From b1e3b1a4ac8c276f503713f6002c3b42efef2ae8 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <eelco.dolstra@logicblox.com>
Date: Tue, 8 Oct 2013 14:45:36 +0200
Subject: [PATCH] Treat undefined variable errors consistently

Previously, a undefined variable inside a "with" caused an EvalError
(which can be caught), while outside, it caused a ParseError (which
cannot be caught).  Now both cause an UndefinedVarError (which cannot
be caught).
---
 src/libexpr/eval.cc    | 7 ++++++-
 src/libexpr/nixexpr.cc | 2 +-
 src/libexpr/nixexpr.hh | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 3d77b94e77..b54f32faf5 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -258,6 +258,11 @@ LocalNoInlineNoReturn(void throwAssertionError(const char * s, const Pos & pos))
     throw AssertionError(format(s) % pos);
 }
 
+LocalNoInlineNoReturn(void throwUndefinedVarError(const char * s, const string & s1, const Pos & pos))
+{
+    throw UndefinedVarError(format(s) % s1 % pos);
+}
+
 LocalNoInline(void addErrorPrefix(Error & e, const char * s, const string & s2))
 {
     e.addPrefix(format(s) % s2);
@@ -315,7 +320,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
             return j->value;
         }
         if (!env->prevWith)
-            throw EvalError(format("undefined variable `%1%' at %2%") % var.name % var.pos);
+            throwUndefinedVarError("undefined variable `%1%' at %2%", var.name, var.pos);
         for (unsigned int l = env->prevWith; l; --l, env = env->up) ;
     }
 }
diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index 03a14695f1..28049bb0d6 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -198,7 +198,7 @@ void ExprVar::bindVars(const StaticEnv & env)
     /* Otherwise, the variable must be obtained from the nearest
        enclosing `with'.  If there is no `with', then we can issue an
        "undefined variable" error now. */
-    if (withLevel == -1) throw ParseError(format("undefined variable `%1%' at %2%") % name % pos);
+    if (withLevel == -1) throw UndefinedVarError(format("undefined variable `%1%' at %2%") % name % pos);
 
     fromWith = true;
     this->level = withLevel;
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index e555a5dff0..f5cc69801e 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -16,6 +16,7 @@ MakeError(ThrownError, AssertionError)
 MakeError(Abort, EvalError)
 MakeError(TypeError, EvalError)
 MakeError(ImportError, EvalError) // error building an imported derivation
+MakeError(UndefinedVarError, Error)
 
 
 /* Position objects. */