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Auto merge of #104179 - Manishearth:rollup-yvsx5hh, r=Manishearth

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Rollup of 7 pull requests

Successful merges:

 - #100508 (avoid making substs of type aliases late bound when used as fn args)
 - #101381 (Test that target feature mix up with homogeneous floats is sound)
 - #103353 (Fix Access Violation when using lld & ThinLTO on windows-msvc)
 - #103521 (Avoid possible infinite  loop when next_point reaching the end of file)
 - #103559 (first move on a nested span_label)
 - #103778 (Update several crates for improved support of the new targets)
 - #103827 (Properly remap and check for substs compatibility in `confirm_impl_trait_in_trait_candidate`)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup
This commit is contained in:
bors 2022-11-09 04:43:43 +00:00
commit 91385d5776
32 changed files with 759 additions and 84 deletions
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104
compiler/rustc_hir_analysis/src/collect/lifetimes.rs
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@ -18,7 +18,7 @@ use rustc_middle::bug;
use rustc_middle::hir::map::Map;
use rustc_middle::hir::nested_filter;
use rustc_middle::middle::resolve_lifetime::*;
use rustc_middle::ty::{self, DefIdTree, TyCtxt};
use rustc_middle::ty::{self, DefIdTree, TyCtxt, TypeSuperVisitable, TypeVisitor};
use rustc_span::def_id::DefId;
use rustc_span::symbol::{sym, Ident};
use rustc_span::Span;
@ -1781,7 +1781,7 @@ fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet<
let mut late_bound = FxIndexSet::default();
let mut constrained_by_input = ConstrainedCollector::default();
let mut constrained_by_input = ConstrainedCollector { regions: Default::default(), tcx };
for arg_ty in decl.inputs {
constrained_by_input.visit_ty(arg_ty);
}
@ -1834,12 +1834,65 @@ fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet<
debug!(?late_bound);
return Some(tcx.arena.alloc(late_bound));
#[derive(Default)]
struct ConstrainedCollector {
/// Visits a `ty::Ty` collecting information about what generic parameters are constrained.
///
/// The visitor does not operate on `hir::Ty` so that it can be called on the rhs of a `type Alias<...> = ...;`
/// which may live in a separate crate so there would not be any hir available. Instead we use the `type_of`
/// query to obtain a `ty::Ty` which will be present even in cross crate scenarios. It also naturally
/// handles cycle detection as we go through the query system.
///
/// This is necessary in the first place for the following case:
/// ```
/// type Alias<'a, T> = <T as Trait<'a>>::Assoc;
/// fn foo<'a>(_: Alias<'a, ()>) -> Alias<'a, ()> { ... }
/// ```
///
/// If we conservatively considered `'a` unconstrained then we could break users who had written code before
/// we started correctly handling aliases. If we considered `'a` constrained then it would become late bound
/// causing an error during astconv as the `'a` is not constrained by the input type `<() as Trait<'a>>::Assoc`
/// but appears in the output type `<() as Trait<'a>>::Assoc`.
///
/// We must therefore "look into" the `Alias` to see whether we should consider `'a` constrained or not.
///
/// See #100508 #85533 #47511 for additional context
struct ConstrainedCollectorPostAstConv {
arg_is_constrained: Box<[bool]>,
}
use std::ops::ControlFlow;
use ty::Ty;
impl<'tcx> TypeVisitor<'tcx> for ConstrainedCollectorPostAstConv {
fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<!> {
match t.kind() {
ty::Param(param_ty) => {
self.arg_is_constrained[param_ty.index as usize] = true;
}
ty::Projection(_) => return ControlFlow::Continue(()),
_ => (),
}
t.super_visit_with(self)
}
fn visit_const(&mut self, _: ty::Const<'tcx>) -> ControlFlow<!> {
ControlFlow::Continue(())
}
fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<!> {
debug!("r={:?}", r.kind());
if let ty::RegionKind::ReEarlyBound(region) = r.kind() {
self.arg_is_constrained[region.index as usize] = true;
}
ControlFlow::Continue(())
}
}
struct ConstrainedCollector<'tcx> {
tcx: TyCtxt<'tcx>,
regions: FxHashSet<LocalDefId>,
}
impl<'v> Visitor<'v> for ConstrainedCollector {
impl<'v> Visitor<'v> for ConstrainedCollector<'_> {
fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) {
match ty.kind {
hir::TyKind::Path(
@ -1850,6 +1903,47 @@ fn is_late_bound_map(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Option<&FxIndexSet<
// (defined above)
}
hir::TyKind::Path(hir::QPath::Resolved(
None,
hir::Path { res: Res::Def(DefKind::TyAlias, alias_def), segments, span },
)) => {
// See comments on `ConstrainedCollectorPostAstConv` for why this arm does not just consider
// substs to be unconstrained.
let generics = self.tcx.generics_of(alias_def);
let mut walker = ConstrainedCollectorPostAstConv {
arg_is_constrained: vec![false; generics.params.len()].into_boxed_slice(),
};
walker.visit_ty(self.tcx.type_of(alias_def));
match segments.last() {
Some(hir::PathSegment { args: Some(args), .. }) => {
let tcx = self.tcx;
for constrained_arg in
args.args.iter().enumerate().flat_map(|(n, arg)| {
match walker.arg_is_constrained.get(n) {
Some(true) => Some(arg),
Some(false) => None,
None => {
tcx.sess.delay_span_bug(
*span,
format!(
"Incorrect generic arg count for alias {:?}",
alias_def
),
);
None
}
}
})
{
self.visit_generic_arg(constrained_arg);
}
}
Some(_) => (),
None => bug!("Path with no segments or self type"),
}
}
hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
// consider only the lifetimes on the final
// segment; I am not sure it's even currently