Refactor fallback code to prepare for never type
This PR contains cherry-picks of some of `@nikomatsakis's` work from #79366, and shouldn't (AFAICT) represent any change in behavior. However, the refactoring is good regardless of the never type work being landed, and will reduce the size of those eventual PR(s) (and rebase pain).
I am not personally an expert on this code, and the commits are essentially 100% `@nikomatsakis's,` but they do seem reasonable to me by my understanding. Happy to edit with review, of course. Commits are best reviewed in sequence rather than all together.
r? `@jackh726` perhaps?
Motivation: in upcoming commits, we are going to create a graph of the
coercion relationships between variables. We want to
distinguish *coercion* specifically from other sorts of subtyping, as
it indicates values flowing from one place to another via assignment.
RFC2229 Add missing edge case
Closes https://github.com/rust-lang/rust/issues/87988
This PR fixes an ICE where a match discriminant is not being read when expected. This ICE was the result of a missing edge case which assumed that if a pattern is of type `PatKind::TupleStruct(..) | PatKind::Path(..) | PatKind::Struct(..) | PatKind::Tuple(..)` then a place could only be a multi variant if the place is of type kind Adt.
We used to avoid doing this because we didn't want to make coercion depend on
the state of inference. For better or worse, we have moved away from this
position over time. Therefore, I am going to go ahead and resolve the `b`
target type early on so that it is done uniformly.
(The older technique for managing this was always something of a hack
regardless; if we really wanted to avoid integrating coercion and inference we
needed to be more disciplined about it.)
Try filtering out non-const impls when we expect const impls
**TL;DR**: Associated types on const impls are now bounded; we now disallow calling a const function with bounds when the specified type param only has a non-const impl.
r? `@oli-obk`
Fix closure migration suggestion when the body is a macro.
Fixes https://github.com/rust-lang/rust/issues/87955
Before:
```
warning: changes to closure capture in Rust 2021 will affect drop order
--> src/main.rs:5:13
|
5 | let _ = || panic!(a.0);
| ^^^^^^^^^^---^
| |
| in Rust 2018, closure captures all of `a`, but in Rust 2021, it only captures `a.0`
6 | }
| - in Rust 2018, `a` would be dropped here, but in Rust 2021, only `a.0` would be dropped here alongside the closure
|
help: add a dummy let to cause `a` to be fully captured
|
20~ ($msg:expr $(,)?) => ({ let _ = &a;
21+ $crate::rt::begin_panic($msg)
22~ }),
|
```
After:
```
warning: changes to closure capture in Rust 2021 will affect drop order
--> src/main.rs:5:13
|
5 | let _ = || panic!(a.0);
| ^^^^^^^^^^---^
| |
| in Rust 2018, closure captures all of `a`, but in Rust 2021, it only captures `a.0`
6 | }
| - in Rust 2018, `a` would be dropped here, but in Rust 2021, only `a.0` would be dropped here alongside the closure
|
help: add a dummy let to cause `a` to be fully captured
|
5 | let _ = || { let _ = &a; panic!(a.0) };
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
Implement `black_box` using intrinsic
Introduce `black_box` intrinsic, as suggested in https://github.com/rust-lang/rust/pull/87590#discussion_r680468700.
This is still codegenned as empty inline assembly for LLVM. For MIR interpretation and cranelift it's treated as identity.
cc `@Amanieu` as this is related to inline assembly
cc `@bjorn3` for rustc_codegen_cranelift changes
cc `@RalfJung` as this affects MIRI
r? `@nagisa` I suppose
Improve formatting of closure capture migration suggestion for multi-line closures.
Fixes https://github.com/rust-lang/rust/issues/87952
Before:
```
help: add a dummy let to cause `a` to be fully captured
|
5 ~ let _ = || { let _ = &a;
6 + dbg!(a.0);
7 ~ };
|
```
After:
```
help: add a dummy let to cause `a` to be fully captured
|
5 ~ let _ = || {
6 + let _ = &a;
7 + dbg!(a.0);
8 ~ };
|
```
Implement `black_box` using intrinsic
Introduce `black_box` intrinsic, as suggested in https://github.com/rust-lang/rust/pull/87590#discussion_r680468700.
This is still codegenned as empty inline assembly for LLVM. For MIR interpretation and cranelift it's treated as identity.
cc `@Amanieu` as this is related to inline assembly
cc `@bjorn3` for rustc_codegen_cranelift changes
cc `@RalfJung` as this affects MIRI
r? `@nagisa` I suppose
The new implementation allows some `memcpy`s to be optimized away,
so the uninit value in ui/sanitize/memory.rs is constructed directly
onto the return place. Therefore the sanitizer now says that the
value is allocated by `main` rather than `random`.
Various refactorings of the TAIT infrastructure
Before this PR we used to store the opaque type knowledge outside the `InferCtxt`, so it got recomputed on every opaque type instantiation.
I also removed a feature gate check that makes no sense in the planned lazy TAIT resolution scheme
Each commit passes all tests, so this PR is best reviewed commit by commit.
r? `@spastorino`
typeck: don't suggest inaccessible fields in struct literals and suggest ignoring inaccessible fields in struct patterns
Fixes#87872.
This PR adjusts the missing field diagnostic logic in typeck so that when any of the missing fields in a struct literal or pattern is inaccessible then the error is less confusing, even if some of the missing fields are accessible.
See also #76524.
correctly handle enum variants in `opt_const_param_of`
Fixes#87542
`opt_const_param_of` was returning `None` for args on an enum variant `Enum::Variant::<10>` because we called `generics_of` on the enum variant which has no generics.
r? `@oli-obk`
Simplify typeck/primary_body_of, fix comment to match return signature
Hi, new contributor here! I'm carefully reading through the various modules just to learn. I noticed this function, `primary_body_of`, which has gone through a couple of refactors over time, adding new `Option`s to its returned tuple. Observations:
1. the `fn`'s documentation was not all up to date with the the current return signature.
2. `FnHeader` and `FnDecl` are always both `Some` or `None`. So I figured it might just return a reference to the full `hir::FnSig`, for simplicity and more precise typing. It's a pure refactor.
I'm learning better by working with code than just reading it, so here goes! If you want to avoid pure refactor PRs that don't really fix anything, I can revert the code change to only update the comment instead.
