Fix empty SET operations now throw error.

Author: niconoe-

src/Components/SetOperation.php

@@ -139,6 +139,11 @@ public static function parse(Parser $parser, TokensList $list, array $options =
             $parser->error('Unexpected token.', $commaLastSeenAt);
         }
 
+        // We got a SET operation without any assignment
+        if ($ret === []) {
+            $parser->error('Missing assignment in SET operation.', $list->tokens[$list->idx]);
+        }
+
         return $ret;
     }
 

tests/data/parser/parseUpdateEmptySet.out

@@ -171,6 +171,14 @@
     },
     "errors": {
         "lexer": [],
-        "parser": []
+        "parser": [
+            [
+                "Missing assignment in SET operation.",
+                {
+                    "@type": "@7"
+                },
+                0
+            ]
+        ]
     }
 }