<!DOCTYPE html>
<html>
<head>
<link rel="author" title="Sammy Gill" href="mailto:sammy.gill@apple.com">
<link rel="help" href="https://drafts.csswg.org/css-box-4/#margin-trim-block">
<meta name="assert" content="The float should contribute its border box size along with the inline-end margin (since that is not trimmed) to the intrinsic sizing of the containing block">
<style>
container {
    display: block;
    direction: rtl;
    width: min-content;
    font-family: monospace;
    font-size: 10px;
    margin-trim: inline-start;
    border: 1px solid black;
}
item {
    display: block;
    float: left;
    width: 50px;
    height: 50px;
    margin-inline: 15px 30px;
    background-color: green;

}
</style>
</head>
<body>
<container>
    <item></item>
    many l e t t e r s s e p a r a t e d b y s p a c e s
</container>
</body>
</html>
