Revive throw as an expression but not for rethrow.

sdk/lib/_internal/compiler/implementation/scanner/parser.dart

Index: sdk/lib/_internal/compiler/implementation/scanner/parser.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/scanner/parser.dart	(revision 15894)
+++ sdk/lib/_internal/compiler/implementation/scanner/parser.dart	(working copy)
@@ -1140,8 +1140,6 @@
       return parseIfStatement(token);
     } else if (identical(value, 'for')) {
       return parseForStatement(token);
-    } else if (identical(value, 'throw')) {
-      return parseThrowStatement(token);
     } else if (identical(value, 'void')) {
       return parseExpressionStatementOrDeclaration(token);
     } else if (identical(value, 'while')) {
@@ -1494,6 +1492,8 @@
         return parseConstExpression(token);
       } else if (identical(value, 'void')) {
         return parseFunctionExpression(token);
+      } else if (identical(value, 'throw')) {
+        return parseThrow(token);
       } else if (token.isIdentifier()) {
         return parseSendOrFunctionLiteral(token);
       } else {
@@ -1970,18 +1970,17 @@
     return expect('}', token);
   }
 
-  Token parseThrowStatement(Token token) {
+  Token parseThrow(Token token) {
     Token throwToken = token;
-    listener.beginThrowStatement(throwToken);
+    listener.beginThrow(throwToken);
     token = expect('throw', token);
     if (optional(';', token)) {
-      listener.endRethrowStatement(throwToken, token);
-      return token.next;
+      listener.endRethrow(throwToken, token);

[kasperl, 2012/12/10 14:50:05]

Add a comment that it's important that you aren't consuming the ; token?

     } else {
       token = parseExpression(token);
-      listener.endThrowStatement(throwToken, token);
-      return expectSemicolon(token);
+      listener.endThrow(throwToken, token);
     }
+    return token;
   }
 
   Token parseTryStatement(Token token) {