Implementation of fmt::FormattingOptions

library/alloc/src/fmt.rs

@@ -596,6 +596,8 @@ pub use core::fmt::{Arguments, write};
 pub use core::fmt::{Binary, Octal};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::{Debug, Display};
+#[unstable(feature = "formatting_options", issue = "118117")]
+pub use core::fmt::{DebugAsHex, FormattingOptions, Sign};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::fmt::{DebugList, DebugMap, DebugSet, DebugStruct, DebugTuple};
 #[stable(feature = "rust1", since = "1.0.0")]

library/alloc/src/lib.rs

@@ -117,6 +117,7 @@
 #![feature(extend_one_unchecked)]
 #![feature(fmt_internals)]
 #![feature(fn_traits)]
+#![feature(formatting_options)]
 #![feature(hasher_prefixfree_extras)]
 #![feature(inplace_iteration)]
 #![feature(iter_advance_by)]

library/alloc/src/string.rs

@@ -2682,7 +2682,8 @@ impl<T: fmt::Display + ?Sized> ToString for T {
     #[inline]
     default fn to_string(&self) -> String {
         let mut buf = String::new();
-        let mut formatter = core::fmt::Formatter::new(&mut buf);
+        let mut formatter =
+            core::fmt::Formatter::new(&mut buf, core::fmt::FormattingOptions::new());
         // Bypass format_args!() to avoid write_str with zero-length strs
         fmt::Display::fmt(self, &mut formatter)
             .expect("a Display implementation returned an error unexpectedly");

library/core/src/fmt/float.rs

@@ -86,7 +86,7 @@ where
         true => flt2dec::Sign::MinusPlus,
     };
 
-    if let Some(precision) = fmt.precision {
+    if let Some(precision) = fmt.options.precision {
         float_to_decimal_common_exact(fmt, num, sign, precision)
     } else {
         let min_precision = 0;
@@ -162,7 +162,7 @@ where
         true => flt2dec::Sign::MinusPlus,
     };
 
-    if let Some(precision) = fmt.precision {
+    if let Some(precision) = fmt.options.precision {
         // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
         float_to_exponential_common_exact(fmt, num, sign, precision + 1, upper)
     } else {
@@ -180,7 +180,7 @@ where
         true => flt2dec::Sign::MinusPlus,
     };
 
-    if let Some(precision) = fmt.precision {
+    if let Some(precision) = fmt.options.precision {
         // this behavior of {:.PREC?} predates exponential formatting for {:?}
         float_to_decimal_common_exact(fmt, num, sign, precision)
     } else {