work in-progress: type checking associated types

9 files changed, 156 insertions, 111 deletions

diff --git a/source/slang/check.cpp b/source/slang/check.cpp
index 0c35c4bf4..fe7498d86 100644
--- a/source/slang/check.cpp
+++ b/source/slang/check.cpp
@@ -1538,7 +1538,48 @@ namespace Slang
                         requiredInitDecl);
                 }
             }
+            else if (auto subStructTypeDecl = dynamic_cast<AggTypeDecl*>(memberDecl))
+            {
+                // this is a sub type (e.g. nested struct declaration) in an aggregate type
+                // check if this sub type declaration satisfies the constraints defined by the associated type
+                if (auto requiredTypeDecl = requiredMemberDeclRef.As<AssocTypeDecl>())
+                {
+                    bool conformance = true;
+                    for (auto & inheritanceDecl : requiredTypeDecl.getDecl()->getMembersOfType<InheritanceDecl>())
+                    {
+                        conformance = conformance && checkConformance(subStructTypeDecl, inheritanceDecl.Ptr());
+                    }
+                    return conformance;
+                }
+            }
+            else if (auto typedefDecl = dynamic_cast<TypeDefDecl*>(memberDecl))
+            {
+                // this is a type-def decl in an aggregate type
+                // check if the specified type satisfies the constraints defined by the associated type
+                if (auto requiredTypeDecl = requiredMemberDeclRef.As<AssocTypeDecl>())
+                {
+                    auto constraintList = requiredTypeDecl.getDecl()->getMembersOfType<InheritanceDecl>();
+                    if (constraintList.Count())
+                    {
+                        auto declRefType = typedefDecl->type->AsDeclRefType();
+                        if (!declRefType)
+                            return false;
 
+                        auto subStructTypeDecl = declRefType->declRef.getDecl()->As<AggTypeDecl>();
+                        //TODO: What do we do if type is a generic specialization?
+                        // i.e. if the struct defines typedef Generic<float> T; 
+                        // how to check if T satisfies the associatedtype constraints?
+                        // the code below will only work when T is defined to be a simple aggregated type (no generics).
+                        bool conformance = true;
+                        for (auto & inheritanceDecl : constraintList)
+                        {
+                            conformance = conformance && checkConformance(subStructTypeDecl, inheritanceDecl.Ptr());
+                        }
+                        return conformance;
+                    }
+                    return true;
+                }
+            }
             // Default: just assume that thing aren't being satisfied.
             return false;
         }
@@ -1623,11 +1664,13 @@ namespace Slang
         // declares conformance to the interface `interfaceDeclRef`,
         // (via the given `inheritanceDecl`) actually provides
         // members to satisfy all the requirements in the interface.
-        void checkInterfaceConformance(
+        bool checkInterfaceConformance(
             AggTypeDecl*        typeDecl,
             InheritanceDecl*    inheritanceDecl,
             DeclRef<InterfaceDecl>  interfaceDeclRef)
         {
+            bool result = true;
+
             // We need to check the declaration of the interface
             // before we can check that we conform to it.
             EnsureDecl(interfaceDeclRef.getDecl());
@@ -1654,7 +1697,7 @@ namespace Slang
                     // to the inherited interface.
                     //
                     // TODO: we *really* need a linearization step here!!!!
-                    checkConformanceToType(
+                    result = result && checkConformanceToType(
                         typeDecl,
                         inheritanceDecl,
                         getBaseType(requiredInheritanceDeclRef));
@@ -1670,16 +1713,20 @@ namespace Slang
                     requiredMemberDeclRef);
 
                 if (!conformanceWitness)
+                {
+                    result = false;
                     continue;
+                }
 
                 // Store that witness into a table stored on the `inheritnaceDecl`
                 // so that it can be used for downstream code generation.
 
                 inheritanceDecl->requirementWitnesses.Add(requiredMemberDeclRef, conformanceWitness);
             }
+            return result;
         }
 
