@Override
  public void visitPrefixExpression(PrefixExpression expr) {
    expr.setExpression(replaceExpr(expr.getExpression()));
  }
Groovy AST visitor that allows to replace both statements and expressions.

@author Peter Niederwieser
spock-core/src/main/java/org/spockframework/compiler/ExpressionReplacingVisitorSupport.java