Less arcane error message for stray backquote

[lkuper]

The lexer's error message when I accidentally have a backquote in a Rust program is less than great: "unknown start of token: 96".

gcc's error is "stray ‘`’ in program". Something like that would be much nicer.

[bblum]

96 is ASCII for backtick. The culprit is libsyntax/parse/lexer.rs:695:next_token_inner.

All the error messages there are bad, and what's more, the span seems to be off-by-one (note where the arrow points):

parse-error.rs:2:18: 2:19 error: unknown character escape: 3232
parse-error.rs:2     #error["%c.%c", '\ಠ', '\ಠ'];
                                   ^

Not gonna touch it myself, for fear that the int-ness is because of some unicode issue.

[lkuper]

It seems to me that anything that's (a) on a standard keyboard layout and (b) part of ASCII 0-127 (notably, backquote) should be explicitly handled, because those are characters likely to be typed accidentally.

Good catch on the off-by-one span.

[Aatch]

This is fixed in current incoming.