bug fixes to get falcor example shader code to compile.

1. prevent cyclic lookups when an interface inherits transitively from itself.
2. in `createGlobalGenericParamSubstitution`, create a default substitution for the base type declref before using it to lookup the witness table.

1 files changed, 3 insertions, 1 deletions

diff --git a/source/slang/ir.cpp b/source/slang/ir.cpp
index 45ad71b67..f65af2ba4 100644
--- a/source/slang/ir.cpp
+++ b/source/slang/ir.cpp
@@ -4889,8 +4889,10 @@ namespace Slang
                         {
                             if (auto subDeclRefType = subtypeWitness->sub.As<DeclRefType>())
                             {
-                                auto genericWitnessTableName = getMangledNameForConformanceWitness(DeclRef<Decl>(subDeclRefType->declRef.getDecl(), nullptr), subtypeWitness->sup);
+                                auto defaultSubst = createDefaultSubstitutions(entryPointRequest->compileRequest->mSession, subDeclRefType->declRef.getDecl());
+                                auto genericWitnessTableName = getMangledNameForConformanceWitness(DeclRef<Decl>(subDeclRefType->declRef.getDecl(), defaultSubst), subtypeWitness->sup);
                                 table = findWitnessTableByName(genericWitnessTableName);
+                                SLANG_ASSERT(table);
                                 WitnessTableSpecializationWorkItem workItem;
                                 workItem.srcTable = (IRWitnessTable*)table;
                                 workItem.dstTable = context->builder->createWitnessTable();