metatables for primitive types, a small suggestion

[Rici Lake <lua@...>]

The reimplementation of metamethods for primitive types is really cool, 
but it still suffers from the problems which tag methods for primitive 
types had in previous versions of Lua: the change to behaviour is not 
localizable.

A quick glance at the code seems to indicate a possibility, though:

ltm.c:70
    default:
      mt = G(L)->mt[ttype(o)];

If this were changed so that the metatable were looked up in the 
function environment, the behaviour change could be localized to the 
function environment. All this would need would be a vector of 
primitive type metatable names (something like __nil, __string, 
__number, etc.)

Then this code could be changed to

    default:
      mt = luaH_getstr(&clvalue(L->ci->func)->l->env, 
G(L)->tmtname[ttype(o)]);

or something of the sort, where tmtname is constructed similarly to 
tmname.

If luaH_getstr were available for in-lining in ltm.c, this would 
probably be reasonably competitive to the current code (which could 
easily be accomplished by combining ltm.c with ltable.c)

R.