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Auto merge of #88865 - guswynn:must_not_suspend, r=oli-obk

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Implement `#[must_not_suspend]`

implements #83310

Some notes on the impl:

1. The code that searches for the attribute on the ADT is basically copied from the `must_use` lint. It's not shared, as the logic did diverge
2. The RFC does specify that the attribute can be placed on fn's (and fn-like objects), like `must_use`. I think this is a direct copy from the `must_use` reference definition. This implementation does NOT support this, as I felt that ADT's (+ `impl Trait` + `dyn Trait`) cover the usecase's people actually want on the RFC, and adding an imp for the fn call case would be significantly harder. The `must_use` impl can do a single check at fn call stmt time, but `must_not_suspend` would need to answer the question: "for some value X with type T, find any fn call that COULD have produced this value". That would require significant changes to `generator_interior.rs`, and I would need mentorship on that. `@eholk` and I are discussing it.
3. `@estebank` do you know a way I can make the user-provided `reason` note pop out? right now it seems quite hidden

Also, I am not sure if we should run perf on this

r? `@nikomatsakis`
This commit is contained in:
bors 2021-09-22 06:43:33 +00:00
commit ce45663e14
27 changed files with 701 additions and 5 deletions
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16
compiler/rustc_passes/src/check_attr.rs
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@ -104,6 +104,7 @@ impl CheckAttrVisitor<'tcx> {
sym::default_method_body_is_const => {
self.check_default_method_body_is_const(attr, span, target)
}
sym::must_not_suspend => self.check_must_not_suspend(&attr, span, target),
sym::rustc_const_unstable
| sym::rustc_const_stable
| sym::unstable
@ -1014,6 +1015,21 @@ impl CheckAttrVisitor<'tcx> {
is_valid
}
/// Checks if `#[must_not_suspend]` is applied to a function. Returns `true` if valid.
fn check_must_not_suspend(&self, attr: &Attribute, span: &Span, target: Target) -> bool {
match target {
Target::Struct | Target::Enum | Target::Union | Target::Trait => true,
_ => {
self.tcx
.sess
.struct_span_err(attr.span, "`must_not_suspend` attribute should be applied to a struct, enum, or trait")
.span_label(*span, "is not a struct, enum, or trait")
.emit();
false
}
}
}
/// Checks if `#[cold]` is applied to a non-function. Returns `true` if valid.
fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
match target {