avoid instantiating infer vars with infer

[lcnr]

fixes #118670

The added assert in instantiate triggers both when compiling std and in 11 existing UI tests, so I did not bother adding another tests.

cc @spastorino this should be the cause of the ICE you encounter in #118247

r? @compiler-errors

[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_f4cb70e3-a79a-4904-be63-f8808e39f50f
GITHUB_EVENT_NAME=pull_request
GITHUB_EVENT_PATH=/home/runner/work/_temp/_github_workflow/event.json
GITHUB_GRAPHQL_URL=https://api.github.com/graphql
GITHUB_HEAD_REF=generalize-instantiate-yikes
GITHUB_JOB=pr
GITHUB_PATH=/home/runner/work/_temp/_runner_file_commands/add_path_f4cb70e3-a79a-4904-be63-f8808e39f50f
GITHUB_REF=refs/pull/118710/merge
GITHUB_REF_NAME=118710/merge
GITHUB_REF_PROTECTED=false
---
Built container sha256:9c3c93a371e5aed5c18185b24f130d95d5140dbd72a9b325e7b6b49e521a4faa
Looks like docker image is the same as before, not uploading
https://ci-caches.rust-lang.org/docker/7ebc15c01a233894034d277c8cce4e949f4e7791f66b4727c8fb6e058a0b8171d6152e1441d677cef0653843ceeee469c097b8699b2bb74249e674f6aa1a8813
sha256:9c3c93a371e5aed5c18185b24f130d95d5140dbd72a9b325e7b6b49e521a4faa
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 Dec  7 15:17:11 UTC 2023
  network time: Thu, 07 Dec 2023 15:17:12 GMT
  network time: Thu, 07 Dec 2023 15:17:12 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', '--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', '--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-missing-tools', '--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: rust.codegen-units-std := 1
---
   Compiling linux-raw-sys v0.4.5
   Compiling bitflags v2.4.0
   Compiling fastrand v2.0.0
   Compiling smallvec v1.10.0
error: invalid `--check-cfg` argument: `values(freebsd10)` (expected `cfg(name, values("value1", "value2", ... "valueN"))`)
error: could not compile `libc` (lib) due to previous error
warning: build failed, waiting for other jobs to finish...
Build completed unsuccessfully in 0:10:38
  local time: Thu Dec  7 15:28:25 UTC 2023

[compiler-errors]

r=me once you figure out wtf is going on with ci lol, looks unrelated?

[lqd]

CI should be fixed by #118706

[matthiaskrgr]

Does this also fix the weird debug warnings (?) of #118696 (screenshot at the bottom)

[compiler-errors]

@bors r+

[bors]

📌 Commit 40aa9f4 has been approved by compiler-errors

It is now in the queue for this repository.