Report chain of macro-expansions in errors.

* eval.c (origin_hash): New global variable.
(lookup_origin): New function.
(expand_macro): Enter original form into origin hash, keyed by
new form.
(eval_init): gc-protect and initialize origin_hash.

* eval.h (lookup_origin): Declared.

* parser.c (repl): Report chain of expansions from
last_form_evaled.

* unwind.c (uw_throw): Likewise.

1 files changed, 12 insertions, 3 deletions

diff --git a/parser.c b/parser.c
index 258c77b8..c3c581e4 100644
--- a/parser.c
+++ b/parser.c
@@ -753,6 +753,7 @@ val repl(val bindings, val in_stream, val out_stream)
       } else if (uw_exception_subtype_p(exsym, error_s)) {
         val info = source_loc_str(last_form_evaled, nil);
         val ex_info = source_loc_str(last_form_expanded, nil);
+        val origin = last_form_evaled;
 
         if (cdr(exvals))
           format(out_stream, lit("** ~!~a ~!~s\n"),
@@ -760,13 +761,21 @@ val repl(val bindings, val in_stream, val out_stream)
         else
           format(out_stream, lit("** ~!~a\n"), car(exvals), nao);
 
-        if (info && exsym != eval_error_s)
-          format(std_error, lit("** possibly triggered at ~a by form ~!~s\n"),
+        if (info && exsym != eval_error_s) {
+          format(out_stream, lit("** possibly triggered at ~a by form ~!~s\n"),
                  info, last_form_evaled, nao);
 
+          while ((origin = lookup_origin(origin))) {
+            val oinfo = source_loc_str(origin, lit("(n/a)"));
+            format(out_stream, lit("** which is an expansion at ~a of ~!~s\n"),
+                   oinfo, origin, nao);
+          }
+        }
+
         if (ex_info)
-          format(std_error, lit("** during expansion at ~a of form ~!~s\n"),
+          format(out_stream, lit("** during expansion at ~a of form ~!~s\n"),
                  ex_info, last_form_expanded, nao);
+
       } else {
         format(out_stream, lit("** ~!~s exception, args: ~!~s\n"),
                exsym, exvals, nao);