src/test/ui/fmt/format-args-capture.rs

   1 // run-pass
   2 #![feature(format_args_capture)]
   3 #![feature(cfg_panic)]
   4
   5 fn main() {
   6     named_argument_takes_precedence_to_captured();
   7     formatting_parameters_can_be_captured();
   8
   9     #[cfg(panic = "unwind")]
  10     {
  11         panic_with_single_argument_does_not_get_formatted();
  12         panic_with_multiple_arguments_is_formatted();
  13     }
  14 }
  15
  16 fn named_argument_takes_precedence_to_captured() {
  17     let foo = "captured";
  18     let s = format!("{foo}", foo="named");
  19     assert_eq!(&s, "named");
  20
  21     let s = format!("{foo}-{foo}-{foo}", foo="named");
  22     assert_eq!(&s, "named-named-named");
  23
  24     let s = format!("{}-{bar}-{foo}", "positional", bar="named");
  25     assert_eq!(&s, "positional-named-captured");
  26 }
  27
  28 #[cfg(panic = "unwind")]
  29 fn panic_with_single_argument_does_not_get_formatted() {
  30     // panic! with a single argument does not perform string formatting.
  31     // RFC #2795 suggests that this may need to change so that captured arguments are formatted.
  32     // For stability reasons this will need to part of an edition change.
  33
  34     #[allow(non_fmt_panic)]
  35     let msg = std::panic::catch_unwind(|| {
  36         panic!("{foo}");
  37     }).unwrap_err();
  38
  39     assert_eq!(msg.downcast_ref::<&str>(), Some(&"{foo}"))
  40 }
  41
  42 #[cfg(panic = "unwind")]
  43 fn panic_with_multiple_arguments_is_formatted() {
  44     let foo = "captured";
  45
  46     let msg = std::panic::catch_unwind(|| {
  47         panic!("{}-{bar}-{foo}", "positional", bar="named");
  48     }).unwrap_err();
  49
  50     assert_eq!(msg.downcast_ref::<String>(), Some(&"positional-named-captured".to_string()))
  51 }
  52
  53 fn formatting_parameters_can_be_captured() {
  54     let width = 9;
  55     let precision = 3;
  56
  57     let x = 7.0;
  58
  59     let s = format!("{x:width$}");
  60     assert_eq!(&s, "        7");
  61
  62     let s = format!("{x:<width$}");
  63     assert_eq!(&s, "7        ");
  64
  65     let s = format!("{x:-^width$}");
  66     assert_eq!(&s, "----7----");
  67
  68     let s = format!("{x:-^width$.precision$}");
  69     assert_eq!(&s, "--7.000--");
  70 }