AutoDiff: Another ugly hack to work around generics invariant violations

Author: slavapestov

lib/SIL/IR/SILFunctionType.cpp

@@ -406,11 +406,33 @@ static CanGenericSignature buildDifferentiableGenericSignature(CanGenericSignatu
                            return t->isEqual(interfaceTy->getRootGenericParam());
                          }) != genericParams.end()) {
           types.insert(interfaceTy->getCanonicalType());
+
           for (auto *proto : at->getConformsTo()) {
             reqs.push_back(Requirement(RequirementKind::Conformance,
                                        interfaceTy,
                                        proto->getDeclaredInterfaceType()));
           }
+
+          // The GSB would add conformance requirements if a nested type
+          // requirement involving a resolved DependentMemberType was added;
+          // eg, if you start with <T> and add T.[P]A == Int, it would also
+          // add the conformance requirement T : P.
+          //
+          // This was not an intended behavior on the part of the GSB, and the
+          // logic here is a complete mess, so just simulate the old behavior
+          // here.
+          auto parentTy = interfaceTy;
+          while (parentTy) {
+            if (auto memberTy = parentTy->getAs<DependentMemberType>()) {
+              parentTy = memberTy->getBase();
+              if (auto *assocTy = memberTy->getAssocType()) {
+                reqs.push_back(Requirement(RequirementKind::Conformance,
+                                           parentTy,
+                                           assocTy->getProtocol()->getDeclaredInterfaceType()));
+              }
+            } else
+              parentTy = Type();
+          }
         }
       }
       return false;

test/AutoDiff/SILOptimizer/generics.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-emit-sil -verify %s | %FileCheck %s -check-prefix=CHECK-SIL
+// RUN: %target-swift-emit-sil -verify %s -requirement-machine-abstract-signatures=verify | %FileCheck %s -check-prefix=CHECK-SIL
 
 import _Differentiation