When I implemented rust-only bootstrapping in rust-lang#92260,
I neglected to test stage0 tools - it turns out they were broken because
they couldn't find the sysroot of the initial bootstrap compiler.

This fixes stage0 tools by using `rustc --print sysroot` instead of assuming rustc is already in a
sysroot and hard-coding the relative directory.

Co-authored-by: Daniel Henry-Mantilla <daniel.henry.mantilla@gmail.com>

…it expressions.

This name makes it to debuginfo and allows debuggers to identify such bindings and
their captured versions in suspended async fns.

…acrum

Fix `cargo run tidy`

When I implemented rust-only bootstrapping in rust-lang#92260,
I neglected to test stage0 tools - it turns out they were broken because
they couldn't find the sysroot of the initial bootstrap compiler.

This fixes stage0 tools by using `rustc --print sysroot` instead of assuming rustc is already in a
sysroot and hard-coding the relative directory.

Fixes rust-lang#94797 (properly, without having to change rustup).

…errors

Add the generic_associated_types_extended feature

Right now, this only ignore obligations that reference new placeholders in `poly_project_and_unify_type`. In the future, this might do other things, like allowing object-safe GATs.

**This feature is *incomplete* and quite likely unsound. This is mostly just for testing out potential future APIs using a "relaxed" set of rules until we figure out *proper* rules.**

Also drive by cleanup of adding a `ProjectAndUnifyResult` enum instead of using a `Result<Result<Option>>`.

r? `@nikomatsakis`

…mandry

async: Give predictable name to binding generated from .await expressions.

This name makes it to debuginfo and allows debuggers to identify such bindings and their captured versions in suspended async fns.

This will be useful for async stack traces, as discussed in https://internals.rust-lang.org/t/async-debugging-logical-stack-traces-setting-goals-collecting-examples/15547.

I don't know if this needs some discussion by ``@rust-lang/compiler,`` e.g. about the name of the binding (`__awaitee`) or about the fact that this PR introduces a (soft) guarantee about a compiler generated name. Although, regarding the later, I think the same reasoning applies here as it does for debuginfo in general.

r? ``@tmandry``

Clean up, categorize and sort unstable features in std.

…ator-in-vec-into-iter, r=oli-obk

Fix double drop of allocator in IntoIter impl of Vec

Fixes rust-lang#95269

The `drop` impl of `IntoIter` reconstructs a `RawVec` from `buf`, `cap` and `alloc`, when that `RawVec` is dropped it also drops the allocator. To avoid dropping the allocator twice we wrap it in `ManuallyDrop` in the `InttoIter` struct.

Note this is my first contribution to the standard library, so I might be missing some details or a better way to solve this.

allow large Size again

This basically reverts most of rust-lang#80042, and instead does the panic in `bits()` with a `#[cold]` function to make sure it does not get inlined.

rust-lang#80042 added a comment about an invariant ("The top 3 bits are ALWAYS zero") that is not actually enforced, and if it were enforced that would be a problem for rust-lang#95388. So I think we should not have that invariant, and I adjusted the code accordingly.

r? `@oli-obk` Cc `@sivadeilra`