Explicitly r_clone() when we zap srcref

Author: DavisVaughan

src/internal/attr.c

@@ -213,11 +213,19 @@ r_obj* fn_zap_srcref(r_obj* x) {
 
   r_obj* out = KEEP(r_new_function(formals, body, env));
 
-  // Copy over attributes, but zap any `srcref` attribute.
-  // `r_attrib_poke()` will clone the attribute pairlist as required
-  // to avoid mutating the attributes of `x`.
-  r_poke_attrib(out, r_attrib(x));
-  r_attrib_poke(out, r_syms.srcref, r_null);
+  // Copy over attributes, but zap any `srcref` attribute
+  if (r_attrib_get(x, r_syms.srcref) == r_null) {
+    // Nothing to zap
+    r_obj* attrib = r_attrib(x);
+    r_poke_attrib(out, attrib);
+  } else {
+    // Clone so we can zap `srcref`
+    r_obj* attrib = r_attrib(x);
+    attrib = KEEP(r_clone(attrib));
+    r_poke_attrib(out, attrib);
+    FREE(1);
+    r_attrib_poke(out, r_syms.srcref, r_null);
+  }
 
   FREE(2);
   return out;