When preparing necessary bindings, we sometimes decide to capture

bound generic type metadata rather than its individual components.
Don't crash when actually restoring that metadata.

Fixes SR-901.

Author: rjmccall

lib/IRGen/GenProto.cpp

@@ -2612,19 +2612,19 @@ void irgen::bindGenericRequirement(IRGenFunction &IGF,
                                    GenericRequirement requirement,
                                    llvm::Value *value,
                                    GetTypeParameterInContextFn getInContext) {
-  // Get the corresponding context archetype.
-  auto archetype = cast<ArchetypeType>(getInContext(requirement.TypeParameter));
+  // Get the corresponding context type.
+  auto type = getInContext(requirement.TypeParameter);
 
   if (auto proto = requirement.Protocol) {
+    assert(isa<ArchetypeType>(type));
     assert(value->getType() == IGF.IGM.WitnessTablePtrTy);
-    setProtocolWitnessTableName(IGF.IGM, value, archetype, proto);
+    setProtocolWitnessTableName(IGF.IGM, value, type, proto);
     auto kind = LocalTypeDataKind::forAbstractProtocolWitnessTable(proto);
-    IGF.setUnscopedLocalTypeData(archetype, kind, value);
+    IGF.setUnscopedLocalTypeData(type, kind, value);
   } else {
     assert(value->getType() == IGF.IGM.TypeMetadataPtrTy);
-    setTypeMetadataName(IGF.IGM, value, archetype);
-    auto kind = LocalTypeDataKind::forTypeMetadata();
-    IGF.setUnscopedLocalTypeData(archetype, kind, value);
+    setTypeMetadataName(IGF.IGM, value, type);
+    IGF.bindLocalTypeDataFromTypeMetadata(type, IsExact, value);
   }
 }
 

test/IRGen/partial_apply.sil

@@ -573,3 +573,17 @@ bb0(%0 : $Int):
 // CHECK-NEXT: [[T0:%.*]] = getelementptr inbounds %swift.type*, %swift.type** [[BUFFER]], i32 2
 // CHECK-NEXT: [[T1:%.*]] = bitcast %swift.type** [[T0]] to i8***
 // CHECK-NEXT: %T.Y.P2 = load i8**, i8*** [[T1]], align 8
+
+struct ComplexBoundedType<T: P2> {}
+
+// SR-901: Ensure that a partial_apply which captures bound generic type
+// metadata doesn't crash when restoring the generic context.
+
+sil hidden_external @generic_function : $@convention(thin) <T> () -> ()
+sil @partial_apply_with_generic_type : $@convention(thin) <U: P2> () -> () {
+bb0:
+  %fn = function_ref @generic_function : $@convention(thin) <T> () -> ()
+  %pa = partial_apply %fn <ComplexBoundedType<U>>() : $@convention(thin) <T> () -> ()
+  %result = tuple ()
+  return %result : $()
+}