From 9918693037dce8aa4bb6f08741b6812923486c18 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 19 Jun 2024 11:26:03 +0200 Subject: Merging upstream version 1.76.0+dfsg1. Signed-off-by: Daniel Baumann --- .../rustc_infer/src/infer/higher_ranked/mod.rs | 136 --------------------- 1 file changed, 136 deletions(-) delete mode 100644 compiler/rustc_infer/src/infer/higher_ranked/mod.rs (limited to 'compiler/rustc_infer/src/infer/higher_ranked') diff --git a/compiler/rustc_infer/src/infer/higher_ranked/mod.rs b/compiler/rustc_infer/src/infer/higher_ranked/mod.rs deleted file mode 100644 index 510b1797d..000000000 --- a/compiler/rustc_infer/src/infer/higher_ranked/mod.rs +++ /dev/null @@ -1,136 +0,0 @@ -//! Helper routines for higher-ranked things. See the `doc` module at -//! the end of the file for details. - -use super::combine::CombineFields; -use super::{HigherRankedType, InferCtxt}; -use crate::infer::CombinedSnapshot; -use rustc_middle::ty::fold::FnMutDelegate; -use rustc_middle::ty::relate::{Relate, RelateResult, TypeRelation}; -use rustc_middle::ty::{self, Binder, Ty, TyCtxt, TypeFoldable}; - -impl<'a, 'tcx> CombineFields<'a, 'tcx> { - /// Checks whether `for<..> sub <: for<..> sup` holds. - /// - /// For this to hold, **all** instantiations of the super type - /// have to be a super type of **at least one** instantiation of - /// the subtype. - /// - /// This is implemented by first entering a new universe. - /// We then replace all bound variables in `sup` with placeholders, - /// and all bound variables in `sub` with inference vars. - /// We can then just relate the two resulting types as normal. - /// - /// Note: this is a subtle algorithm. For a full explanation, please see - /// the [rustc dev guide][rd] - /// - /// [rd]: https://rustc-dev-guide.rust-lang.org/borrow_check/region_inference/placeholders_and_universes.html - #[instrument(skip(self), level = "debug")] - pub fn higher_ranked_sub( - &mut self, - sub: Binder<'tcx, T>, - sup: Binder<'tcx, T>, - sub_is_expected: bool, - ) -> RelateResult<'tcx, ()> - where - T: Relate<'tcx>, - { - let span = self.trace.cause.span; - // First, we instantiate each bound region in the supertype with a - // fresh placeholder region. Note that this automatically creates - // a new universe if needed. - let sup_prime = self.infcx.instantiate_binder_with_placeholders(sup); - - // Next, we instantiate each bound region in the subtype - // with a fresh region variable. These region variables -- - // but no other preexisting region variables -- can name - // the placeholders. - let sub_prime = self.infcx.instantiate_binder_with_fresh_vars(span, HigherRankedType, sub); - - debug!("a_prime={:?}", sub_prime); - debug!("b_prime={:?}", sup_prime); - - // Compare types now that bound regions have been replaced. - let result = self.sub(sub_is_expected).relate(sub_prime, sup_prime)?; - - debug!("OK result={result:?}"); - // NOTE: returning the result here would be dangerous as it contains - // placeholders which **must not** be named afterwards. - Ok(()) - } -} - -impl<'tcx> InferCtxt<'tcx> { - /// Replaces all bound variables (lifetimes, types, and constants) bound by - /// `binder` with placeholder variables in a new universe. This means that the - /// new placeholders can only be named by inference variables created after - /// this method has been called. - /// - /// This is the first step of checking subtyping when higher-ranked things are involved. - /// For more details visit the relevant sections of the [rustc dev guide]. - /// - /// [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/traits/hrtb.html - #[instrument(level = "debug", skip(self), ret)] - pub fn instantiate_binder_with_placeholders(&self, binder: ty::Binder<'tcx, T>) -> T - where - T: TypeFoldable> + Copy, - { - if let Some(inner) = binder.no_bound_vars() { - return inner; - } - - let next_universe = self.create_next_universe(); - - let delegate = FnMutDelegate { - regions: &mut |br: ty::BoundRegion| { - ty::Region::new_placeholder( - self.tcx, - ty::PlaceholderRegion { universe: next_universe, bound: br }, - ) - }, - types: &mut |bound_ty: ty::BoundTy| { - Ty::new_placeholder( - self.tcx, - ty::PlaceholderType { universe: next_universe, bound: bound_ty }, - ) - }, - consts: &mut |bound_var: ty::BoundVar, ty| { - ty::Const::new_placeholder( - self.tcx, - ty::PlaceholderConst { universe: next_universe, bound: bound_var }, - ty, - ) - }, - }; - - debug!(?next_universe); - self.tcx.replace_bound_vars_uncached(binder, delegate) - } - - /// See [RegionConstraintCollector::leak_check][1]. We only check placeholder - /// leaking into `outer_universe`, i.e. placeholders which cannot be named by that - /// universe. - /// - /// [1]: crate::infer::region_constraints::RegionConstraintCollector::leak_check - pub fn leak_check( - &self, - outer_universe: ty::UniverseIndex, - only_consider_snapshot: Option<&CombinedSnapshot<'tcx>>, - ) -> RelateResult<'tcx, ()> { - // If the user gave `-Zno-leak-check`, or we have been - // configured to skip the leak check, then skip the leak check - // completely. The leak check is deprecated. Any legitimate - // subtyping errors that it would have caught will now be - // caught later on, during region checking. However, we - // continue to use it for a transition period. - if self.tcx.sess.opts.unstable_opts.no_leak_check || self.skip_leak_check { - return Ok(()); - } - - self.inner.borrow_mut().unwrap_region_constraints().leak_check( - self.tcx, - outer_universe, - self.universe(), - only_consider_snapshot, - ) - } -} -- cgit v1.2.3