Add `Steal::risky_hack_borrow_mut`

I'm working on a rustc driver (Creusot) which needs to modify the MIR read by two queries, `mir_borrowck` and `check_liveness`, in different ways for each query. Both of these queries use `mir_promoted` to read the MIR, which is immutable (until it is stolen).

This adds an escape hatch so rustc drivers can mutate MIR for specific queries. And this removes `get_mut` which is unused and also unusable now that there's no way to get a `&mut Steal` from the rustc API.

Another approach may be to override the queries to modify the MIR after having read it from `mir_promoted`. However the implementation of queries is largely hidden, so I can't just copy their code to then modify it. A solution would be to parameterize the queries with callbacks which get instantiated with `mir_promoted` by default, but that seems more involved and ad hoc. That's why I'm proposing this smaller change instead.

Add `Steal::risky_hack_borrow_mut`

I'm working on a rustc driver (Creusot) which needs to modify the MIR read by two queries, `mir_borrowck` and `check_liveness`, in different ways for each query. Both of these queries use `mir_promoted` to read the MIR, which is immutable (until it is stolen).

This adds an escape hatch so rustc drivers can mutate MIR for specific queries. And this removes `get_mut` which is unused and also unusable now that there's no way to get a `&mut Steal` from the rustc API.

Another approach may be to override the queries to modify the MIR after having read it from `mir_promoted`. However the implementation of queries is largely hidden, so I can't just copy their code to then modify it. A solution would be to parameterize the queries with callbacks which get instantiated with `mir_promoted` by default, but that seems more involved and ad hoc. That's why I'm proposing this smaller change instead.

Add `Steal::risky_hack_borrow_mut`

I'm working on a rustc driver (Creusot) which needs to modify the MIR read by two queries, `mir_borrowck` and `check_liveness`, in different ways for each query. Both of these queries use `mir_promoted` to read the MIR, which is immutable (until it is stolen).

This adds an escape hatch so rustc drivers can mutate MIR for specific queries. And this removes `get_mut` which is unused and also unusable now that there's no way to get a `&mut Steal` from the rustc API.

Another approach may be to override the queries to modify the MIR after having read it from `mir_promoted`. However the implementation of queries is largely hidden, so I can't just copy their code to then modify it. A solution would be to parameterize the queries with callbacks which get instantiated with `mir_promoted` by default, but that seems more involved and ad hoc. That's why I'm proposing this smaller change instead.

Rollup of 9 pull requests

Successful merges:

 - #148480 (Add `Steal::risky_hack_borrow_mut`)
 - #148608 (Add test for --test-builder success path)
 - #148667 (a few small clippy fixes)
 - #148712 (Port `cfg_select!` to the new attribute parsing system)
 - #148760 (rustc_target: hide TargetOptions::vendor)
 - #148775 (Fix a typo in the documentation for the strict_shr function)
 - #148779 (Implement DynSend and DynSync for std::panic::Location.)
 - #148781 ([rustdoc] Remove unneeded `allow(rustc::potential_query_instability)`)
 - #148791 (fix "is_closure_like" doc comment)

r? `@ghost`
`@rustbot` modify labels: rollup

Add `Steal::risky_hack_borrow_mut`

I'm working on a rustc driver (Creusot) which needs to modify the MIR read by two queries, `mir_borrowck` and `check_liveness`, in different ways for each query. Both of these queries use `mir_promoted` to read the MIR, which is immutable (until it is stolen).

This adds an escape hatch so rustc drivers can mutate MIR for specific queries. And this removes `get_mut` which is unused and also unusable now that there's no way to get a `&mut Steal` from the rustc API.

Another approach may be to override the queries to modify the MIR after having read it from `mir_promoted`. However the implementation of queries is largely hidden, so I can't just copy their code to then modify it. A solution would be to parameterize the queries with callbacks which get instantiated with `mir_promoted` by default, but that seems more involved and ad hoc. That's why I'm proposing this smaller change instead.

Add `Steal::risky_hack_borrow_mut`

I'm working on a rustc driver (Creusot) which needs to modify the MIR read by two queries, `mir_borrowck` and `check_liveness`, in different ways for each query. Both of these queries use `mir_promoted` to read the MIR, which is immutable (until it is stolen).

This adds an escape hatch so rustc drivers can mutate MIR for specific queries. And this removes `get_mut` which is unused and also unusable now that there's no way to get a `&mut Steal` from the rustc API.

Another approach may be to override the queries to modify the MIR after having read it from `mir_promoted`. However the implementation of queries is largely hidden, so I can't just copy their code to then modify it. A solution would be to parameterize the queries with callbacks which get instantiated with `mir_promoted` by default, but that seems more involved and ad hoc. That's why I'm proposing this smaller change instead.

