Number grammar

[mikesamuel]

http://doc.rust-lang.org/doc/rust.html#number-literals

The number literal grammar in 3.5.3.2 has one probable type and a few surprising consequences that may not be spec errors.

num_lit : nonzero_dec [ dec_digit | '_' ] * num_suffix ?
    | '0' [       [ dec_digit | '_' ] + num_suffix ?
          | 'b'   [ '1' | '0' | '_' ] + int_suffix ?
          | 'x'   [ hex_digit | '-' ] + int_suffix ? ] ;

0x-0 is a number literal. This is not an ambiguity, but perhaps the '-' should be a '_'.

Nits:

0b_ is a valid binary literal and 0x_ is a valid hex literal which is surprising but not ambiguous.

Hex digits can be mixed case but the letter indicating the base cannot be -- 0xABCD is ok, but 0XABCD is not.

[graydon]

relative of #2234

[graydon]

This was fixed long ago. Closing.