Document::lastVisibleSymbolAt is looking for last visible symbol at current location.

If this last visible symbol is a lambda, Document::functionAt will consider it as a Function, and will return this lambda as enclosing function.

This algorithm is not working correctly if we're trying to find enslosing function for a local variable which is declared immediately after a lambda declaration.

In the attached screenshot, I've marked current symbol attributes in red, and result of  Document::functionAt in green