From a693a9fa4b92df0d3283a9de8b1e968378a026d2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Domen=20Ko=C5=BEar?= <domen@dev.si>
Date: Thu, 9 Apr 2020 09:45:15 +0200
Subject: [PATCH] Attach pos to if expression errors

---
 src/libexpr/eval.cc    | 2 +-
 src/libexpr/nixexpr.hh | 3 ++-
 src/libexpr/parser.y   | 2 +-
 3 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index b91a021b4..f963a42ca 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -1256,7 +1256,7 @@ void ExprWith::eval(EvalState & state, Env & env, Value & v)
 
 void ExprIf::eval(EvalState & state, Env & env, Value & v)
 {
-    (state.evalBool(env, cond) ? then : else_)->eval(state, env, v);
+    (state.evalBool(env, cond, pos) ? then : else_)->eval(state, env, v);
 }
 
 
diff --git a/src/libexpr/nixexpr.hh b/src/libexpr/nixexpr.hh
index 8c96de37c..25798cac6 100644
--- a/src/libexpr/nixexpr.hh
+++ b/src/libexpr/nixexpr.hh
@@ -262,8 +262,9 @@ struct ExprWith : Expr
 
 struct ExprIf : Expr
 {
+    Pos pos;
     Expr * cond, * then, * else_;
-    ExprIf(Expr * cond, Expr * then, Expr * else_) : cond(cond), then(then), else_(else_) { };
+    ExprIf(const Pos & pos, Expr * cond, Expr * then, Expr * else_) : pos(pos), cond(cond), then(then), else_(else_) { };
     COMMON_METHODS
 };
 
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index b33ab908b..1993fa6c1 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -335,7 +335,7 @@ expr_function
   ;
 
 expr_if
-  : IF expr THEN expr ELSE expr { $$ = new ExprIf($2, $4, $6); }
+  : IF expr THEN expr ELSE expr { $$ = new ExprIf(CUR_POS, $2, $4, $6); }
   | expr_op
   ;