specialize witness tables when needed when specializing `lookup_witness_table` instruction. (#376)

3 files changed, 21 insertions, 1 deletions

diff --git a/source/slang/ir.cpp b/source/slang/ir.cpp
index 7318bff4c..1d3c91979 100644
--- a/source/slang/ir.cpp
+++ b/source/slang/ir.cpp
@@ -4862,6 +4862,20 @@ namespace Slang
                             auto interfaceDeclRef = ((IRDeclRef*)lookupInst->interfaceType.usedValue)->declRef;
                             auto mangledName = getMangledNameForConformanceWitness(srcDeclRef, interfaceDeclRef);
                             witnessTables.TryGetValue(mangledName, witnessTable);
+                            
+                            if (!witnessTable)
+                            {
+                                // try specialize the witness table
+                                auto genDeclRef = srcDeclRef;
+                                genDeclRef.substitutions = createDefaultSubstitutions(module->session, genDeclRef.decl);
+                                auto genName = getMangledNameForConformanceWitness(genDeclRef, interfaceDeclRef);
+                                IRWitnessTable* genTable = nullptr;
+                                if (witnessTables.TryGetValue(genName, genTable))
+                                {
+                                    witnessTable = specializeWitnessTable(sharedContext, genTable, srcDeclRef, nullptr);
+                                    witnessTables.AddIfNotExists(witnessTable->mangledName, witnessTable);
+                                }
+                            }
                             if (witnessTable)
                             {
                                 lookupInst->replaceUsesWith(witnessTable);
diff --git a/source/slang/syntax.cpp b/source/slang/syntax.cpp
index ab4a5f94c..3bccf51ce 100644
--- a/source/slang/syntax.cpp
+++ b/source/slang/syntax.cpp
@@ -856,7 +856,12 @@ void Type::accept(IValVisitor* visitor, void* extra)
 
     Type* ErrorType::CreateCanonicalType()
     {
-        return  this;
+        return this;
+    }
+
+    RefPtr<Val> ErrorType::SubstituteImpl(SubstitutionSet /*subst*/, int* /*ioDiff*/)
+    {
+        return this;
     }
 
     int ErrorType::GetHashCode()
diff --git a/source/slang/type-defs.h b/source/slang/type-defs.h
index c4ec09f1d..db9630c0e 100644
--- a/source/slang/type-defs.h
+++ b/source/slang/type-defs.h
@@ -36,6 +36,7 @@ public:
 
 protected:
     virtual bool EqualsImpl(Type * type) override;
+    virtual RefPtr<Val> SubstituteImpl(SubstitutionSet subst, int* ioDiff) override;
     virtual Type* CreateCanonicalType() override;
     virtual int GetHashCode() override;
 )