Diagnostic for no type conformance + bug fix. (#1985)

* Diagnostic for no type conformance + bug fix.

* Fixes.

* Fix.

* Include heterogeneous example only with --enable-experimental-projects premake flag

Co-authored-by: Yong He <yhe@nvidia.com>
Co-authored-by: jsmall-nvidia <jsmall@nvidia.com>

4 files changed, 74 insertions, 30 deletions

diff --git a/source/slang/slang-diagnostic-defs.h b/source/slang/slang-diagnostic-defs.h
index 2add5792b..897aa9f6f 100644
--- a/source/slang/slang-diagnostic-defs.h
+++ b/source/slang/slang-diagnostic-defs.h
@@ -545,6 +545,8 @@ DIAGNOSTIC(51090, Error, cannotGenerateCodeForExternComponentType, "cannot gener
 DIAGNOSTIC(51091, Error, typeCannotBePlacedInATexture, "type '$0' cannot be placed in a texture.")
 DIAGNOSTIC(51092, Error, stageDoesntHaveInputWorld, "'$0' doesn't appear to have any input world")
 
+DIAGNOSTIC(50100, Error, noTypeConformancesFoundForInterface, "No type conformances are found for interface '$0'. Code generation for current target requires at least one implementation type present in the linkage.")
+
 DIAGNOSTIC(52000, Error, multiLevelBreakUnsupported, "control flow appears to require multi-level `break`, which Slang does not yet support")
 
 DIAGNOSTIC(52001, Warning, dxilNotFound, "dxil shared library not found, so 'dxc' output cannot be signed! Shader code will not be runnable in non-development environments.")
diff --git a/source/slang/slang-ir-generics-lowering-context.h b/source/slang/slang-ir-generics-lowering-context.h
index 78dd068b8..c875566b0 100644
--- a/source/slang/slang-ir-generics-lowering-context.h
+++ b/source/slang/slang-ir-generics-lowering-context.h
@@ -103,4 +103,28 @@ namespace Slang
     // Ptr(RTTIType).
     bool isTypeValue(IRInst* typeInst);
 
+    template<typename TFunc>
+    void workOnModule(SharedGenericsLoweringContext* sharedContext, const TFunc& func)
+    {
+        SharedIRBuilder* sharedBuilder = &sharedContext->sharedBuilderStorage;
+        sharedBuilder->module = sharedContext->module;
+        sharedBuilder->session = sharedContext->module->session;
+
+        sharedContext->addToWorkList(sharedContext->module->getModuleInst());
+
+        while (sharedContext->workList.getCount() != 0)
+        {
+            IRInst* inst = sharedContext->workList.getLast();
+
+            sharedContext->workList.removeLast();
+            sharedContext->workListSet.Remove(inst);
+
+            func(inst);
+
+            for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
+            {
+                sharedContext->addToWorkList(child);
+            }
+        }
+    }
 }
diff --git a/source/slang/slang-ir-lower-generics.cpp b/source/slang/slang-ir-lower-generics.cpp
index 241827561..95046787a 100644
--- a/source/slang/slang-ir-lower-generics.cpp
+++ b/source/slang/slang-ir-lower-generics.cpp
@@ -117,6 +117,36 @@ namespace Slang
         cleanUpInterfaceTypes(sharedContext);
     }
 
+    void checkTypeConformanceExists(SharedGenericsLoweringContext* context)
+    {
+        HashSet<IRInst*> implementedInterfaces;
+
+        // Add all interface type that are implemented by at least one type to a set.
+        for (auto inst : context->module->getGlobalInsts())
+        {
+            if (inst->getOp() == kIROp_WitnessTable)
+            {
+                auto interfaceType = cast<IRWitnessTableType>(inst->getDataType())->getConformanceType();
+                implementedInterfaces.Add(interfaceType);
+            }
+        }
+        // Check if an interface type has any implementations.
+        workOnModule(context, [&](IRInst* inst)
+            {
+                if (auto lookupWitnessMethod = as<IRLookupWitnessMethod>(inst))
+                {
+                    auto witnessTableType = lookupWitnessMethod->getWitnessTable()->getDataType();
+                    auto interfaceType = cast<IRWitnessTableType>(witnessTableType)->getConformanceType();
+                    if (!implementedInterfaces.Contains(interfaceType))
+                    {
+                        context->sink->diagnose(interfaceType->sourceLoc, Diagnostics::noTypeConformancesFoundForInterface, interfaceType);
+                        // Add to set to prevent duplicate diagnostic messages.
+                        implementedInterfaces.Add(interfaceType);
+                    }
+                }
+            });
+    }
+
     void lowerGenerics(
         TargetRequest*          targetReq,
         IRModule*               module,
@@ -127,6 +157,8 @@ namespace Slang
         sharedContext.module = module;
         sharedContext.sink = sink;
 
