Rollup of 12 pull requests

[jonas-schievink]

Successful merges:

• Use less divisions in display u128/i128 #76017 (Use less divisions in display u128/i128)
• Add missing code examples on HashMap types #76917 (Add missing code examples on HashMap types)
• Refactor memchr to allow optimization #76971 (Refactor memchr to allow optimization)
• Add accessors to Command. #77029 (Add accessors to Command.)
• Enable const propagation into operands at mir_opt_level=2 #77107 (Enable const propagation into operands at mir_opt_level=2)
• Update cargo #77129 (Update cargo)
• Fix FIXME in core::num test: Check sign of zero in min/max tests. #77167 (Fix FIXME in core::num test: Check sign of zero in min/max tests.)
• Rust vec bench import specific rand::RngCore #77184 (Rust vec bench import specific rand::RngCore)
• Late link args order #77208 (Late link args order)
• Fix documentation highlighting in ty::BorrowKind #77209 (Fix documentation highlighting in ty::BorrowKind)
• Move helper function for missing_const_for_fn out of rustc to clippy #77231 (Move helper function for missing_const_for_fn out of rustc to clippy)
• pretty-print-reparse hack: Rename some variables for clarity #77235 (pretty-print-reparse hack: Rename some variables for clarity)

Failed merges:

r? @ghost

[jonas-schievink]

@bors r+ rollup=never p=12

@rustbot modify labels: rollup

[bors]

📌 Commit fb98604 has been approved by jonas-schievink

[rust-log-analyzer]

The job x86_64-gnu-llvm-8 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

Initialized empty Git repository in /home/runner/work/rust/rust/.git/
##[command]git remote add origin https://github.com/rust-lang/rust
##[command]git config gc.auto 0
##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/77240/merge:refs/remotes/pull/77240/merge
---
   Compiling libc v0.2.77
   Compiling std v0.0.0 (/checkout/library/std)
   Compiling compiler_builtins v0.1.35
   Compiling unwind v0.0.0 (/checkout/library/unwind)
error[E0599]: no function or associated item named `first_ptr_mut` found for union `mem::maybe_uninit::MaybeUninit<_>` in the current scope
   --> library/core/src/fmt/num.rs:484:32
    |
484 |     let buf_ptr = MaybeUninit::first_ptr_mut(buf);
    |                                ^^^^^^^^^^^^^ function or associated item not found in `mem::maybe_uninit::MaybeUninit<_>`
   ::: library/core/src/mem/maybe_uninit.rs:221:1
    |
221 | pub union MaybeUninit<T> {
221 | pub union MaybeUninit<T> {
    | ------------------------ function or associated item `first_ptr_mut` not found for this

error[E0599]: no function or associated item named `first_ptr_mut` found for union `mem::maybe_uninit::MaybeUninit<_>` in the current scope
   --> library/core/src/fmt/num.rs:598:32
    |
598 |     let buf_ptr = MaybeUninit::first_ptr_mut(&mut buf);
    |                                ^^^^^^^^^^^^^ function or associated item not found in `mem::maybe_uninit::MaybeUninit<_>`
   ::: library/core/src/mem/maybe_uninit.rs:221:1
    |
221 | pub union MaybeUninit<T> {
221 | pub union MaybeUninit<T> {
    | ------------------------ function or associated item `first_ptr_mut` not found for this
error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0599`.
error: could not compile `core`.
---
== clock drift check ==
  local time: Sat Sep 26 21:03:05 UTC 2020
  network time: Sat, 26 Sep 2020 21:03:05 GMT
== end clock drift check ==
##[error]Process completed with exit code 1.
Terminate orphan process: pid (2947) (node)
Terminate orphan process: pid (2956) (python)

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