
   }
 
   Token parseBreakStatement(Token token) {
     assert(optional('break', token));
     Token breakKeyword = token;
     token = token.next;
     bool hasTarget = false;
     if (isIdentifier(token)) {
       token = parseIdentifier(token);
@@ skipping 14 matching lines @@
     }
     listener.handleContinueStatement(hasTarget, continueKeyword, token);
     return expectSemicolon(token);
   }
 
   Token parseEmptyStatement(Token token) {
     listener.handleEmptyStatement(token);
     return expectSemicolon(token);
   }
 }