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Wrap some overlong comments.

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This commit is contained in:
Nicholas Nethercote 2023-10-30 15:33:05 +11:00
parent 85e56e81f8
commit a60d6438dc
1 changed files with 12 additions and 10 deletions
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22
compiler/rustc_interface/src/passes.rs
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@ -880,16 +880,18 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(tcx, tr));
// A slightly edited version of the code in `rustc_trait_selection::traits::vtable::vtable_entries`,
// that works without self type and just counts number of entries.
// A slightly edited version of the code in
// `rustc_trait_selection::traits::vtable::vtable_entries`, that works without self
// type and just counts number of entries.
//
// Note that this is technically wrong, for traits which have associated types in supertraits:
// Note that this is technically wrong, for traits which have associated types in
// supertraits:
//
// trait A: AsRef<Self::T> + AsRef<()> { type T; }
//
// Without self type we can't normalize `Self::T`, so we can't know if `AsRef<Self::T>` and
// `AsRef<()>` are the same trait, thus we assume that those are different, and potentially
// over-estimate how many vtable entries there are.
// Without self type we can't normalize `Self::T`, so we can't know if `AsRef<Self::T>`
// and `AsRef<()>` are the same trait, thus we assume that those are different, and
// potentially over-estimate how many vtable entries there are.
//
// Similarly this is wrong for traits that have methods with possibly-impossible bounds.
// For example:
@ -916,10 +918,10 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
let own_existential_entries =
tcx.own_existential_vtable_entries(trait_ref.def_id());
// The original code here ignores the method if its predicates are impossible.
// We can't really do that as, for example, all not trivial bounds on generic
// parameters are impossible (since we don't know the parameters...),
// see the comment above.
// The original code here ignores the method if its predicates are
// impossible. We can't really do that as, for example, all not trivial
// bounds on generic parameters are impossible (since we don't know the
// parameters...), see the comment above.
entries_ignoring_upcasting += own_existential_entries.len();
if emit_vptr {