Patterns: represent constants as valtrees
Const patterns are always valtrees now. Let's represent that in the types. We use `ty::Value` for this since it nicely packages value and type, and has some convenient methods.
Cc `@Nadrieril` `@BoxyUwU`
When trying to construct a struct that has a public field of a private type, suggest using `..` if that field has a default value.
```
error[E0603]: struct `Priv1` is private
--> $DIR/non-exhaustive-ctor.rs:25:39
|
LL | let _ = S { field: (), field1: m::Priv1 {} };
| ------ ^^^^^ private struct
| |
| while setting this field
|
note: the struct `Priv1` is defined here
--> $DIR/non-exhaustive-ctor.rs:14:4
|
LL | struct Priv1 {}
| ^^^^^^^^^^^^
help: the field `field1` you're trying to set has a default value, you can use `..` to use it
|
LL | let _ = S { field: (), .. };
| ~~
```
add a scope for `if let` guard temporaries and bindings
This fixes my concern with `if let` guard drop order, namely that the guard's bindings and temporaries were being dropped after their arm's pattern's bindings, instead of before (https://github.com/rust-lang/rust/pull/141295#issuecomment-2968975596). The guard's bindings and temporaries now live in a new scope, which extends until (but not past) the end of the arm, guaranteeing they're dropped before the arm's pattern's bindings.
This only introduces a new scope for match arms with guards. Perf results (https://github.com/rust-lang/rust/pull/143376#issuecomment-3034922617) seemed to indicate there wasn't a significant hit to introduce a new scope on all match arms, but guard patterns (rust-lang/rust#129967) will likely benefit from only adding new scopes when necessary (with some patterns requiring multiple nested scopes).
Tracking issue for `if_let_guard`: rust-lang/rust#51114
Tests are adapted from examples by `@traviscross,` `@est31,` and myself on rust-lang/rust#141295.
atomicrmw on pointers: move integer-pointer cast hacks into backend
Conceptually, we want to have atomic operations on pointers of the form `fn atomic_add(ptr: *mut T, offset: usize, ...)`. However, LLVM does not directly support such operations (https://github.com/llvm/llvm-project/issues/120837), so we have to cast the `offset` to a pointer somewhere.
This PR moves that hack into the LLVM backend, so that the standard library, intrinsic, and Miri all work with the conceptual operation we actually want. Hopefully, one day LLVM will gain a way to represent these operations without integer-pointer casts, and then the hack will disappear entirely.
Cc ```@nikic``` -- this is the best we can do right now, right?
Fixes https://github.com/rust-lang/rust/issues/134617
Use `tcx.short_string()` in more diagnostics
`TyCtxt::short_string` ensures that user visible type paths aren't overwhelming on the terminal output, and properly saves the long name to disk as a side-channel. We already use these throughout the compiler and have been using them as needed when users find cases where the output is verbose. This is a proactive search of some cases to use `short_string`.
We add support for shortening the path of "trait path only".
Every manual use of `short_string` is a bright marker that that error should be using structured diagnostics instead (as they have proper handling of long types without the maintainer having to think abou tthem).
coverage: Remove all unstable support for MC/DC instrumentation
Preliminary support for a partial implementation of “Modified Condition/Decision Coverage” instrumentation was added behind the unstable flag `-Zcoverage-options=mcdc` in 2024. These are the most substantial PRs involved:
- rust-lang/rust#123409
- rust-lang/rust#126733
At the time, I accepted these PRs with relatively modest scrutiny, because I did not want to stand in the way of independent work on MC/DC instrumentation. My hope was that ongoing work by interested contributors would lead to the code becoming clearer and more maintainable over time.
---
However, that MC/DC code has proven itself to be a major burden on overall maintenance of coverage instrumentation, and a major obstacle to other planned improvements, such as internal changes needed for proper support of macro expansion regions.
I have also become reluctant to accept any further MC/DC-related changes that would increase this burden.
That tension has resulted in an unhappy impasse. On one hand, the present MC/DC implementation is not yet complete, and shows little sign of being complete at an acceptable level of code quality in the foreseeable future. On the other hand, the continued existence of this partial MC/DC implementation is imposing serious maintenance burdens on every other aspect of coverage instrumentation, and is preventing some of the very improvements that would make it easier to accept expanded MC/DC support in the future.
While I know this will be disappointing to some, I think the healthy way forward is accept that I made the wrong call in accepting the current implementation, and to remove it entirely from the compiler.
Add support for `ty::Instance` path shortening in diagnostics
Make `ty::Instance` able to use `short_string` and usable in structured errors directly. Remove some ad-hoc type shortening logic.
`TyCtxt::short_string` ensures that user visible type paths aren't overwhelming on the terminal output, and properly saves the long name to disk as a side-channel. We already use these throughout the compiler and have been using them as needed when users find cases where the output is verbose. This is a proactive search of some cases to use `short_string`.
We add support for shortening the path of "trait path only".
Every manual use of `short_string` is a bright marker that that error should be using structured diagnostics instead (as they have proper handling of long types without the maintainer having to think abou tthem).
When we don't actually print out a shortened type we don't need the "use `--verbose`" note.
On E0599 show type identity to avoid expanding the receiver's generic parameters.
Unify wording on `long_ty_path` everywhere.
Simplify dead code lint
This PR scratches a few itches I had when looking at that code.
The perf improvement comes from keeping the `scanned` set through several marking phases. This pretty much divides by 2 the number of HIR traversals.
The use of `print_value_path` means the value namespace is always used
and the `guess_def_namespace` call is unnecessary. This commit removes
the `guess_def_namespace` call and hard-codes `ValueNS`. It also changes
the `print_value_path` to `print_def_path` for consistency with
`def_path_str_with_args`.
`Printer` cleanups
The trait `Printer` is implemented by six types, and the sub-trait `PrettyPrinter` is implemented by three of those types. The traits and the impls are complex and a bit of a mess. This PR starts to clean them up.
r? ``@davidtwco``
