message: Remove needless is_not_nightly closure.
diff: @@ -21,7 +21,7 @@ pub fn cargo_test(attr: TokenStream, item: TokenStream) -> TokenStream {
  let mut ignore = false;
  let mut requires_reason = false;
  let mut found_reason = false;
  - let is_not_nightly = || !version().1;
  + let is_not_nightly = !version().1;
  for rule in split_rules(attr) {
  match rule.as_str() {
  "build_std_real" => {
  @@ -29,19 +29,19 @@ pub fn cargo_test(attr: TokenStream, item: TokenStream) -> TokenStream {
  // explicit opt-in (these generally only work on linux, and
  // have some extra requirements, and are slow, and can pollute
  // the environment since it downloads dependencies).
  - ignore |= is_not_nightly();
  + ignore |= is_not_nightly;
  ignore |= option_env!("CARGO_RUN_BUILD_STD_TESTS").is_none();
  }
  "build_std_mock" => {
  // Only run the "mock" build-std tests on nightly and disable
  // for windows-gnu which is missing object files (see
  // https://github.com/rust-lang/wg-cargo-std-aware/issues/46).
  - ignore |= is_not_nightly();
  + ignore |= is_not_nightly;
  ignore |= cfg!(all(target_os = "windows", target_env = "gnu"));
  }
  "nightly" => {
  requires_reason = true;
  - ignore |= is_not_nightly();
  + ignore |= is_not_nightly;
  }
  s if s.starts_with("requires_") => {
  let command = &s[9..];
  