Different between future prefect vs simple future + until
what's different in meaning between these two sentences?
- The decorator will have painted the wall by Thursday.
- The decorator will paint the wall until Thursday.
Does the second sentence mean the decorator will finish painting exactly before Thursday start or it could finish before for example in Wednesday like Future Prefect Tense.
Sentence #1 means that on Thursday, we can expect the work of painting the wall to be completed, regardless of the exact time at which the decorator stopped.
Sentence #2 means that the decorator will be painting until Thursday and then stop, with no indication either way on whether the work will actually be "finished" at that point.
Both sentences have a degree of ambiguity on whether Thursday is included in the scope of the work - see this question on ELL about inclusive/exclusive "until", and this one on "by" when used with dates.