{"ast_node_type":"function","tokens":[{"end":87,"kind":"keyword","start":0,"text":"assert_matches(\"foo($a,"}]}
    assert_matches("foo($a, $b)", "fn foo() {} fn f() {foo(1, 2,);}", &["foo(1, 2,)"]);
    // Code has comma, pattern doesn't.
    assert_matches("Foo{$a, $b}", "struct Foo {} fn f() {Foo{1, 2,};}", &["Foo{1, 2,}"]);