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Auto merge of #93179 - Urgau:unreachable-2021, r=m-ou-se,oli-obk

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Fix invalid special casing of the unreachable! macro

This pull-request fix an invalid special casing of the `unreachable!` macro in the same way the `panic!` macro was solved, by adding two new internal only macros `unreachable_2015` and `unreachable_2021` edition dependent and turn `unreachable!` into a built-in macro that do dispatching. This logic is stolen from the `panic!` macro.

~~This pull-request also adds an internal feature `format_args_capture_non_literal` that allows capturing arguments from formatted string that expanded from macros. The original RFC #2795 mentioned this as a future possibility. This feature is [required](https://github.com/rust-lang/rust/issues/92137#issuecomment-1018630522) because of concatenation that needs to be done inside the macro:~~
```rust
$crate::concat!("internal error: entered unreachable code: ", $fmt)
```

**In summary** the new behavior for the `unreachable!` macro with this pr is:

Edition 2021:
```rust
let x = 5;
unreachable!("x is {x}");
```
```
internal error: entered unreachable code: x is 5
```

Edition <= 2018:
```rust
let x = 5;
unreachable!("x is {x}");
```
```
internal error: entered unreachable code: x is {x}
```

Also note that the change in this PR are **insta-stable** and **breaking changes** but this a considered as being a [bug](https://github.com/rust-lang/rust/issues/92137#issuecomment-998441613).
If someone could start a perf run and then a crater run this would be appreciated.

Fixes https://github.com/rust-lang/rust/issues/92137
This commit is contained in:
bors 2022-02-07 00:26:52 +00:00
commit 25b21a1d16
22 changed files with 326 additions and 80 deletions
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7
compiler/rustc_builtin_macros/src/lib.rs
View file

@ -32,12 +32,12 @@ mod concat_bytes;
mod concat_idents;
mod derive;
mod deriving;
mod edition_panic;
mod env;
mod format;
mod format_foreign;
mod global_allocator;
mod log_syntax;
mod panic;
mod source_util;
mod test;
mod trace_macros;
@ -83,8 +83,9 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
log_syntax: log_syntax::expand_log_syntax,
module_path: source_util::expand_mod,
option_env: env::expand_option_env,
core_panic: panic::expand_panic,
std_panic: panic::expand_panic,
core_panic: edition_panic::expand_panic,
std_panic: edition_panic::expand_panic,
unreachable: edition_panic::expand_unreachable,
stringify: source_util::expand_stringify,
trace_macros: trace_macros::expand_trace_macros,
}