convert AdtDef::destructor to on-demand

This removes the `Cell` from `AdtDef`. Also, moving destructor validity
checking to on-demand (forced during item-type checking) ensures that
invalid destructors can't cause ICEs.

Fixes #38868.
Fixes #40132.

r? @EddyB

rustbuild: use deterministic step ordering and respect path order on the command-line.

Restores similar behavior to `make` rules, where:
* the step order was always the same, e.g. the testsuite order in `make check`
* `make check-stage1-{cfail,rpass}` would *always* run `cfail` before `rpass`
  * `./x.py test--stage 1 src/test/{compile-fail,run-pass}` is now equivalent

r? @alexcrichton

transition borrowck to visit all **bodies** and not item-likes

This is a better structure for incremental compilation and also more compatible with the eventual borrowck mir. It also fixes #38520 as a drive-by fix.

r? @EddyB

Rollup of 7 pull requests

- Successful merges: #39832, #40104, #40110, #40117, #40129, #40139, #40166
- Failed merges:

Allow types passed to [] to coerce, like .index()

Fixes #40085

Basically steals the relevant part of [check_argument_types](https://github.com/rust-lang/rust/blob/1.15.1/src/librustc_typeck/check/mod.rs#L2653-L2672).

std::process for fuchsia: updated to latest liblaunchpad

Our liblaunchpad changed a bit and so fuchsia's std::process impl needs to change a bit.

@raphlinus

Implement function-like procedural macros ( `#[proc_macro]`)

Adds the `#[proc_macro]` attribute, which expects bare functions of the kind `fn(TokenStream) -> TokenStream`, which can be invoked like `my_macro!()`.

cc rust-lang/rfcs#1913, #38356

r? @jseyfried
cc @nrc

Panic on errors in `format!` or `<T: Display>::to_string`

… instead of silently ignoring a result.

`fmt::Write for String` never returns `Err`, so implementations of `Display` (or other traits of that family) never should either.

Fixes #40103

Made no_stack_check a stable_removed attribute

r? @brson

[MIR] Rvalue::ty infallible + remove TypedConstVal

Feel free to r+ whenever there aren't any big bit-rot sensitive PRs in the queue.

r? @EddyB

Add support for the x86-interrupt calling convention

This calling convention can be used for definining interrupt handlers on 32-bit and 64-bit x86 targets. The compiler then uses `iret` instead of `ret` for returning and ensures that all registers are restored to their
original values.

Usage:

```rust
extern "x86-interrupt" fn handler(stack_frame: &ExceptionStackFrame) {…}
```

for interrupts and exceptions without error code and

```rust
extern "x86-interrupt" fn handler_with_err_code(stack_frame: &ExceptionStackFrame,
                                                error_code: u64) {…}
```

for exceptions that push an error code (e.g., page faults or general protection faults). The programmer must ensure that the correct version is used for each interrupt.

For more details see the [LLVM PR][1] and the corresponding [proposal][2].

[1]: https://reviews.llvm.org/D15567
[2]: http://lists.llvm.org/pipermail/cfe-dev/2015-September/045171.html

It is also possible to implement interrupt handlers on x86 through [naked functions](https://github.com/rust-lang/rfcs/blob/master/text/1201-naked-fns.md). In fact, almost all existing Rust OS projects for x86 use naked functions for this, including [Redox](https://github.com/redox-os/kernel/blob/b9793deb59c7650f0805dea96adb6b773ad99336/arch/x86_64/src/lib.rs#L109-L147), [IntermezzOS](https://github.com/intermezzOS/kernel/blob/f959cc18c78b1ba153f3ff7039d9ecc07f397628/interrupts/src/lib.rs#L28-L72), and [blog_os](https://github.com/phil-opp/blog_os/blob/844d739379ffdea6a7ede88365ec6e21a725bbf5/src/interrupts/mod.rs#L49-L64). So support for the `x86-interrupt` calling convention isn't absolutely needed.

