From 70bcb39d3fe272164c122979ee36cf2f2ea8f084 Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Tue, 30 Jun 2020 15:44:19 -0600
Subject: [PATCH] double addtrace for 'called from'

---
 src/libexpr/eval.cc  | 13 +++++--------
 src/libutil/error.cc |  2 +-
 2 files changed, 6 insertions(+), 9 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 1cbbb7ade..e89948b94 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -597,11 +597,6 @@ LocalNoInline(void addErrorTrace(Error & e, const char * s, const string & s2))
     e.addTrace(std::nullopt, s, s2);
 }
 
-LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, const ExprLambda & fun))
-{
-    e.addTrace(pos, s, fun.showNamePos());
-}
-
 LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, const string & s2))
 {
     e.addTrace(pos, s, s2);
@@ -1241,9 +1236,11 @@ void EvalState::callFunction(Value & fun, Value & arg, Value & v, const Pos & po
         try {
             lambda.body->eval(*this, env2, v);
         } catch (Error & e) {
-            // TODO something different for 'called from' than usual addTrace?
-            // addErrorTrace(e, pos, "while evaluating %1%, called from %2%:", lambda);
-            addErrorTrace(e, pos, "while evaluating %1%:", lambda);
+            addErrorTrace(e, lambda.pos, "while evaluating %s", 
+              (lambda.name.set() 
+                  ? "'" + (string) lambda.name + "'" 
+                  : "anonymous lambdaction"));
+            addErrorTrace(e, pos, "from call site%s", "");
             throw;
         }
     else
diff --git a/src/libutil/error.cc b/src/libutil/error.cc
index 02eb3f7cb..229c1e6ed 100644
--- a/src/libutil/error.cc
+++ b/src/libutil/error.cc
@@ -330,7 +330,7 @@ std::ostream& showErrorInfo(std::ostream &out, const ErrorInfo &einfo, bool show
     // traces
     if (showTrace && !einfo.traces.empty())
     {
-        const string tracetitle(" show-trace output ");
+        const string tracetitle(" show-trace ");
 
         int fill = errwidth - tracetitle.length();
         int lw = 0;