Document unreachable! custom panic message

[edmorley]

The unreachable! docs previously did not mention that there was a second form, unreachable!("message") that could be used to specify a custom panic message,

The docs now mention this feature in the same wording as currently used for unimplemented!:
https://doc.rust-lang.org/core/macro.unimplemented.html#panics

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @dtolnay (or someone else) soon.

Please see the contribution instructions for more information.

[rust-log-analyzer]

The job x86_64-gnu-llvm-12 failed! Check out the build log: (web) (plain)

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

---- [ui] ui/cmse-nonsecure/cmse-nonsecure-entry/params-on-stack.rs stdout ----
diff of stderr:

1 error: <unknown>:0:0: in function entry_function i32 (i32, i32, i32, i32, i32): secure entry function requires arguments on stack
3 
+ thread '<unnamed>' panicked at 'assertion failed: `(left == right)`
+   left: `LLVMing`,
+   left: `LLVMing`,
+  right: `Codegenning`', /checkout/compiler/rustc_codegen_ssa/src/back/write.rs:1470:21
+ note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
+ error: internal compiler error: unexpected panic
+ 
+ note: the compiler unexpectedly panicked. this is a bug.
+ 
+ 
+ note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md
+ 
+ note: rustc 1.58.0-nightly (cdf5100e7 2021-11-11) running on x86_64-unknown-linux-gnu
Some tests failed in compiletest suite=ui mode=ui host=x86_64-unknown-linux-gnu target=x86_64-unknown-linux-gnu
+ 
+ note: compiler flags: -Z threads=1 -Z ui-testing -Z deduplicate-diagnostics=no -Z emit-future-incompat-report -C codegen-units=1 -C prefer-dynamic -C rpath -C debuginfo=0 --crate-type lib
+ query stack during panic:
+ end of query stack
4 error: aborting due to previous error
5 
---
To only update this specific test, also pass `--test-args cmse-nonsecure/cmse-nonsecure-entry/params-on-stack.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/cmse-nonsecure/cmse-nonsecure-entry/params-on-stack.rs" "-Zthreads=1" "--error-format" "json" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-Zemit-future-incompat-report" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/cmse-nonsecure/cmse-nonsecure-entry/params-on-stack" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target" "thumbv8m.main-none-eabi" "--crate-type" "lib" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/cmse-nonsecure/cmse-nonsecure-entry/params-on-stack/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error: <unknown>:0:0: in function entry_function i32 (i32, i32, i32, i32, i32): secure entry function requires arguments on stack

thread '<unnamed>' panicked at 'assertion failed: `(left == right)`
  left: `LLVMing`,
  left: `LLVMing`,
 right: `Codegenning`', /checkout/compiler/rustc_codegen_ssa/src/back/write.rs:1470:21

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.
note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: rustc 1.58.0-nightly (cdf5100e7 2021-11-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z threads=1 -Z ui-testing -Z deduplicate-diagnostics=no -Z emit-future-incompat-report -C codegen-units=1 -C prefer-dynamic -C rpath -C debuginfo=0 --crate-type lib
query stack during panic:
end of query stack
error: aborting due to previous error

---
test result: FAILED. 12278 passed; 1 failed; 111 ignored; 0 measured; 0 filtered out; finished in 141.16s



command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--suite" "ui" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-12/bin/FileCheck" "--nodejs" "/usr/bin/node" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python3" "--lldb-python" "/usr/bin/python3" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "12.0.0" "--llvm-components" "aarch64 aarch64asmparser aarch64codegen aarch64desc aarch64disassembler aarch64info aarch64utils aggressiveinstcombine all all-targets amdgpu amdgpuasmparser amdgpucodegen amdgpudesc amdgpudisassembler amdgpuinfo amdgpuutils analysis arm armasmparser armcodegen armdesc armdisassembler arminfo armutils asmparser asmprinter avr avrasmparser avrcodegen avrdesc avrdisassembler avrinfo binaryformat bitreader bitstreamreader bitwriter bpf bpfasmparser bpfcodegen bpfdesc bpfdisassembler bpfinfo cfguard codegen core coroutines coverage debuginfocodeview debuginfodwarf debuginfogsym debuginfomsf debuginfopdb demangle dlltooldriver dwarflinker engine executionengine extensions filecheck frontendopenacc frontendopenmp fuzzmutate globalisel hellonew hexagon hexagonasmparser hexagoncodegen hexagondesc hexagondisassembler hexagoninfo instcombine instrumentation interfacestub interpreter ipo irreader jitlink lanai lanaiasmparser lanaicodegen lanaidesc lanaidisassembler lanaiinfo libdriver lineeditor linker lto mc mca mcdisassembler mcjit mcparser mips mipsasmparser mipscodegen mipsdesc mipsdisassembler mipsinfo mirparser msp430 msp430asmparser msp430codegen msp430desc msp430disassembler msp430info native nativecodegen nvptx nvptxcodegen nvptxdesc nvptxinfo objcarcopts object objectyaml option orcjit orcshared orctargetprocess passes perfjitevents powerpc powerpcasmparser powerpccodegen powerpcdesc powerpcdisassembler powerpcinfo profiledata remarks riscv riscvasmparser riscvcodegen riscvdesc riscvdisassembler riscvinfo runtimedyld scalaropts selectiondag sparc sparcasmparser sparccodegen sparcdesc sparcdisassembler sparcinfo support symbolize systemz systemzasmparser systemzcodegen systemzdesc systemzdisassembler systemzinfo tablegen target textapi transformutils vectorize webassembly webassemblyasmparser webassemblycodegen webassemblydesc webassemblydisassembler webassemblyinfo windowsmanifest x86 x86asmparser x86codegen x86desc x86disassembler x86info xcore xcorecodegen xcoredesc xcoredisassembler xcoreinfo xray" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--channel" "nightly" "--color" "always"


Build completed unsuccessfully in 0:13:29

[dtolnay]

Thanks!

[dtolnay]

@bors r+

[bors]

📌 Commit b41b2e5 has been approved by dtolnay