-        void checkConformanceToType(
+        bool checkConformanceToType(
             AggTypeDecl*        typeDecl,
             InheritanceDecl*    inheritanceDecl,
             Type*               baseType)
@@ -1692,29 +1739,29 @@ namespace Slang
                     // The type is stating that it conforms to an interface.
                     // We need to check that it provides all of the members
                     // required by that interface.
-                    checkInterfaceConformance(
+                    return checkInterfaceConformance(
                         typeDecl,
                         inheritanceDecl,
                         baseInterfaceDeclRef);
-                    return;
                 }
             }
 
             getSink()->diagnose(inheritanceDecl, Diagnostics::unimplemented, "type not supported for inheritance");
+            return false;
         }
 
         // Check that the type declaration `typeDecl`, which
         // declares that it inherits from another type via
         // `inheritanceDecl` actually does what it needs to
         // for that inheritance to be valid.
-        void checkConformance(
+        bool checkConformance(
             AggTypeDecl*        typeDecl,
             InheritanceDecl*    inheritanceDecl)
         {
             // Look at the type being inherited from, and validate
             // appropriately.
             auto baseType = inheritanceDecl->base.type;
-            checkConformanceToType(typeDecl, inheritanceDecl, baseType);
+            return checkConformanceToType(typeDecl, inheritanceDecl, baseType);
         }
 
         void visitAggTypeDecl(AggTypeDecl* decl)
@@ -1758,6 +1805,11 @@ namespace Slang
                 // Don't check that an interface conforms to the
                 // things it inherits from.
             }
+            else if (auto assocTypeDecl = dynamic_cast<AssocTypeDecl*>(decl))
+            {
+                // Don't check that an associated type decl conforms to the
+                // things it inherits from.
+            }
             else
             {
                 // For non-interface types we need to check conformance.
@@ -1794,6 +1846,24 @@ namespace Slang
             decl->SetCheckState(DeclCheckState::Checked);
         }
 
+        void visitAssocTypeDecl(AssocTypeDecl* decl)
+        {
+            if (decl->IsChecked(DeclCheckState::Checked)) return;
+            decl->SetCheckState(DeclCheckState::CheckedHeader);
+
+            // assoctype only allowed in an interface
+            auto interfaceDecl = decl->ParentDecl->As<InterfaceDecl>();
+            if (!interfaceDecl)
+                getSink()->diagnose(decl, Slang::Diagnostics::assocTypeInInterfaceOnly);
+
+            // Now check all of the member declarations.
+            for (auto member : decl->Members)
+            {
+                checkDecl(member);
+            }
+            decl->SetCheckState(DeclCheckState::Checked);
+        }
+
         void checkStmt(Stmt* stmt)
         {
             if (!stmt) return;
@@ -5647,8 +5717,13 @@ namespace Slang
 
         RefPtr<Expr> visitInvokeExpr(InvokeExpr *expr)
         {
+            if (auto appExpr = expr->FunctionExpr->As<GenericAppExpr>())
+                if (auto varExpr = appExpr->FunctionExpr->As<VarExpr>())
+                    if (varExpr->name->text == "test")
+                        printf("break");
             // check the base expression first
             expr->FunctionExpr = CheckExpr(expr->FunctionExpr);
+     
 
             // Next check the argument expressions
             for (auto & arg : expr->Arguments)
@@ -6386,7 +6461,12 @@ namespace Slang
             auto type = getFuncType(session, funcDeclRef);
             return QualType(type);
         }
-
+        else if (auto assocTypeDeclRef = declRef.As<AssocTypeDecl>())
+        {
+            auto type = DeclRefType::Create(session, assocTypeDeclRef);
+            *outTypeResult = type;
+            return QualType(getTypeType(type));
+        }
         if( sink )
         {
             sink->diagnose(declRef, Diagnostics::unimplemented, "cannot form reference to this kind of declaration");
diff --git a/source/slang/decl-defs.h b/source/slang/decl-defs.h
index 4021f5a38..bb8c26f58 100644
--- a/source/slang/decl-defs.h
+++ b/source/slang/decl-defs.h
@@ -122,9 +122,8 @@ SYNTAX_CLASS(TypeDefDecl, SimpleTypeDecl)
     SYNTAX_FIELD(TypeExp, type)
 END_SYNTAX_CLASS()
 
