Don't emit derive_partial_eq_without_eq lint if the type has the non_exhaustive attribute

Author: GuillaumeGomez

clippy_lints/src/derive.rs

@@ -11,8 +11,8 @@ use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::traits::Reveal;
 use rustc_middle::ty::{
-    self, ClauseKind, GenericArgKind, GenericParamDefKind, ImplPolarity, ParamEnv, ToPredicate, TraitPredicate, Ty,
-    TyCtxt,
+    self, AdtDef, ClauseKind, GenericArgKind, GenericParamDefKind, ImplPolarity, ParamEnv, ToPredicate, TraitPredicate,
+    Ty, TyCtxt,
 };
 use rustc_session::declare_lint_pass;
 use rustc_span::def_id::LocalDefId;
@@ -442,13 +442,25 @@ impl<'tcx> Visitor<'tcx> for UnsafeVisitor<'_, 'tcx> {
     }
 }
 
+fn has_non_exhaustive_attr(cx: &LateContext<'_>, adt: AdtDef<'_>) -> bool {
+    adt.is_variant_list_non_exhaustive()
+        || cx.tcx.has_attr(adt.did(), sym::non_exhaustive)
+        || adt.variants().iter().any(|variant_def| {
+            variant_def.is_field_list_non_exhaustive() || cx.tcx.has_attr(variant_def.def_id, sym::non_exhaustive)
+        })
+        || adt
+            .all_fields()
+            .any(|field_def| cx.tcx.has_attr(field_def.did, sym::non_exhaustive))
+}
+
 /// Implementation of the `DERIVE_PARTIAL_EQ_WITHOUT_EQ` lint.
 fn check_partial_eq_without_eq<'tcx>(cx: &LateContext<'tcx>, span: Span, trait_ref: &hir::TraitRef<'_>, ty: Ty<'tcx>) {
     if let ty::Adt(adt, args) = ty.kind()
         && cx.tcx.visibility(adt.did()).is_public()
         && let Some(eq_trait_def_id) = cx.tcx.get_diagnostic_item(sym::Eq)
         && let Some(def_id) = trait_ref.trait_def_id()
         && cx.tcx.is_diagnostic_item(sym::PartialEq, def_id)
+        && !has_non_exhaustive_attr(cx, *adt)
         && let param_env = param_env_for_derived_eq(cx.tcx, adt.did(), eq_trait_def_id)
         && !implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, adt.did(),&[])
         // If all of our fields implement `Eq`, we can implement `Eq` too