Add a b'x' byte literal of type u8.

src/librustc/middle/const_eval.rs

@@ -506,6 +506,7 @@ pub fn lit_to_const(lit: &Lit) -> const_val {
         LitBinary(ref data) => {
             const_binary(Rc::new(data.iter().map(|x| *x).collect()))
         }
+        LitByte(n) => const_uint(n as u64),
         LitChar(n) => const_uint(n as u64),
         LitInt(n, _) => const_int(n),
         LitUint(n, _) => const_uint(n),

src/librustc/middle/lint.rs

@@ -805,6 +805,7 @@ fn check_type_limits(cx: &Context, e: &ast::Expr) {
                     } else { t };
                     let (min, max) = uint_ty_range(uint_type);
                     let lit_val: u64 = match lit.node {
+                        ast::LitByte(_v) => return,  // _v is u8, within range by definition
                         ast::LitInt(v, _) => v as u64,
                         ast::LitUint(v, _) => v,
                         ast::LitIntUnsuffixed(v) => v as u64,

src/librustc/middle/trans/consts.rs

@@ -43,6 +43,7 @@ pub fn const_lit(cx: &CrateContext, e: &ast::Expr, lit: ast::Lit)
     -> ValueRef {
     let _icx = push_ctxt("trans_lit");
     match lit.node {
+        ast::LitByte(b) => C_integral(Type::uint_from_ty(cx, ast::TyU8), b as u64, false),
         ast::LitChar(i) => C_integral(Type::char(cx), i as u64, false),
         ast::LitInt(i, t) => C_integral(Type::int_from_ty(cx, t), i as u64, true),
         ast::LitUint(u, t) => C_integral(Type::uint_from_ty(cx, t), u, false),

src/librustc/middle/typeck/check/mod.rs

@@ -1715,6 +1715,7 @@ pub fn check_lit(fcx: &FnCtxt, lit: &ast::Lit) -> ty::t {
         ast::LitBinary(..) => {
             ty::mk_slice(tcx, ty::ReStatic, ty::mt{ ty: ty::mk_u8(), mutbl: ast::MutImmutable })
         }
+        ast::LitByte(_) => ty::mk_u8(),
         ast::LitChar(_) => ty::mk_char(),
         ast::LitInt(_, t) => ty::mk_mach_int(t),
         ast::LitUint(_, t) => ty::mk_mach_uint(t),