Better error messages for some polymorphic functions

New auxiliary functions/macros 'luaL_argexpected'/'luaL_typeerror'
ease the creation of error messages such as

  bad argument #2 to 'setmetatable' (nil or table expected, got boolean)

(The novelty being the "got boolean" part...)

1 files changed, 5 insertions, 0 deletions

diff --git a/lauxlib.h b/lauxlib.h
index 9ec0f531..e5d378ae 100644
--- a/lauxlib.h
+++ b/lauxlib.h
@@ -48,6 +48,7 @@ LUALIB_API int (luaL_getmetafield) (lua_State *L, int obj, const char *e);
 LUALIB_API int (luaL_callmeta) (lua_State *L, int obj, const char *e);
 LUALIB_API const char *(luaL_tolstring) (lua_State *L, int idx, size_t *len);
 LUALIB_API int (luaL_argerror) (lua_State *L, int arg, const char *extramsg);
+LUALIB_API int (luaL_typeerror) (lua_State *L, int arg, const char *tname);
 LUALIB_API const char *(luaL_checklstring) (lua_State *L, int arg,
                                                           size_t *l);
 LUALIB_API const char *(luaL_optlstring) (lua_State *L, int arg,
@@ -126,6 +127,10 @@ LUALIB_API void (luaL_requiref) (lua_State *L, const char *modname,
 
 #define luaL_argcheck(L, cond,arg,extramsg)     \
                 ((void)((cond) || luaL_argerror(L, (arg), (extramsg))))
+
+#define luaL_argexpected(L,cond,arg,tname)      \
+                ((void)((cond) || luaL_typeerror(L, (arg), (tname))))
+
 #define luaL_checkstring(L,n)   (luaL_checklstring(L, (n), NULL))
 #define luaL_optstring(L,n,d)   (luaL_optlstring(L, (n), (d), NULL))