diff --git a/src/hir_conv/constant_evaluation.cpp b/src/hir_conv/constant_evaluation.cpp
index 6945e4b1..3a6a7736 100644
--- a/src/hir_conv/constant_evaluation.cpp
+++ b/src/hir_conv/constant_evaluation.cpp
@@ -1668,6 +1668,8 @@ namespace HIR {
 
     using namespace ::MIR::eval;
 
+    unsigned int Evaluator::s_next_eval_index = 0;
+
     Evaluator::CsePtr::~CsePtr()
     {
         if( m_inner ) {
@@ -1735,7 +1737,7 @@ namespace HIR {
     void Evaluator::run_statement(::MIR::eval::CallStackEntry& local_state, const ::MIR::Statement& stmt)
     {
         const auto& state = local_state.state;
-        DEBUG("F" << local_state.frame_index << " " << state << stmt);
+        DEBUG("E" << this->eval_index << " F" << local_state.frame_index << " " << state << stmt);
 
         TU_MATCH_HDRA( (stmt), { )
         TU_ARMA(Assign, e) {
@@ -2137,7 +2139,7 @@ namespace HIR {
     unsigned Evaluator::run_terminator(::MIR::eval::CallStackEntry& local_state, const ::MIR::Terminator& terminator)
     {
         const auto& state = local_state.state;
-        DEBUG("F" << local_state.frame_index << " " << state << terminator);
+        DEBUG("E" << this->eval_index << " F" << local_state.frame_index << " " << state << terminator);
 
         TU_MATCH_HDRA( (terminator), {)
         default:
@@ -2426,6 +2428,17 @@ namespace HIR {
 
                 // TODO: Set m_const during parse and check here
 
+                if( !fcn.m_code && !fcn.m_code.m_mir ) {
+                    if( fcn.m_linkage.name == "" ) {
+                    }
+                    else if( fcn.m_linkage.name == "panic_impl" ) {
+                        MIR_TODO(state, "panic in constant evaluation");
+                    }
+                    else {
+                        MIR_TODO(state, "Call extern function `" << fcn.m_linkage.name << "`");
+                    }
+                }
+
                 // Call by invoking evaluate_constant on the function
                 const auto* mir = this->resolve.m_crate.get_or_gen_mir( ::HIR::ItemPath(*fcnp), fcn );
                 MIR_ASSERT(state, mir, "No MIR for function " << fcnp);
diff --git a/src/hir_conv/constant_evaluation.hpp b/src/hir_conv/constant_evaluation.hpp
index 5e96c09f..e0a21054 100644
--- a/src/hir_conv/constant_evaluation.hpp
+++ b/src/hir_conv/constant_evaluation.hpp
@@ -38,15 +38,19 @@ struct Evaluator
     Span    root_span;
     StaticTraitResolve  resolve;
     Newval& nvs;
+    unsigned int eval_index;
     unsigned int num_frames;
     // Note: Pointer is needed to maintain internal reference stability
     ::std::vector<CsePtr>   call_stack;
 
+    static unsigned s_next_eval_index;
+
 public:
     Evaluator(const Span& sp, const ::HIR::Crate& crate, Newval& nvs):
         root_span(sp),
         resolve(crate),
         nvs( nvs )
+        , eval_index(s_next_eval_index++)
         , num_frames(0)
     {
     }