add a map function on homogenous tuples

[bend-n]

• I did not use an LLM to create a change in this PR.
• I used an LLM to create a change in this PR, and I have explained below how it was used.

This adds a function to map homogenous tuples, up to length 12. I thought about maps of heterogenous tuples, for each set partition, however it's impossible.

Will tracking issue etc if good.

[rustbot]

r? @nia-e

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Why was this reviewer chosen?

The reviewer was selected based on:

• Owners of files modified in this PR: libs
• libs expanded to 12 candidates
• Random selection from JohnTitor, Mark-Simulacrum, clarfonthey, nia-e

[bend-n]

@rustbot label +T-libs-api

[nia-e]

Thanks for the PR! Since this is a public-facing change it should go through ACP first, so if you could write up the motivation and design considerations in a relevant issue, that would be appreciated ^^

[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)

normalized stderr:
warning: a method with this name may be added to the standard library in the future
##[warning]  --> $DIR/nested-rpit-with-lifetimes.rs:46:26
   |
LL |     (TakeWhile1::new(),).map()
   |                          ^^^
   |
   = help: call with fully qualified syntax `Parser::map(...)` to keep using the current method
   = warning: once this associated item is added to the standard library, the ambiguity may cause an error or change in behavior!
   = note: for more information, see issue #48919 <https://github.com/rust-lang/rust/issues/48919>
   = note: `#[warn(unstable_name_collisions)]` (part of `#[warn(future_incompatible)]`) on by default
help: add `#![feature(tuple_map)]` to the crate attributes to enable `core::tuple::<impl (T,)>::map`
   |
LL + #![feature(tuple_map)]
   |

warning: 1 warning emitted


---
To only update this specific test, also pass `--test-args type-alias-impl-trait/nested-rpit-with-lifetimes.rs`

error: 1 errors occurred comparing output.
status: exit status: 0
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/type-alias-impl-trait/nested-rpit-with-lifetimes.rs" "-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/type-alias-impl-trait/nested-rpit-with-lifetimes" "-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"
stdout: none
--- stderr -------------------------------
warning: a method with this name may be added to the standard library in the future
##[warning]  --> /checkout/tests/ui/type-alias-impl-trait/nested-rpit-with-lifetimes.rs:46:26
   |
LL |     (TakeWhile1::new(),).map()
   |                          ^^^
   |
   = help: call with fully qualified syntax `Parser::map(...)` to keep using the current method
   = warning: once this associated item is added to the standard library, the ambiguity may cause an error or change in behavior!
   = note: for more information, see issue #48919 <https://github.com/rust-lang/rust/issues/48919>
   = note: `#[warn(unstable_name_collisions)]` (part of `#[warn(future_incompatible)]`) on by default
help: add `#![feature(tuple_map)]` to the crate attributes to enable `core::tuple::<impl (T,)>::map`
   |
LL + #![feature(tuple_map)]
   |

warning: 1 warning emitted
------------------------------------------