Improve codegen for optional struct types

stdlib/types.h

@@ -80,4 +80,14 @@ Text_t Type$as_text(const void *typeinfo, bool colorize, const TypeInfo_t *type)
                              .tag=TypeInfoInfo, .TypeInfoInfo.type_str=typestr, \
                              .metamethods={.serialize=cannot_serialize, .deserialize=cannot_deserialize, .as_text=Type$as_text}})
 
+#define DEFINE_OPTIONAL_TYPE(t, unpadded_size, name) \
+    typedef struct { \
+        union { \
+            t value; \
+            struct { \
+                char _padding[unpadded_size]; \
+                Bool_t is_none:1; \
+            }; \
+        }; \
+    } name
 // vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0

structs.c

@@ -61,15 +61,8 @@ CORD compile_struct_header(env_t *env, ast_t *ast)
         "struct ", full_name, "$$struct {\n",
         fields,
         "};\n",
-        "typedef struct {\n",
-        "union {\n",
-        full_name, "$$type value;\n"
-        "struct {\n"
-        "char _padding[", heap_strf("%zu", unpadded_struct_size(t)), "];\n",
-        "Bool_t is_none:1;\n"
-        "};\n"
-        "};\n"
-        "} ", namespace_prefix(env, env->namespace), "$Optional", def->name, "$$type;\n"
+        "DEFINE_OPTIONAL_TYPE(", full_name, "$$type, ", heap_strf("%zu", unpadded_struct_size(t)),
+        ", ", namespace_prefix(env, env->namespace), "$Optional", def->name, "$$type);\n"
         // Constructor macro:
         "#define ", namespace_prefix(env, env->namespace), def->name,
             "(...) ((", namespace_prefix(env, env->namespace), def->name, "$$type){__VA_ARGS__})\n"