txr: gather: report list of missing required vars.

* match.c (v_gather): Identify all required variables that are
missing, and list them all in the diagnostic.

1 files changed, 8 insertions, 2 deletions

diff --git a/match.c b/match.c
index d95331e3..2fa61026 100644
--- a/match.c
+++ b/match.c
@@ -3134,19 +3134,25 @@ static val v_gather(match_files_ctx *c)
 
   if (have_vars) {
     val iter;
+    val missing = nil;
 
     for (iter = vars; iter != nil; iter = cdr(iter)) {
       cons_bind (var, dfl_val, car(iter));
       if (!tx_lookup_var(var, c->bindings)) {
         if (dfl_val == noval_s) {
-          debuglf(specline, lit("gather failed to match some required vars"), nao);
-          return nil;
+          push(var, &missing);
         } else {
           c->bindings = acons(var, dfl_val, c->bindings);
         }
       }
     }
 
+    if (missing) {
+      debuglf(specline, lit("gather failed to match required vars ~s"),
+              missing, nao);
+      return nil;
+    }
+
     debuglf(specline, lit("gather matched all required vars"), nao);
     return next_spec_k;
   }