This is a syntax error.
Using the maximum munching rule is i+++indicated as:
i ++ +
The latter +is a binary addition operator. But, obviously, it does not have two operands, which leads to a parser error.
EDIT:
Question from the comment: Can we i++++j?
It is designated as:
i ++ ++ j
which is again a syntax error because it ++is a unary operator.
Similar lines are i+++++jindicated by the scanner as:
i++ ++ + j
, ((i++)++) + j, i++ l, ++ .