diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs index feef7295254a9..da52388654a87 100644 --- a/compiler/rustc_feature/src/active.rs +++ b/compiler/rustc_feature/src/active.rs @@ -400,6 +400,8 @@ declare_features! ( (active, generic_arg_infer, "1.55.0", Some(85077), None), /// Allows associated types to be generic, e.g., `type Foo;` (RFC 1598). (active, generic_associated_types, "1.23.0", Some(44265), None), + /// An extension to the `generic_associated_types` feature, allowing incomplete features. + (incomplete, generic_associated_types_extended, "1.61.0", Some(95451), None), /// Allows non-trivial generic constants which have to have wfness manually propagated to callers (incomplete, generic_const_exprs, "1.56.0", Some(76560), None), /// Allows using `..X`, `..=X`, `...X`, and `X..` as a pattern. diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs index 388109e6512dd..075928c889d83 100644 --- a/compiler/rustc_middle/src/ty/fold.rs +++ b/compiler/rustc_middle/src/ty/fold.rs @@ -1379,3 +1379,50 @@ impl<'tcx> TypeVisitor<'tcx> for LateBoundRegionsCollector { ControlFlow::CONTINUE } } + +/// Finds the max universe present +pub struct MaxUniverse { + max_universe: ty::UniverseIndex, +} + +impl MaxUniverse { + pub fn new() -> Self { + MaxUniverse { max_universe: ty::UniverseIndex::ROOT } + } + + pub fn max_universe(self) -> ty::UniverseIndex { + self.max_universe + } +} + +impl<'tcx> TypeVisitor<'tcx> for MaxUniverse { + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow { + if let ty::Placeholder(placeholder) = t.kind() { + self.max_universe = ty::UniverseIndex::from_u32( + self.max_universe.as_u32().max(placeholder.universe.as_u32()), + ); + } + + t.super_visit_with(self) + } + + fn visit_const(&mut self, c: ty::consts::Const<'tcx>) -> ControlFlow { + if let ty::ConstKind::Placeholder(placeholder) = c.val() { + self.max_universe = ty::UniverseIndex::from_u32( + self.max_universe.as_u32().max(placeholder.universe.as_u32()), + ); + } + + c.super_visit_with(self) + } + + fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow { + if let ty::RePlaceholder(placeholder) = *r { + self.max_universe = ty::UniverseIndex::from_u32( + self.max_universe.as_u32().max(placeholder.universe.as_u32()), + ); + } + + ControlFlow::CONTINUE + } +} diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index 84dbad846dd29..ee29a1e96eb28 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -722,6 +722,7 @@ symbols! { generators, generic_arg_infer, generic_associated_types, + generic_associated_types_extended, generic_const_exprs, generic_param_attrs, get_context, diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs index 36eddf7784b32..d95512bb88f36 100644 --- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs +++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs @@ -5,6 +5,7 @@ use super::*; use crate::infer::region_constraints::{Constraint, RegionConstraintData}; use crate::infer::InferCtxt; +use crate::traits::project::ProjectAndUnifyResult; use rustc_middle::ty::fold::TypeFolder; use rustc_middle::ty::{Region, RegionVid, Term}; @@ -751,7 +752,7 @@ impl<'tcx> AutoTraitFinder<'tcx> { debug!("Projecting and unifying projection predicate {:?}", predicate); match project::poly_project_and_unify_type(select, &obligation.with(p)) { - Err(e) => { + ProjectAndUnifyResult::MismatchedProjectionTypes(e) => { debug!( "evaluate_nested_obligations: Unable to unify predicate \ '{:?}' '{:?}', bailing out", @@ -759,11 +760,11 @@ impl<'tcx> AutoTraitFinder<'tcx> { ); return false; } - Ok(Err(project::InProgress)) => { + ProjectAndUnifyResult::Recursive => { debug!("evaluate_nested_obligations: recursive projection predicate"); return false; } - Ok(Ok(Some(v))) => { + ProjectAndUnifyResult::Holds(v) => { // We only care about sub-obligations // when we started out trying to unify // some inference variables. See the comment above @@ -782,7 +783,7 @@ impl<'tcx> AutoTraitFinder<'tcx> { } } } - Ok(Ok(None)) => { + ProjectAndUnifyResult::FailedNormalization => { // It's ok not to make progress when have no inference variables - // in that case, we were only performing unification to check if an // error occurred (which would indicate that it's impossible for our diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs index 1b8628344671d..d0b8b0281c5bf 100644 --- a/compiler/rustc_trait_selection/src/traits/fulfill.rs +++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs @@ -14,7 +14,7 @@ use rustc_middle::ty::{self, Binder, Const, Ty, TypeFoldable}; use std::marker::PhantomData; use super::const_evaluatable; -use super::project; +use super::project::{self, ProjectAndUnifyResult}; use super::select::SelectionContext; use super::wf; use super::CodeAmbiguity; @@ -753,8 +753,8 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> { } match project::poly_project_and_unify_type(self.selcx, &project_obligation) { - Ok(Ok(Some(os))) => ProcessResult::Changed(mk_pending(os)), - Ok(Ok(None)) => { + ProjectAndUnifyResult::Holds(os) => ProcessResult::Changed(mk_pending(os)), + ProjectAndUnifyResult::FailedNormalization => { stalled_on.clear(); stalled_on.extend(substs_infer_vars( self.selcx, @@ -763,10 +763,12 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> { ProcessResult::Unchanged } // Let the caller handle the recursion - Ok(Err(project::InProgress)) => ProcessResult::Changed(mk_pending(vec![ + ProjectAndUnifyResult::Recursive => ProcessResult::Changed(mk_pending(vec![ project_obligation.with(project_obligation.predicate.to_predicate(tcx)), ])), - Err(e) => ProcessResult::Error(CodeProjectionError(e)), + ProjectAndUnifyResult::MismatchedProjectionTypes(e) => { + ProcessResult::Error(CodeProjectionError(e)) + } } } } diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs index d4ec677a0b1c5..2251f992e4dc6 100644 --- a/compiler/rustc_trait_selection/src/traits/project.rs +++ b/compiler/rustc_trait_selection/src/traits/project.rs @@ -28,7 +28,7 @@ use rustc_hir::def_id::DefId; use rustc_hir::lang_items::LangItem; use rustc_infer::infer::resolve::OpportunisticRegionResolver; use rustc_middle::traits::select::OverflowError; -use rustc_middle::ty::fold::{TypeFoldable, TypeFolder}; +use rustc_middle::ty::fold::{MaxUniverse, TypeFoldable, TypeFolder}; use rustc_middle::ty::subst::Subst; use rustc_middle::ty::{self, Term, ToPredicate, Ty, TyCtxt}; use rustc_span::symbol::sym; @@ -144,6 +144,18 @@ impl<'tcx> ProjectionCandidateSet<'tcx> { } } +/// Takes the place of a +/// Result< +/// Result>>, InProgress>, +/// MismatchedProjectionTypes<'tcx>, +/// > +pub(super) enum ProjectAndUnifyResult<'tcx> { + Holds(Vec>), + FailedNormalization, + Recursive, + MismatchedProjectionTypes(MismatchedProjectionTypes<'tcx>), +} + /// Evaluates constraints of the form: /// /// for<...> ::U == V @@ -167,19 +179,47 @@ impl<'tcx> ProjectionCandidateSet<'tcx> { pub(super) fn poly_project_and_unify_type<'cx, 'tcx>( selcx: &mut SelectionContext<'cx, 'tcx>, obligation: &PolyProjectionObligation<'tcx>, -) -> Result< - Result>>, InProgress>, - MismatchedProjectionTypes<'tcx>, -> { +) -> ProjectAndUnifyResult<'tcx> { let infcx = selcx.infcx(); - infcx.commit_if_ok(|_snapshot| { + let r = infcx.commit_if_ok(|_snapshot| { + let old_universe = infcx.universe(); let placeholder_predicate = infcx.replace_bound_vars_with_placeholders(obligation.predicate); + let new_universe = infcx.universe(); let placeholder_obligation = obligation.with(placeholder_predicate); - let result = project_and_unify_type(selcx, &placeholder_obligation)?; - Ok(result) - }) + match project_and_unify_type(selcx, &placeholder_obligation) { + ProjectAndUnifyResult::MismatchedProjectionTypes(e) => Err(e), + ProjectAndUnifyResult::Holds(obligations) + if old_universe != new_universe + && selcx.tcx().features().generic_associated_types_extended => + { + // If the `generic_associated_types_extended` feature is active, then we ignore any + // obligations references lifetimes from any universe greater than or equal to the + // universe just created. Otherwise, we can end up with something like `for<'a> I: 'a`, + // which isn't quite what we want. Ideally, we want either an implied + // `for<'a where I: 'a> I: 'a` or we want to "lazily" check these hold when we + // substitute concrete regions. There is design work to be done here; until then, + // however, this allows experimenting potential GAT features without running into + // well-formedness issues. + let new_obligations = obligations + .into_iter() + .filter(|obligation| { + let mut visitor = MaxUniverse::new(); + obligation.predicate.visit_with(&mut visitor); + visitor.max_universe() < new_universe + }) + .collect(); + Ok(ProjectAndUnifyResult::Holds(new_obligations)) + } + other => Ok(other), + } + }); + + match r { + Ok(inner) => inner, + Err(err) => ProjectAndUnifyResult::MismatchedProjectionTypes(err), + } } /// Evaluates constraints of the form: @@ -189,15 +229,11 @@ pub(super) fn poly_project_and_unify_type<'cx, 'tcx>( /// If successful, this may result in additional obligations. /// /// See [poly_project_and_unify_type] for an explanation of the return value. +#[tracing::instrument(level = "debug", skip(selcx))] fn project_and_unify_type<'cx, 'tcx>( selcx: &mut SelectionContext<'cx, 'tcx>, obligation: &ProjectionObligation<'tcx>, -) -> Result< - Result>>, InProgress>, - MismatchedProjectionTypes<'tcx>, -> { - debug!(?obligation, "project_and_unify_type"); - +) -> ProjectAndUnifyResult<'tcx> { let mut obligations = vec![]; let infcx = selcx.infcx(); @@ -210,8 +246,8 @@ fn project_and_unify_type<'cx, 'tcx>( &mut obligations, ) { Ok(Some(n)) => n, - Ok(None) => return Ok(Ok(None)), - Err(InProgress) => return Ok(Err(InProgress)), + Ok(None) => return ProjectAndUnifyResult::FailedNormalization, + Err(InProgress) => return ProjectAndUnifyResult::Recursive, }; debug!(?normalized, ?obligations, "project_and_unify_type result"); let actual = obligation.predicate.term; @@ -231,11 +267,11 @@ fn project_and_unify_type<'cx, 'tcx>( match infcx.at(&obligation.cause, obligation.param_env).eq(normalized, actual) { Ok(InferOk { obligations: inferred_obligations, value: () }) => { obligations.extend(inferred_obligations); - Ok(Ok(Some(obligations))) + ProjectAndUnifyResult::Holds(obligations) } Err(err) => { - debug!("project_and_unify_type: equating types encountered error {:?}", err); - Err(MismatchedProjectionTypes { err }) + debug!("equating types encountered error {:?}", err); + ProjectAndUnifyResult::MismatchedProjectionTypes(MismatchedProjectionTypes { err }) } } } diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs index 42f17721f9b54..4f033d45c1f32 100644 --- a/compiler/rustc_trait_selection/src/traits/select/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs @@ -21,6 +21,7 @@ use super::{ use crate::infer::{InferCtxt, InferOk, TypeFreshener}; use crate::traits::error_reporting::InferCtxtExt; +use crate::traits::project::ProjectAndUnifyResult; use crate::traits::project::ProjectionCacheKeyExt; use crate::traits::ProjectionCacheKey; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; @@ -525,7 +526,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { let data = bound_predicate.rebind(data); let project_obligation = obligation.with(data); match project::poly_project_and_unify_type(self, &project_obligation) { - Ok(Ok(Some(mut subobligations))) => { + ProjectAndUnifyResult::Holds(mut subobligations) => { 'compute_res: { // If we've previously marked this projection as 'complete', then // use the final cached result (either `EvaluatedToOk` or @@ -573,9 +574,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { res } } - Ok(Ok(None)) => Ok(EvaluatedToAmbig), - Ok(Err(project::InProgress)) => Ok(EvaluatedToRecur), - Err(_) => Ok(EvaluatedToErr), + ProjectAndUnifyResult::FailedNormalization => Ok(EvaluatedToAmbig), + ProjectAndUnifyResult::Recursive => Ok(EvaluatedToRecur), + ProjectAndUnifyResult::MismatchedProjectionTypes(_) => Ok(EvaluatedToErr), } } diff --git a/src/test/ui/feature-gates/feature-gate-generic_associated_types_extended.rs b/src/test/ui/feature-gates/feature-gate-generic_associated_types_extended.rs new file mode 100644 index 0000000000000..258b8cd35c777 --- /dev/null +++ b/src/test/ui/feature-gates/feature-gate-generic_associated_types_extended.rs @@ -0,0 +1,6 @@ +#![feature(generic_associated_types)] + +// This feature doesn't *currently* fire on any specific code; it's just a +// behavior change. Future changes might. +#[rustc_error] //~ the +fn main() {} diff --git a/src/test/ui/feature-gates/feature-gate-generic_associated_types_extended.stderr b/src/test/ui/feature-gates/feature-gate-generic_associated_types_extended.stderr new file mode 100644 index 0000000000000..6a5eba38cacc6 --- /dev/null +++ b/src/test/ui/feature-gates/feature-gate-generic_associated_types_extended.stderr @@ -0,0 +1,11 @@ +error[E0658]: the `#[rustc_error]` attribute is just used for rustc unit tests and will never be stable + --> $DIR/feature-gate-generic_associated_types_extended.rs:5:1 + | +LL | #[rustc_error] + | ^^^^^^^^^^^^^^ + | + = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0658`. diff --git a/src/test/ui/generic-associated-types/extended/lending_iterator.base.stderr b/src/test/ui/generic-associated-types/extended/lending_iterator.base.stderr new file mode 100644 index 0000000000000..c5588b0912ba8 --- /dev/null +++ b/src/test/ui/generic-associated-types/extended/lending_iterator.base.stderr @@ -0,0 +1,26 @@ +error[E0276]: impl has stricter requirements than trait + --> $DIR/lending_iterator.rs:14:45 + | +LL | fn from_iter LendingIterator = A>>(iter: T) -> Self; + | ------------------------------------------------------------------------ definition of `from_iter` from trait +... +LL | fn from_iter LendingIterator = A>>(mut iter: I) -> Self { + | ^^^^^^^^^^^^ impl has extra requirement `I: 'x` + +error[E0311]: the parameter type `Self` may not live long enough + --> $DIR/lending_iterator.rs:35:9 + | +LL | >::from_iter(self) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = help: consider adding an explicit lifetime bound `Self: 'a`... + = note: ...so that the type `Self` will meet its required lifetime bounds... +note: ...that is required by this bound + --> $DIR/lending_iterator.rs:10:45 + | +LL | fn from_iter LendingIterator = A>>(iter: T) -> Self; + | ^^^^^^^^^^^^ + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0276`. diff --git a/src/test/ui/generic-associated-types/extended/lending_iterator.rs b/src/test/ui/generic-associated-types/extended/lending_iterator.rs new file mode 100644 index 0000000000000..df11ab2124986 --- /dev/null +++ b/src/test/ui/generic-associated-types/extended/lending_iterator.rs @@ -0,0 +1,40 @@ +// revisions: base extended +//[base] check-fail +//[extended] check-pass + +#![feature(generic_associated_types)] +#![cfg_attr(extended, feature(generic_associated_types_extended))] +#![cfg_attr(extended, allow(incomplete_features))] + +pub trait FromLendingIterator: Sized { + fn from_iter LendingIterator = A>>(iter: T) -> Self; +} + +impl FromLendingIterator for Vec { + fn from_iter LendingIterator = A>>(mut iter: I) -> Self { + //[base]~^ impl has stricter + let mut v = vec![]; + while let Some(item) = iter.next() { + v.push(item); + } + v + } +} + +pub trait LendingIterator { + type Item<'z> + where + Self: 'z; + fn next(&mut self) -> Option>; + + fn collect>(self) -> B + where + Self: Sized, + Self: for<'q> LendingIterator = A>, + { + >::from_iter(self) + //[base]~^ the parameter type + } +} + +fn main() {} diff --git a/src/test/ui/generic-associated-types/extended/lending_iterator_2.base.stderr b/src/test/ui/generic-associated-types/extended/lending_iterator_2.base.stderr new file mode 100644 index 0000000000000..6c2a624ca11d5 --- /dev/null +++ b/src/test/ui/generic-associated-types/extended/lending_iterator_2.base.stderr @@ -0,0 +1,12 @@ +error[E0276]: impl has stricter requirements than trait + --> $DIR/lending_iterator_2.rs:14:45 + | +LL | fn from_iter LendingIterator = A>>(iter: T) -> Self; + | ------------------------------------------------------------------------ definition of `from_iter` from trait +... +LL | fn from_iter LendingIterator = A>>(mut iter: I) -> Self { + | ^^^^^^^^^^^^ impl has extra requirement `I: 'x` + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0276`. diff --git a/src/test/ui/generic-associated-types/extended/lending_iterator_2.rs b/src/test/ui/generic-associated-types/extended/lending_iterator_2.rs new file mode 100644 index 0000000000000..3c4a2184db90c --- /dev/null +++ b/src/test/ui/generic-associated-types/extended/lending_iterator_2.rs @@ -0,0 +1,31 @@ +// revisions: base extended +//[base] check-fail +//[extended] check-pass + +#![feature(generic_associated_types)] +#![cfg_attr(extended, feature(generic_associated_types_extended))] +#![cfg_attr(extended, allow(incomplete_features))] + +pub trait FromLendingIterator: Sized { + fn from_iter LendingIterator = A>>(iter: T) -> Self; +} + +impl FromLendingIterator for Vec { + fn from_iter LendingIterator = A>>(mut iter: I) -> Self { + //[base]~^ impl has stricter + let mut v = vec![]; + while let Some(item) = iter.next() { + v.push(item); + } + v + } +} + +pub trait LendingIterator { + type Item<'a> + where + Self: 'a; + fn next(&mut self) -> Option>; +} + +fn main() {}