Delegation: support generics in associated items

Author: Bryanskiy

compiler/rustc_hir_analysis/messages.ftl

@@ -316,7 +316,7 @@ hir_analysis_must_implement_not_function_span_note = required by this annotation
 hir_analysis_must_implement_one_of_attribute = the `#[rustc_must_implement_one_of]` attribute must be used with at least 2 args
 
 hir_analysis_not_supported_delegation =
-    {$descr} is not supported yet
+    {$descr}
     .label = callee defined here
 
 hir_analysis_only_current_traits_adt = `{$name}` is not defined in the current crate

compiler/rustc_hir_analysis/src/collect/generics_of.rs

@@ -56,10 +56,8 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
     }
 
     // For a delegation item inherit generics from callee.
-    if let Some(sig_id) = tcx.hir().opt_delegation_sig_id(def_id)
-        && let Some(generics) = inherit_generics_for_delegation_item(tcx, def_id, sig_id)
-    {
-        return generics;
+    if let Some(sig_id) = tcx.hir().opt_delegation_sig_id(def_id) {
+        return inherit_generics_for_delegation_item(tcx, def_id, sig_id);
     }
 
     let hir_id = tcx.local_def_id_to_hir_id(def_id);

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -3,7 +3,6 @@ use crate::collect::ItemCtxt;
 use crate::constrained_generic_params as cgp;
 use crate::delegation::inherit_predicates_for_delegation_item;
 use crate::hir_ty_lowering::{HirTyLowerer, OnlySelfBounds, PredicateFilter, RegionInferReason};
-use crate::hir_ty_lowering::{HirTyLowerer, OnlySelfBounds, PredicateFilter};
 use hir::{HirId, Node};
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
@@ -117,10 +116,8 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
     }
 
     // For a delegation item inherit predicates from callee.
-    if let Some(sig_id) = tcx.hir().opt_delegation_sig_id(def_id)
-        && let Some(predicates) = inherit_predicates_for_delegation_item(tcx, def_id, sig_id)
-    {
-        return predicates;
+    if let Some(sig_id) = tcx.hir().opt_delegation_sig_id(def_id) {
+        return inherit_predicates_for_delegation_item(tcx, def_id, sig_id);
     }
 
     let hir_id = tcx.local_def_id_to_hir_id(def_id);