Refactoring should check for new name before applying rename

When you refactor a variable name and change its name to one that already exists, and this existing variable has the same type (e.g. int), you're going to merge these two variables.

This can be dangerous - you don't get a warning.

Solution: Before refactoring, check if that name already exists, and put out a warning asking the user if he REALLY wants this.

Sometimes merging is intended. Maybe automatically check the types of the variables, and if they are NOT the same, refuse the merging/refactoring completely?