allow extension of a concrete type to implement additional interface

Also support the scenario that the extension declares conformance to interface I, and a method M in I is already supported by the base implementation.

Author: csyonghe

source/slang/check.cpp

@@ -1794,7 +1794,7 @@ namespace Slang
         // `requiredMemberDeclRef` is a required member of
         // the interface.
         RefPtr<Decl> findWitnessForInterfaceRequirement(
-            DeclRef<AggTypeDecl>    typeDeclRef,
+            DeclRef<AggTypeDeclBase>    typeDeclRef,
             InheritanceDecl*        inheritanceDecl,
             DeclRef<InterfaceDecl>  interfaceDeclRef,
             DeclRef<Decl>           requiredMemberDeclRef,
@@ -1833,22 +1833,20 @@ namespace Slang
 
             // Make sure that by-name lookup is possible.
             buildMemberDictionary(typeDeclRef.getDecl());
-
-            Decl* firstMemberOfName = nullptr;
-            typeDeclRef.getDecl()->memberDictionary.TryGetValue(name, firstMemberOfName);
-
-            if (!firstMemberOfName)
+            auto lookupResult = lookUpLocal(getSession(), this, name, typeDeclRef);
+            
+            if (!lookupResult.isValid())
             {
                 getSink()->diagnose(inheritanceDecl, Diagnostics::typeDoesntImplementInterfaceRequirement, typeDeclRef, requiredMemberDeclRef);
                 return nullptr;
             }
 
             // Iterate over the members and look for one that matches
             // the expected signature for the requirement.
-            for (auto memberDecl = firstMemberOfName; memberDecl; memberDecl = memberDecl->nextInContainerWithSameName)
+            for (auto member : lookupResult)
             {
-                if (doesMemberSatisfyRequirement(DeclRef<Decl>(memberDecl, typeDeclRef.substitutions), requiredMemberDeclRef, requirementWitness))
-                    return memberDecl;
+                if (doesMemberSatisfyRequirement(member.declRef, requiredMemberDeclRef, requirementWitness))
+                    return member.declRef.getDecl();
             }
 
             // No suitable member found, although there were candidates.
@@ -1867,7 +1865,7 @@ namespace Slang
         // (via the given `inheritanceDecl`) actually provides
         // members to satisfy all the requirements in the interface.
         bool checkInterfaceConformance(
-            DeclRef<AggTypeDecl>        typeDeclRef,
+            DeclRef<AggTypeDeclBase>        typeDeclRef,
             InheritanceDecl*    inheritanceDecl,
             DeclRef<InterfaceDecl>  interfaceDeclRef)
         {
@@ -1925,7 +1923,7 @@ namespace Slang
         }
 
         bool checkConformanceToType(
-            DeclRef<AggTypeDecl> typeDeclRef,
+            DeclRef<AggTypeDeclBase> typeDeclRef,
             InheritanceDecl*     inheritanceDecl,
             Type*                baseType)
         {
@@ -1953,7 +1951,7 @@ namespace Slang
         // `inheritanceDecl` actually does what it needs to
         // for that inheritance to be valid.
         bool checkConformance(
-            DeclRef<AggTypeDecl>        typeDecl,
+            DeclRef<AggTypeDeclBase>        typeDecl,
             InheritanceDecl*            inheritanceDecl)
         {
             // Look at the type being inherited from, and validate
@@ -1963,10 +1961,10 @@ namespace Slang
         }
 
         bool checkConformance(
-            AggTypeDecl*        typeDecl,
+            AggTypeDeclBase*        typeDecl,
             InheritanceDecl*    inheritanceDecl)
         {
-            return checkConformance(DeclRef<AggTypeDecl>(typeDecl, SubstitutionSet()), inheritanceDecl);
+            return checkConformance(DeclRef<AggTypeDeclBase>(typeDecl, SubstitutionSet()), inheritanceDecl);
         }
 
         void visitAggTypeDecl(AggTypeDecl* decl)
@@ -3479,10 +3477,11 @@ namespace Slang
 
             // TODO: need to check that the target type names a declaration...
 
