okfor[ir.OADD] = okforadd[:]
	okfor[ir.OAND] = okforand[:]
	okfor[ir.OANDAND] = okforbool[:]
	okfor[ir.OANDNOT] = okforand[:]
	okfor[ir.ODIV] = okforarith[:]
	okfor[ir.OEQ] = okforeq[:]
	okfor[ir.OGE] = types.IsOrdered[:]
	okfor[ir.OGT] = types.IsOrdered[:]
	okfor[ir.OLE] = types.IsOrdered[:]
	okfor[ir.OLT] = types.IsOrdered[:]
	okfor[ir.OMOD] = okforand[:]
	okfor[ir.OMUL] = okforarith[:]
	okfor[ir.ONE] = okforeq[:]

			return l, r, nil
		}
	}

	if t.Kind() == types.TIDEAL {
		t = mixUntyped(l.Type(), r.Type())
	}
	if dt := defaultType(t); !okfor[op][dt.Kind()] {
		base.Errorf("invalid operation: %v (operator %v not defined on %s)", n, op, typekind(t))
		return l, r, nil
	}

	// okfor allows any array == array, map == map, func == func.
	// restrict to slice/map/func == nil and nil == slice/map/func.

	switch op {
	case ir.OCOMPLEX:
		if t.IsComplex() {
			return types.FloatForComplex(t)
		}
	case ir.OREAL, ir.OIMAG:
		if t.IsFloat() {
			return types.ComplexForFloat(t)
		}
	default:
		if okfor[op][t.Kind()] {
			return t
		}
	}
	return nil
}

// ConvertVal converts v into a representation appropriate for t. If
// no such representation exists, it returns constant.MakeUnknown()
// instead.