Merging upstream version 1.71.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 371 insertions, 361 deletions

diff --git a/library/core/src/fmt/builders.rs b/library/core/src/fmt/builders.rs
index 7da49b04a..36f49d51c 100644
--- a/library/core/src/fmt/builders.rs
+++ b/library/core/src/fmt/builders.rs
@@ -60,7 +60,7 @@ impl fmt::Write for PadAdapter<'_, '_> {
 /// }
 ///
 /// impl fmt::Debug for Foo {
-///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 ///         fmt.debug_struct("Foo")
 ///            .field("bar", &self.bar)
 ///            .field("baz", &self.baz)
@@ -109,14 +109,14 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
     ///            .field("bar", &self.bar) // We add `bar` field.
     ///            .field("another", &self.another) // We add `another` field.
     ///            // We even add a field which doesn't exist (because why not?).
-    ///            .field("not_existing_field", &1)
+    ///            .field("nonexistent_field", &1)
     ///            .finish() // We're good to go!
     ///     }
     /// }
     ///
     /// assert_eq!(
     ///     format!("{:?}", Bar { bar: 10, another: "Hello World".to_string() }),
-    ///     "Bar { bar: 10, another: \"Hello World\", not_existing_field: 1 }",
+    ///     "Bar { bar: 10, another: \"Hello World\", nonexistent_field: 1 }",
     /// );
     /// ```
     #[stable(feature = "debug_builders", since = "1.2.0")]
@@ -249,7 +249,7 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
 /// struct Foo(i32, String);
 ///
 /// impl fmt::Debug for Foo {
-///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 ///         fmt.debug_tuple("Foo")
 ///            .field(&self.0)
 ///            .field(&self.1)
@@ -418,7 +418,7 @@ impl<'a, 'b: 'a> DebugInner<'a, 'b> {
 /// struct Foo(Vec<i32>);
 ///
 /// impl fmt::Debug for Foo {
-///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 ///         fmt.debug_set().entries(self.0.iter()).finish()
 ///     }
 /// }
@@ -548,7 +548,7 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
 /// struct Foo(Vec<i32>);
 ///
 /// impl fmt::Debug for Foo {
-///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 ///         fmt.debug_list().entries(self.0.iter()).finish()
 ///     }
 /// }
@@ -678,7 +678,7 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
 /// struct Foo(Vec<(String, i32)>);
 ///
 /// impl fmt::Debug for Foo {
-///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
 ///         fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
 ///     }
 /// }
diff --git a/library/core/src/fmt/float.rs b/library/core/src/fmt/float.rs
index 89d5fac30..3bbf5d877 100644
--- a/library/core/src/fmt/float.rs
+++ b/library/core/src/fmt/float.rs
@@ -45,7 +45,8 @@ where
         &mut buf,
         &mut parts,
     );
-    fmt.pad_formatted_parts(&formatted)
+    // SAFETY: `to_exact_fixed_str` and `format_exact` produce only ASCII characters.
+    unsafe { fmt.pad_formatted_parts(&formatted) }
 }
 
 // Don't inline this so callers that call both this and the above won't wind
@@ -71,7 +72,8 @@ where
         &mut buf,
         &mut parts,
     );
-    fmt.pad_formatted_parts(&formatted)
+    // SAFETY: `to_shortest_str` and `format_shortest` produce only ASCII characters.
+    unsafe { fmt.pad_formatted_parts(&formatted) }
 }
 
 fn float_to_decimal_display<T>(fmt: &mut Formatter<'_>, num: &T) -> Result
@@ -116,7 +118,8 @@ where
         &mut buf,
         &mut parts,
     );
-    fmt.pad_formatted_parts(&formatted)
+    // SAFETY: `to_exact_exp_str` and `format_exact` produce only ASCII characters.
+    unsafe { fmt.pad_formatted_parts(&formatted) }
 }
 
 // Don't inline this so callers that call both this and the above won't wind
@@ -143,7 +146,8 @@ where
         &mut buf,
         &mut parts,
     );
-    fmt.pad_formatted_parts(&formatted)
+    // SAFETY: `to_shortest_exp_str` and `format_shortest` produce only ASCII characters.
+    unsafe { fmt.pad_formatted_parts(&formatted) }
 }
 
 // Common code of floating point LowerExp and UpperExp.
diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index fcda097f0..1786b309c 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -18,6 +18,7 @@ mod float;
 #[cfg(no_fp_fmt_parse)]
 mod nofloat;
 mod num;
+mod rt;
 
 #[stable(feature = "fmt_flags_align", since = "1.28.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "Alignment")]
@@ -38,12 +39,6 @@ pub enum Alignment {
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub use self::builders::{DebugList, DebugMap, DebugSet, DebugStruct, DebugTuple};
 
-#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-#[doc(hidden)]
-pub mod rt {
-    pub mod v1;
-}
-
 /// The type returned by formatter methods.
 ///
 /// # Examples
@@ -227,7 +222,7 @@ impl<W: Write + ?Sized> Write for &mut W {
 pub struct Formatter<'a> {
     flags: u32,
     fill: char,
-    align: rt::v1::Alignment,
+    align: rt::Alignment,
     width: Option<usize>,
     precision: Option<usize>,
 