+            DeclRef<AggTypeDecl> aggTypeDeclRef;
             if (auto targetDeclRefType = decl->targetType->As<DeclRefType>())
             {
                 // Attach our extension to that type as a candidate...
-                if (auto aggTypeDeclRef = targetDeclRefType->declRef.As<AggTypeDecl>())
+                if (aggTypeDeclRef = targetDeclRefType->declRef.As<AggTypeDecl>())
                 {
                     auto aggTypeDecl = aggTypeDeclRef.getDecl();
                     decl->nextCandidateExtension = aggTypeDecl->candidateExtensions;
@@ -3516,6 +3515,14 @@ namespace Slang
                 EnsureDecl(m);
             }
 
+            if (aggTypeDeclRef)
+            {
+                for (auto inheritanceDecl : decl->getMembersOfType<InheritanceDecl>())
+                {
+                    checkConformance(aggTypeDeclRef.getDecl(), inheritanceDecl);
+                }
+            }
+            
             decl->SetCheckState(DeclCheckState::Checked);
         }
 
@@ -3802,7 +3809,7 @@ namespace Slang
 
                 if( auto aggTypeDeclRef = declRef.As<AggTypeDecl>() )
                 {
-                    for( auto inheritanceDeclRef : getMembersOfType<InheritanceDecl>(aggTypeDeclRef))
+                    for( auto inheritanceDeclRef : getMembersOfTypeWithExt<InheritanceDecl>(aggTypeDeclRef))
                     {
                         EnsureDecl(inheritanceDeclRef.getDecl());
 

source/slang/lower-to-ir.cpp

@@ -2788,19 +2788,30 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
         // TODO: if this inheritance declaration is under an extension,
         // then we should construct the type that is being extended,
         // and not a reference to the extension itself.
-        auto parentDecl = inheritanceDecl->ParentDecl;
-        RefPtr<Type> type = DeclRefType::Create(
-            context->getSession(),
-            makeDeclRef(parentDecl));
 
+        auto parentDecl = inheritanceDecl->ParentDecl;
+        RefPtr<Type> type;
+        if (auto extParentDecl = dynamic_cast<ExtensionDecl*>(parentDecl))
+        {
+            type = extParentDecl->targetType.type;
+            if (auto declRefType = type.As<DeclRefType>())
+            {
+                if (auto aggTypeDecl = declRefType->declRef.As<AggTypeDecl>())
+                    parentDecl = aggTypeDecl.getDecl();
+            }
+        }
+        else
+        {
+            type = DeclRefType::Create(
+                context->getSession(),
+                makeDeclRef(parentDecl));
+        }
         // What is the super-type that we have declared we inherit from?
         RefPtr<Type> superType = inheritanceDecl->base.type;
 
         // Construct the mangled name for the witness table, which depends
         // on the type that is conforming, and the type that it conforms to.
-        String mangledName = getMangledNameForConformanceWitness(
-            makeDeclRef(parentDecl),
-            superType);
+        String mangledName = getMangledNameForConformanceWitness(type, superType);
 
         // Build an IR level witness table, which will represent the
         // conformance of the type to its super-type.

source/slang/syntax.h

@@ -978,6 +978,30 @@ namespace Slang
         {
             return items.Count() > 1 ? items[0].declRef.GetName() : item.declRef.GetName();
         }
+        LookupResultItem* begin()
+        {
+            if (isValid())
+            {
+                if (isOverloaded())
+                    return items.begin();
+                else
+                    return &item;
+            }
+            else
+                return nullptr;
+        }
+        LookupResultItem* end()
+        {
+            if (isValid())
+            {
+                if (isOverloaded())
+                    return items.end();
+                else
+                    return &item + 1;
+            }
+            else
+                return nullptr;
+        }
     };
 
     struct SemanticsVisitor;
@@ -1085,6 +1109,27 @@ namespace Slang
         return FilteredMemberRefList<T>(declRef.getDecl()->Members, declRef.substitutions);
     }
 
