{"ast_node_type":"function","tokens":[{"end":86,"kind":"keyword","start":0,"text":"assert_matches(\"foo($a,"}]}
    assert_matches("foo($a, $b,)", "fn foo() {} fn f() {foo(1, 2);}", &["foo(1, 2)"]);
    // Pattern has comma, code doesn't.
    assert_matches("Foo{$a, $b,}", "struct Foo {} fn f() {Foo{1, 2};}", &["Foo{1, 2}"]);