A: 

ctrl-space inside the parens

lordscarlet
Doesn't help. What if I wanted to know the type of Value?
André Neves
A: 

I just found that the equivalent to mouse hovering is View -> IntelliSense -> Quick Info. If the solution does not arise here, I'll just use the shortcut Ctrl+K, Ctrl+I.

André Neves
Problem with this one: F1 still goes to the documentation of the error, not of whatever else I want.
André Neves
+1  A: 

Cut the first part of the line ("DateTime duracao = ") into the clipboard, then you should be able to hover over "Subtract" and see the return type. Not ideal, but I find myself doing it all the time!

Danny Tuppeny
+1  A: 

Select "Build|Clean Solution" - this cleans up intermediate files and other things. More importantly, it also clears the list of error messages, restoring normal behaviour of Intellisense.

Bevan
A: 

Since duracao is a DateTime, and the error message is 'cannot convert Timespan to DateTime' - you can already see the subtract function is returning a Timespan

korro