src/tools/clippy/tests/ui/format.rs

   1 // run-rustfix
   2
   3 #![allow(
   4     unused_tuple_struct_fields,
   5     clippy::print_literal,
   6     clippy::redundant_clone,
   7     clippy::to_string_in_format_args,
   8     clippy::needless_borrow
   9 )]
  10 #![warn(clippy::useless_format)]
  11
  12 struct Foo(pub String);
  13
  14 macro_rules! foo {
  15     ($($t:tt)*) => (Foo(format!($($t)*)))
  16 }
  17
  18 fn main() {
  19     format!("foo");
  20     format!("{{}}");
  21     format!("{{}} abc {{}}");
  22     format!(
  23         r##"foo {{}}
  24 " bar"##
  25     );
  26
  27     let _ = format!("");
  28
  29     format!("{}", "foo");
  30     format!("{:?}", "foo"); // Don't warn about `Debug`.
  31     format!("{:8}", "foo");
  32     format!("{:width$}", "foo", width = 8);
  33     format!("{:+}", "foo"); // Warn when the format makes no difference.
  34     format!("{:<}", "foo"); // Warn when the format makes no difference.
  35     format!("foo {}", "bar");
  36     format!("{} bar", "foo");
  37
  38     let arg: String = "".to_owned();
  39     format!("{}", arg);
  40     format!("{:?}", arg); // Don't warn about debug.
  41     format!("{:8}", arg);
  42     format!("{:width$}", arg, width = 8);
  43     format!("{:+}", arg); // Warn when the format makes no difference.
  44     format!("{:<}", arg); // Warn when the format makes no difference.
  45     format!("foo {}", arg);
  46     format!("{} bar", arg);
  47
  48     // We don’t want to warn for non-string args; see issue #697.
  49     format!("{}", 42);
  50     format!("{:?}", 42);
  51     format!("{:+}", 42);
  52     format!("foo {}", 42);
  53     format!("{} bar", 42);
  54
  55     // We only want to warn about `format!` itself.
  56     println!("foo");
  57     println!("{}", "foo");
  58     println!("foo {}", "foo");
  59     println!("{}", 42);
  60     println!("foo {}", 42);
  61
  62     // A `format!` inside a macro should not trigger a warning.
  63     foo!("should not warn");
  64
  65     // Precision on string means slicing without panicking on size.
  66     format!("{:.1}", "foo"); // Could be `"foo"[..1]`
  67     format!("{:.10}", "foo"); // Could not be `"foo"[..10]`
  68     format!("{:.prec$}", "foo", prec = 1);
  69     format!("{:.prec$}", "foo", prec = 10);
  70
  71     format!("{}", 42.to_string());
  72     let x = std::path::PathBuf::from("/bar/foo/qux");
  73     format!("{}", x.display().to_string());
  74
  75     // False positive
  76     let a = "foo".to_string();
  77     let _ = Some(format!("{}", a + "bar"));
  78
  79     // Wrap it with braces
  80     let v: Vec<String> = vec!["foo".to_string(), "bar".to_string()];
  81     let _s: String = format!("{}", &*v.join("\n"));
  82
  83     format!("prepend {:+}", "s");
  84
  85     // Issue #8290
  86     let x = "foo";
  87     let _ = format!("{x}");
  88     let _ = format!("{x:?}"); // Don't lint on debug
  89     let _ = format!("{y}", y = x);
  90
  91     // Issue #9234
  92     let abc = "abc";
  93     let _ = format!("{abc}");
  94     let xx = "xx";
  95     let _ = format!("{xx}");
  96 }