public void SetBuiltinType(BuiltinTypeSpec pts)
 {
     var found = types[pts.Name];
     cached_types.Remove (pts.Name);
     if (found.Count == 1) {
         types[pts.Name][0] = pts;
     } else {
         throw new NotImplementedException ();
     }
 }

		//
		// Replaces normal spec with predefined one when compiling corlib
		// and this type container defines predefined type
		//
		public void SetPredefinedSpec (BuiltinTypeSpec spec)
		{
			// When compiling build-in types we start with two
			// version of same type. One is of BuiltinTypeSpec and
			// second one is ordinary TypeSpec. The unification
			// happens at later stage when we know which type
			// really matches the builtin type signature. However
			// that means TypeSpec create during CreateType of this
			// type has to be replaced with builtin one
			// 
			spec.SetMetaInfo (TypeBuilder);
			spec.MemberCache = this.spec.MemberCache;
			spec.DeclaringType = this.spec.DeclaringType;

			this.spec = spec;
			current_type = null;
		}

		public void ReplaceTypeWithPredefined (TypeSpec ts, BuiltinTypeSpec pts)
		{
			var found = types [ts.Name];
			cached_types.Remove (ts.Name);
			if (found.Count == 1) {
				types[ts.Name][0] = pts;
			} else {
				throw new NotImplementedException ();
			}
		}