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Improve the impl and diag output of lint type_alias_bounds

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This commit is contained in:
León Orell Valerian Liehr 2024-06-15 21:34:44 +02:00
parent a8b3dfd253
commit fdf8f024ad
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13 changed files with 385 additions and 319 deletions
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92
compiler/rustc_lint/src/builtin.rs
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@ -31,12 +31,12 @@ use crate::{
BuiltinIncompleteFeaturesHelp, BuiltinInternalFeatures, BuiltinKeywordIdents,
BuiltinMissingCopyImpl, BuiltinMissingDebugImpl, BuiltinMissingDoc,
BuiltinMutablesTransmutes, BuiltinNoMangleGeneric, BuiltinNonShorthandFieldPatterns,
BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds, BuiltinTypeAliasGenericBounds,
BuiltinTypeAliasGenericBoundsSuggestion, BuiltinTypeAliasWhereClause,
BuiltinUngatedAsyncFnTrackCaller, BuiltinUnpermittedTypeInit,
BuiltinUnpermittedTypeInitSub, BuiltinUnreachablePub, BuiltinUnsafe,
BuiltinUnstableFeatures, BuiltinUnusedDocComment, BuiltinUnusedDocCommentSub,
BuiltinWhileTrue, InvalidAsmLabel, SuggestChangingAssocTypes,
BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds, BuiltinTypeAliasBounds,
BuiltinTypeAliasParamBoundsSuggestion, BuiltinUngatedAsyncFnTrackCaller,
BuiltinUnpermittedTypeInit, BuiltinUnpermittedTypeInitSub, BuiltinUnreachablePub,
BuiltinUnsafe, BuiltinUnstableFeatures, BuiltinUnusedDocComment,
BuiltinUnusedDocCommentSub, BuiltinWhileTrue, InvalidAsmLabel,
TypeAliasBoundsQualifyAssocTysSugg,
},
EarlyContext, EarlyLintPass, LateContext, LateLintPass, Level, LintContext,
};
@ -1406,23 +1406,6 @@ declare_lint_pass!(
TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
);
impl TypeAliasBounds {
pub(crate) fn is_type_variable_assoc(qpath: &hir::QPath<'_>) -> bool {
match *qpath {
hir::QPath::TypeRelative(ty, _) => {
// If this is a type variable, we found a `T::Assoc`.
match ty.kind {
hir::TyKind::Path(hir::QPath::Resolved(None, path)) => {
matches!(path.res, Res::Def(DefKind::TyParam, _))
}
_ => false,
}
}
hir::QPath::Resolved(..) | hir::QPath::LangItem(..) => false,
}
}
}
impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
let hir::ItemKind::TyAlias(hir_ty, generics) = &item.kind else { return };
@ -1437,7 +1420,6 @@ impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
return;
}
// FIXME(generic_const_exprs): Revisit this before stabilization.
// See also `tests/ui/const-generics/generic_const_exprs/type-alias-bounds.rs`.
let ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
@ -1455,6 +1437,8 @@ impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
let mut where_spans = Vec::new();
let mut inline_spans = Vec::new();
let mut inline_sugg = Vec::new();
let mut affects_object_lifetime_defaults = false;
for p in generics.predicates {
let span = p.span();
if p.in_where_clause() {
@ -1465,31 +1449,61 @@ impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
}
inline_sugg.push((span, String::new()));
}
// FIXME(fmease): Move this into a "diagnostic decorator" for increased laziness
// Bounds of the form `T: 'a` where `T` is a type param of
// the type alias affect object lifetime defaults.
if !affects_object_lifetime_defaults
&& let hir::WherePredicate::BoundPredicate(pred) = p
&& pred.bounds.iter().any(|bound| matches!(bound, hir::GenericBound::Outlives(_)))
&& pred.bound_generic_params.is_empty()
&& let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = pred.bounded_ty.kind
&& let Res::Def(DefKind::TyParam, _) = path.res
{
affects_object_lifetime_defaults = true;
}
}
let mut suggested_changing_assoc_types = false;
if !where_spans.is_empty() {
let sub = (!suggested_changing_assoc_types).then(|| {
suggested_changing_assoc_types = true;
SuggestChangingAssocTypes { ty: hir_ty }
});
// FIXME(fmease): Add a disclaimer (in the form of a multi-span note) that the removal of
// type-param-outlives-bounds affects OLDs and explicit object lifetime
// bounds might be required [...].
// FIXME(fmease): The applicability should also depend on the outcome of the HIR walker
// inside of `TypeAliasBoundsQualifyAssocTysSugg`: Whether it found a
// shorthand projection or not.
let applicability = if affects_object_lifetime_defaults {
Applicability::MaybeIncorrect
} else {
Applicability::MachineApplicable
};
let mut qualify_assoc_tys_sugg = Some(TypeAliasBoundsQualifyAssocTysSugg { ty: hir_ty });
let enable_feat_help = cx.tcx.sess.is_nightly_build().then_some(());
if let [.., label_sp] = *where_spans {
cx.emit_span_lint(
TYPE_ALIAS_BOUNDS,
where_spans,
BuiltinTypeAliasWhereClause { suggestion: generics.where_clause_span, sub },
BuiltinTypeAliasBounds::WhereClause {
label: label_sp,
enable_feat_help,
suggestion: (generics.where_clause_span, applicability),
qualify_assoc_tys_sugg: qualify_assoc_tys_sugg.take(),
},
);
}
if !inline_spans.is_empty() {
let suggestion = BuiltinTypeAliasGenericBoundsSuggestion { suggestions: inline_sugg };
let sub = (!suggested_changing_assoc_types).then(|| {
suggested_changing_assoc_types = true;
SuggestChangingAssocTypes { ty: hir_ty }
});
if let [.., label_sp] = *inline_spans {
cx.emit_span_lint(
TYPE_ALIAS_BOUNDS,
inline_spans,
BuiltinTypeAliasGenericBounds { suggestion, sub },
BuiltinTypeAliasBounds::ParamBounds {
label: label_sp,
enable_feat_help,
suggestion: BuiltinTypeAliasParamBoundsSuggestion {
suggestions: inline_sugg,
applicability,
},
qualify_assoc_tys_sugg,
},
);
}
}