Introduce perma-unstable `wasm-c-abi` flag
Now that `wasm-bindgen` v0.2.88 supports the spec-compliant C ABI, the idea is to switch to that in a future version of Rust. In the meantime it would be good to let people test and play around with it.
This PR introduces a new perma-unstable `-Zwasm-c-abi` compiler flag, which switches to the new spec-compliant C ABI when targeting `wasm32-unknown-unknown`.
Alternatively, we could also stabilize this and then deprecate it when we switch. I will leave this to the Rust maintainers to decide.
This is a companion PR to #117918, but they could be merged independently.
MCP: https://github.com/rust-lang/compiler-team/issues/703
Tracking issue: https://github.com/rust-lang/rust/issues/122532
Outline default query and hook provider function implementations
The default query and hook provider functions call `bug!` with a decently long message.
Due to argument inlining in `format_args!` ([`flatten_format_args`](https://github.com/rust-lang/rust/issues/78356)), this ends up duplicating the message for each query, adding ~90KB to `librustc_driver.so` of unreachable panic messages.
To avoid this, we can outline the common `bug!` logic.
Move size assertions for `mir::syntax` types into the same file
A redundant size assertion for `StatementKind` was added in #122937, because the existing assertion was in a different file.
This PR cleans that up, and also moves the `TerminatorKind` assertion into the same file where it belongs, to avoid the same thing happening again.
r? `@nnethercote`
Implement syntax for `impl Trait` to specify its captures explicitly (`feature(precise_capturing)`)
Implements `impl use<'a, 'b, T, U> Sized` syntax that allows users to explicitly list the captured parameters for an opaque, rather than inferring it from the opaque's bounds (or capturing *all* lifetimes under 2024-edition capture rules). This allows us to exclude some implicit captures, so this syntax may be used as a migration strategy for changes due to #117587.
We represent this list of captured params as `PreciseCapturingArg` in AST and HIR, resolving them between `rustc_resolve` and `resolve_bound_vars`. Later on, we validate that the opaques only capture the parameters in this list.
We artificially limit the feature to *require* mentioning all type and const parameters, since we don't currently have support for non-lifetime bivariant generics. This can be relaxed in the future.
We also may need to limit this to require naming *all* lifetime parameters for RPITIT, since GATs have no variance. I have to investigate this. This can also be relaxed in the future.
r? `@oli-obk`
Tracking issue:
- https://github.com/rust-lang/rust/issues/123432
A redundant size assertion for `StatementKind` was added in #122937, because
the existing assertion was in a different file.
This patch cleans that up, and also moves the `TerminatorKind` assertion into
the same file where it belongs, to avoid the same thing happening again.
Fix pretty HIR for anon consts in diagnostics
This removes the `NoAnn` printer which skips over nested bodies altogether, which is confusing, and requires users of `{ty|qpath|pat}_to_string` to pass in `&tcx` which now impleemnts `hir_pretty::PpAnn`.
There's one case where this "regresses" by actually printing out the body of the anon const -- we could suppress that, but I don't expect people to actually get anon consts like that unless they're fuzzing, tbh.
r? estebank
Don't even parse an intrinsic unless the feature gate is enabled
Don't return true in `tcx.is_intrinsic` if the function is defined locally and `#![feature(intrinsics)]` is not enabled. This is a slightly more general fix than #123526, since #123587 shows that we have simplifying assumptions about intrinsics elsewhere in the compiler.
This will make the code ICE again if the user **enables** `#[feature(intrinsics)]`, but I kind of feel like if we want to fix that, we should make the `INTERNAL_FEATURES` lint `Deny` again. Perhaps we could do that on non-nightly compilers. Or we should just stop compilation altogether if they have `#![feature]` enabled on a non-nightly compiler.
As for the UX of *real* cases of hitting these ICEs, I believe pretty strongly that if a compiler/stdlib dev is modifying internal intrinsics (intentionally, like when making a change to rustc) we have no guarantee to make the ICE better looking for them. Honestly, *not* spitting out a stack trace is probably a disservice to the people who hit those ICEs in that case.
r? `@Nilstrieb` `@estebank`
Remove `TypeVariableOriginKind` and `ConstVariableOriginKind`
It's annoying to have to import `TypeVariableOriginKind` just to fill it with `MiscVariable` for almost every use. Every other usage other than `TypeParameterDefinition` wasn't even used -- I can see how it may have been useful once for debugging, but I do quite a lot of typeck debugging and I've never really needed it.
So let's just remove it, and keep around the only useful thing which is the `DefId` of the param for `var_for_def`.
This is based on #123006, which removed the special use of `TypeVariableOriginKind::OpaqueInference`, which I'm pretty sure I was the one that added.
r? lcnr or re-roll to types
Make the computation of `coroutine_captures_by_ref_ty` more sophisticated
Currently, we treat all the by-(mut/)ref borrows of a coroutine-closure as having a "closure env" borrowed lifetime.
When we have the given code:
```rust
let x: &'a i32 = ...;
let c = async || {
let _x = *x;
};
```
Then when we call:
```rust
c()
// which, because `AsyncFn` takes a `&self`, we insert an autoref:
(&c /* &'env {coroutine-closure} */)()
```
We will return a future whose captures contain `&'env i32` instead of `&'a i32`, which is way more restrictive than necessary. We should be able to drop `c` while the future is alive since it's not actually borrowing any data *originating from within* the closure's captures, but since the capture has that `'env` lifetime, this is not possible.
This wouldn't be true, for example, if the closure captured `i32` instead of `&'a i32`, because the `'env` lifetime is actually *necessary* since the data (`i32`) is owned by the closure.
This PR identifies two criteria where we *need* to take the borrow with the closure env lifetime:
1. If the closure borrows data from inside the closure's captures. This is not true if the parent capture is by-ref, OR if the parent capture is by-move and the child capture begins with a deref projection. This is the example described above.
2. If we're dealing with mutable references, since we cannot reborrow `&'env mut &'a mut i32` into `&'a mut i32`, *only* `&'env mut i32`.
See the documentation on `should_reborrow_from_env_of_parent_coroutine_closure` for more info.
**important:** As disclaimer states on that function, luckily, if this heuristic is not correct, then the program is not unsound, since we still borrowck and validate the choices made from this function -- the only side-effect is that the user may receive unnecessary borrowck errors.
Fixes#123241
