1 files changed, 29 insertions, 17 deletions
diff --git a/source/slang/slang-syntax.cpp b/source/slang/slang-syntax.cpp
index 9a7200e9d..5b4b61849 100644
--- a/source/slang/slang-syntax.cpp
+++ b/source/slang/slang-syntax.cpp
@@ -838,28 +838,40 @@ Index getFilterCountImpl(const ReflectClassInfo& clsInfo, MemberFilterStyle filt
                 // Otherwise, check if we are trying to apply
                 // a this-type substitution to the given interface
                 //
-                for(auto s = substsToApply; s; s = s->outer)
+                // Note: We want to skip the ThisTypeSubstitution that specializes
+                // declToSpecialize itself (when declToSpecialize is an interface
+                // decl and the subst specializes it), and only pull the
+                // ThisTypeSubstitution when the decl is referencing a child of
+                // the interface decl being specialized. This is because
+                // by default an interface declref type is a "free" existential
+                // type that shouldn't be specialized by someone else, unless
+                // there is an "implicit" ThisType reference preceeding a child
+                // reference.
+                if (declToSpecialize != ancestorInterfaceDecl)
                 {
-                    auto appThisTypeSubst = as<ThisTypeSubstitution>(s);
-                    if(!appThisTypeSubst)
-                        continue;
+                    for (auto s = substsToApply; s; s = s->outer)
+                    {
+                        auto appThisTypeSubst = as<ThisTypeSubstitution>(s);
+                        if (!appThisTypeSubst)
+                            continue;
 
-                    if(appThisTypeSubst->interfaceDecl != ancestorInterfaceDecl)
-                        continue;
+                        if (appThisTypeSubst->interfaceDecl != ancestorInterfaceDecl)
+                            continue;
 
-                    int diff = 0;
-                    auto restSubst = specializeSubstitutions(
-                        astBuilder,
-                        ancestorInterfaceDecl->parentDecl,
-                        substsToSpecialize,
-                        substsToApply,
-                        &diff);
+                        int diff = 0;
+                        auto restSubst = specializeSubstitutions(
+                            astBuilder,
+                            ancestorInterfaceDecl->parentDecl,
+                            substsToSpecialize,
+                            substsToApply,
+                            &diff);
 
-                    ThisTypeSubstitution* firstSubst = astBuilder->getOrCreateThisTypeSubstitution(
-                        ancestorInterfaceDecl, appThisTypeSubst->witness, restSubst);
+                        ThisTypeSubstitution* firstSubst = astBuilder->getOrCreateThisTypeSubstitution(
+                            ancestorInterfaceDecl, appThisTypeSubst->witness, restSubst);
 
-                    (*ioDiff)++;
-                    return firstSubst;
+                        (*ioDiff)++;
+                        return firstSubst;
+                    }
                 }
             }
         }