static libraries with ar_archive_writer

Fixes rust-lang#107495

rustc is just one tool/executable, even if at the center of the toolchain

Move the length check to before using `index` with `ptr::add` to prevent
an out of bounds pointer from being formed.

Fixes rust-lang#122760

These assertions detect situations where a BCB node would have both a physical
counter and one or more in-edge counters/expressions.

For most BCBs that situation would indicate an implementation bug. However,
it's perfectly fine in the case of a BCB having an edge that loops back to
itself.

Given the complexity and risk involved in fixing the assertions, and the fact
that nothing relies on them actually being true, this patch just removes them
instead.

…iler-errors

pattern analysis: add a custom test harness

There are two features of the pattern analysis code that are hard to test: the newly-added pattern complexity limit, and the computation of arm intersections. This PR adds some crate-specific tests for that, including an unmaintainable but pretty macro to help construct patterns.

r? `@compiler-errors`

…thercote

Use same file permissions for ar_archive_writer as the LLVM archive writer

This is required to switch to ar_archive_writer in the future without regressions. In addition to this PR support for reading thin archives needs to be added (rust-lang#107407) to fix all known regressions.

Fixes rust-lang#107495

use more accurate terminology

rustc is just one tool/executable, even if at the center of the toolchain

…jubilee,Nilstrieb

fix OOB pointer formed in Vec::index

Move the length check to before using `index` with `ptr::add` to prevent an out of bounds pointer from being formed.

Fixes rust-lang#122760

coverage: Remove incorrect assertions from counter allocation

These assertions detect situations where a BCB node (in the coverage graph) would have both a physical counter and one or more in-edge counters/expressions.

For most BCBs that situation would indicate an implementation bug. However, it's perfectly fine in the case of a BCB having an edge that loops back to itself.

Given the complexity and risk involved in fixing the assertions, and the fact that nothing relies on them actually being true, this patch just removes them instead.

Fixes rust-lang#122738.

`@rustbot` label +A-code-coverage

…ng-usize-max, r=Nilstrieb

Add `usize::MAX` arg tests for Vec

Tests to prevent recurrence of the UB from the rust-lang#122760 issue.

I skipped the `with_capacity`, `drain`, `reserve`, etc. APIs because they actually had a good assortment of tests earlier in the same file.

r? Nilstrieb

…li-obk

Rename `hir::Let` into `hir::LetExpr`

As discussed on [zulip](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Improve.20naming.20of.20.60ExprKind.3A.3ALet.60.3F).

r? `@Zalathar`