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Don't call instantiate_type_scheme during method probing

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It can introduce obligations to the fulfillment context, which would
incorrectly still remain after the probe finished.

Fixes #25679.
This commit is contained in:
Ariel Ben-Yehuda 2015-06-13 23:34:03 +03:00 • committed by Ariel Ben-Yehuda
parent 0d82fb55db
commit 1af72660a7
2 changed files with 37 additions and 1 deletions
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10
src/librustc_typeck/check/method/probe.rs
View file

@ -398,11 +398,19 @@ impl<'a,'tcx> ProbeContext<'a,'tcx> {
}
let (impl_ty, impl_substs) = self.impl_ty_and_substs(impl_def_id);
let impl_ty = self.fcx.instantiate_type_scheme(self.span, &impl_substs, &impl_ty);
// We can't use instantiate_type_scheme here as it will pollute
// the fcx's fulfillment context if this probe is rolled back.
let cause = traits::ObligationCause::misc(self.span, self.fcx.body_id);
let mut selcx = &mut traits::SelectionContext::new(self.fcx.infcx(), self.fcx);
let traits::Normalized { value: impl_ty, .. } =
traits::normalize(selcx, cause, &impl_ty.subst(self.tcx(), &impl_substs));
// Determine the receiver type that the method itself expects.
let xform_self_ty =
self.xform_self_ty(&item, impl_ty, &impl_substs);
debug!("assemble_inherent_impl_probe: self ty = {:?}",
xform_self_ty.repr(self.tcx()));
self.inherent_candidates.push(Candidate {
xform_self_ty: xform_self_ty,

28
src/test/run-pass/issue-25679.rs Normal file
View file

@ -0,0 +1,28 @@
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
trait Device {
type Resources;
}
struct Foo<D, R>(D, R);
impl<D: Device, S> Foo<D, S> {
fn present(&self) {}
}
struct Res;
struct Dev;
impl Device for Dev { type Resources = Res; }
fn main() {
let foo = Foo(Dev, Res);
foo.present();
}