Remove unreachable panics from VecDeque::{front/back}[_mut]

[bugadani]

VecDeque's front, front_mut, back and back_mut methods are implemented in terms of the index operator, which causes these functions to contain unreachable panic calls.

This PR reimplements these methods in terms of get[_mut] instead.

[rust-highfive]

r? @joshtriplett

(rust-highfive has picked a reviewer for you, use r? to override)

[rust-log-analyzer]

The job x86_64-gnu-llvm-9 failed! Check out the build log: (web) (plain)

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

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---
Suite("src/test/codegen") not skipped for "bootstrap::test::Codegen" -- not in ["src/tools/tidy"]
Check compiletest suite=codegen mode=codegen (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)

running 239 tests
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Some tests failed in compiletest suite=codegen mode=codegen host=x86_64-unknown-linux-gnu target=x86_64-unknown-linux-gnu


---- [codegen] codegen/vecdeque_front_panic.rs stdout ----

error: verification with 'FileCheck' failed
status: exit code: 1
command: "/usr/lib/llvm-9/bin/FileCheck" "--input-file" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/codegen/vecdeque_front_panic/vecdeque_front_panic.ll" "/checkout/src/test/codegen/vecdeque_front_panic.rs"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
/checkout/src/test/codegen/vecdeque_front_panic.rs:13:16: error: CHECK-NOT: excluded string found in input
 // CHECK-NOT: panic
               ^
/checkout/obj/build/x86_64-unknown-linux-gnu/test/codegen/vecdeque_front_panic/vecdeque_front_panic.ll:32:14: note: found here
; call core::panicking::panic

------------------------------------------


---
test result: FAILED. 193 passed; 1 failed; 45 ignored; 0 measured; 0 filtered out; finished in 3.00s



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/codegen" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/codegen" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--suite" "codegen" "--mode" "codegen" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-9/bin/FileCheck" "--nodejs" "/usr/bin/node" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "9.0.0" "--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 codegen core coroutines coverage debuginfocodeview debuginfodwarf debuginfogsym debuginfomsf debuginfopdb demangle dlltooldriver engine executionengine fuzzmutate globalisel hexagon hexagonasmparser hexagoncodegen hexagondesc hexagondisassembler hexagoninfo instcombine instrumentation 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 passes perfjitevents powerpc powerpcasmparser powerpccodegen powerpcdesc powerpcdisassembler powerpcinfo profiledata remarks riscv riscvasmparser riscvcodegen riscvdesc riscvdisassembler riscvinfo riscvutils 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 x86utils xcore xcorecodegen xcoredesc xcoredisassembler xcoreinfo xray" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"


failed to run: /checkout/obj/build/bootstrap/debug/bootstrap --stage 2 test --exclude src/tools/tidy
Build completed unsuccessfully in 0:16:50

[LingMan]

Maybe call the test file vecdeque_no_panic.rs? You're already testing more than just front() and with this name it could be naturally extended to cover other methods in the future. The no makes it clearer from the outside what the desired behaviour is. The current name could be interpreted as "check that front() panics under the right conditions".

[bugadani]

@LingMan you are of course right, thank you.

[oli-obk]

@bors r+

[bors]

📌 Commit a398106 has been approved by oli-obk

[m-ou-se]

@bors r-

This failed in #81002:

---

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

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

test [codegen] codegen/sanitizer-recover.rs#MSAN-RECOVER-LTO ... ok

failures:

---- [codegen] codegen/vecdeque_no_panic.rs stdout ----

error: verification with 'FileCheck' failed
status: exit code: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/llvm/build/bin/FileCheck" "--input-file" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/codegen/vecdeque_no_panic/vecdeque_no_panic.ll" "/checkout/src/test/codegen/vecdeque_no_panic.rs"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
/checkout/src/test/codegen/vecdeque_no_panic.rs:14:16: error: CHECK-NOT: excluded string found in input
 // CHECK-NOT: panic
               ^
/checkout/obj/build/x86_64-unknown-linux-gnu/test/codegen/vecdeque_no_panic/vecdeque_no_panic.ll:32:14: note: found here
; call core::panicking::panic


