// dddErrPos returns the positioner for reporting an invalid ... use in a call.
func dddErrPos(call *ast.CallExpr) positioner { return atPos(call.Ellipsis) }

// argErrPos returns positioner for reporting an invalid argument count.
func argErrPos(call *ast.CallExpr) positioner { return inNode(call, call.Rparen) }

// startPos returns the start position of node n.
func startPos(n ast.Node) token.Pos { return n.Pos() }

func dddErrPos(call *syntax.CallExpr) *syntax.CallExpr {
	// TODO(gri) should use "..." instead of call position
	return call
}

// argErrPos returns the node (poser) for reporting an invalid argument count.
func argErrPos(call *syntax.CallExpr) *syntax.CallExpr { return call }

// ExprString returns a string representation of x.
func ExprString(x syntax.Node) string { return syntax.String(x) }

	}

	// check argument count
	{
		msg := ""
		if nargs < bin.nargs {
			msg = "not enough"
		} else if !bin.variadic && nargs > bin.nargs {
			msg = "too many"
		}
		if msg != "" {
			check.errorf(argErrPos(call), WrongArgCount, invalidOp+"%s arguments for %v (expected %d, found %d)", msg, call, bin.nargs, nargs)
			return
		}
	}

	switch id {
	case _Append:
		// append(s S, x ...T) S, where T is the element type of S

	}

	// check argument count
	{
		msg := ""
		if nargs < bin.nargs {
			msg = "not enough"
		} else if !bin.variadic && nargs > bin.nargs {
			msg = "too many"
		}
		if msg != "" {
			check.errorf(argErrPos(call), WrongArgCount, invalidOp+"%s arguments for %v (expected %d, found %d)", msg, call, bin.nargs, nargs)
			return
		}
	}

	switch id {
	case _Append:
		// append(s S, x ...T) S, where T is the element type of S