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Rollup merge of #78208 - liketechnik:issue-69399, r=oli-obk

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replace `#[allow_internal_unstable]` with `#[rustc_allow_const_fn_unstable]` for `const fn`s

`#[allow_internal_unstable]` is currently used to side-step feature gate and stability checks.
While it was originally only meant to be used only on macros, its use was expanded to `const fn`s.

This pr adds stricter checks for the usage of `#[allow_internal_unstable]` (only on macros) and introduces the `#[rustc_allow_const_fn_unstable]` attribute for usage on `const fn`s.

This pr does not change any of the functionality associated with the use of `#[allow_internal_unstable]` on macros or the usage of `#[rustc_allow_const_fn_unstable]` (instead of `#[allow_internal_unstable]`) on `const fn`s (see https://github.com/rust-lang/rust/issues/69399#issuecomment-712911540).

Note: The check for `#[rustc_allow_const_fn_unstable]` currently only validates that the attribute is used on a function, because I don't know how I would check if the function is a `const fn` at the place of the check. I therefore openend this as a 'draft pull request'.

Closes rust-lang/rust#69399

r? @oli-obk
This commit is contained in:
Yuki Okushi 2020-10-25 18:43:40 +09:00 • committed by GitHub
commit 72e02b015e
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31 changed files with 177 additions and 41 deletions
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53
compiler/rustc_passes/src/check_attr.rs
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@ -85,6 +85,10 @@ impl CheckAttrVisitor<'tcx> {
self.check_export_name(&attr, span, target)
} else if self.tcx.sess.check_name(attr, sym::rustc_args_required_const) {
self.check_rustc_args_required_const(&attr, span, target, item)
} else if self.tcx.sess.check_name(attr, sym::allow_internal_unstable) {
self.check_allow_internal_unstable(&attr, span, target, &attrs)
} else if self.tcx.sess.check_name(attr, sym::rustc_allow_const_fn_unstable) {
self.check_rustc_allow_const_fn_unstable(hir_id, &attr, span, target)
} else {
// lint-only checks
if self.tcx.sess.check_name(attr, sym::cold) {
@ -719,6 +723,55 @@ impl CheckAttrVisitor<'tcx> {
}
}
}
/// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
/// (Allows proc_macro functions)
fn check_allow_internal_unstable(
&self,
attr: &Attribute,
span: &Span,
target: Target,
attrs: &[Attribute],
) -> bool {
debug!("Checking target: {:?}", target);
if target == Target::Fn {
for attr in attrs {
if self.tcx.sess.is_proc_macro_attr(attr) {
debug!("Is proc macro attr");
return true;
}
}
debug!("Is not proc macro attr");
}
self.tcx
.sess
.struct_span_err(attr.span, "attribute should be applied to a macro")
.span_label(*span, "not a macro")
.emit();
false
}
/// Outputs an error for `#[allow_internal_unstable]` which can only be applied to macros.
/// (Allows proc_macro functions)
fn check_rustc_allow_const_fn_unstable(
&self,
hir_id: HirId,
attr: &Attribute,
span: &Span,
target: Target,
) -> bool {
if let Target::Fn | Target::Method(_) = target {
if self.tcx.is_const_fn_raw(self.tcx.hir().local_def_id(hir_id)) {
return true;
}
}
self.tcx
.sess
.struct_span_err(attr.span, "attribute should be applied to `const fn`")
.span_label(*span, "not a `const fn`")
.emit();
false
}
}
impl Visitor<'tcx> for CheckAttrVisitor<'tcx> {