-// An 'assoctype' declaration
-SYNTAX_CLASS(AssocTypeDecl, SimpleTypeDecl)
-    SYNTAX_FIELD(TypeExp, constraint)
+// An 'assoctype' declaration, it is a container of inheritance clauses
+SYNTAX_CLASS(AssocTypeDecl, ContainerDecl)
 END_SYNTAX_CLASS()
 
 // A scope for local declarations (e.g., as part of a statement)
diff --git a/source/slang/diagnostic-defs.h b/source/slang/diagnostic-defs.h
index cca1c4869..86b9b74ec 100644
--- a/source/slang/diagnostic-defs.h
+++ b/source/slang/diagnostic-defs.h
@@ -191,83 +191,10 @@ DIAGNOSTIC(30035, Error, componentOverloadTypeMismatch, "'$0': type of overloade
 DIAGNOSTIC(30041, Error, bitOperationNonIntegral, "bit operation: operand must be integral type.")
 DIAGNOSTIC(30047, Error, argumentExpectedLValue, "argument passed to parameter '$0' must be l-value.")
 DIAGNOSTIC(30051, Error, invalidValueForArgument, "invalid value for argument '$0'")
-DIAGNOSTIC(30052, Error, ordinaryFunctionAsModuleArgument, "ordinary functions not allowed as argument to function-typed module parameter.")
-DIAGNOSTIC(30079, Error, selectPrdicateTypeMismatch, "selector must evaluate to bool.");
-DIAGNOSTIC(30080, Error, selectValuesTypeMismatch, "the two value expressions in a select clause must have same type.");
-DIAGNOSTIC(31040, Error, undefinedTypeName, "undefined type name: '$0'.")
-DIAGNOSTIC(32013, Error, circularReferenceNotAllowed, "'$0': circular reference is not allowed.");
-DIAGNOSTIC(32014, Error, shaderDoesProvideRequirement, "shader '$0' does not provide '$1' as required by '$2'.")
-DIAGNOSTIC(32015, Error, argumentNotAvilableInWorld, "argument '$0' is not available in world '$1' as required by '$2'.")
-DIAGNOSTIC(32015, Error, componentNotAvilableInWorld, "component '$0' is not available in world '$1' as required by '$2'.")
-DIAGNOSTIC(32047, Error, firstArgumentToImportNotComponent, "first argument of an import operator call does not resolve to a component.");
-DIAGNOSTIC(32051, Error, componentTypeNotWhatPipelineRequires, "component '$0' has type '$1', but pipeline '$2' requires it to be '$3'.")
-DIAGNOSTIC(32052, Error, shaderDoesNotDefineComponentAsRequiredByPipeline, "shader '$0' does not define '$1' as required by pipeline '$2''.")
-DIAGNOSTIC(33001, Error, worldNameAlreadyDefined, "world '$0' is already defined.")
-DIAGNOSTIC(33002, Error, explicitPipelineSpecificationRequiredForShader, "explicit pipeline specification required for shader '$0' because multiple pipelines are defined in current context.")
-DIAGNOSTIC(33003, Error, cannotDefineComponentsInAPipeline, "cannot define components in a pipeline.")
-DIAGNOSTIC(33004, Error, undefinedWorldName, "undefined world name '$0'.")
-DIAGNOSTIC(33005, Error, abstractWorldAsTargetOfImport, "abstract world cannot appear as target as an import operator.")
-
-// Note(tfoley): This is a duplicate of 33004 above.
-DIAGNOSTIC(33006, Error, undefinedWorldName2, "undefined world name '$0'.")
-
-DIAGNOSTIC(33007, Error, importOperatorCircularity, "import operator '$0' creates a circular dependency between world '$1' and '$2'")
-DIAGNOSTIC(33009, Error, parametersOnlyAllowedInModules, "parameters can only be defined in modules.")
-DIAGNOSTIC(33010, Error, undefinedPipelineName, "pipeline '$0' is undefined.")
