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comment some ugly points in check_match

This commit is contained in:
Ariel Ben-Yehuda 2016-09-24 16:12:37 +03:00
parent a6b3b01b5f
commit e5c01f4633
1 changed files with 23 additions and 15 deletions
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38
src/librustc_const_eval/check_match.rs
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@ -851,8 +851,11 @@ pub fn constructor_arity(_cx: &MatchCheckCtxt, ctor: &Constructor, ty: Ty) -> us
ty::TyBox(_) => 1,
ty::TySlice(_) => match *ctor {
Slice(length) => length,
ConstantValue(_) => 0,
_ => bug!()
ConstantValue(_) => {
// TODO: this is utterly wrong, but required for byte arrays
0
}
_ => bug!("bad slice pattern {:?} {:?}", ctor, ty)
},
ty::TyRef(..) => 1,
ty::TyAdt(adt, _) => {
@ -981,20 +984,25 @@ pub fn specialize<'a, 'b, 'tcx>(
Some(vec![wpat(&**inner)]),
PatKind::Lit(ref expr) => {
if let Some(&ty::TyS { sty: ty::TyRef(_, mt), .. }) = r[col].1 {
// HACK: handle string literals. A string literal pattern
// serves both as an unary reference pattern and as a
// nullary value pattern, depending on the type.
Some(vec![(pat, Some(mt.ty))])
} else {
let expr_value = eval_const_expr(cx.tcx, &expr);
match range_covered_by_constructor(
cx.tcx, expr.span, constructor, &expr_value, &expr_value
) {
Ok(true) => Some(vec![]),
Ok(false) => None,
Err(ErrorReported) => None,
match r[col].1 {
Some(&ty::TyS { sty: ty::TyRef(_, mt), .. }) => {
// HACK: handle string literals. A string literal pattern
// serves both as an unary reference pattern and as a
// nullary value pattern, depending on the type.
Some(vec![(pat, Some(mt.ty))])
}
Some(ty) => {
assert_eq!(constructor_arity(cx, constructor, ty), 0);
let expr_value = eval_const_expr(cx.tcx, &expr);
match range_covered_by_constructor(
cx.tcx, expr.span, constructor, &expr_value, &expr_value
) {
Ok(true) => Some(vec![]),
Ok(false) => None,
Err(ErrorReported) => None,
}
}
None => span_bug!(pat.span, "literal pattern {:?} has no type", pat)
}
}