Proper error message when computed properties are used in destructuring

We don't support it, but we want to give back a proper error message
rather than a generic assertion failed.

rhino/src/main/java/org/mozilla/javascript/IRFactory.java

@@ -2524,6 +2524,9 @@ void decompile(AstNode node) {
             case Token.THIS:
                 decompiler.addToken(node.getType());
                 break;
+            case Token.COMPUTED_PROPERTY:
+                parser.reportError("msg.bad.computed.property.in.destruct");
+                break;
             default:
                 Kit.codeBug("unexpected token: " + Token.typeToName(node.getType()));
         }

rhino/src/main/java/org/mozilla/javascript/Parser.java

@@ -4154,6 +4154,9 @@ boolean destructuringObject(
             } else if (id instanceof NumberLiteral) {
                 Node s = createNumber((int) ((NumberLiteral) id).getNumber());
                 rightElem = new Node(Token.GETELEM, createName(tempName), s);
+            } else if (id instanceof ComputedPropertyKey) {
+                reportError("msg.bad.computed.property.in.destruct");
+                return false;
             } else {
                 throw codeBug();
             }

rhino/src/main/resources/org/mozilla/javascript/resources/Messages.properties

@@ -100,6 +100,9 @@ msg.mult.index =\
 msg.bad.for.in.destruct =\
     Left hand side of for..in loop must be an array of length 2 to accept \
     key/value pair.
+
+msg.bad.computed.property.in.destruct =\
+    Unsupported computed property in destructuring.
 
 msg.cant.convert =\
     Can''t convert to type "{0}".

tests/src/test/java/org/mozilla/javascript/tests/ComputedPropertiesTest.java

@@ -246,4 +246,30 @@ public void notSupportedUnderVersionLesserThanEsLatest() {
             assertEquals("invalid property id (test#1)", ex.getMessage());
         }
     }
+
+    @Test
+    public void unsupportedInDestructuringInFunctionArguments() {
+        String script = "function({ [a]: b }) {};";
+        assertComputedPropertiesAreUnsupportedInDestructuring(
+                script, "Unsupported computed property in destructuring. (test#1)");
+    }
+
+    @Test
+    public void unsupportedInDestructuringInVariableDeclaration() {
+        String script = "var { [a]: b } = {};";
+        assertComputedPropertiesAreUnsupportedInDestructuring(
+                script, "Unsupported computed property in destructuring.");
+    }
+
+    private void assertComputedPropertiesAreUnsupportedInDestructuring(
+            String script, String message) {
+        try (Context cx = Context.enter()) {
+            cx.setLanguageVersion(Context.VERSION_ES6);
+            EvaluatorException ex =
+                    assertThrows(
+                            EvaluatorException.class,
+                            () -> cx.compileString(script, "test", 1, null));
+            assertEquals(message, ex.getMessage());
+        }
+    }
 }