trace when the `foo` part of `foo.bar.baz` errors

Turns errors like:

let
  errpkg = throw "invalid foobar";
in errpkg.meta

error:
       … while calling the 'throw' builtin
         at «string»:2:12:
            1| let
            2|   errpkg = throw "invalid foobar";
             |            ^
            3| in errpkg.meta

       error: invalid foobar

into errors like:

let
  errpkg = throw "invalid foobar";
in errpkg.meta

error:
       … while evaluating 'errpkg' to select 'meta' on it
         at «string»:3:4:
            2|   errpkg = throw "invalid foobar";
            3| in errpkg.meta
             |    ^

       … while calling the 'throw' builtin
         at «string»:2:12:
            1| let
            2|   errpkg = throw "invalid foobar";
             |            ^
            3| in errpkg.meta

       error: invalid foobar

For the low price of one try/catch, you too can have the incorrect line
of code actually show up in the trace!

Change-Id: If8d6200ec1567706669d405c34adcd7e2d2cd29d

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/functional/lang/eval-fail-recursion.err.exp b/tests/functional/lang/eval-fail-recursion.err.exp
index 19380dc65..f0057b2d5 100644
--- a/tests/functional/lang/eval-fail-recursion.err.exp
+++ b/tests/functional/lang/eval-fail-recursion.err.exp
@@ -1,4 +1,10 @@
 error:
+       … while evaluating 'a' to select 'foo' on it
+         at /pwd/lang/eval-fail-recursion.nix:1:21:
+            1| let a = {} // a; in a.foo
+             |                     ^
+            2|
+
        … in the right operand of the update (//) operator
          at /pwd/lang/eval-fail-recursion.nix:1:12:
             1| let a = {} // a; in a.foo