diff options
| -rw-r--r-- | compiler/rustc_hir_typeck/src/method/probe.rs | 124 |
1 files changed, 114 insertions, 10 deletions
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs index c92f00a54dd..66ff71f729c 100644 --- a/compiler/rustc_hir_typeck/src/method/probe.rs +++ b/compiler/rustc_hir_typeck/src/method/probe.rs @@ -1144,6 +1144,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { &self, pick_diag_hints: &mut PickDiagHints<'b, 'tcx>, ) -> Option<PickResult<'tcx>> { + let track_unstable_candidates = pick_diag_hints.unstable_candidates.is_some(); self.steps .iter() // At this point we're considering the types to which the receiver can be converted, @@ -1167,22 +1168,125 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> { .unwrap_or_else(|_| { span_bug!(self.span, "{:?} was applicable but now isn't?", step.self_ty) }); - self.pick_by_value_method(step, self_ty, pick_diag_hints).or_else(|| { - self.pick_autorefd_method(step, self_ty, hir::Mutability::Not, pick_diag_hints) - .or_else(|| { - self.pick_autorefd_method( + + let by_value_pick = self.pick_by_value_method(step, self_ty, pick_diag_hints); + + // Check for shadowing of a by-reference method by a by-value method (see comments on check_for_shadowing) + if let Some(by_value_pick) = by_value_pick { + if let Ok(by_value_pick) = by_value_pick.as_ref() { + if by_value_pick.kind == PickKind::InherentImplPick { + if let Err(e) = self.check_for_shadowed_autorefd_method( + by_value_pick, + step, + self_ty, + hir::Mutability::Not, + track_unstable_candidates, + ) { + return Some(Err(e)); + } + if let Err(e) = self.check_for_shadowed_autorefd_method( + by_value_pick, step, self_ty, hir::Mutability::Mut, - pick_diag_hints, - ) - }) - .or_else(|| self.pick_const_ptr_method(step, self_ty, pick_diag_hints)) - .or_else(|| self.pick_reborrow_pin_method(step, self_ty, pick_diag_hints)) - }) + track_unstable_candidates, + ) { + return Some(Err(e)); + } + } + } + return Some(by_value_pick); + } + + let autoref_pick = + self.pick_autorefd_method(step, self_ty, hir::Mutability::Not, pick_diag_hints); + // Check for shadowing of a by-mut-ref method by a by-reference method (see comments on check_for_shadowing) + if let Some(autoref_pick) = autoref_pick { + if let Ok(autoref_pick) = autoref_pick.as_ref() { + // Check we're not shadowing others + if autoref_pick.kind == PickKind::InherentImplPick { + if let Err(e) = self.check_for_shadowed_autorefd_method( + autoref_pick, + step, + self_ty, + hir::Mutability::Mut, + track_unstable_candidates, + ) { + return Some(Err(e)); + } + } + } + return Some(autoref_pick); + } + + // Note that no shadowing errors are produced from here on, + // as we consider const ptr methods. + // We allow new methods that take *mut T to shadow + // methods which took *const T, so there is no entry in + // this list for the results of `pick_const_ptr_method`. + // The reason is that the standard pointer cast method + // (on a mutable pointer) always already shadows the + // cast method (on a const pointer). So, if we added + // `pick_const_ptr_method` to this method, the anti- + // shadowing algorithm would always complain about + // the conflict between *const::cast and *mut::cast. + // In practice therefore this does constrain us: + // we cannot add new + // self: *mut Self + // methods to types such as NonNull or anything else + // which implements Receiver, because this might in future + // shadow existing methods taking + // self: *const NonNull<Self> + // in the pointee. In practice, methods taking raw pointers + // are rare, and it seems that it should be easily possible + // to avoid such compatibility breaks. + // We also don't check for reborrowed pin methods which + // may be shadowed; these also seem unlikely to occur. + self.pick_autorefd_method(step, self_ty, hir::Mutability::Mut, pick_diag_hints) + .or_else(|| self.pick_const_ptr_method(step, self_ty, pick_diag_hints)) + .or_else(|| self.pick_reborrow_pin_method(step, self_ty, pick_diag_hints)) }) } + /// Check for cases where arbitrary self types allows shadowing + /// of methods that might be a compatibility break. Specifically, + /// we have something like: + /// ```ignore (illustrative) + /// struct A; + /// impl A { + /// fn foo(self: &NonNull<A>) {} + /// // note this is by reference + /// } + /// ``` + /// then we've come along and added this method to `NonNull`: + /// ```ignore (illustrative) + /// fn foo(self) // note this is by value + /// ``` + /// Report an error in this case. + fn check_for_shadowed_autorefd_method( + &self, + _possible_shadower: &Pick<'tcx>, + step: &CandidateStep<'tcx>, + self_ty: Ty<'tcx>, + mutbl: hir::Mutability, + track_unstable_candidates: bool, + ) -> Result<(), MethodError<'tcx>> { + // We don't want to remember any of the diagnostic hints from this + // shadow search, but we do need to provide Some/None for the + // unstable_candidates in order to reflect the behavior of the + // main search. + let mut pick_diag_hints = PickDiagHints { + unstable_candidates: if track_unstable_candidates { Some(Vec::new()) } else { None }, + unsatisfied_predicates: &mut Vec::new(), + }; + let _potentially_shadowed_pick = + self.pick_autorefd_method(step, self_ty, mutbl, &mut pick_diag_hints); + + // At the moment, this function does no checks. A future + // commit will fill out the body here. + Ok(()) + } + /// For each type `T` in the step list, this attempts to find a method where /// the (transformed) self type is exactly `T`. We do however do one /// transformation on the adjustment: if we are passing a region pointer in, |