rescue NameError from class variable access like `@@foo ||= 42`; fix #3138

mrbgems/mruby-compiler/core/codegen.c

@@ -1221,13 +1221,12 @@ codegen(codegen_scope *s, node *tree, int val)
       int onerr, noexc, exend, pos1, pos2, tmp;
       struct loopinfo *lp;
 
+      if (tree->car == NULL) return;
       onerr = genop(s, MKOP_Bx(OP_ONERR, 0));
       lp = loop_push(s, LOOP_BEGIN);
       lp->pc1 = onerr;
-      if (tree->car) {
-        codegen(s, tree->car, val);
-        if (val) pop();
-      }
+      codegen(s, tree->car, VAL);
+      pop();
       lp->type = LOOP_RESCUE;
       noexc = genop(s, MKOP_Bx(OP_JMP, 0));
       dispatch(s, onerr);
@@ -1709,7 +1708,7 @@ codegen(codegen_scope *s, node *tree, int val)
         pop();
         gen_assignment(s, tree->car, cursp(), val);
         dispatch(s, pos);
-        break;
+        return;
       }
       codegen(s, tree->cdr->cdr->car, VAL);
       push(); pop();

mrbgems/mruby-compiler/core/parse.y

@@ -707,7 +707,13 @@ new_masgn(parser_state *p, node *a, node *b)
 static node*
 new_op_asgn(parser_state *p, node *a, mrb_sym op, node *b)
 {
+  if (op == mrb_intern_lit(p->mrb, "||") && (intptr_t)a->car == NODE_CVAR) {
+    return new_rescue(p, a, list1(list3(list1(new_cvar(p, mrb_intern_lit(p->mrb, "NameError"))),
+                                        0, new_asgn(p, a, b))), NULL);
+  }
+  else {
     return list4((node*)NODE_OP_ASGN, a, nsym(op), b);
+  }
 }
 
 /* (:int . i) */