Add non_exhaustive_omitted_patterns lint related to rfc-2008-non_exhaustive
Fixes: #84332
This PR adds `non_exhaustive_omitted_patterns`, an allow by default lint that is triggered when a `non_exhaustive` type is missing explicit patterns. The warning or deny attribute can be put above the wildcard `_` pattern on enums or on the expression for enums or structs. The lint is capable of warning about multiple types within the same pattern. This lint will not be triggered for `if let ..` patterns.
```rust
// crate A
#[non_exhaustive]
pub struct Foo {
a: u8,
b: usize,
}
#[non_exhaustive]
pub enum Bar {
A(Foo),
B,
}
// crate B
#[deny(non_exhaustive_omitted_patterns)] // here
match Bar::B {
Bar::B => {}
#[deny(non_exhaustive_omitted_patterns)] // or here
_ => {}
}
#[warn(non_exhaustive_omitted_patterns)] // only here
let Foo { a, .. } = Foo::default();
#[deny(non_exhaustive_omitted_patterns)]
match Bar::B {
// triggers for Bar::B, and Foo.b
Bar::A(Foo { a, .. }) => {}
// if the attribute was here only Bar::B would cause a warning
_ => {}
}
```
When a macro is used in the trailing expression position of a block
(e.g. `fn foo() { my_macro!() }`), we currently parse it as an
expression, rather than a statement. As a result, we ended up
using the `NodeId` of the containing statement as our `lint_node_id`,
even though we don't normally do this for macro calls.
If such a macro expands to an expression with a `#[cfg]` attribute,
then the trailing statement can get removed entirely. This lead to
an ICE, since we were usng the `NodeId` of the expression to emit
a lint.
Ths commit makes us skip updating `lint_node_id` when handling
a macro in trailing expression position. This will cause us to
lint at the closest parent of the macro call.
It's possible to use the same `InferCtxt` with both
an intercrate and non-intercrate `SelectionContext`. However,
the local (inferctxt) evaluation cache is not aware of this
distinction, so this kind of `InferCtxt` re-use will pollute
the cache wth bad results.
This commit avoids the issue by disabling the evaluation cache
entirely during intercrate mode.
Highlight the `const fn` if error happened because of a bound on the impl block
Currently, for the following code, the compiler produces the errors like the
following:
```rust
struct Type<T>(T);
impl<T: Clone> Type<T> {
const fn f() {}
}
```
```text
error[E0658]: trait bounds other than `Sized` on const fn parameters are unstable
--> ./test.rs:3:6
|
3 | impl<T: Clone> Type<T> {
| ^
|
= note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
= help: add `#![feature(const_fn_trait_bound)]` to the crate attributes to enable
```
This can be confusing (especially to newcomers) since the error mentions "const fn parameters", but highlights only the impl.
This PR adds function highlighting, changing the error to the following:
```text
error[E0658]: trait bounds other than `Sized` on const fn parameters are unstable
--> ./test.rs:3:6
|
3 | impl<T: Clone> Type<T> {
| ^
4 | pub const fn f() {}
| ---------------- function declared as const here
|
= note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
= help: add `#![feature(const_fn_trait_bound)]` to the crate attributes to enable
```
---
I've originally wanted to point directly to `const` token, but couldn't find a way to get it's span. It seems like this span is lost during the AST -> HIR lowering.
Also, since the errors for object casts in `const fn`s (`&T` -> `&dyn Trait`) seem to trigger the same error, this PR accidentally changes these errors too. Not sure if it's desired or how to fix this.
P.S. it's my first time contributing to diagnostics, so feedback is very appreciated!
---
r? ```@estebank```
```@rustbot``` label: +A-diagnostics
Revert anon union parsing
Revert PR #84571 and #85515, which implemented anonymous union parsing in a manner that broke the context-sensitivity for the `union` keyword and thus broke stable Rust code.
Fix#88583.
Accept `m!{ .. }.method()` and `m!{ .. }?` statements.
This PR fixes something that I keep running into when using `quote!{}.into()` in a proc macro to convert the `proc_macro2::TokenStream` to a `proc_macro::TokenStream`:
Before:
```
error: expected expression, found `.`
--> src/lib.rs:6:6
|
4 | quote! {
5 | ...
6 | }.into()
| ^ expected expression
```
After:
```
```
(No output, compiles fine.)
---
Context:
For expressions like `{ 1 }` and `if true { 1 } else { 2 }`, we accept them as full statements without a trailing `;`, which means the following is not accepted:
```rust
{ 1 } - 1 // error
```
since that is parsed as two statements: `{ 1 }` and `-1`. Syntactically correct, but the type of `{ 1 }` should be `()` as there is no `;`.
However, for specifically `.` and `?` after the `}`, we do [continue parsing it as an expression](13db8440bb/compiler/rustc_parse/src/parser/expr.rs (L864-L876)):
```rust
{ "abc" }.len(); // ok
```
For braced macro invocations, we do not do this:
```rust
vec![1, 2, 3].len(); // ok
vec!{1, 2, 3}.len(); // error
```
(It parses `vec!{1, 2, 3}` as a full statement, and then complains about `.len()` not being a valid expression.)
