trait_selection: fix assumptions-on-binders diagnostics

[Dnreikronos]

fixes #157732

the assumptions-on-binders outlives paths were still emitting placeholder text (:3 and meoow :c), and the ui tests blessed it. imo the small, honest diagnostic is better here than trying to guess a source-level fix while the flag is still wip.

this adds an explicit outlives fulfillment error for the flag, uses higher-ranked lifetime bound could not be satisfied across trait selection, region reporting, and borrowck, and updates the ui output incl. the new regression test.

future work, maybe: carry the failed outlives predicate or originating binder through this path so the diagnostic can name what failed. idk that it's sound for this pr; it needs more data than these callers have rn.

[rustbot]

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

[rustbot]

r? @folkertdev

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[rust-log-analyzer]

The job aarch64-gnu-llvm-21-1 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

To only update this specific test, also pass `--test-args assumptions_on_binders/alias_outlives.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/assumptions_on_binders/alias_outlives.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/assumptions_on_binders/alias_outlives" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers" "-Znext-solver" "-Zassumptions-on-binders"
stdout: none
--- stderr -------------------------------
error: higher-ranked lifetime bound could not be satisfied
##[error]  --> /checkout/tests/ui/assumptions_on_binders/alias_outlives.rs:37:1
   |
LL | const REGIONCK_ENV_FAIL<'a, T: AliasHaver>: ReqTrait<T::Assoc> = todo!()
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: higher-ranked lifetime bound could not be satisfied
##[error]  --> /checkout/tests/ui/assumptions_on_binders/alias_outlives.rs:25:1
   |
LL | / fn borrowck_env_fail<'a, T: AliasHaver>()
LL | | //~^ ERROR: higher-ranked lifetime bound could not be satisfied
LL | | where
LL | |     <T as AliasHaver>::Assoc: 'a,
   | |_________________________________^

error: aborting due to 2 previous errors
------------------------------------------

---
To only update this specific test, also pass `--test-args assumptions_on_binders/higher-ranked-outlives-issue-157732.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/assumptions_on_binders/higher-ranked-outlives-issue-157732.rs" "-Zthreads=1" "-Zsimulate-remapped-rust-src-base=/rustc/FAKE_PREFIX" "-Ztranslate-remapped-path-to-local-path=no" "-Z" "ignore-directory-in-diagnostics-source-blocks=/cargo" "-Z" "ignore-directory-in-diagnostics-source-blocks=/checkout/vendor" "--sysroot" "/checkout/obj/build/aarch64-unknown-linux-gnu/stage2" "--target=aarch64-unknown-linux-gnu" "--check-cfg" "cfg(test,FALSE)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/aarch64-unknown-linux-gnu/test/ui/assumptions_on_binders/higher-ranked-outlives-issue-157732" "-A" "unused" "-W" "unused_attributes" "-A" "internal_features" "-A" "incomplete_features" "-A" "unused_parens" "-A" "unused_braces" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/aarch64-unknown-linux-gnu/native/rust-test-helpers" "-Zassumptions-on-binders" "-Znext-solver=globally"
stdout: none
--- stderr -------------------------------
error: higher-ranked lifetime bound could not be satisfied
##[error]  --> /checkout/tests/ui/assumptions_on_binders/higher-ranked-outlives-issue-157732.rs:10:5
   |

[folkertdev]

r? types

[lcnr]

r? BoxyUwU

We intend to fully rework the way these diagnostics work and the errors are currently intentionally bad as they don't even have span information (they point to the whole containing function).

I think keeping the status quo is preferable as a very explicit "this is still very WIP" and would personally prefer to close this PR

[rustbot]

BoxyUwU is currently at their maximum review capacity.
They may take a while to respond.

[Dnreikronos]

r? BoxyUwU

We intend to fully rework the way these diagnostics work and the errors are currently intentionally bad as they don't even have span information (they point to the whole containing function).

I think keeping the status quo is preferable as a very explicit "this is still very WIP" and would personally prefer to close this PR

thanks, that makes sense. i was mostly looking at this as remove the placeholder text, but imo you're right that the nicer message is a bit misleading if the span is still basically wrong.

i'll wait for boxyuwu's opinion before closing the pr. if i poke at this again later, i think i'd rather start by carrying more of the failed outlives predicate / binder info through first, then make the diagnostic nicer once it has enough data to not lie.