Minor refactor

Author: hmac

ruby/ql/lib/codeql/ruby/dataflow/internal/SsaImplSpecific.qll

@@ -23,13 +23,14 @@ class SourceVariable = LocalVariable;
  */
 predicate variableWrite(BasicBlock bb, int i, SourceVariable v, boolean certain) {
   (
-    // We consider the `self` variable to have a single write at the entry to a method block...
-    v.(SelfVariable).getDeclaringScope() = bb.(BasicBlocks::EntryBasicBlock).getScope() and
-    i = 0
-    or
-    // ...or a class or module block.
-    bb.getNode(i).getNode() =
-      v.(SelfVariable).getDeclaringScope().(ModuleBase).getAControlFlowEntryNode()
+    exists(Scope scope | scope = v.(SelfVariable).getDeclaringScope() |
+      // We consider the `self` variable to have a single write at the entry to a method block...
+      scope = bb.(BasicBlocks::EntryBasicBlock).getScope() and
+      i = 0
+      or
+      // ...or a class or module block.
+      bb.getNode(i).getNode() = scope.(ModuleBase).getAControlFlowEntryNode()
+    )
     or
     SsaImpl::uninitializedWrite(bb, i, v)
     or