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make probe priority logic clearer

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This commit is contained in:
Ariel Ben-Yehuda 2017-08-14 15:06:14 +03:00
parent 6f82dea299
commit fceab9fb34
1 changed files with 28 additions and 38 deletions
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40
src/librustc_typeck/check/method/probe.rs
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@ -1116,21 +1116,17 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
let steps = self.steps.clone();
// find the first step that works
steps.iter().filter_map(|step| self.pick_step(step)).next()
}
fn pick_step(&mut self, step: &CandidateStep<'tcx>) -> Option<PickResult<'tcx>> {
debug!("pick_step: step={:?}", step);
if step.self_ty.references_error() {
return None;
}
if let Some(result) = self.pick_by_value_method(step) {
return Some(result);
}
self.pick_autorefd_method(step)
steps
.iter()
.filter(|step| {
debug!("pick_core: step={:?}", step);
!step.self_ty.references_error()
}).flat_map(|step| {
self.pick_by_value_method(step).or_else(|| {
self.pick_autorefd_method(step, hir::MutImmutable).or_else(|| {
self.pick_autorefd_method(step, hir::MutMutable)
})})})
.next()
}
fn pick_by_value_method(&mut self, step: &CandidateStep<'tcx>) -> Option<PickResult<'tcx>> {
@ -1161,26 +1157,22 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
})
}
fn pick_autorefd_method(&mut self, step: &CandidateStep<'tcx>) -> Option<PickResult<'tcx>> {
fn pick_autorefd_method(&mut self, step: &CandidateStep<'tcx>, mutbl: hir::Mutability)
-> Option<PickResult<'tcx>> {
let tcx = self.tcx;
// In general, during probing we erase regions. See
// `impl_self_ty()` for an explanation.
let region = tcx.types.re_erased;
// Search through mutabilities in order to find one where pick works:
[hir::MutImmutable, hir::MutMutable]
.iter()
.filter_map(|&m| {
let autoref_ty = tcx.mk_ref(region,
ty::TypeAndMut {
ty: step.self_ty,
mutbl: m,
ty: step.self_ty, mutbl
});
self.pick_method(autoref_ty).map(|r| {
r.map(|mut pick| {
pick.autoderefs = step.autoderefs;
pick.autoref = Some(m);
pick.autoref = Some(mutbl);
pick.unsize = if step.unsize {
Some(step.self_ty)
} else {
@ -1189,8 +1181,6 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
pick
})
})
})
.nth(0)
}
fn pick_method(&mut self, self_ty: Ty<'tcx>) -> Option<PickResult<'tcx>> {