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reintroduce commit_if_ok call into higher_ranked_sub

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This commit is contained in:
Niko Matsakis 2019-02-19 18:38:42 -05:00
parent 3cd286bac2
commit 6cb4ffbe14
1 changed files with 25 additions and 26 deletions
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51
src/librustc/infer/higher_ranked/mod.rs
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@ -29,27 +29,29 @@ impl<'a, 'gcx, 'tcx> CombineFields<'a, 'gcx, 'tcx> {
let span = self.trace.cause.span;
// First, we instantiate each bound region in the supertype with a
// fresh placeholder region.
let (b_prime, _) = self.infcx.replace_bound_vars_with_placeholders(b);
return self.infcx.commit_if_ok(|_snapshot| {
// First, we instantiate each bound region in the supertype with a
// fresh placeholder region.
let (b_prime, _) = self.infcx.replace_bound_vars_with_placeholders(b);
// Next, we instantiate each bound region in the subtype
// with a fresh region variable. These region variables --
// but no other pre-existing region variables -- can name
// the placeholders.
let (a_prime, _) =
self.infcx
.replace_bound_vars_with_fresh_vars(span, HigherRankedType, a);
// Next, we instantiate each bound region in the subtype
// with a fresh region variable. These region variables --
// but no other pre-existing region variables -- can name
// the placeholders.
let (a_prime, _) =
self.infcx
.replace_bound_vars_with_fresh_vars(span, HigherRankedType, a);
debug!("a_prime={:?}", a_prime);
debug!("b_prime={:?}", b_prime);
debug!("a_prime={:?}", a_prime);
debug!("b_prime={:?}", b_prime);
// Compare types now that bound regions have been replaced.
let result = self.sub(a_is_expected).relate(&a_prime, &b_prime)?;
// Compare types now that bound regions have been replaced.
let result = self.sub(a_is_expected).relate(&a_prime, &b_prime)?;
debug!("higher_ranked_sub: OK result={:?}", result);
debug!("higher_ranked_sub: OK result={:?}", result);
Ok(ty::Binder::bind(result))
Ok(ty::Binder::bind(result))
});
}
}
@ -72,10 +74,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
/// [rustc guide]: https://rust-lang.github.io/rustc-guide/traits/hrtb.html
pub fn replace_bound_vars_with_placeholders<T>(
&self,
binder: &ty::Binder<T>
binder: &ty::Binder<T>,
) -> (T, PlaceholderMap<'tcx>)
where
T: TypeFoldable<'tcx>
T: TypeFoldable<'tcx>,
{
let next_universe = self.create_next_universe();
@ -97,14 +99,11 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
debug!(
"replace_bound_vars_with_placeholders(\
next_universe={:?}, \
binder={:?}, \
result={:?}, \
map={:?})",
next_universe,
binder,
result,
map,
next_universe={:?}, \
binder={:?}, \
result={:?}, \
map={:?})",
next_universe, binder, result, map,
);
(result, map)