yeet type const

[khyperia]

tracking issue: #132980

zulip thread context (design decussion of future of gca): #project-const-generics > talkies at last @ 💬

this PR does two things:

• implement #[rustc_always_gca] (bikeshed name thread: #project-const-generics > #[always_gca] bikeshed )
• remove type const syntax

it also migrates the test suite to the syntax introduced in #162179 i.e. the new way to write type const is now const ITEM: T = core::direct_const_arg!(V); (ouch my hands, that took a while)

r? @BoxyUwU

[rustbot]

This PR changes rustc_public

cc @oli-obk, @celinval, @ouz-a, @makai410

Some changes occurred in match checking

cc @Nadrieril

The parser was modified, potentially altering the grammar of (stable) Rust
which would be a breaking change.

cc @fmease

HIR ty lowering was modified

cc @fmease

Some changes occurred in compiler/rustc_attr_ir

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

rustfmt is developed in its own repository. If possible, consider making this change to rust-lang/rustfmt instead.

cc @rust-lang/rustfmt

clippy is developed in its own repository. If possible, consider making this change to rust-lang/rust-clippy instead.

cc @rust-lang/clippy

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann, @JonathanBrouwer

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

[rustbot]

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