I saw several the following examples beginning with "All I did was":
- All I did was see something.
- All I did was hire her.
- All I did was tell him the truth.
Are these sentences correct?
Why a verb that following "was" is in a bare form, instead of a form that would be more appropriate for an object?
If those are correct, what is an object?
If those are grammatically incorrect, so how does a correct form look like?