However, it has a number of benefits to naked functions:

- **No inline assembly needed**: [Inline assembly](https://doc.rust-lang.org/book/inline-assembly.html) is highly unstable and dangerous. It's pretty easy to mess things up. Also, it uses an arcane syntax and requires that the programmer knows x86 assembly.
- **Higher performance**: A naked wrapper function always saves _all_ registers before calling the Rust function. This isn't needed for a compiler supported calling convention, since the compiler knows which registers are clobbered by the interrupt handler. Thus, only these registers need to be saved and restored.
- **Safer interfaces**: We can write a `set_handler` function that takes a `extern "x86-interrupt" fn(&ExceptionStackFrame)` and the compiler ensures that we always use the right function type for all handler functions. This isn't possible with the `#[naked]` attribute.
- **More convenient**: Instead of writing [tons of assembly boilerplate](https://github.com/redox-os/kernel/blob/b9793deb59c7650f0805dea96adb6b773ad99336/arch/x86_64/src/lib.rs#L109-L147) and desperately trying to improve things [through macros](https://github.com/phil-opp/blog_os/blob/844d739379ffdea6a7ede88365ec6e21a725bbf5/src/interrupts/mod.rs#L17-L92), we can just write [code like this](https://github.com/phil-opp/blog_os/blob/e6a61f9507a4c4fef6fb4e3474bc596391bc97d2/src/interrupts/mod.rs#L85-L89).
- **Naked functions are unreliable**: It is allowed to use Rust code inside a naked function, which sometimes works and sometimes not. For example, [calling a function](https://github.com/redox-os/kernel/blob/b9793deb59c7650f0805dea96adb6b773ad99336/arch/x86_64/src/lib.rs#L132) through Rust code seems to work fine without function prologue, but [code declaring a variable](https://is.gd/NQYXqE) silently adds a prologue even though the function is naked (look at the generated assembly, there is a `movl` instruction before the `nop`).

**Edit**: See the [tracking issue](https://github.com/rust-lang/rust/issues/40180) for an updated list of issues.

Unfortunately, the implementation of the `x86-interrupt` calling convention in LLVM has some issues that make it unsuitable for 64-bit kernels at the moment:

- LLVM always tries to backup the `xmm` registers on 64-bit platforms even if the target doesn't support SSE. This leads to invalid opcode exceptions whenever an interrupt handler is invoked. I submitted a fix to LLVM in [D29959](https://reviews.llvm.org/D29959). The fix is really small (<10 lines), so maybe we could backport it to [Rust's LLVM fork](https://github.com/rust-lang/llvm)?. **Edit**: The fix was merged to LLVM trunk in [rL295347](https://reviews.llvm.org/rL295347). Backported in https://github.com/rust-lang/llvm/pull/63.

- On targets with SSE support, LLVM uses the `movaps` instruction for saving the `xmm` registers, which requires an alignment of 16. For handlers with error codes, however, the stack alignment is only 8, so a alignment exception occurs. This issue is tracked in [bug 26413](https://bugs.llvm.org/show_bug.cgi?id=26413). ~~Unfortunately, I don't know enough about LLVM to fix this.~~ **Edit**: Fix submitted in [D30049](https://reviews.llvm.org/D30049).

This PR adds experimental support for this calling convention under the `abi_x86_interrupt` feature gate. The implementation is very similar to #38465 and was surprisingly simple :).

There is no accepted RFC for this change. In fact, the [RFC for interrupt calling convention](https://github.com/rust-lang/rfcs/pull/1275) from 2015 was closed in favor of naked functions. However, the reactions to the recent [PR](https://github.com/rust-lang/rust/pull/38465) for a MSP430 interrupt calling convention were [in favor of experimental interrupt ABIs](https://github.com/rust-lang/rust/pull/38465#issuecomment-270015470).

