Remove ty::ClosureKind::from_def_id

…in favour of `TyCtxt::fn_trait_kind_from_def_id`

Author: WaffleLapkin

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -2089,7 +2089,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             && let maybe_trait_item_def_id = assoc_item.trait_item_def_id.unwrap_or(def_id)
             && let maybe_trait_def_id = self.tcx.parent(maybe_trait_item_def_id)
             // Just an easy way to check "trait_def_id == Fn/FnMut/FnOnce"
-            && let Some(call_kind) = ty::ClosureKind::from_def_id(self.tcx, maybe_trait_def_id)
+            && let Some(call_kind) = self.tcx.fn_trait_kind_from_def_id(maybe_trait_def_id)
             && let Some(callee_ty) = callee_ty
         {
             let callee_ty = callee_ty.peel_refs();
@@ -2115,7 +2115,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         {
                             if let ty::PredicateKind::Clause(ty::Clause::Trait(pred)) = predicate.kind().skip_binder()
                                 && pred.self_ty().peel_refs() == callee_ty
-                                && ty::ClosureKind::from_def_id(self.tcx, pred.def_id()).is_some()
+                                && self.tcx.fn_trait_kind_from_def_id(pred.def_id()).is_some()
                             {
                                 err.span_note(span, "callable defined here");
                                 return;

compiler/rustc_middle/src/ty/closure.rs

@@ -118,18 +118,9 @@ impl<'tcx> ClosureKind {
         }
     }
 
-    pub fn from_def_id(tcx: TyCtxt<'_>, def_id: DefId) -> Option<ClosureKind> {
-        if Some(def_id) == tcx.lang_items().fn_once_trait() {
-            Some(ClosureKind::FnOnce)
-        } else if Some(def_id) == tcx.lang_items().fn_mut_trait() {
-            Some(ClosureKind::FnMut)
-        } else if Some(def_id) == tcx.lang_items().fn_trait() {
-            Some(ClosureKind::Fn)
-        } else {
-            None
-        }
-    }
-
+    /// Converts `self` to a [`DefId`] of the corresponding trait.
+    ///
+    /// Note: the inverse of this function is [`TyCtxt::fn_trait_kind_from_def_id`]
     pub fn to_def_id(&self, tcx: TyCtxt<'_>) -> DefId {
         tcx.require_lang_item(
             match self {

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -357,7 +357,8 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
                 ocx.register_obligation(obligation);
                 if ocx.select_all_or_error().is_empty() {
                     return Ok((
-                        ty::ClosureKind::from_def_id(self.tcx, trait_def_id)
+                        self.tcx
+                            .fn_trait_kind_from_def_id(trait_def_id)
                             .expect("expected to map DefId to ClosureKind"),
                         ty.rebind(self.resolve_vars_if_possible(var)),
                     ));
@@ -686,7 +687,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 }
                                 ObligationCauseCode::BindingObligation(def_id, _)
                                 | ObligationCauseCode::ItemObligation(def_id)
-                                    if ty::ClosureKind::from_def_id(tcx, *def_id).is_some() =>
+                                    if tcx.fn_trait_kind_from_def_id(*def_id).is_some() =>
                                 {
                                     err.code(rustc_errors::error_code!(E0059));
                                     err.set_primary_message(format!(
@@ -847,7 +848,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         }
 
                         let is_fn_trait =
-                            ty::ClosureKind::from_def_id(tcx, trait_ref.def_id()).is_some();
+                            tcx.fn_trait_kind_from_def_id(trait_ref.def_id()).is_some();
                         let is_target_feature_fn = if let ty::FnDef(def_id, _) =
                             *trait_ref.skip_binder().self_ty().kind()
                         {
@@ -877,7 +878,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                             // Note if the `FnMut` or `FnOnce` is less general than the trait we're trying
                             // to implement.
                             let selected_kind =
-                                ty::ClosureKind::from_def_id(self.tcx, trait_ref.def_id())
+                                self.tcx.fn_trait_kind_from_def_id(trait_ref.def_id())
                                     .expect("expected to map DefId to ClosureKind");
                             if !implemented_kind.extends(selected_kind) {
                                 err.note(

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -1752,7 +1752,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             && let predicates = self.tcx.predicates_of(def_id).instantiate_identity(self.tcx)
             && let Some(pred) = predicates.predicates.get(*idx)
             && let ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred)) = pred.kind().skip_binder()
-            && ty::ClosureKind::from_def_id(self.tcx, trait_pred.def_id()).is_some()
+            && self.tcx.fn_trait_kind_from_def_id(trait_pred.def_id()).is_some()
         {
             let expected_self =
                 self.tcx.anonymize_late_bound_regions(pred.kind().rebind(trait_pred.self_ty()));
@@ -1766,7 +1766,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 .enumerate()
                 .find(|(other_idx, (pred, _))| match pred.kind().skip_binder() {
                     ty::PredicateKind::Clause(ty::Clause::Trait(trait_pred))
-                        if ty::ClosureKind::from_def_id(self.tcx, trait_pred.def_id())
+                        if self.tcx.fn_trait_kind_from_def_id(trait_pred.def_id())
                             .is_some()
                             && other_idx != idx
                             // Make sure that the self type matches