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Rollup merge of #78626 - fusion-engineering-forks:deprecated-trait-impl, r=estebank

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Improve errors about #[deprecated] attribute

This change:

1. Turns `#[deprecated]` on a trait impl block into an error, which fixes #78625;
2. Changes these and other errors about `#[deprecated]` to use the span of the attribute instead of the item; and
3. Turns this error into a lint, to make sure it can be capped with `--cap-lints` and doesn't break any existing dependencies.

Can be reviewed per commit.

---
Example:
```rust
struct X;

#[deprecated = "a"]
impl Default for X {
    #[deprecated = "b"]
    fn default() -> Self {
        X
    }
}
```

Before:
```
error: This deprecation annotation is useless
 --> src/main.rs:6:5
  |
6 | /     fn default() -> Self {
7 | |         X
8 | |     }
  | |_____^
```

After:
```
error: this `#[deprecated]' annotation has no effect
 --> src/main.rs:3:1
  |
3 | #[deprecated = "a"]
  | ^^^^^^^^^^^^^^^^^^^ help: try removing the deprecation attribute
  |
  = note: `#[deny(useless_deprecated)]` on by default

error: this `#[deprecated]' annotation has no effect
 --> src/main.rs:5:5
  |
5 |     #[deprecated = "b"]
  |     ^^^^^^^^^^^^^^^^^^^ help: try removing the deprecation attribute
```
This commit is contained in:
Mara Bos 2020-11-03 19:32:36 +01:00 • committed by GitHub
commit f0112928cb
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8 changed files with 96 additions and 38 deletions
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33
compiler/rustc_passes/src/stability.rs
View file

@ -15,7 +15,7 @@ use rustc_middle::middle::privacy::AccessLevels;
use rustc_middle::middle::stability::{DeprecationEntry, Index};
use rustc_middle::ty::{self, query::Providers, TyCtxt};
use rustc_session::lint;
use rustc_session::lint::builtin::INEFFECTIVE_UNSTABLE_TRAIT_IMPL;
use rustc_session::lint::builtin::{INEFFECTIVE_UNSTABLE_TRAIT_IMPL, USELESS_DEPRECATED};
use rustc_session::parse::feature_err;
use rustc_session::Session;
use rustc_span::symbol::{sym, Symbol};
@ -31,6 +31,8 @@ enum AnnotationKind {
Required,
// Annotation is useless, reject it
Prohibited,
// Deprecation annotation is useless, reject it. (Stability attribute is still required.)
DeprecationProhibited,
// Annotation itself is useless, but it can be propagated to children
Container,
}
@ -83,14 +85,22 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
did_error = self.forbid_staged_api_attrs(hir_id, attrs, inherit_deprecation.clone());
}
let depr =
if did_error { None } else { attr::find_deprecation(&self.tcx.sess, attrs, item_sp) };
let depr = if did_error { None } else { attr::find_deprecation(&self.tcx.sess, attrs) };
let mut is_deprecated = false;
if let Some(depr) = &depr {
if let Some((depr, span)) = &depr {
is_deprecated = true;
if kind == AnnotationKind::Prohibited {
self.tcx.sess.span_err(item_sp, "This deprecation annotation is useless");
if kind == AnnotationKind::Prohibited || kind == AnnotationKind::DeprecationProhibited {
self.tcx.struct_span_lint_hir(USELESS_DEPRECATED, hir_id, *span, |lint| {
lint.build("this `#[deprecated]` annotation has no effect")
.span_suggestion_short(
*span,
"remove the unnecessary deprecation attribute",
String::new(),
rustc_errors::Applicability::MachineApplicable,
)
.emit()
});
}
// `Deprecation` is just two pointers, no need to intern it
@ -114,7 +124,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
}
} else {
self.recurse_with_stability_attrs(
depr.map(|d| DeprecationEntry::local(d, hir_id)),
depr.map(|(d, _)| DeprecationEntry::local(d, hir_id)),
None,
None,
visit_children,
@ -139,11 +149,11 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
}
}
if depr.as_ref().map_or(false, |d| d.is_since_rustc_version) {
if let Some((rustc_attr::Deprecation { is_since_rustc_version: true, .. }, span)) = &depr {
if stab.is_none() {
struct_span_err!(
self.tcx.sess,
item_sp,
*span,
E0549,
"rustc_deprecated attribute must be paired with \
either stable or unstable attribute"
@ -166,7 +176,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
// Check if deprecated_since < stable_since. If it is,
// this is *almost surely* an accident.
if let (&Some(dep_since), &attr::Stable { since: stab_since }) =
(&depr.as_ref().and_then(|d| d.since), &stab.level)
(&depr.as_ref().and_then(|(d, _)| d.since), &stab.level)
{
// Explicit version of iter::order::lt to handle parse errors properly
for (dep_v, stab_v) in
@ -212,7 +222,7 @@ impl<'a, 'tcx> Annotator<'a, 'tcx> {
}
self.recurse_with_stability_attrs(
depr.map(|d| DeprecationEntry::local(d, hir_id)),
depr.map(|(d, _)| DeprecationEntry::local(d, hir_id)),
stab,
const_stab,
visit_children,
@ -322,6 +332,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> {
}
hir::ItemKind::Impl { of_trait: Some(_), .. } => {
self.in_trait_impl = true;
kind = AnnotationKind::DeprecationProhibited;
}
hir::ItemKind::Struct(ref sd, _) => {
if let Some(ctor_hir_id) = sd.ctor_hir_id() {