docs: private static Matcher<CompoundAssignmentTree> variableFromCompoundAssignmentTree(
        final Matcher<ExpressionTree> exprMatcher) {
      return new Matcher<CompoundAssignmentTree>() {
        @Override
        public boolean matches(CompoundAssignmentTree tree, VisitorState state) {
          return exprMatcher.matches(tree.getVariable(), state);
        }
      };
    }