return ir.OCONVIFACE, ""
		}
		return ir.OXXX, ":\n\t" + why
	}

	if isptrto(dst, types.TINTER) {
		why := fmt.Sprintf(":\n\t%v is pointer to interface, not interface", dst)
		return ir.OXXX, why
	}

	if src.IsInterface() && dst.Kind() != types.TBLANK {
		var why string
		if Implements(dst, src) {
			why = ": need type assertion"
		}
		return ir.OXXX, why
	}

	l, r = defaultlit2(l, r, false)
	if l.Type() == nil || r.Type() == nil {
		return l, r, nil
	}
	t := l.Type()
	if t.Kind() == types.TIDEAL {
		t = r.Type()
	}
	aop := ir.OXXX
	if n.Op().IsCmp() && t.Kind() != types.TIDEAL && !types.Identical(l.Type(), r.Type()) {
		// comparison is okay as long as one side is
		// assignable to the other.  convert so they have
		// the same type.
		//

				base.ErrorfAt(ncase.Pos(), errors.UndefinedOp, "invalid case %L in switch (incomparable type)", n1)
			} else {
				op1, _ := assignOp(n1.Type(), t)
				op2, _ := assignOp(t, n1.Type())
				if op1 == ir.OXXX && op2 == ir.OXXX {
					if n.Tag != nil {
						base.ErrorfAt(ncase.Pos(), errors.MismatchedTypes, "invalid case %v in switch on %v (mismatched types %v and %v)", n1, n.Tag, n1.Type(), t)
					} else {

	// TODO(mdempsky): Handle all untyped types correctly.
	if src == types.UntypedBool && dst.Type().IsBoolean() {
		return
	}

	if op, why := assignOp(src, dst.Type()); op == ir.OXXX {
		base.Errorf("cannot assign %v to %L in multiple assignment%s", src, dst, why)
		return
	}
}

// The result of stringtoruneslit MUST be assigned back to n, e.g.
//