Rework method selection for ?i and ?f vars

[compiler-errors]

just for demo

r? @ghost

[rust-log-analyzer]

The job x86_64-gnu-llvm-16 failed! Check out the build log: (web) (plain)

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

GITHUB_ENV=/home/runner/work/_temp/_runner_file_commands/set_env_5c7de763-9d1e-4991-b47c-07365a300a20
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GITHUB_EVENT_PATH=/home/runner/work/_temp/_github_workflow/event.json
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GITHUB_HEAD_REF=num-var-ambig
GITHUB_JOB=pr
GITHUB_PATH=/home/runner/work/_temp/_runner_file_commands/add_path_5c7de763-9d1e-4991-b47c-07365a300a20
GITHUB_REF=refs/pull/121459/merge
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---
#12 writing image sha256:9a3f0233c4a7597b1f1bd836f1999ae7ec611c1424cab6eaaf1a6d5026a83ff7 done
#12 naming to docker.io/library/rust-ci done
#12 DONE 10.0s
##[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-16]
##[group]Clock drift check
  local time: Thu Feb 22 15:32:28 UTC 2024
  network time: Thu, 22 Feb 2024 15:32:28 GMT
  network time: Thu, 22 Feb 2024 15:32:28 GMT
##[endgroup]
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-16', '--enable-llvm-link-shared', '--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', 'build.optimized-compiler-builtins', '--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-16/bin/llvm-config
configure: llvm.link-shared     := True
configure: rust.thin-lto-import-instr-limit := 10
configure: change-id            := 99999999
---
   Compiling rustc-std-workspace-core v1.99.0 (/checkout/library/rustc-std-workspace-core)
error[E0034]: multiple applicable items in scope
   --> /cargo/registry/src/index.crates.io-6f17d22bba15001f/compiler_builtins-0.1.108/src/float/div.rs:216:23
    |
216 |                     0.wrapping_sub((x_uq0_hw as u32).wrapping_mul(b_uq1_hw.cast()) >> hw) as u16;
    |                       ^^^^^^^^^^^^ multiple `wrapping_sub` found
    = note: candidate #1 is defined in an impl for the type `i8`
    = note: candidate #2 is defined in an impl for the type `i16`
    = note: candidate #3 is defined in an impl for the type `i32`
    = note: candidate #4 is defined in an impl for the type `i64`
    = note: candidate #4 is defined in an impl for the type `i64`
    = note: and 8 others

error[E0034]: multiple applicable items in scope
   --> /cargo/registry/src/index.crates.io-6f17d22bba15001f/compiler_builtins-0.1.108/src/float/div.rs:316:35
    |
316 |             let corr_uq1: u32 = 0.wrapping_sub(
    |                                   ^^^^^^^^^^^^ multiple `wrapping_sub` found
    = note: candidate #1 is defined in an impl for the type `i8`
    = note: candidate #2 is defined in an impl for the type `i16`
    = note: candidate #3 is defined in an impl for the type `i32`
    = note: candidate #4 is defined in an impl for the type `i64`
    = note: candidate #4 is defined in an impl for the type `i64`
    = note: and 8 others

error[E0034]: multiple applicable items in scope
   --> /cargo/registry/src/index.crates.io-6f17d22bba15001f/compiler_builtins-0.1.108/src/float/div.rs:665:23
    |
665 |                     0.wrapping_sub(((x_uq0_hw as u64).wrapping_mul(b_uq1_hw as u64)) >> hw) as u32;
    |                       ^^^^^^^^^^^^ multiple `wrapping_sub` found
    = note: candidate #1 is defined in an impl for the type `i8`
    = note: candidate #2 is defined in an impl for the type `i16`
    = note: candidate #3 is defined in an impl for the type `i32`
    = note: candidate #4 is defined in an impl for the type `i64`
    = note: candidate #4 is defined in an impl for the type `i64`
    = note: and 8 others

error[E0034]: multiple applicable items in scope
   --> /cargo/registry/src/index.crates.io-6f17d22bba15001f/compiler_builtins-0.1.108/src/float/div.rs:766:35
    |
766 |             let corr_uq1: u64 = 0.wrapping_sub(
    |                                   ^^^^^^^^^^^^ multiple `wrapping_sub` found
    = note: candidate #1 is defined in an impl for the type `i8`
    = note: candidate #2 is defined in an impl for the type `i16`
    = note: candidate #3 is defined in an impl for the type `i32`
    = note: candidate #4 is defined in an impl for the type `i64`