fix recovery on ||= and &&= in dart2js

Bug: #31061
Change-Id: I3f8667d5dab92d256122484a6fc83b3527228085
Reviewed-on: https://dart-review.googlesource.com/12760
Reviewed-by: Johnni Winther <[email protected]>

Author: sigmundch

pkg/compiler/lib/src/diagnostics/messages.dart

@@ -424,6 +424,7 @@ enum MessageKind {
   UNSUPPORTED_BANG_EQ_EQ,
   UNSUPPORTED_EQ_EQ_EQ,
   UNSUPPORTED_LITERAL_SYMBOL,
+  UNSUPPORTED_OPERATOR,
   UNSUPPORTED_PREFIX_PLUS,
   MISSING_EXPRESSION_IN_THROW,
   UNTERMINATED_COMMENT,
@@ -2473,6 +2474,10 @@ main() => A.A = 1;
           "'!==' is not an operator. "
           "Did you mean '#{lhs} != #{rhs}' or '!identical(#{lhs}, #{rhs})'?"),
 
+      MessageKind.UNSUPPORTED_OPERATOR: const MessageTemplate(
+          MessageKind.UNSUPPORTED_OPERATOR,
+          "'#{operator}' is not an operator. "),
+
       MessageKind.UNSUPPORTED_PREFIX_PLUS: const MessageTemplate(
           MessageKind.UNSUPPORTED_PREFIX_PLUS, "'+' is not a prefix operator. ",
           howToFix: "Try removing '+'.",

pkg/compiler/lib/src/parser/node_listener.dart

@@ -457,6 +457,13 @@ class NodeListener extends ElementListener {
     if (send == null || !(send.isPropertyAccess || send.isIndex)) {
       reportNotAssignable(node);
     }
+    var tokenString = token.stringValue;
+    if (tokenString == '||=' || tokenString == '&&=') {
+      reporter.reportErrorMessage(reporter.spanFromToken(token),
+          MessageKind.UNSUPPORTED_OPERATOR, {'operator': tokenString});
+      pushNode(arg);
+      return;
+    }
     if (send.asSendSet() != null) internalError(node: send);
     NodeList arguments;
     if (send.isIndex) {