That doesn't (in theory) prevent a parser from taking a guess what the user meant though, for example by incorporating formatting (that is otherwise irrelevant

That doesn't (in theory) prevent a parser from taking a guess what the user meant though, for example by incorporating formatting (that is otherwise irrelevant to the parsing). In C++ terms, a missing a semicolon after a class definition is a problem, but almost always the next token is not on the same line but multiple lines further down if this is what happened. A parser that encounters a class definition followed by one or more newlines and then an unexpected token could very reasonably output a hint that there is probably a missing semicolon here (and possibly continue under the pretense that it was there).