-DIAGNOSTIC(33011, Error, shaderCircularity, "shader '$0' involves circular reference.")
-DIAGNOSTIC(33012, Error, worldIsNotDefinedInPipeline, "'$0' is not a defined world in '$1'.")
-DIAGNOSTIC(33013, Error, abstractWorldCannotAppearWithOthers, "abstract world cannot appear with other worlds.")
-DIAGNOSTIC(33014, Error, nonAbstractComponentMustHaveImplementation, "non-abstract component must have an implementation.")
-DIAGNOSTIC(33016, Error, usingInComponentDefinition, "'using': importing not allowed in component definition.")
-DIAGNOSTIC(33018, Error, nameAlreadyDefined, "'$0' is already defined.")
-DIAGNOSTIC(33018, Error, shaderAlreadyDefined, "shader '$0' has already been defined.")
-DIAGNOSTIC(33019, Error, componentMarkedExportMustHaveWorld, "component '$0': definition marked as 'export' must have an explicitly specified world.")
-DIAGNOSTIC(33020, Error, componentIsAlreadyDefined, "'$0' is already defined.")
-DIAGNOSTIC(33020, Error, componentIsAlreadyDefinedInThatWorld, "'$0' is already defined at '$1'.")
-DIAGNOSTIC(33021, Error, inconsistentSignatureForComponent, "'$0': inconsistent signature.")
-DIAGNOSTIC(33022, Error, nameAlreadyDefinedInCurrentScope, "'$0' is already defined in current scope.")
-DIAGNOSTIC(33022, Error, parameterNameConflictsWithExistingDefinition, "'$0': parameter name conflicts with existing definition.")
-DIAGNOSTIC(33023, Error, parameterOfModuleIsUnassigned, "parameter '$0' of module '$1' is unassigned.")
-DIAGNOSTIC(33027, Error, argumentTypeDoesNotMatchParameterType, "argument type ($0) does not match parameter type ($1)")
-DIAGNOSTIC(33028, Error, nameIsNotAParameterOfCallee, "'$0' is not a parameter of '$1'.")
-DIAGNOSTIC(33029, Error, requirementsClashWithPreviousDef, "'$0': requirement clash with previous definition.")
-DIAGNOSTIC(33030, Error, positionArgumentAfterNamed, "positional argument cannot appear after a named argument.")
-DIAGNOSTIC(33032, Error, functionRedefinition, "'$0': function redefinition.")
-DIAGNOSTIC(33034, Error, recordTypeVariableInImportOperator, "cannot declare a record-typed variable in an import operator.")
-DIAGNOSTIC(33037, Error, componetMarkedExportCannotHaveParameters, "component '$0': definition marked as 'export' cannot have parameters.")
-DIAGNOSTIC(33039, Error, componentInInputWorldCantHaveCode, "'$0': no code allowed for component defined in input world.")
-DIAGNOSTIC(33040, Error, requireWithComputation, "'require': cannot define computation on component requirements.")
-DIAGNOSTIC(33042, Error, paramWithComputation, "'param': cannot define computation on parameters.")
-DIAGNOSTIC(33041, Error, pipelineOfModuleIncompatibleWithPipelineOfShader, "pipeline '$0' targeted by module '$1' is incompatible with pipeline '$2' targeted by shader '$3'.")
 DIAGNOSTIC(33070, Error, expectedFunction, "expression preceding parenthesis of apparent call must have function type.")
-DIAGNOSTIC(33071, Error, importOperatorCalledFromAutoPlacedComponent, "cannot call an import operator from an auto-placed component '$0'. try qualify the component with explicit worlds.")
-DIAGNOSTIC(33072, Error, noApplicableImportOperator, "'$0' is an import operator defined in pipeline '$1', but none of the import operator overloads converting to world '$2' matches argument list ($3).")