+        checkTypeConformanceExists(&sharedContext);
+
         // Replace all `makeExistential` insts with `makeExistentialWithRTTI`
         // before making any other changes. This is necessary because a parameter of
         // generic type will be lowered into `AnyValueType`, and after that we can no longer
diff --git a/source/slang/slang-ir-specialize-dynamic-associatedtype-lookup.cpp b/source/slang/slang-ir-specialize-dynamic-associatedtype-lookup.cpp
index 059531107..e2d321ed4 100644
--- a/source/slang/slang-ir-specialize-dynamic-associatedtype-lookup.cpp
+++ b/source/slang/slang-ir-specialize-dynamic-associatedtype-lookup.cpp
@@ -157,44 +157,30 @@ struct AssociatedTypeLookupSpecializationContext
     {
         if (inst->getRTTIOperand()->getDataType()->getOp() == kIROp_WitnessTableIDType)
         {
+            // If the operand is a witness table id, just return the operand.
             inst->replaceUsesWith(inst->getRTTIOperand());
             inst->removeAndDeallocate();
         }
-    }
-
-    template<typename TFunc>
-    void workOnModule(const TFunc& func)
-    {
-        SharedIRBuilder* sharedBuilder = &sharedContext->sharedBuilderStorage;
-        sharedBuilder->module = sharedContext->module;
-        sharedBuilder->session = sharedContext->module->session;
-
-        sharedContext->addToWorkList(sharedContext->module->getModuleInst());
-
-        while (sharedContext->workList.getCount() != 0)
+        else if (inst->getRTTIOperand()->getDataType()->getOp() == kIROp_VectorType)
         {
-            IRInst* inst = sharedContext->workList.getLast();
-
-            sharedContext->workList.removeLast();
-            sharedContext->workListSet.Remove(inst);
-
-            func(inst);
-            if (inst->getOp() == kIROp_lookup_interface_method)
-            {
-                processLookupInterfaceMethodInst(cast<IRLookupWitnessMethod>(inst));
-            }
-
-            for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
-            {
-                sharedContext->addToWorkList(child);
-            }
+            // If the operand is a witness table, it is already replaced with a uint2
+            // at this point, where the first element in the uint2 is the id of the
+            // witneess table.
+            auto vectorType = inst->getRTTIOperand()->getDataType();
+            IRBuilder builder;
+            builder.sharedBuilder = &sharedContext->sharedBuilderStorage;
+            builder.setInsertBefore(inst);
+            UInt index = 0;
+            auto id = builder.emitSwizzle(as<IRVectorType>(vectorType)->getElementType(), inst->getRTTIOperand(), 1, &index);
+            inst->replaceUsesWith(id);
+            inst->removeAndDeallocate();
         }
     }
 
     void processModule()
     {
         // Replace all `lookup_interface_method():IRWitnessTable` with call to specialized functions.
-        workOnModule([this](IRInst* inst)
+        workOnModule(sharedContext, [this](IRInst* inst)
         {
             if (inst->getOp() == kIROp_lookup_interface_method)
             {
@@ -203,7 +189,7 @@ struct AssociatedTypeLookupSpecializationContext
         });
 
         // Replace all direct uses of IRWitnessTables with its sequential ID.
-        workOnModule([this](IRInst* inst)
+        workOnModule(sharedContext, [this](IRInst* inst)
         {
             if (inst->getOp() == kIROp_WitnessTable)
             {
@@ -252,7 +238,7 @@ struct AssociatedTypeLookupSpecializationContext
         }
 
         // `GetSequentialID(WitnessTableIDOperand)` becomes just `WitnessTableIDOperand`.
-        workOnModule([this](IRInst* inst)
+        workOnModule(sharedContext, [this](IRInst* inst)
         {
             if (inst->getOp() == kIROp_GetSequentialID)
             {