libexpr/parser: Fix small error position mistake

In one of the cases it pointed to the first instead of the second
occurence, which is a bit confusing

Change-Id: Ie508d1f84feb434708804d45aa8a9c8b1e3c5f69

lix/libexpr/parser/state.hh

@@ -177,7 +177,7 @@ inline void State::addAttr(ExprAttrs * attrs, AttrPath && attrPath, std::unique_
                 for (auto & ad : ae->attrs) {
                     auto j2 = jAttrs->attrs.find(ad.first);
                     if (j2 != jAttrs->attrs.end()) // Attr already defined in iAttrs, error.
-                        return dupAttr(ad.first, j2->second.pos, ad.second.pos);
+                        return dupAttr(ad.first, ad.second.pos, j2->second.pos);
                     if (ad.second.kind == ExprAttrs::AttrDef::Kind::InheritedFrom) {
                         auto & sel = dynamic_cast<ExprSelect &>(*ad.second.e);
                         auto & from = dynamic_cast<ExprInheritFrom &>(*sel.e);

tests/functional2/lang/parser-merge-attrs/parse-fail-err1.err.exp

@@ -1,6 +1,6 @@
-error: attribute 'z' already defined at /pwd/in.nix:3:16
-       at /pwd/in.nix:2:3:
-            1| {
+error: attribute 'z' already defined at /pwd/in.nix:2:3
+       at /pwd/in.nix:3:16:
             2|   x.z = 3;
-             |   ^
             3|   x = { y = 3; z = 3; };
+             |                ^
+            4| }

tests/functional2/lang/parser-merge-attrs/parse-fail-err2.err.exp

@@ -1,6 +1,6 @@
-error: attribute 'y' already defined at /pwd/in.nix:3:9
-       at /pwd/in.nix:2:3:
-            1| {
+error: attribute 'y' already defined at /pwd/in.nix:2:3
+       at /pwd/in.nix:3:9:
             2|   x.y.y = 3;
-             |   ^
             3|   x = { y.y= 3; z = 3; };
+             |         ^
+            4| }