-DIAGNOSTIC(33073, Error, importOperatorCalledFromMultiWorldComponent, "cannot call an import operator from a multi-world component definition. consider qualify the component with only one explicit world.")
-DIAGNOSTIC(33080, Error, componentTypeDoesNotMatchInterface, "'$0': component type does not match definition in interface '$1'.")
-DIAGNOSTIC(33081, Error, shaderDidNotDefineComponentFunction, "shader '$0' did not define component function $1 as required by interface '$2'.")
-DIAGNOSTIC(33082, Error, shaderDidNotDefineComponent, "shader '$0' did not define component '$1' as required by interface '$2'.")
-DIAGNOSTIC(33083, Error, interfaceImplMustBePublic, "'$0': component fulfilling interface '$1' must be declared as 'public'.")
-DIAGNOSTIC(33084, Error, defaultParamNotAllowedInInterface, "'$0': default parameter value not allowed in interface definition.")
-
-DIAGNOSTIC(33100, Error, componentCantBeComputedAtWorldBecauseDependentNotAvailable, "'$0' cannot be computed at '$1' because the dependent component '$2' is not accessible.")
-DIAGNOSTIC(33101, Warning, worldIsNotAValidChoiceForKey, "'$0' is not a valid choice for '$1'.")
-DIAGNOSTIC(33102, Error, componentDefinitionCircularity, "component definition '$0' involves circular reference.")
-DIAGNOSTIC(34024, Error, componentAlreadyDefinedWhenCompiling, "component named '$0' is already defined when compiling '$1'.")
-DIAGNOSTIC(34025, Error, globalComponentConflictWithPreviousDeclaration, "'$0': global component conflicts with previous declaration.")
-DIAGNOSTIC(34026, Warning, componentIsAlreadyDefinedUseRequire, "'$0': component is already defined when compiling shader '$1'. use 'require' to declare it as a parameter.")
-DIAGNOSTIC(34062, Error, cylicReference, "cyclic reference: $0");
-DIAGNOSTIC(34064, Error, noApplicableImplicitImportOperator, "cannot find import operator to import component '$0' to world '$1' when compiling '$2'.")
-DIAGNOSTIC(34065, Error, resourceTypeMustBeParamOrRequire, "'$0': resource typed component must be declared as 'param' or 'require'.");
-DIAGNOSTIC(34066, Error, cannotDefineComputationOnResourceType, "'$0': cannot define computation on resource typed component.");
-
-DIAGNOSTIC(35001, Error, fragDepthAttributeCanOnlyApplyToOutput, "FragDepth attribute can only apply to an output component.");
-DIAGNOSTIC(35002, Error, fragDepthAttributeCanOnlyApplyToFloatComponent, "FragDepth attribute can only apply to a float component.");
-
-
-DIAGNOSTIC(36001, Error, insufficientTemplateShaderArguments, "instantiating template shader '$0': insufficient arguments.");
-DIAGNOSTIC(36002, Error, tooManyTemplateShaderArguments, "instantiating template shader '$0': too many arguments.");
-DIAGNOSTIC(36003, Error, templateShaderArgumentIsNotDefined, "'$0' provided as template shader argument to '$1' is not a defined module.");
-DIAGNOSTIC(36004, Error, templateShaderArgumentDidNotImplementRequiredInterface, "module '$0' provided as template shader argument to '$1' did not implement required interface '$2'.");
+
+// 303xx: interfaces and associated types
+DIAGNOSTIC(30300, Error, assocTypeInInterfaceOnly, "'associatedtype' can only be defined in an 'interface'.")
 
