1 files changed, 41 insertions, 20 deletions

diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 36a1061c9..4d2839b8d 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -1926,23 +1926,33 @@ namespace Slang
             requiredMemberDeclRef.getDecl(),
             RequirementWitness(satisfyingMemberDeclRef));
 
-        if (hasForwardDerivative)
+        if (hasForwardDerivative || hasBackwardDerivative)
         {
-            auto reqDecl = requiredMemberDeclRef.getDecl()->getMembersOfType<ForwardDerivativeRequirementDecl>();
-            SLANG_RELEASE_ASSERT(reqDecl.isNonEmpty());
-            ForwardDifferentiateVal* val = m_astBuilder->create<ForwardDifferentiateVal>();
-            val->func = satisfyingMemberDeclRef;
-            witnessTable->add(reqDecl.getFirst(), RequirementWitness(val));
-        }
+            int fwdReqFound = 0;
+            int bwdReqFound = 0;
+            for (auto reqRefDecl : requiredMemberDeclRef.getDecl()->getMembersOfType<DerivativeRequirementReferenceDecl>())
+            {
+                if (auto fwdReq = as<ForwardDerivativeRequirementDecl>(reqRefDecl->referencedDecl))
+                {
+                    ForwardDifferentiateVal* val = m_astBuilder->create<ForwardDifferentiateVal>();
+                    val->func = satisfyingMemberDeclRef;
+                    witnessTable->add(fwdReq, RequirementWitness(val));
+                    fwdReqFound++;
+                }
+                else if (auto bwdReq = as<BackwardDerivativeRequirementDecl>(reqRefDecl->referencedDecl))
+                {
+                    BackwardDifferentiateVal* val = m_astBuilder->create<BackwardDifferentiateVal>();
+                    val->func = satisfyingMemberDeclRef;
+                    witnessTable->add(bwdReq, RequirementWitness(val));
+                    bwdReqFound++;
+                }
+            }
 
-        if (hasBackwardDerivative)
-        {
-            auto reqDecl = requiredMemberDeclRef.getDecl()->getMembersOfType<BackwardDerivativeRequirementDecl>();
-            SLANG_RELEASE_ASSERT(reqDecl.isNonEmpty());
-            BackwardDifferentiateVal* val = m_astBuilder->create<BackwardDifferentiateVal>();
-            val->func = satisfyingMemberDeclRef;
-            witnessTable->add(reqDecl.getFirst(), RequirementWitness(val));
+            SLANG_RELEASE_ASSERT(
+                fwdReqFound == (hasForwardDerivative ? 1 : 0) &&
+                bwdReqFound == (hasBackwardDerivative ? 1 : 0));
         }
+
         return true;
     }
 
@@ -3706,7 +3716,8 @@ namespace Slang
         {
             if(isAssociatedTypeDecl(requiredMemberDeclRef))
                 continue;
-
+            if (requiredMemberDeclRef.as<DerivativeRequirementDecl>())
+                continue;
             auto requirementSatisfied = findWitnessForInterfaceRequirement(
                 context,
                 subType,
@@ -5617,7 +5628,7 @@ namespace Slang
         }
         decl->errorType = errorType;
 
-        if (isInterfaceRequirement(decl))
+        if (auto interfaceDecl = findParentInterfaceDecl(decl))
         {
             if (decl->hasModifier<ForwardDifferentiableAttribute>())
             {
@@ -5626,8 +5637,13 @@ namespace Slang
                 auto declRef = DeclRef<CallableDecl>(decl, createDefaultSubstitutions(m_astBuilder, this, decl));
                 auto diffFuncType = getForwardDiffFuncType(getFuncType(m_astBuilder, declRef));
                 setFuncTypeIntoRequirementDecl(reqDecl, as<FuncType>(diffFuncType));
-                decl->members.add(reqDecl);
-                reqDecl->parentDecl = decl;
+                interfaceDecl->members.add(reqDecl);
+                reqDecl->parentDecl = interfaceDecl;
+
+                auto reqRef = m_astBuilder->create<DerivativeRequirementReferenceDecl>();
+                reqRef->referencedDecl = reqDecl;
+                reqRef->parentDecl = decl;
+                decl->members.add(reqRef);
             }
             if (decl->hasModifier<BackwardDifferentiableAttribute>())
             {
@@ -5636,8 +5652,13 @@ namespace Slang
                 auto declRef = DeclRef<CallableDecl>(decl, createDefaultSubstitutions(m_astBuilder, this, decl));
                 auto diffFuncType = getBackwardDiffFuncType(getFuncType(m_astBuilder, declRef));
                 setFuncTypeIntoRequirementDecl(reqDecl, as<FuncType>(diffFuncType));
-                decl->members.add(reqDecl);
-                reqDecl->parentDecl = decl;
+                interfaceDecl->members.add(reqDecl);
+                reqDecl->parentDecl = interfaceDecl;
+
+                auto reqRef = m_astBuilder->create<DerivativeRequirementReferenceDecl>();
+                reqRef->referencedDecl = reqDecl;
+                reqRef->parentDecl = decl;
+                decl->members.add(reqRef);
             }
         }
     }