Control shift

In generative syntax, a control shift is the phenomenon that the restrictions on the interpretation of PRO (see Control Theory) are relaxed or changed.

Examples
In (i) the subject of to go must refer to John, but in (ii) the subject of to be allowed can be John or Susan.

(i) John promised Susan [PRO to go]

(ii) John promised Susan [PRO to be allowed to go]

Link
Utrecht Lexicon of Linguistics