From 7c3138844ca9ab92e2f231a7d17d7aee420ae76e Mon Sep 17 00:00:00 2001
From: Ben Burdette <bburdette@gmail.com>
Date: Mon, 11 May 2020 17:34:57 -0600
Subject: [PATCH] more pos reporting

---
 src/libexpr/nixexpr.cc | 8 ++++++--
 src/libexpr/parser.y   | 8 +++++---
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/libexpr/nixexpr.cc b/src/libexpr/nixexpr.cc
index a9955f6df..91a508305 100644
--- a/src/libexpr/nixexpr.cc
+++ b/src/libexpr/nixexpr.cc
@@ -267,8 +267,12 @@ 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 UndefinedVarError("undefined variable '%1%' at %2%", name, pos);
-
+    if (withLevel == -1) 
+        throw UndefinedVarError(
+            ErrorInfo {
+                .hint = hintfmt("undefined variable '%1%'", name),
+                .nixCode = NixCode { .errPos = pos }
+            });
     fromWith = true;
     this->level = withLevel;
 }
diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 6d50d74ba..3ae7bbafd 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -31,7 +31,7 @@ namespace nix {
         Expr * result;
         Path basePath;
         Symbol path;
-        string error;
+        ErrorInfo error;
         Symbol sLetBody;
         ParseData(EvalState & state)
             : state(state)
@@ -261,8 +261,10 @@ static inline Pos makeCurPos(const YYLTYPE & loc, ParseData * data)
 
 void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * error)
 {
-    data->error = (format("%1%, at %2%")
-        % error % makeCurPos(*loc, data)).str();
+    data->error = ErrorInfo { 
+        .hint = hintfmt(error),
+        .nixCode = NixCode { .errPos = makeCurPos(*loc, data) }
+        };
 }