+    inline ExtensionDecl* GetCandidateExtensions(DeclRef<AggTypeDecl> const& declRef)
+    {
+        return declRef.getDecl()->candidateExtensions;
+    }
+
+    template<typename T>
+    inline FilteredMemberRefList<T> getMembersOfTypeWithExt(DeclRef<ContainerDecl> const& declRef)
+    {
+        auto rs = getMembersOfType<T>(declRef);
+        if (auto aggDeclRef = declRef.As<AggTypeDecl>())
+        {
+            for (auto ext = GetCandidateExtensions(aggDeclRef); ext; ext = ext->nextCandidateExtension)
+            {
+                auto extMembers = getMembersOfType<T>(DeclRef<ContainerDecl>(ext, declRef.substitutions));
+                const_cast<List<RefPtr<Decl>>&>(rs.decls).AddRange(extMembers.decls);
+            }
+        }
+        return rs;
+    }
+
+
     inline RefPtr<Type> GetType(DeclRef<VarDeclBase> const& declRef)
     {
         return declRef.Substitute(declRef.getDecl()->type.Ptr());
@@ -1099,12 +1144,7 @@ namespace Slang
     {
         return declRef.Substitute(declRef.getDecl()->targetType.Ptr());
     }
-
-    inline ExtensionDecl* GetCandidateExtensions(DeclRef<AggTypeDecl> const& declRef)
-    {
-        return declRef.getDecl()->candidateExtensions;
-    }
-
+    
     inline FilteredMemberRefList<StructField> GetFields(DeclRef<StructDecl> const& declRef)
     {
         return getMembersOfType<StructField>(declRef);

tests/compute/extension-multi-interface.slang

@@ -0,0 +1,49 @@
+//TEST(compute):COMPARE_COMPUTE:-xslang -use-ir
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):dxbinding(0),glbinding(0),out
+
+RWStructuredBuffer<float> outputBuffer;
+
+interface IAdd
+{
+    float addf(float u, float v);
+}
+
+interface ISub
+{
+    float subf(float u, float v);
+}
+
+interface IAddAndSub
+{
+    float addf(float u, float v);
+    float subf(float u, float v);    
+}
+
+struct Simple : IAdd
+{
+    float addf(float u, float v)
+    {
+        return u+v;
+    }
+};
+
+__extension Simple : ISub, IAddAndSub
+{
+    float subf(float u, float v)
+    {
+        return u-v;
+    }
+};
+
+float testAddSub<T:IAddAndSub>(T t)
+{
+    return t.subf(t.addf(1.0, 1.0), 1.0);
+}
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    Simple s;
+	float outVal = testAddSub(s);
+	outputBuffer[dispatchThreadID.x] = outVal;
+}

tests/compute/extension-multi-interface.slang.expected.txt

@@ -0,0 +1,4 @@
+3F800000
+3F800000
+3F800000
+3F800000

tests/compute/multi-interface.slang

@@ -0,0 +1,45 @@
+//TEST(compute):COMPARE_COMPUTE:-xslang -use-ir
+//TEST_INPUT:ubuffer(data=[0 0 0 0], stride=4):dxbinding(0),glbinding(0),out
+
+RWStructuredBuffer<float> outputBuffer;
+
+interface IAdd
+{
+    float addf(float u, float v);
+}
+
+interface ISub
+{
+    float subf(float u, float v);
+}
+
+interface IAddAndSub
+{
+    float addf(float u, float v);
+    float subf(float u, float v);    
+}
+
+struct Simple : IAdd, ISub, IAddAndSub
+{
+    float addf(float u, float v)
+    {
+        return u+v;
+    }
+    float subf(float u, float v)
+    {
+        return u-v;
+    }
+};
+
+float testAddSub<T:IAddAndSub>(T t)
+{
+    return t.subf(t.addf(1.0, 1.0), 1.0);
+}
+
+[numthreads(4, 1, 1)]
+void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
+{
+    Simple s;
+	float outVal = testAddSub(s);
+	outputBuffer[dispatchThreadID.x] = outVal;
+}

tests/compute/multi-interface.slang.expected.txt

@@ -0,0 +1,4 @@
+3F800000
+3F800000
+3F800000
+3F800000