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Generalize NaN pattern detection using walk_pat

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This commit is contained in:
Etienne Millon 2013-07-24 23:17:10 +02:00
parent 5c729c0dca
commit fdd71bece2
2 changed files with 19 additions and 9 deletions
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23
src/librustc/middle/check_match.rs
View file

@ -104,18 +104,23 @@ pub fn check_arms(cx: &MatchCheckCtxt, arms: &[arm]) {
for arm.pats.iter().advance |pat| {
// Check that we do not match against a static NaN (#6804)
match cx.tcx.def_map.find(&pat.id) {
Some(&def_static(did, false)) => {
let const_expr = lookup_const_by_id(cx.tcx, did).get();
match eval_const_expr(cx.tcx, const_expr) {
const_float(f) if f.is_NaN() => {
let msg = "unmatchable NaN in pattern, use is_NaN() in a guard instead";
cx.tcx.sess.span_warn(pat.span, msg);
let pat_matches_nan: &fn(@pat) -> bool = |p| {
match cx.tcx.def_map.find(&p.id) {
Some(&def_static(did, false)) => {
let const_expr = lookup_const_by_id(cx.tcx, did).get();
match eval_const_expr(cx.tcx, const_expr) {
const_float(f) if f.is_NaN() => true,
_ => false
}
_ => {}
}
_ => false
}
};
for walk_pat(*pat) |p| {
if pat_matches_nan(p) {
cx.tcx.sess.span_warn(p.span, "unmatchable NaN in pattern, \
use is_NaN() in a guard instead");
}
_ => {}
}
let v = ~[*pat];

5
src/test/compile-fail/issue-6804.rs
View file

@ -9,6 +9,11 @@ fn main() {
_ => {},
};
//~^^^ WARNING unmatchable NaN in pattern, use is_NaN() in a guard instead
match [x, 1.0] {
[NaN, _] => {},
_ => {},
};
//~^^^ WARNING unmatchable NaN in pattern, use is_NaN() in a guard instead
}
// At least one error is needed so that compilation fails