- [x] Add compile-fail tests for the feature gate.
- [x] Create tracking issue for the `abi_x86_interrupt` feature (and link it in code). **Edit**: Tracking issue: #40180
- [x] Backport [rL295347](https://reviews.llvm.org/rL295347) to Rust's LLVM fork. **Edit**: Done in https://github.com/rust-lang/llvm/pull/63

@tari @steveklabnik @jackpot51 @ticki @hawkw @thepowersgang, you might be interested in this.

Tracking issue: https://github.com/rust-lang/rust/issues/40180

This calling convention can be used for definining interrupt handlers on
32-bit and 64-bit x86 targets. The compiler then uses `iret` instead of
`ret` for returning and ensures that all registers are restored to their
original values.

Usage:

```
extern "x86-interrupt" fn handler(stack_frame: &ExceptionStackFrame) {…}
```

for interrupts and exceptions without error code and

```
extern "x86-interrupt" fn page_fault_handler(stack_frame: &ExceptionStackFrame,
                                             error_code: u64) {…}
```

for exceptions that push an error code (e.g., page faults or general
protection faults). The programmer must ensure that the correct version
is used for each interrupt.

For more details see the [LLVM PR][1] and the corresponding [proposal][2].

[1]: https://reviews.llvm.org/D15567
[2]: http://lists.llvm.org/pipermail/cfe-dev/2015-September/045171.html

suggest doubling recursion limit in more situations

Fixes #38852.

r? @bluss

Rollup of 9 pull requests

- Successful merges: #40081, #40144, #40168, #40169, #40170, #40173, #40175, #40191, #40194
- Failed merges:

Fix wrong word used in book page "const and static"

Add abi_x86_interrupt to the unstable book

This PR closes #40181.

doc: fix inconsistency in error output in guessing-game.md

The line '.expect("failed to read line");' is partly started with a
lower case 'f' and partly with an uppercase one, adding additional
spurious changes to otherwise clean diffs if each sample is
copy-and-pasted over the previous.
This change starts the string with an uppercase everywhere which is in
line with the style of the other strings.

Add a reference to the dl library to the Makefile of the test issue-2…

…4445.

It prevents the test to fail on ppc64el at least.

Part of #39015

Fix link in `if let` docs

r? @steveklabnik

String docs: Add "the"

r? @steveklabnik

Add compile fail test for abi_ptx

Issue #39059.

Unit-like structs doc: Improve code sample

r? @steveklabnik

BTW it seems that
```Rust
let p = Proton {};
```
compiles without an error. That's why I didn't add it to the example. It's about consistency anyway.

Add missing url in sync structs

r? @frewsxcv

inhibit enum layout optimizations under `#[repr(C)]` or `#[repr(u8)]`

Fixes #40029

Add a test that -fPIC is applied

r? @alexcrichton Can it really be this simple? I've tested it works, but still testing that it used to fail.

… instead of silently ignoring a result.

`fmt::Write for String` never returns `Err`,
so implementations of `Display` (or other traits of that family)
never should either.

Fixes #40103

Fixes #40029

This removes the Cell from AdtDef. Also, moving destructor validity
checking to on-demand (forced during item-type checking) ensures that
invalid destructors can't cause ICEs.

Fixes #38868.
Fixes #40132.

The line '.expect("failed to read line");' is partly started with a
lower case 'f' and partly with an uppercase one, adding additional
spurious changes to otherwise clean diffs if each sample is
copy-and-pasted over the previous.
This change starts the string with an uppercase everywhere which is in
line with the style of the other strings.

It prevents the test to fail on ppc64el at least.

Part of #39015

Make transmuting from fn item types to pointer-sized types a hard error.

Closes #19925 by removing the future compatibility lint and the associated workarounds.
This is a `[breaking-change]` if you `transmute` from a function item without casting first.
For more information on how to fix your code, see https://github.com/rust-lang/rust/issues/19925.