Initial implementation of unsafe binder types

[compiler-errors]

I've written up some motivation about unsafe binders here: https://hackmd.io/@compiler-errors/HkXwoBPaR

Specifically, I'd like to provide a coherent way to represent lifetimes in structs which are unnameable and can't be plugged by 'static. This has been toyed around with in the past, such as 'unsafe lifetimes¹, but the document above calls out some questions in that design and proposes a different solution via "unsafe binder types". Making these their own distinct type solves a lot of those problems, and while users still need to be careful with these types by using unsafe {} when interconverting them, they're far more self-contained.

r? @ghost

I'll be opening a lang team experiment for this before I put this up for actual review. I'm mostly putting this here so we can reference it.

Footnotes

1. https://internals.rust-lang.org/t/rfc-basic-unsafe-lifetime/16873 ↩

[rust-log-analyzer]

The job x86_64-gnu-llvm-17 failed! Check out the build log: (web) (plain)

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 > importing cache manifest from ghcr.io/rust-lang/rust-ci-cache:fb97a1d6377f6cf2227825318ca4bbde3889e0c420746f5a03ba46a07e9a862725c26a09b9fc49a0d129ebd75935d3f6cd19acf41cc4267a6846fd4aa574b12c:
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##[endgroup]
Setting extra environment values for docker:  --env ENABLE_GCC_CODEGEN=1 --env GCC_EXEC_PREFIX=/usr/lib/gcc/
[CI_JOB_NAME=x86_64-gnu-llvm-17]
---
sccache: Starting the server...
##[group]Configure the build
configure: processing command line
configure: 
configure: build.configure-args := ['--build=x86_64-unknown-linux-gnu', '--llvm-root=/usr/lib/llvm-17', '--enable-llvm-link-shared', '--set', 'rust.randomize-layout=true', '--set', 'rust.thin-lto-import-instr-limit=10', '--set', 'change-id=99999999', '--enable-verbose-configure', '--enable-sccache', '--disable-manage-submodules', '--enable-locked-deps', '--enable-cargo-native-static', '--set', 'rust.codegen-units-std=1', '--set', 'dist.compression-profile=balanced', '--dist-compression-formats=xz', '--set', 'rust.lld=false', '--disable-dist-src', '--release-channel=nightly', '--enable-debug-assertions', '--enable-overflow-checks', '--enable-llvm-assertions', '--set', 'rust.verify-llvm-ir', '--set', 'rust.codegen-backends=llvm,cranelift,gcc', '--set', 'llvm.static-libstdcpp', '--enable-new-symbol-mangling']
configure: target.x86_64-unknown-linux-gnu.llvm-config := /usr/lib/llvm-17/bin/llvm-config
configure: llvm.link-shared     := True
configure: rust.randomize-layout := True
configure: rust.thin-lto-import-instr-limit := 10
---

---- [ui] tests/ui/symbol-names/basic.rs#legacy stdout ----
diff of stderr:

- error: symbol-name(_ZN5basic4main17had874e876c8b1028E)
+ error: symbol-name(_ZN5basic4main17h144191e1523a280eE)
3    |
4 LL | #[rustc_symbol_name]

5    | ^^^^^^^^^^^^^^^^^^^^
---
10 LL | #[rustc_symbol_name]


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/symbol-names/basic.legacy/basic.legacy.stderr
To only update this specific test, also pass `--test-args symbol-names/basic.rs`

error in revision `legacy`: 1 errors occurred comparing output.
status: exit status: 1
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/symbol-names/basic.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/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--cfg" "legacy" "--check-cfg" "cfg(FALSE,legacy,v0)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/symbol-names/basic.legacy" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/symbol-names/basic.legacy/auxiliary" "-Z" "unstable-options" "-C" "symbol-mangling-version=legacy"
--- stderr -------------------------------
--- stderr -------------------------------
error: symbol-name(_ZN5basic4main17h144191e1523a280eE)
   |
LL | #[rustc_symbol_name]
   | ^^^^^^^^^^^^^^^^^^^^

---

---- [ui] tests/ui/symbol-names/issue-60925.rs#legacy stdout ----
diff of stderr:

- error: symbol-name(_ZN11issue_609253foo37Foo$LT$issue_60925..llv$u6d$..Foo$GT$3foo17haf0d0ad2255e29c6E)
+ error: symbol-name(_ZN11issue_609253foo37Foo$LT$issue_60925..llv$u6d$..Foo$GT$3foo17h71f988fda3b6b180E)
3    |
4 LL |         #[rustc_symbol_name]

5    |         ^^^^^^^^^^^^^^^^^^^^
5    |         ^^^^^^^^^^^^^^^^^^^^
6 
- error: demangling(issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo::haf0d0ad2255e29c6)
+ error: demangling(issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo::h71f988fda3b6b180)
9    |
10 LL |         #[rustc_symbol_name]



The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/symbol-names/issue-60925.legacy/issue-60925.legacy.stderr
To only update this specific test, also pass `--test-args symbol-names/issue-60925.rs`

error in revision `legacy`: 1 errors occurred comparing output.
status: exit status: 1
status: exit status: 1
command: env -u RUSTC_LOG_COLOR RUSTC_ICE="0" RUST_BACKTRACE="short" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/tests/ui/symbol-names/issue-60925.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/x86_64-unknown-linux-gnu/stage2" "--target=x86_64-unknown-linux-gnu" "--cfg" "legacy" "--check-cfg" "cfg(FALSE,legacy,v0)" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zwrite-long-types-to-disk=no" "-Cstrip=debuginfo" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/symbol-names/issue-60925.legacy" "-A" "unused" "-A" "internal_features" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/symbol-names/issue-60925.legacy/auxiliary" "-Z" "unstable-options" "-C" "symbol-mangling-version=legacy"
--- stderr -------------------------------
--- stderr -------------------------------
error: symbol-name(_ZN11issue_609253foo37Foo$LT$issue_60925..llv$u6d$..Foo$GT$3foo17h71f988fda3b6b180E)
   |
LL |         #[rustc_symbol_name]
   |         ^^^^^^^^^^^^^^^^^^^^


error: demangling(issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo::h71f988fda3b6b180)
   |
LL |         #[rustc_symbol_name]
   |         ^^^^^^^^^^^^^^^^^^^^


error: demangling-alt(issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo)
   |
LL |         #[rustc_symbol_name]
   |         ^^^^^^^^^^^^^^^^^^^^