3 files changed, 36 insertions, 11 deletions
diff --git a/src/nvim/api/private/defs.h b/src/nvim/api/private/defs.h
index 60bf38265f..2144c80d6a 100644
--- a/src/nvim/api/private/defs.h
+++ b/src/nvim/api/private/defs.h
@@ -5,6 +5,8 @@
 #include <stdbool.h>
 #include <string.h>
 
+#include "nvim/func_attr.h"
+
 #define ARRAY_DICT_INIT {.size = 0, .capacity = 0, .items = NULL}
 #define STRING_INIT {.data = NULL, .size = 0}
 #define OBJECT_INIT { .type = kObjectTypeNil }
@@ -36,8 +38,27 @@ typedef enum {
 /// Used as the message ID of notifications.
 #define NO_RESPONSE UINT64_MAX
 
-/// Used as channel_id when the call is local.
-#define INTERNAL_CALL UINT64_MAX
+/// Mask for all internal calls
+#define INTERNAL_CALL_MASK (((uint64_t)1) << (sizeof(uint64_t) * 8 - 1))
+
+/// Internal call from VimL code
+#define VIML_INTERNAL_CALL INTERNAL_CALL_MASK
+
+/// Internal call from lua code
+#define LUA_INTERNAL_CALL (VIML_INTERNAL_CALL + 1)
+
+static inline bool is_internal_call(uint64_t channel_id)
+  REAL_FATTR_ALWAYS_INLINE REAL_FATTR_CONST;
+
+/// Check whether call is internal
+///
+/// @param[in]  channel_id  Channel id.
+///
+/// @return true if channel_id refers to internal channel.
+static inline bool is_internal_call(const uint64_t channel_id)
+{
+  return !!(channel_id & INTERNAL_CALL_MASK);
+}
 
 typedef struct {
   ErrorType type;
@@ -78,16 +99,17 @@ typedef struct {
 } Dictionary;
 
 typedef enum {
-  kObjectTypeBuffer,
-  kObjectTypeWindow,
-  kObjectTypeTabpage,
-  kObjectTypeNil,
+  kObjectTypeNil = 0,
   kObjectTypeBoolean,
   kObjectTypeInteger,
   kObjectTypeFloat,
   kObjectTypeString,
   kObjectTypeArray,
   kObjectTypeDictionary,
+  // EXT types, cannot be split or reordered, see #EXT_OBJECT_TYPE_SHIFT
+  kObjectTypeBuffer,
+  kObjectTypeWindow,
+  kObjectTypeTabpage,
 } ObjectType;
 
 struct object {
diff --git a/src/nvim/api/private/helpers.c b/src/nvim/api/private/helpers.c
index 69cb19c14f..4cc4b600d5 100644
--- a/src/nvim/api/private/helpers.c
+++ b/src/nvim/api/private/helpers.c
@@ -353,7 +353,7 @@ void set_option_to(void *to, int type, String name, Object value, Error *err)
 #define TYPVAL_ENCODE_CONV_UNSIGNED_NUMBER TYPVAL_ENCODE_CONV_NUMBER
 
 #define TYPVAL_ENCODE_CONV_FLOAT(tv, flt) \
-    kv_push(edata->stack, FLOATING_OBJ((Float)(flt)))
+    kv_push(edata->stack, FLOAT_OBJ((Float)(flt)))
 
 #define TYPVAL_ENCODE_CONV_STRING(tv, str, len) \
     do { \
@@ -864,15 +864,18 @@ static void init_type_metadata(Dictionary *metadata)
   Dictionary types = ARRAY_DICT_INIT;
 
   Dictionary buffer_metadata = ARRAY_DICT_INIT;
-  PUT(buffer_metadata, "id", INTEGER_OBJ(kObjectTypeBuffer));
+  PUT(buffer_metadata, "id",
+      INTEGER_OBJ(kObjectTypeBuffer - EXT_OBJECT_TYPE_SHIFT));
   PUT(buffer_metadata, "prefix", STRING_OBJ(cstr_to_string("nvim_buf_")));
 
   Dictionary window_metadata = ARRAY_DICT_INIT;
-  PUT(window_metadata, "id", INTEGER_OBJ(kObjectTypeWindow));
+  PUT(window_metadata, "id",
+      INTEGER_OBJ(kObjectTypeWindow - EXT_OBJECT_TYPE_SHIFT));
   PUT(window_metadata, "prefix", STRING_OBJ(cstr_to_string("nvim_win_")));
 
   Dictionary tabpage_metadata = ARRAY_DICT_INIT;
-  PUT(tabpage_metadata, "id", INTEGER_OBJ(kObjectTypeTabpage));
+  PUT(tabpage_metadata, "id",
+      INTEGER_OBJ(kObjectTypeTabpage - EXT_OBJECT_TYPE_SHIFT));
   PUT(tabpage_metadata, "prefix", STRING_OBJ(cstr_to_string("nvim_tabpage_")));
 
   PUT(types, "Buffer", DICTIONARY_OBJ(buffer_metadata));
diff --git a/src/nvim/api/private/helpers.h b/src/nvim/api/private/helpers.h
index 681945ac9c..159b9d5c2a 100644
--- a/src/nvim/api/private/helpers.h
+++ b/src/nvim/api/private/helpers.h
@@ -18,7 +18,7 @@
     .type = kObjectTypeInteger, \
     .data.integer = i })
 
-#define FLOATING_OBJ(f) ((Object) { \
+#define FLOAT_OBJ(f) ((Object) { \
     .type = kObjectTypeFloat, \
     .data.floating = f })