Rollup of 16 pull requests

Successful merges:

 - #141470 (Add new `function_casts_as_integer` lint)
 - #143619 (`c_variadic`: Add future-incompatibility warning for `...` arguments without a pattern outside of `extern` blocks)
 - #146495 (rustdoc: Erase `#![doc(document_private_items)]`)
 - #147771 (Rename `*exact_{div,shr,shl}` to `*{div,shr,shl}_exact`)
 - #147833 (rustdoc-json: move `target` to `json::conversions`)
 - #147952 (Add a timeout to the `remote-test-client` connection)
 - #147955 (compiletest: Migrate `TestProps` directive handling to a system of named handlers)
 - #148480 (Add `Steal::risky_hack_borrow_mut`)
 - #148506 (Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`)
 - #148508 (Provide more context when mutably borrowing an imutably borrowed value)
 - #148530 (update the bootstrap readme)
 - #148608 (Add test for --test-builder success path)
 - #148636 (bootstrap: respect `build.python` on macOS)
 - #148639 (test(rustdoc): move tests into jump-to-def)
 - #148647 (Check unsafety for non-macro attributes in `validate_attr`)
 - #148667 (a few small clippy fixes)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 16 pull requests

Successful merges:

 - #141470 (Add new `function_casts_as_integer` lint)
 - #143619 (`c_variadic`: Add future-incompatibility warning for `...` arguments without a pattern outside of `extern` blocks)
 - #146495 (rustdoc: Erase `#![doc(document_private_items)]`)
 - #147771 (Rename `*exact_{div,shr,shl}` to `*{div,shr,shl}_exact`)
 - #147833 (rustdoc-json: move `target` to `json::conversions`)
 - #147952 (Add a timeout to the `remote-test-client` connection)
 - #147955 (compiletest: Migrate `TestProps` directive handling to a system of named handlers)
 - #148480 (Add `Steal::risky_hack_borrow_mut`)
 - #148506 (Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`)
 - #148508 (Provide more context when mutably borrowing an imutably borrowed value)
 - #148530 (update the bootstrap readme)
 - #148608 (Add test for --test-builder success path)
 - #148636 (bootstrap: respect `build.python` on macOS)
 - #148639 (test(rustdoc): move tests into jump-to-def)
 - #148647 (Check unsafety for non-macro attributes in `validate_attr`)
 - #148667 (a few small clippy fixes)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup of 15 pull requests

Successful merges:

 - #141470 (Add new `function_casts_as_integer` lint)
 - #143619 (`c_variadic`: Add future-incompatibility warning for `...` arguments without a pattern outside of `extern` blocks)
 - #146495 (rustdoc: Erase `#![doc(document_private_items)]`)
 - #147771 (Rename `*exact_{div,shr,shl}` to `*{div,shr,shl}_exact`)
 - #147833 (rustdoc-json: move `target` to `json::conversions`)
 - #147955 (compiletest: Migrate `TestProps` directive handling to a system of named handlers)
 - #148480 (Add `Steal::risky_hack_borrow_mut`)
 - #148506 (Special case detecting `'static` lifetime requirement coming from `-> Box<dyn Trait>`)
 - #148508 (Provide more context when mutably borrowing an imutably borrowed value)
 - #148530 (update the bootstrap readme)
 - #148608 (Add test for --test-builder success path)
 - #148636 (bootstrap: respect `build.python` on macOS)
 - #148639 (test(rustdoc): move tests into jump-to-def)
 - #148647 (Check unsafety for non-macro attributes in `validate_attr`)
 - #148667 (a few small clippy fixes)

r? `@ghost`
`@rustbot` modify labels: rollup

Rollup merge of #148480 - Lysxia:steal-mut, r=davidtwco

Add `Steal::risky_hack_borrow_mut`

I'm working on a rustc driver (Creusot) which needs to modify the MIR read by two queries, `mir_borrowck` and `check_liveness`, in different ways for each query. Both of these queries use `mir_promoted` to read the MIR, which is immutable (until it is stolen).

This adds an escape hatch so rustc drivers can mutate MIR for specific queries. And this removes `get_mut` which is unused and also unusable now that there's no way to get a `&mut Steal` from the rustc API.

Another approach may be to override the queries to modify the MIR after having read it from `mir_promoted`. However the implementation of queries is largely hidden, so I can't just copy their code to then modify it. A solution would be to parameterize the queries with callbacks which get instantiated with `mir_promoted` by default, but that seems more involved and ad hoc. That's why I'm proposing this smaller change instead.