Input file: /checkout/obj/build/x86_64-unknown-linux-gnu/test/codegen/vecdeque_no_panic/vecdeque_no_panic.ll
Check file: /checkout/src/test/codegen/vecdeque_no_panic.rs

-dump-input=help explains the following input dump.
Input was:
<<<<<<
        .
        .
        .
        .
       27:  %7 = icmp eq i64 %6, 1
       28:  %or.cond.i.i = or i1 %7, %_3.i.i
       29:  br i1 %or.cond.i.i, label %"_ZN5alloc11collections9vec_deque17VecDeque$LT$T$GT$8back_mut17h5c160ed0372e8d5bE.exit", label %bb3.i.i.i.i
       30: 
       31: bb3.i.i.i.i: ; preds = %start
       32: ; call core::panicking::panic
not:14                  !~~~~            error: no match expected
       33:  tail call void @_ZN4core9panicking5panic17h4efaac1bbbb60eabE([0 x i8]* noalias nonnull readonly align 1 bitcast (<{ [40 x i8] }>* @alloc2 to [0 x i8]*), i64 40, %"std::panic::Location"* noalias readonly align 8 dereferenceable(24) bitcast (<{ i8*, [16 x i8] }>* @alloc4 to %"std::panic::Location"*)), !noalias !15
       34:  unreachable
       35: 
       36: "_ZN5alloc11collections9vec_deque17VecDeque$LT$T$GT$8back_mut17h5c160ed0372e8d5bE.exit": ; preds = %start
       37:  ret void
        .
        .
>>>>>>

---
test result: FAILED. 207 passed; 1 failed; 31 ignored; 0 measured; 0 filtered out; finished in 4.54s



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/codegen" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/codegen" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--suite" "codegen" "--mode" "codegen" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/checkout/obj/build/x86_64-unknown-linux-gnu/llvm/build/bin/FileCheck" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -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" "--llvm-version" "11.0.1-rust-1.51.0-nightly" "--llvm-components" "aarch64 aarch64asmparser aarch64codegen aarch64desc aarch64disassembler aarch64info aarch64utils aggressiveinstcombine all all-targets analysis arm armasmparser armcodegen armdesc armdisassembler arminfo armutils asmparser asmprinter avr avrasmparser avrcodegen avrdesc avrdisassembler avrinfo binaryformat bitreader bitstreamreader bitwriter cfguard codegen core coroutines coverage debuginfocodeview debuginfodwarf debuginfogsym debuginfomsf debuginfopdb demangle dlltooldriver dwarflinker engine executionengine extensions frontendopenmp fuzzmutate globalisel gtest gtest_main hexagon hexagonasmparser hexagoncodegen hexagondesc hexagondisassembler hexagoninfo instcombine instrumentation interpreter ipo irreader jitlink 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 orcerror orcjit passes powerpc powerpcasmparser powerpccodegen powerpcdesc powerpcdisassembler powerpcinfo profiledata remarks riscv riscvasmparser riscvcodegen riscvdesc riscvdisassembler riscvinfo riscvutils runtimedyld scalaropts selectiondag sparc sparcasmparser sparccodegen sparcdesc sparcdisassembler sparcinfo support symbolize systemz systemzasmparser systemzcodegen systemzdesc systemzdisassembler systemzinfo tablegen target testingsupport textapi transformutils vectorize webassembly webassemblyasmparser webassemblycodegen webassemblydesc webassemblydisassembler webassemblyinfo windowsmanifest x86 x86asmparser x86codegen x86desc x86disassembler x86info xray" "--cc" "" "--cxx" "" "--cflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"


failed to run: /checkout/obj/build/bootstrap/debug/bootstrap --stage 2 test
Build completed unsuccessfully in 0:23:20

[bugadani]

I am reasonably sure the failure is caused by a debug_assert in wrap_index. I added a test directive to ignore when debug assertions are enabled.

[m-ou-se]

@bors r=oli-obk

[bors]

📌 Commit 744f885 has been approved by oli-obk