Arbitrary self types v2: abstract PushCandidate

This commit has no functional changes. It moves the creation of a
Candidate struct into push_candidate.

In a subsequent change, we'll build the Candidate in a slightly more
sophisticated way which it's better to do in one place.

Author: adetaylor

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -498,11 +498,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let trait_ref = ty::TraitRef::new_from_args(self.tcx, trait_def_id, trait_args);
 
                     probe_cx.push_candidate(
-                        Candidate {
-                            item,
-                            kind: CandidateKind::TraitCandidate(ty::Binder::dummy(trait_ref)),
-                            import_ids: smallvec![],
-                        },
+                        item,
+                        CandidateKind::TraitCandidate(ty::Binder::dummy(trait_ref)),
+                        smallvec![],
                         false,
                     );
                 }
@@ -700,7 +698,14 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     ///////////////////////////////////////////////////////////////////////////
     // CANDIDATE ASSEMBLY
 
-    fn push_candidate(&mut self, candidate: Candidate<'tcx>, is_inherent: bool) {
+    fn push_candidate(
+        &mut self,
+        item: ty::AssocItem,
+        kind: CandidateKind<'tcx>,
+        import_ids: SmallVec<[LocalDefId; 1]>,
+        is_inherent: bool,
+    ) {
+        let candidate = Candidate { item, kind, import_ids };
         let is_accessible = if let Some(name) = self.method_name {
             let item = candidate.item;
             let hir_id = self.tcx.local_def_id_to_hir_id(self.body_id);
@@ -818,14 +823,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 self.record_static_candidate(CandidateSource::Impl(impl_def_id));
                 continue;
             }
-            self.push_candidate(
-                Candidate {
-                    item,
-                    kind: InherentImplCandidate(impl_def_id),
-                    import_ids: smallvec![],
-                },
-                true,
-            );
+            self.push_candidate(item, InherentImplCandidate(impl_def_id), smallvec![], true);
         }
     }
 
@@ -854,14 +852,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         self.assemble_candidates_for_bounds(
             traits::supertraits(self.tcx, trait_ref),
             |this, new_trait_ref, item| {
-                this.push_candidate(
-                    Candidate {
-                        item,
-                        kind: ObjectCandidate(new_trait_ref),
-                        import_ids: smallvec![],
-                    },
-                    true,
-                );
+                this.push_candidate(item, ObjectCandidate(new_trait_ref), smallvec![], true);
             },
         );
     }
@@ -890,14 +881,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         });
 
         self.assemble_candidates_for_bounds(bounds, |this, poly_trait_ref, item| {
-            this.push_candidate(
-                Candidate {
-                    item,
-                    kind: WhereClauseCandidate(poly_trait_ref),
-                    import_ids: smallvec![],
-                },
-                true,
-            );
+            this.push_candidate(item, WhereClauseCandidate(poly_trait_ref), smallvec![], true);
         });
     }
 
@@ -984,11 +968,9 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         ));
                     } else {
                         self.push_candidate(
-                            Candidate {
-                                item,
-                                import_ids: import_ids.clone(),
-                                kind: TraitCandidate(bound_trait_ref),
-                            },
+                            item,
+                            TraitCandidate(bound_trait_ref),
+                            import_ids.clone(),
                             false,
                         );
                     }
@@ -1007,11 +989,9 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     continue;
                 }
                 self.push_candidate(
-                    Candidate {
-                        item,
-                        import_ids: import_ids.clone(),
-                        kind: TraitCandidate(ty::Binder::dummy(trait_ref)),
-                    },
+                    item,
+                    TraitCandidate(ty::Binder::dummy(trait_ref)),
+                    import_ids.clone(),
                     false,
                 );
             }