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     capture_raw_strings_and_idents();
   9
  10     #[cfg(panic = "unwind")]
  11     {
  12         panic_with_single_argument_does_not_get_formatted();
  13         panic_with_multiple_arguments_is_formatted();
  14     }
  15 }
  16
  17 fn named_argument_takes_precedence_to_captured() {
  18     let foo = "captured";
  19     let s = format!("{foo}", foo = "named");
  20     assert_eq!(&s, "named");
  21
  22     let s = format!("{foo}-{foo}-{foo}", foo = "named");
  23     assert_eq!(&s, "named-named-named");
  24
  25     let s = format!("{}-{bar}-{foo}", "positional", bar = "named");
  26     assert_eq!(&s, "positional-named-captured");
  27 }
  28
  29 fn capture_raw_strings_and_idents() {
  30     let r#type = "apple";
  31     let s = format!(r#"The fruit is an {type}"#);
  32     assert_eq!(&s, "The fruit is an apple");
  33
  34     let r#type = "orange";
  35     let s = format!(r"The fruit is an {type}");
  36     assert_eq!(&s, "The fruit is an orange");
  37 }
  38
  39 #[cfg(panic = "unwind")]
  40 fn panic_with_single_argument_does_not_get_formatted() {
  41     // panic! with a single argument does not perform string formatting.
  42     // RFC #2795 suggests that this may need to change so that captured arguments are formatted.
  43     // For stability reasons this will need to part of an edition change.
  44
  45     #[allow(non_fmt_panics)]
  46     let msg = std::panic::catch_unwind(|| {
  47         panic!("{foo}");
  48     })
  49     .unwrap_err();
  50
  51     assert_eq!(msg.downcast_ref::<&str>(), Some(&"{foo}"))
  52 }
  53
  54 #[cfg(panic = "unwind")]
  55 fn panic_with_multiple_arguments_is_formatted() {
  56     let foo = "captured";
  57
  58     let msg = std::panic::catch_unwind(|| {
  59         panic!("{}-{bar}-{foo}", "positional", bar = "named");
  60     })
  61     .unwrap_err();
  62
  63     assert_eq!(msg.downcast_ref::<String>(), Some(&"positional-named-captured".to_string()))
  64 }
  65
  66 fn formatting_parameters_can_be_captured() {
  67     let width = 9;
  68     let precision = 3;
  69
  70     let x = 7.0;
  71
  72     let s = format!("{x:width$}");
  73     assert_eq!(&s, "        7");
  74
  75     let s = format!("{x:<width$}");
  76     assert_eq!(&s, "7        ");
  77
  78     let s = format!("{x:-^width$}");
  79     assert_eq!(&s, "----7----");
  80
  81     let s = format!("{x:-^width$.precision$}");
  82     assert_eq!(&s, "--7.000--");
  83 }