 // TODO: need to assign numbers to all these extra diagnostics...
 
diff --git a/source/slang/emit.cpp b/source/slang/emit.cpp
index 2e8ab58d4..3454a3f85 100644
--- a/source/slang/emit.cpp
+++ b/source/slang/emit.cpp
@@ -1039,7 +1039,6 @@ struct EmitVisitor
     UNEXPECTED(PtrType);
 
 #undef UNEXPECTED
-
     void visitNamedExpressionType(NamedExpressionType* type, TypeEmitArg const& arg)
     {
         // Named types are valid for GLSL
@@ -1053,6 +1052,11 @@ struct EmitVisitor
         EmitDeclarator(arg.declarator);
     }
 
+    void visitAssocTypeDeclRefType(AssocTypeDeclRefType* /*type*/, TypeEmitArg const& /*arg*/)
+    {
+        SLANG_UNREACHABLE("visitAssocTypeDeclRefType in EmitVisitor");
+    }
+
     void visitBasicExpressionType(BasicExpressionType* basicType, TypeEmitArg const& arg)
     {
         auto declarator = arg.declarator;
@@ -3009,6 +3013,12 @@ struct EmitVisitor
         Emit(";\n");
     }
 
+    void visitAssocTypeDecl(AssocTypeDecl * /*assocType*/, DeclEmitArg const&)
+    {
+        SLANG_UNREACHABLE("visitAssocTypeDecl in EmitVisitor");
+    }
+
+
     void visitImportDecl(ImportDecl* decl, DeclEmitArg const&)
     {
         // When in "rewriter" mode, we need to emit the code of the imported
diff --git a/source/slang/lower.cpp b/source/slang/lower.cpp
index 0f16a8ad7..776a55530 100644
--- a/source/slang/lower.cpp
+++ b/source/slang/lower.cpp
@@ -765,6 +765,7 @@ struct LoweringVisitor
             loweredDeclRef.As<Decl>());
     }
 
+
     RefPtr<Type> visitNamedExpressionType(NamedExpressionType* type)
     {
         if (shared->target == CodeGenTarget::GLSL)
@@ -778,6 +779,13 @@ struct LoweringVisitor
             translateDeclRef(DeclRef<Decl>(type->declRef)).As<TypeDefDecl>());
     }
 
+    RefPtr<Type> visitAssocTypeDeclRefType(AssocTypeDeclRefType* type)
+    {
+        // not supported by lowering
+        SLANG_UNREACHABLE("visitAssocTypeDeclRefType in LowerVisitor");
+        return nullptr;
+    }
+
     RefPtr<Type> visitTypeType(TypeType* type)
     {
         return getTypeType(lowerType(type->type));
@@ -2820,6 +2828,13 @@ struct LoweringVisitor
         return LoweredDecl();
     }
 
+    LoweredDecl visitAssocTypeDecl(AssocTypeDecl * /*assocType*/)
+    {
+        // not supported
+        SLANG_UNREACHABLE("visitAssocTypeDecl in LowerVisitor");
+        return LoweredDecl();
+    }
+
     LoweredDecl visitTypeDefDecl(TypeDefDecl* decl)
     {
         if (shared->target == CodeGenTarget::GLSL)
diff --git a/source/slang/parser.cpp b/source/slang/parser.cpp
index 554eebc18..224450a66 100644
--- a/source/slang/parser.cpp
+++ b/source/slang/parser.cpp
@@ -544,21 +544,6 @@ namespace Slang
         return typeDefDecl;
     }
 
-    RefPtr<RefObject> ParseAssocType(Parser * parser, void *)
-    {
-        RefPtr<AssocTypeDecl> assocTypeDecl = new AssocTypeDecl();
-
-        auto nameToken = parser->ReadToken(TokenType::Identifier);
-        assocTypeDecl->nameAndLoc = NameLoc(nameToken);
-        assocTypeDecl->loc = nameToken.loc;
-        if (parser->LookAheadToken(TokenType::Colon))
-        {
-            auto type = parser->ParseTypeExp();
-            assocTypeDecl->constraint = type;
-        }
-        return assocTypeDecl;
-    }
-
     // Add a modifier to a list of modifiers being built
     static void AddModifier(RefPtr<Modifier>** ioModifierLink, RefPtr<Modifier> modifier)
     {
@@ -2102,7 +2087,7 @@ namespace Slang
         return decl;
     }
 
-    static void parseOptionalInheritanceClause(Parser* parser, AggTypeDecl* decl)
+    static void parseOptionalInheritanceClause(Parser* parser, ContainerDecl* decl)
     {
         if( AdvanceIf(parser, TokenType::Colon) )
         {
@@ -2121,6 +2106,18 @@ namespace Slang
         }
     }
 
