JS: fix parsing of wrong delete operation in js function.

See KT-15294

js/js.parser/src/com/google/gwt/dev/js/JsAstMapper.java

@@ -392,9 +392,7 @@ public class JsAstMapper {
                     JsUnaryOperator.DELETE, to);
         }
         else {
-            throw createParserException(
-                    "'delete' can only operate on property names and array elements",
-                    from);
+            return new JsNullLiteral();
         }
     }
 

js/js.parser/src/com/google/gwt/dev/js/rhino/MessagesBundle.java

@@ -81,5 +81,7 @@ public class MessagesBundle extends ListResourceBundle {
         {"msg.catch.unreachable", "any catch clauses following an unqualified catch are unreachable"},
         {"msg.no.name.after.dot", "missing name after . operator"},
         {"msg.jsni.expected.identifier", "Expected an identifier in JSNI reference"},
+        {"msg.wrong.delete argument", "Wrong argument for ''delete'' operation. " +
+                                      "Must be either property reference or array subscript expression."},
     };
 }

js/js.parser/src/com/google/gwt/dev/js/rhino/Parser.java

@@ -37,6 +37,8 @@
 
 package com.google.gwt.dev.js.rhino;
 
+import org.jetbrains.annotations.NotNull;
+
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
@@ -890,8 +892,13 @@ public class Parser {
             case TokenStream.DEC:
                 return nf.createUnary(tt, TokenStream.PRE, memberExpr(ts, true), position);
 
-            case TokenStream.DELPROP:
-                return nf.createUnary(TokenStream.DELPROP, unaryExpr(ts), position);
+            case TokenStream.DELPROP: {
+                Node argument = unaryExpr(ts);
+                if (!isValidDeleteArgument(argument)) {
+                    Context.reportError("msg.wrong.delete argument", argument.getPosition(), ts.lastPosition);
+                }
+                return nf.createUnary(TokenStream.DELPROP, argument, position);
+            }
 
             case TokenStream.ERROR:
                 break;
@@ -922,6 +929,10 @@ public class Parser {
         return nf.createName("err", position); // Only reached on error. Try to continue.
     }
 
+    private static boolean isValidDeleteArgument(@NotNull Node node) {
+        return node.type == TokenStream.GETPROP || node.type == TokenStream.GETELEM;
+    }
+
     private Node argumentList(TokenStream ts, Node listNode) throws IOException, JavaScriptException {
         boolean matched;
         ts.flags |= TokenStream.TSF_REGEXP;