Pull implied bound computation out of borrowck

[tiif]

Open this draft PR so it's easier to discuss, feel free to point out any logic / soundness / error handling issues :>

Current status:

• The implementation is mostly done, currently trying to get core to build and resolve ICEs found in test suite
• The test for normalizing opaques while computing implied bounds trait-system-refactor-initiative#159 successfully error in the new solver
• need more clean ups
• need to add test for super trait bounds can result in unconstrained regions #136547

[tiif]

This change in this file is mainly duplicating the existing function to not use nll var. The new implied bound query needs these functions, but it doesn't makes sense to use nll var there. boxy gave some ideas on how to deduplicate this, but I haven't got to it yet.

[rust-log-analyzer]

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

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fmt: checked 7075 files
tidy check
tidy [rustdoc_json (src)]: `rustdoc-json-types` modified, checking format version
tidy: Skipping binary file check, read-only filesystem
tidy [style (compiler)]: /checkout/compiler/rustc_trait_selection/src/traits/query/type_op/implied_outlives_bounds.rs:174: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
tidy [style (tests)]: /checkout/tests/ui/borrowck/test-rename-later.rs: missing trailing newline
tidy [style (tests)]: /checkout/tests/ui/borrowck/manual_test.rs:1: line longer than 100 chars
tidy [style (tests)]: /checkout/tests/ui/borrowck/manual_test.rs: missing trailing newline
tidy [style (tests)]: /checkout/tests/ui/borrowck/manual_test0.rs:1: line longer than 100 chars
tidy [style (tests)]: /checkout/tests/ui/borrowck/manual_test0.rs: missing trailing newline
tidy [style (compiler)]: /checkout/compiler/rustc_borrowck/src/compute_rename_later.rs:1: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
tidy [style (compiler)]: /checkout/compiler/rustc_borrowck/src/lib.rs:356: TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
tidy [style (compiler)]: /checkout/compiler/rustc_borrowck/src/type_check/free_region_relations.rs:287: the `todo!` macro is used for tasks that should be done before merging a PR. If you want to panic here, use `panic!`, `unimplemented!`, `unreachable!`, `rustc_middle::bug!` or an assertion
tidy [style (compiler)]: FAIL
tidy [style (tests)]: FAIL
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'venv'
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'virtualenv'
Requirement already satisfied: pip in ./build/venv/lib/python3.10/site-packages (26.1.2)
Collecting pip
---
typechecking javascript files
tidy: The following checks failed: style (compiler), style (tests)
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Currently active steps:
test::Tidy {  } at src/bootstrap/src/core/build_steps/test.rs:1606
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/rust-tidy --root-path=/checkout --cargo-path=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo --output-dir=/checkout/obj/build --concurrency=4 --npm-path=/node/bin/yarn --ci=true --extra-checks=py,cpp,js,spellcheck` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1627:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1684:29

Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:02:33
  local time: Mon Aug  3 13:10:44 UTC 2026
  network time: Mon, 03 Aug 2026 13:10:44 GMT
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"

[lcnr]

closing in favor of #160491