This PR changes this to also look for a `.` and `?` after a braced macro invocation. We can be sure the macro is an expression and not a full statement in those cases, since no statement can start with a `.` or `?`.
Introduce -Z remap-cwd-prefix switch
This switch remaps any absolute paths rooted under the current
working directory to a new value. This includes remapping the
debug info in `DW_AT_comp_dir` and `DW_AT_decl_file`.
Importantly, this flag does not require passing the current working
directory to the compiler, such that the command line can be
run on any machine (with the same input files) and produce the
same results. This is critical property for debugging compiler
issues that crop up on remote machines.
This is based on adetaylor's dbc4ae7cba
Major Change Proposal: https://github.com/rust-lang/compiler-team/issues/450
Discussed on #38322. Would resolve issue #87325.
Specify a log level in tracing instrument macro explicitly.
Additionally reduce the used log level from a default info level to a
debug level (all of those appear to be developer oriented logs, so there
should be no need to include them in release builds).
Querying layout of a generator requires its optimized MIR. Thus
computing layout during MIR optimization of a generator might create a
query cycle. Disable RemoveZsts in generators to avoid the issue
(similar approach is used in ConstProp transform already).
Use a separate interner type for UniqueTypeId
Using symbol::Interner makes it very easy to mixup UniqueTypeId symbols
with the global interner. In fact the Debug implementation of
UniqueTypeId did exactly this.
Using a separate interner type also avoids prefilling the interner with
unused symbols and allow for optimizing the symbol interner for parallel
access without negatively affecting the single threaded module codegen.
Const drop
The changes are pretty primitive at this point. But at least it works. ^-^
Problems with the current change that I can think of now:
- [x] `~const Drop` shouldn't change anything in the non-const world.
- [x] types that do not have drop glues shouldn't fail to satisfy `~const Drop` in const contexts. `struct S { a: u8, b: u16 }` This might not fail for `needs_non_const_drop`, but it will fail in `rustc_trait_selection`.
- [x] The current change accepts types that have `const Drop` impls but have non-const `Drop` glue.
Fixes#88424.
Significant Changes:
- `~const Drop` is no longer treated as a normal trait bound. In non-const contexts, this bound has no effect, but in const contexts, this restricts the input type and all of its transitive fields to either a) have a `const Drop` impl or b) can be trivially dropped (i.e. no drop glue)
- `T: ~const Drop` will not be linted like `T: Drop`.
- Instead of recursing and iterating through the type in `rustc_mir::transform::check_consts`, we use the trait system to special case `~const Drop`. See [`rustc_trait_selection::...::candidate_assembly#assemble_const_drop_candidates`](https://github.com/fee1-dead/rust/blob/const-drop/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs#L817) and others.
Changes not related to `const Drop`ping and/or changes that are insignificant:
- `Node.constness_for_typeck` no longer returns `hir::Constness::Const` for type aliases in traits. This was previously used to hack how we determine default bound constness for items. But because we now use an explicit opt-in, it is no longer needed.
- Removed `is_const_impl_raw` query. We have `impl_constness`, and the only existing use of that query uses `HirId`, which means we can just operate it with hir.
- `ty::Destructor` now has a field `constness`, which represents the constness of the destructor.
r? `@oli-obk`
Fixes#88910
When we initially store a `NormalizedTy` in the projection cache,
we discard all obligations that we can (while ensuring that we
don't cause any issues with incremental compilation).
Marking a projection cache entry as 'completed' discards all
obligations associated with it. This can only cause problems,
since any obligations stored in the cache are there for a reason
(e.g. they evaluate to `EvaluatedToOkModuloRegions`).
This commit removes `complete` and `complete_normalized` entirely.
Add linting on non_exhaustive structs and enum variants
Add ui tests for non_exhaustive reachable lint
Rename to non_exhaustive_omitted_patterns and avoid triggering on if let
This encoding allows for random access without an expensive upfront decoding
state which in turn allows simplifying the DefPathIndex lookup logic without
regressing performance.
Enum should prefer discriminant zero for niche
Given an enum with unassigned zero-discriminant, rust should prefer it for niche selection.
Zero as discriminant for `Option<Enum>` makes it possible for LLVM to optimize resulting asm.
- Eliminate branch when expected value coincides.
- Use smaller instruction `test eax, eax` instead of `cmp eax, ?`
- Possible interaction with zeroed memory?
Example:
```rust
pub enum Size {
One = 1,
Two = 2,
Three = 3,
}
pub fn handle(x: Option<Size>) -> u8 {
match x {
None => {0}
Some(size) => {size as u8}
}
}
```
In this case discriminant zero is available as a niche.
Above example on nightly:
```asm
mov eax, edi
cmp al, 4
jne .LBB0_2
xor eax, eax
.LBB0_2:
ret
```
PR:
```asm
mov eax, edi
ret
```
I created this PR because I had a performance regression when I tried to use an enum to represent legal grapheme byte-length for utf8.
Using an enum instead of `NonZeroU8` [here](d683304f5d/src/internal/decoder_incomplete.rs (L90))
resulted in a performance regression of about 5%.
I consider this to be a somewhat realistic benchmark.
Thanks to `@ogoffart` for pointing me in the right direction!
Edit: Updated description