+    RefPtr<RefObject> ParseAssocType(Parser * parser, void *)
+    {
+        RefPtr<AssocTypeDecl> assocTypeDecl = new AssocTypeDecl();
+
+        auto nameToken = parser->ReadToken(TokenType::Identifier);
+        assocTypeDecl->nameAndLoc = NameLoc(nameToken);
+        assocTypeDecl->loc = nameToken.loc;
+        parseOptionalInheritanceClause(parser, assocTypeDecl.Ptr());
+        parser->ReadToken(TokenType::Semicolon);
+        return assocTypeDecl;
+    }
+
     static RefPtr<RefObject> parseInterfaceDecl(Parser* parser, void* /*userData*/)
     {
         RefPtr<InterfaceDecl> decl = new InterfaceDecl();
@@ -4062,7 +4059,7 @@ namespace Slang
     #define DECL(KEYWORD, CALLBACK) \
         addBuiltinSyntax<Decl>(session, scope, #KEYWORD, &CALLBACK)
         DECL(typedef,       ParseTypeDef);
-        DECL(assoctype,     ParseAssocType);
+        DECL(associatedtype,ParseAssocType);
         DECL(cbuffer,       parseHLSLCBufferDecl);
         DECL(tbuffer,       parseHLSLTBufferDecl);
         DECL(__generic,     ParseGenericDecl);
diff --git a/source/slang/syntax.cpp b/source/slang/syntax.cpp
index 165b2d132..97f3cfb15 100644
--- a/source/slang/syntax.cpp
+++ b/source/slang/syntax.cpp
@@ -957,6 +957,20 @@ void Type::accept(IValVisitor* visitor, void* extra)
         return false;
     }
 
+    RefPtr<Val> AssocTypeDeclRefType::SubstituteImpl(Substitutions* subst, int* ioDiff)
+    {
+        auto parentType = this->GetDeclRef().GetParent().SubstituteImpl(subst, ioDiff);
+        if (auto aggDeclRef = parentType.As<AggTypeDecl>())
+        {
+            Decl* targetTypeDecl = nullptr;
+            if (aggDeclRef.getDecl()->memberDictionary.TryGetValue(this->GetDeclRef().decl->getName(), targetTypeDecl))
+            {
+                return DeclRefType::Create(this->session, DeclRef<Decl>(targetTypeDecl, parentType.substitutions));
+            }
+        }
+        return this;
+    }
+
     int AssocTypeDeclRefType::GetHashCode()
     {
         return declRef.GetHashCode();
diff --git a/source/slang/type-defs.h b/source/slang/type-defs.h
index 7648e0b87..15dfe3e07 100644
--- a/source/slang/type-defs.h
+++ b/source/slang/type-defs.h
@@ -495,6 +495,7 @@ END_SYNTAX_CLASS()
 // The "type" of an expression that references a asscoiated type decl (via 'assoctype' keyword).
 SYNTAX_CLASS(AssocTypeDeclRefType, Type)
     DECL_FIELD(DeclRef<AssocTypeDecl>, declRef)
+
     RAW(
     AssocTypeDeclRefType()
     {}
@@ -509,6 +510,7 @@ SYNTAX_CLASS(AssocTypeDeclRefType, Type)
     virtual String ToString() override;
 
     protected:
+        virtual RefPtr<Val> SubstituteImpl(Substitutions* subst, int* ioDiff) override;
         virtual bool EqualsImpl(Type * type) override;
         virtual int GetHashCode() override;
         virtual Type* CreateCanonicalType() override;
diff --git a/tests/compute/assoctype-simple.slang b/tests/compute/assoctype-simple.slang
index 5a2c339a6..e03bb4e54 100644
--- a/tests/compute/assoctype-simple.slang
+++ b/tests/compute/assoctype-simple.slang
@@ -7,21 +7,21 @@ RWStructuredBuffer<float> outputBuffer;
 
 interface ISimple
 {
-    assoctype T;
-    T add(T v0, T v1);
+    associatedtype U;
+    U add(U v0, U v1);
 }
 
 struct Simple : ISimple
 {
-    typedef float T;
-    T add(T v0, float v1)
+    typedef float U;
+    U add(U v0, float v1)
     {
         return v0 + v1;
     }
 };
 
 __generic<T:ISimple>
-T.T test(T simple, T.T v0, T.T v1)
+T.U test(T simple, T.U v0, T.U v1)
 {
     return simple.add(v0, v1);
 }
@@ -29,6 +29,7 @@ T.T test(T simple, T.T v0, T.T v1)
 [numthreads(4, 1, 1)]
 void computeMain(uint3 dispatchThreadID : SV_DispatchThreadID)
 {
-	float outVal = test<Simple>(Simple(), 2.0, 1.0); // == 3.0
+    Simple s;
+	float outVal = test<Simple>(s, 2.0, 1.0); // == 3.0
 	outputBuffer[tid] = outVal;
 }
\ No newline at end of file