Improved error reporting, particularly for macro expansion.

* eval.c (last_form_expanded): New variable.
(do_expand): New static function; contains previous expand
function.
(expand): Becomes a wrapper for do_expand, with re-entry
counting.
(eval_init): GC-protect last_form_expanded.

* eval.h (last_form_expanded): Declared.

* parser.l (regex_parse, lisp_parse): Just use a simple word for
the name of the regex or string parse location, not the entire
expression itself.

* unwind.c (uw_throw): Check whether expansion was going on
when the unhandled exception was thrown and print additional
information.

5 files changed, 58 insertions, 10 deletions

diff --git a/ChangeLog b/ChangeLog
index e4351d31..ab51ffc5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,24 @@
+2015-02-21  Kaz Kylheku  <kaz@kylheku.com>
+
+	Improved error reporting, particularly for macro expansion.
+
+	* eval.c (last_form_expanded): New variable.
+	(do_expand): New static function; contains previous expand
+	function.
+	(expand): Becomes a wrapper for do_expand, with re-entry
+	counting.
+	(eval_init): GC-protect last_form_expanded.
+
+	* eval.h (last_form_expanded): Declared.
+
+	* parser.l (regex_parse, lisp_parse): Just use a simple word for
+	the name of the regex or string parse location, not the entire
+	expression itself.
+
+	* unwind.c (uw_throw): Check whether expansion was going on
+	when the unhandled exception was thrown and print additional
+	information.
+
 2015-02-20  Kaz Kylheku  <kaz@kylheku.com>
 
 	* regex.c (match_regex_right): Bugfix: zero length matches
diff --git a/eval.c b/eval.c
index 5721aa85..dce7e949 100644
--- a/eval.c
+++ b/eval.c
@@ -87,7 +87,7 @@ val opip_s, oand_s, chain_s, chand_s;
 
 val special_s, whole_k, symacro_k, fun_k;
 
-val last_form_evaled;
+val last_form_evaled, last_form_expanded;
 
 val call_f;
 
@@ -2806,7 +2806,7 @@ static val expand_save_specials(val form, val specials)
   return rlcp(cons(with_saved_vars_s, cons(form, nil)), form);
 }
 
-val expand(val form, val menv)
+static val do_expand(val form, val menv)
 {
   val macro = nil;
 
@@ -3023,6 +3023,28 @@ tail:
   }
 }
 
+val expand(val form, val menv)
+{
+  val ret = nil;
+  static int reentry_count;
+
+  uw_simple_catch_begin;
+
+  reentry_count++;
+
+  last_form_expanded = form;
+  ret = do_expand(form, menv);
+
+  uw_unwind {
+    if (--reentry_count == 0)
+      last_form_expanded = nil;
+  }
+
+  uw_catch_end;
+
+  return ret;
+}
+
 static val macro_form_p(val form, val menv)
 {
   menv = default_bool_arg(menv);
@@ -3675,7 +3697,8 @@ static val merge_wrap(val seq1, val seq2, val lessfun, val keyfun)
 void eval_init(void)
 {
   protect(&top_vb, &top_fb, &top_mb, &top_smb, &special, &dyn_env,
-          &op_table, &last_form_evaled, &call_f, convert(val *, 0));
+          &op_table, &last_form_evaled, &last_form_expanded,
+          &call_f, convert(val *, 0));
   top_fb = make_hash(t, nil, nil);
   top_vb = make_hash(t, nil, nil);
   top_mb = make_hash(t, nil, nil);
diff --git a/eval.h b/eval.h
index b30e6615..f027de1a 100644
--- a/eval.h
+++ b/eval.h
@@ -27,7 +27,7 @@
 extern val dwim_s, lambda_s, vector_lit_s, vector_list_s;
 extern val hash_lit_s, hash_construct_s;
 extern val eval_error_s;
-extern val last_form_evaled;
+extern val last_form_evaled, last_form_expanded;
 
 val make_env(val fbindings, val vbindings, val up_env);
 val env_fbind(val env, val sym, val fun);
diff --git a/parser.l b/parser.l
index 6d47078b..0c3ba64e 100644
--- a/parser.l
+++ b/parser.l
@@ -985,9 +985,7 @@ val regex_parse(val string, val error_stream)
 
   {
     int gc = gc_state(0);
-    val name = if3(std_error != std_null,
-                   format(nil, lit("regex --> ~a"), string, nao),
-                   lit(""));
+    val name = if3(std_error != std_null, lit("regex"), lit(""));
     parse(stream, name, &parser);
     gc_state(gc);
   }
@@ -1004,7 +1002,7 @@ val lisp_parse(val source_in, val error_stream, val error_return_val)
                          or2(source, std_input));
   val secret_token_stream = make_string_byte_input_stream(lit("@\x01" "E"));
   val name = if3(stringp(source),
-                 format(nil, lit("expr --> ~a"), source, nao),
+                 lit("string"),
                  stream_get_prop(input_stream, name_k));
   val stream = make_catenated_stream(list(secret_token_stream, input_stream, nao));
   val saved_dyn = dyn_env;
diff --git a/unwind.c b/unwind.c
index 5d358e42..51c2dae0 100644
--- a/unwind.c
+++ b/unwind.c
@@ -315,12 +315,18 @@ val uw_throw(val sym, val args)
       val msg_or_args = if3(is_msg, car(args), args);
       val info = if2(source_loc(last_form_evaled),
                      source_loc_str(last_form_evaled));
+      val ex_info = if2(source_loc(last_form_expanded),
+                        source_loc_str(last_form_expanded));
       format(std_error, lit("~a: unhandled exception of type ~a:\n"),
              prog_string, sym, nao);
 
       if (info && sym != eval_error_s)
-        format(std_error, lit("~a: possibly triggered by ~a\n"),
-               prog_string, info, nao);
+        format(std_error, lit("~a: possibly triggered at ~a by form ~s\n"),
+               prog_string, info, last_form_evaled, nao);
+
+      if (ex_info)
+        format(std_error, lit("~a: during expansion at ~a of form ~s\n"),
+               prog_string, ex_info, last_form_expanded, nao);
 
       format(std_error,
              if3(is_msg,