Fix weak table creation, processing

src/core/org/luaj/lib/BaseLib.java

@@ -194,7 +194,7 @@ public class BaseLib extends LFunction {
 			LTable t = vm.checktable(2);
 			LValue v = vm.checkany(3);
 			vm.argcheck(v.isTable() || v.isNil(), 3, "table or nil expected");
-			t.luaSetMetatable(v);
+			t = t.luaSetMetatable(v);
 			vm.resettop();
 			vm.pushlvalue(t);
 			break;

src/core/org/luaj/vm/LTable.java

@@ -267,7 +267,7 @@ public class LTable extends LValue {
 	}
 
 	/** Valid for tables */
-	public LValue luaSetMetatable(LValue metatable) {
+	public LTable luaSetMetatable(LValue metatable) {
 		if ( m_metatable != null && m_metatable.containsKey(TM_METATABLE) )
 			throw new LuaErrorException("cannot change a protected metatable");
 		if ( metatable == null || metatable.isNil() )
@@ -279,10 +279,10 @@ public class LTable extends LValue {
 				return new LWeakTable(this);
 			}
 			this.m_metatable = t;
+		} else {
+			throw new LuaErrorException("not a table: "+metatable.luaGetTypeName());
 		}
-		else
+		return this;
-			throw new LuaErrorException("nil or table expected, got "+metatable.luaGetTypeName());
-		return null;
 	}
 
 	public String toJavaString() {

src/core/org/luaj/vm/LValue.java

@@ -177,9 +177,11 @@ public class LValue {
 	}
 
 	/** Valid for tables 
-	 * @return TODO*/
+	 * @param the new LTable, or null or LNil.NIL to reset the metatable to none
-	public LValue luaSetMetatable(LValue metatable) {
+	 * @return this if unchanged, or new LTable if copied using weak table 
-		throw new LuaErrorException( "bad argument #1 to 'setmetatable' (table expected, got "+metatable.luaGetTypeName()+")");
+	 */
+	public LTable luaSetMetatable(LValue metatable) {
+		throw new LuaErrorException( "cannot set metatable for "+metatable.luaGetTypeName());
 	}
 
 	/** Valid for all types: return the int value identifying the type of this value */

src/test/res/weaktable.lua

@@ -1,5 +1,4 @@
 
-
 -- normalized printing
 function eles(t,f)
 	f = f or pairs