Fixes for indexing into lists with optional item types

1 files changed, 4 insertions, 2 deletions

diff --git a/src/typecheck.c b/src/typecheck.c
index 3c820fa9..eff894be 100644
--- a/src/typecheck.c
+++ b/src/typecheck.c
@@ -934,8 +934,10 @@ type_t *get_type(env_t *env, ast_t *ast) {
         if (value_t->tag == ListType) {
             if (!indexing->index) return indexed_t;
             type_t *index_t = get_type(env, indexing->index);
-            if (index_t->tag == IntType || index_t->tag == BigIntType || index_t->tag == ByteType)
-                return Type(OptionalType, Match(value_t, ListType)->item_type);
+            if (index_t->tag == IntType || index_t->tag == BigIntType || index_t->tag == ByteType) {
+                type_t *item_type = Match(value_t, ListType)->item_type;
+                return item_type->tag == OptionalType ? item_type : Type(OptionalType, item_type);
+            }
             code_err(indexing->index, "I only know how to index lists using integers, not ", type_to_text(index_t));
         } else if (value_t->tag == TableType) {
             DeclareMatch(table_type, value_t, TableType);