…share some code

Follow up to e3f2edc

Fix: Write access check of `prefix` and `sysconfdir`
when DESTDIR is present.

Improvement: Instead of repeatedly reading `DESTDIR` within
each `fn prepare_dir` usage, read it once and pass it to
the `fn prepare_dir`.

Signed-off-by: onur-ozkan <work@onurozkan.dev>

For a local pattern with no space between `let` and `(` e.g.:

  let(_a) = 3;

we were previously suggesting this illegal code:

  let_a =3;

After this change the suggestion will instead be:

  let _a =3;

(Note the space after `let`)

If a function incorrectly contains multiple `...` args, and is also not
foreign or `unsafe extern "C"`, only emit the latter error once.

Trying to use C-variadics in a const function would previously fail with
an error like "destructor of `VaListImpl<'_>` cannot be evaluated at
compile-time".

Add an explicit check for const C-variadics to provide a clearer error:
"functions cannot be both `const` and C-variadic".

share some track_caller logic between interpret and codegen

Also move the code that implements the track_caller intrinsics out of the core interpreter engine -- it's just a helper creating a const-allocation, doesn't need to be part of the interpreter core.

Rename a few remaining references to abort terminator

Follow up to e3f2edc

…iadic-errors, r=oli-obk

C-variadic error improvements

A couple improvements for c-variadic errors:

1. Fix the bad-c-variadic error being emitted multiple times. If a function incorrectly contains multiple `...` args, and is also not foreign or `unsafe extern "C"`, only emit the latter error once rather than once per `...`.

2. Explicitly reject `const` C-variadic functions. Trying to use C-variadics in a const function would previously fail with an error like "destructor of `VaListImpl<'_>` cannot be evaluated at compile-time". Add an explicit check for const C-variadics to provide a clearer error: "functions cannot be both `const` and C-variadic". This also addresses one of the concerns in rust-lang#44930: "Ensure that even when this gets stabilized for regular functions, it is still rejected on const fn."

…larsan68

improve and fix `x install`

Fix: Write access check of `prefix` and `sysconfdir` when DESTDIR is present.

Improvement: Instead of repeatedly reading `DESTDIR` within each `fn prepare_dir` usage, read it once and pass it to the `fn prepare_dir`.

Fixes rust-lang#117203

Some diagnostics improvements of `gen` blocks

These are leftovers from rust-lang#116447

…d-macro, r=estebank

Fix unused variables lint issue for args in macro

Fixes rust-lang#117284
r? ``@estebank``

…Nilstrieb

Fix missing leading space in suggestion

For a local pattern with no space between `let` and `(` e.g.:
```rust
  let(_a) = 3;
```
we were previously suggesting this illegal code:
```rust
  let_a = 3;
```
After this change the suggestion will instead be:
```rust
  let _a = 3;
```
Fixes rust-lang#117380