This fixes a bug where after calling pad_integral with appropriate flags, the
fill and alignment flags would be set to '0' and 'Right' and left as such even
after exiting pad_integral, which meant that future calls on the same Formatter
would get incorrect flags reported.

This is quite difficult to observe in practice, as almost all formatting
implementations in practice don't call `Display::fmt` directly, but rather use
`write!` or a similar macro, which means that they cannot observe the effects of
the wrong flags (as `write!` creates a fresh Formatter instance). However, we
include a test case.

Using `#![feature(trivial_bounds)]`, it's possible to write functions
with unsatisfiable 'where' clauses, making them uncallable. However, the
user can act as if these 'where' clauses are true inside the body of the
function, leading to code that would normally be impossible to write.

Since const propgation can run even without any user-written calls to a
function, we need to explcitly check for these uncallable functions.

This avoids a strange linker error that we get with only "--emit=mir"
and "check-pass"

…on unevaluated consts

which requires a lot of unnecessary work to evaluate them further down the line.

This is primarily updating the `curl` dependency, but also went ahead
and applied a few updates for other packages that Cargo depends on.

…dependent on the

number of bits within consts.

…ation, r=oli-obk

Add unreachable propagation mir optimization pass

@oli-obk suggested we create a MIR pass that optimizes away basic blocks that lead only to basic blocks with terminator kind **unreachable**. This is a first take on this, which we started with @gilescope at RustFest Impl Days.

The test currently fails when the compiled program runs (undefined behaviour). Is there a way to avoid running the compiled program?

…al, r=dtolnay

Reset Formatter flags on exit from pad_integral

This fixes a bug where after calling pad_integral with appropriate flags, the
fill and alignment flags would be set to '0' and 'Right' and left as such even
after exiting pad_integral, which meant that future calls on the same Formatter
would get incorrect flags reported.

This is quite difficult to observe in practice, as almost all formatting
implementations in practice don't call `Display::fmt` directly, but rather use
`write!` or a similar macro, which means that they cannot observe the effects of
the wrong flags (as `write!` creates a fresh Formatter instance). However, we
include a test case.

A manual check leads me to believe this is the only case where we failed to reset the flags appropriately, but I could have missed something.

…, r=matthewjasper,oli-obk

Don't run const propagation on items with inconsistent bounds

Fixes rust-lang#67696

Using `#![feature(trivial_bounds)]`, it's possible to write functions
with unsatisfiable 'where' clauses, making them uncallable. However, the
user can act as if these 'where' clauses are true inside the body of the
function, leading to code that would normally be impossible to write.

Since const propgation can run even without any user-written calls to a
function, we need to explcitly check for these uncallable functions.

…rk-Simulacrum

Update some of Cargo's dependencies

This is primarily updating the `curl` dependency, but also went ahead
and applied a few updates for other packages that Cargo depends on.

Clean up some diagnostics by making them more consistent

In general:

- Diagnostic should start with a lowercase letter.
- Diagnostics should not end with a full stop.
- Ellipses contain three dots.
- Backticks should encode Rust code.

I also reworded a couple of messages to make them read more clearly.

It might be sensible to create a style guide for diagnostics, so these informal conventions are written down somewhere, after which we could audit the existing diagnostics.

r? @Centril

perf: Eagerly convert literals to consts

Previousely even literal constants were being converted to an `Unevaluted` constant for evaluation later. This seems unecessary as no more information is needed to be able to convert the literal to a mir constant.

Hopefully this will also minimise the performance impact of rust-lang#67717, as far less constant evaluations are needed.

Implement Cursor for linked lists. (RFC 2570).

cc. rust-lang#58533 cc. @Gankra

r? @Amanieu