Variable detected as non-empty-list<…> fails some array shape checks that list<…> passes

[MatmaRex]

Variable detected as non-empty-list<…> fails some array shape checks that list<…> passes.

Example:

<?
/**
 * @param array<string,int|string> $a
 */
function a($a): void {
    var_dump($a);
}

/**
 * @param list<array<string,int|string>> $a
 */
function b($a): void {
    var_dump($a);
}


$x = [ 'a' => 1, 'b' => '2' ];
a($x);

$xx = [];
foreach ( [1,2,3] as $u ) {
    $xx[] = $x;
}
b($xx);

$zz = [];
foreach ( range(1,3) as $u ) {
    $zz[] = $x;
}
b($zz);

$yy = [ $x, $x, $x ];
b($yy);

Output:

input:24: PhanTypeMismatchArgument Argument 1 ($a) is $xx of type non-empty-list<array{a:1,b:'2'}> but \b() takes list<array<string,int>>|list<array<string,string>> defined at input:12

That's an incorrect error from the first foreach, but the second foreach and the literal pass.

Demo: https://phan.github.io/demo/?code=%3C%3F%0A%2F**%0A+*+%40param+array%3Cstring%2Cint|string%3E+%24a%0A+*%2F%0Afunction+a(%24a)%3A+void+{%0A++++var_dump(%24a)%3B%0A}%0A%0A%2F**%0A+*+%40param+list%3Carray%3Cstring%2Cint|string%3E%3E+%24a%0A+*%2F%0Afunction+b(%24a)%3A+void+{%0A++++var_dump(%24a)%3B%0A}%0A%0A%0A%24x+%3D+[+'a'+%3D%3E+1%2C+'b'+%3D%3E+'2'+]%3B%0Aa(%24x)%3B%0A%0A%24xx+%3D+[]%3B%0Aforeach+(+[1%2C2%2C3]+as+%24u+)+{%0A++++%24xx[]+%3D+%24x%3B%0A}%0Ab(%24xx)%3B%0A%0A%24zz+%3D+[]%3B%0Aforeach+(+range(1%2C3)+as+%24u+)+{%0A++++%24zz[]+%3D+%24x%3B%0A}%0Ab(%24zz)%3B%0A%0A%24yy+%3D+[+%24x%2C+%24x%2C+%24x+]%3B%0Ab(%24yy)%3B

Compare to PHPStan: https://phpstan.org/r/1c5904e5-ccde-47c2-ab40-6431fc5d494a