avoid trivial fn map_bound validations

[lcnr]

when compiling zerocopy a lot of time is spent simply checking the bound vars in Clause::kind because it does

        self.0.internee.map_bound(|kind| match kind {
            PredicateKind::Clause(clause) => clause,
            _ => unreachable!(),
        })

let's make performance with debug_assertions a bit better:

zerocopy with -Znext-solver:

16884862 counts
(  1) 12189626 (72.2%, 72.2%): Binder::map_bound called at compiler/rustc_middle/src/ty/predicate.rs:174:25
(  2)  1853971 (11.0%, 83.2%): Binder::map_bound called at compiler/rustc_type_ir/src/binder.rs:89:14
(  3)  1443803 ( 8.6%, 91.7%): Binder::map_bound called at compiler/rustc_type_ir/src/inherent.rs:493:14
(  4)   572570 ( 3.4%, 95.1%): Binder::map_bound called at compiler/rustc_type_ir/src/predicate.rs:234:14
(  5)   272733 ( 1.6%, 96.7%): Binder::map_bound called at compiler/rustc_type_ir/src/inherent.rs:507:14
(  6)   184934 ( 1.1%, 97.8%): Binder::map_bound called at compiler/rustc_middle/src/ty/predicate.rs:523:14
(  7)   183998 ( 1.1%, 98.9%): Binder::map_bound called at compiler/rustc_type_ir/src/predicate.rs:251:14

zerocopy with -Znext-solver=no

13476410 counts
(  1)  9906183 (73.5%, 73.5%): Binder::map_bound called at compiler/rustc_middle/src/ty/predicate.rs:174:25
(  2)  2107825 (15.6%, 89.1%): Binder::map_bound called at compiler/rustc_type_ir/src/binder.rs:89:14
(  3)   376524 ( 2.8%, 91.9%): Binder::map_bound called at compiler/rustc_type_ir/src/inherent.rs:493:14
(  4)   321976 ( 2.4%, 94.3%): Binder::map_bound called at compiler/rustc_type_ir/src/predicate.rs:251:14
(  5)   262305 ( 1.9%, 96.3%): Binder::map_bound called at compiler/rustc_middle/src/ty/predicate.rs:523:14
(  6)    84143 ( 0.6%, 96.9%): Binder::map_bound called at compiler/rustc_infer/src/infer/outlives/verify.rs:49:47
(  7)    83876 ( 0.6%, 97.5%): Binder::map_bound called at compiler/rustc_infer/src/traits/mod.rs:183:24

compiling std:

32803629 counts
(  1) 12234204 (37.3%, 37.3%): Binder::map_bound called at compiler/rustc_type_ir/src/binder.rs:89:14
(  2)  9624749 (29.3%, 66.6%): Binder::map_bound called at compiler/rustc_middle/src/ty/predicate.rs:174:25
(  3)  3805442 (11.6%, 78.2%): Binder::map_bound called at compiler/rustc_type_ir/src/inherent.rs:493:14
(  4)  2542468 ( 7.8%, 86.0%): Binder::map_bound called at compiler/rustc_type_ir/src/predicate.rs:234:14
(  5)  1229480 ( 3.7%, 89.7%): Binder::map_bound called at compiler/rustc_middle/src/ty/predicate.rs:523:14
(  6)  1176716 ( 3.6%, 93.3%): Binder::map_bound called at compiler/rustc_type_ir/src/predicate.rs:251:14
(  7)   385823 ( 1.2%, 94.5%): Binder::map_bound called at compiler/rustc_type_ir/src/inherent.rs:507:14

Could spend more effort to avoid the validation in trivial Binder::fold_with, but that's not worth it I think.

cc https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/casual.20chat.20and.20support/near/628479010

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[oli-obk]

@bors r+ rollup

View changes since this review

[rust-bors]

📌 Commit ee2a5df has been approved by oli-obk

It is now in the queue for this repository.