Retire the `unnamed_fields` feature for now
`#![feature(unnamed_fields)]` was implemented in part in #115131 and #115367, however work on that feature has (afaict) stalled and in the mean time there have been some concerns raised (e.g.[^1][^2]) about whether `unnamed_fields` is worthwhile to have in the language, especially in its current desugaring. Because it represents a compiler implementation burden including a new kind of anonymous ADT and additional complication to field selection, and is quite prone to bugs today, I'm choosing to remove the feature.
However, since I'm not one to really write a bunch of words, I'm specifically *not* going to de-RFC this feature. This PR essentially *rolls back* the state of this feature to "RFC accepted but not yet implemented"; however if anyone wants to formally unapprove the RFC from the t-lang side, then please be my guest. I'm just not totally willing to summarize the various language-facing reasons for why this feature is or is not worthwhile, since I'm coming from the compiler side mostly.
Fixes#117942Fixes#121161Fixes#121263Fixes#121299Fixes#121722Fixes#121799Fixes#126969Fixes#131041
Tracking:
* https://github.com/rust-lang/rust/issues/49804
[^1]: https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Unnamed.20struct.2Funion.20fields
[^2]: https://github.com/rust-lang/rust/issues/49804#issuecomment-1972619108
Fix anon const def-creation when macros are involved take 2
Fixes#130321
There were two cases that #129137 did not handle correctly:
- Given a const argument `Foo<{ bar!() }>` in which `bar!()` expands to `N`, we would visit the anon const and then visit the `{ bar() }` expression instead of visiting the macro call. This meant that we would build a def for the anon const as `{ bar!() }` is not a trivial const argument as `bar!()` is not a path.
- Given a const argument `Foo<{ bar!() }>` is which `bar!()` expands to `{ qux!() }` in which `qux!()` expands to `N`, it should not be considered a trivial const argument as `{{ N }}` has two pairs of braces. If we only looked at `qux`'s expansion it would *look* like a trivial const argument even though it is not. We have to track whether we have "unwrapped" a brace already when recursing into the expansions of `bar`/`qux`/any macro
r? `@camelid`
...and remove the `const_arg_path` feature gate as a result. It was only
a stopgap measure to fix the regression that the new lowering introduced
(which should now be fixed by this PR).
Simplify some nested `if` statements
Applies some but not all instances of `clippy::collapsible_if`. Some ended up looking worse afterwards, though, so I left those out. Also applies instances of `clippy::collapsible_else_if`
Review with whitespace disabled please.
This is needed for Clippy to know that the `#[allow(unused)]` attributes
added by the expansion of `?` are part of the desugaring, and that they
do not come from the user code.
rust-lang/rust-clippy#13380 exhibits a manifestation of this problem.
Remove `ParamMode::ExplicitNamed`
This was introduced as a hack to improve a diagnostics suggestion in #61679. It was subsequently broken, but also it was an incomplete hack that I don't believe we need to support, so let's just remove it.
Add `#[warn(unreachable_pub)]` to a bunch of compiler crates
By default `unreachable_pub` identifies things that need not be `pub` and tells you to make them `pub(crate)`. But sometimes those things don't need any kind of visibility. So they way I did these was to remove the visibility entirely for each thing the lint identifies, and then add `pub(crate)` back in everywhere the compiler said it was necessary. (Or occasionally `pub(super)` when context suggested that was appropriate.) Tedious, but results in more `pub` removal.
There are plenty more crates to do but this seems like enough for a first PR.
r? `@compiler-errors`
Retroactively feature gate `ConstArgKind::Path`
This puts the lowering introduced by #125915 under a feature gate until we fix the regressions introduced by it. Alternative to whole sale reverting the PR since it didn't seem like a very clean revert and I think this is generally a step in the right direction and don't want to get stuck landing and reverting the PR over and over :)
cc #129137 ``@camelid,`` tests taken from there. beta is branching soon so I think it makes sense to not try and rush that fix through since it wont have much time to bake and if it has issues we can't simply revert it on beta.
Fixes#128016
Use shorthand field initialization syntax more aggressively in the compiler
Caught these when cleaning up #129344 and decided to run clippy to find the rest
Use more slice patterns inside the compiler
Nothing super noteworthy. Just replacing the common 'fragile' pattern of "length check followed by indexing or unwrap" with slice patterns for legibility and 'robustness'.
r? ghost
