fn definitions can contain semicolons

[TheEdda]

Current grammar doesn't allow semicolons in function definitions. This leads to the following highlighting errors:

Since foo ends with the semicolon in the first parameter, the inline param2 impl is treated as a normal impl block and doesn't end until a curly open brace.

When defining Traits which often don't contain function implementations (and therefore don't contain open curly braces) this gets really annoying.