@@ -248,7 +243,7 @@ impl<'a> Formatter<'a> {
         Formatter {
             flags: 0,
             fill: ' ',
-            align: rt::v1::Alignment::Unknown,
+            align: rt::Alignment::Unknown,
             width: None,
             precision: None,
             buf,
@@ -256,145 +251,48 @@ impl<'a> Formatter<'a> {
     }
 }
 
-// NB. Argument is essentially an optimized partially applied formatting function,
-// equivalent to `exists T.(&T, fn(&T, &mut Formatter<'_>) -> Result`.
-
-extern "C" {
-    type Opaque;
-}
-
-/// This struct represents the generic "argument" which is taken by the Xprintf
-/// family of functions. It contains a function to format the given value. At
-/// compile time it is ensured that the function and the value have the correct
-/// types, and then this struct is used to canonicalize arguments to one type.
-#[lang = "format_argument"]
+/// This structure represents a safely precompiled version of a format string
+/// and its arguments. This cannot be generated at runtime because it cannot
+/// safely be done, so no constructors are given and the fields are private
+/// to prevent modification.
+///
+/// The [`format_args!`] macro will safely create an instance of this structure.
+/// The macro validates the format string at compile-time so usage of the
+/// [`write()`] and [`format()`] functions can be safely performed.
+///
+/// You can use the `Arguments<'a>` that [`format_args!`] returns in `Debug`
+/// and `Display` contexts as seen below. The example also shows that `Debug`
+/// and `Display` format to the same thing: the interpolated format string
+/// in `format_args!`.
+///
+/// ```rust
+/// let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2));
+/// let display = format!("{}", format_args!("{} foo {:?}", 1, 2));
+/// assert_eq!("1 foo 2", display);
+/// assert_eq!(display, debug);
+/// ```
+///
+/// [`format()`]: ../../std/fmt/fn.format.html
+#[lang = "format_arguments"]
+#[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Copy, Clone)]
-#[allow(missing_debug_implementations)]
-#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-#[doc(hidden)]
-pub struct ArgumentV1<'a> {
-    value: &'a Opaque,
-    formatter: fn(&Opaque, &mut Formatter<'_>) -> Result,
-}
-
-/// This struct represents the unsafety of constructing an `Arguments`.
-/// It exists, rather than an unsafe function, in order to simplify the expansion
-/// of `format_args!(..)` and reduce the scope of the `unsafe` block.
-#[lang = "format_unsafe_arg"]
-#[allow(missing_debug_implementations)]
-#[doc(hidden)]
-#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-pub struct UnsafeArg {
-    _private: (),
-}
-
-impl UnsafeArg {
-    /// See documentation where `UnsafeArg` is required to know when it is safe to
-    /// create and use `UnsafeArg`.
-    #[doc(hidden)]
-    #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-    #[inline(always)]
-    pub unsafe fn new() -> Self {
-        Self { _private: () }
-    }
-}
-
-// This guarantees a single stable value for the function pointer associated with
-// indices/counts in the formatting infrastructure.
-//
-// Note that a function defined as such would not be correct as functions are
-// always tagged unnamed_addr with the current lowering to LLVM IR, so their
-// address is not considered important to LLVM and as such the as_usize cast
-// could have been miscompiled. In practice, we never call as_usize on non-usize
-// containing data (as a matter of static generation of the formatting
-// arguments), so this is merely an additional check.
-//
-// We primarily want to ensure that the function pointer at `USIZE_MARKER` has
-// an address corresponding *only* to functions that also take `&usize` as their
-// first argument. The read_volatile here ensures that we can safely ready out a
-// usize from the passed reference and that this address does not point at a
-// non-usize taking function.
-#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-static USIZE_MARKER: fn(&usize, &mut Formatter<'_>) -> Result = |ptr, _| {
-    // SAFETY: ptr is a reference
-    let _v: usize = unsafe { crate::ptr::read_volatile(ptr) };
-    loop {}
-};
-
-macro_rules! arg_new {
-    ($f: ident, $t: ident) => {
-        #[doc(hidden)]
-        #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-        #[inline]
-        pub fn $f<'b, T: $t>(x: &'b T) -> ArgumentV1<'_> {
-            Self::new(x, $t::fmt)
-        }
-    };
-}
-
-#[rustc_diagnostic_item = "ArgumentV1Methods"]
-impl<'a> ArgumentV1<'a> {
-    #[doc(hidden)]
-    #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-    #[inline]
-    pub fn new<'b, T>(x: &'b T, f: fn(&T, &mut Formatter<'_>) -> Result) -> ArgumentV1<'b> {
-        // SAFETY: `mem::transmute(x)` is safe because
-        //     1. `&'b T` keeps the lifetime it originated with `'b`
-        //              (so as to not have an unbounded lifetime)
-        //     2. `&'b T` and `&'b Opaque` have the same memory layout
-        //              (when `T` is `Sized`, as it is here)
-        // `mem::transmute(f)` is safe since `fn(&T, &mut Formatter<'_>) -> Result`
-        // and `fn(&Opaque, &mut Formatter<'_>) -> Result` have the same ABI
-        // (as long as `T` is `Sized`)
-        unsafe { ArgumentV1 { formatter: mem::transmute(f), value: mem::transmute(x) } }
-    }
-
-    arg_new!(new_display, Display);
-    arg_new!(new_debug, Debug);
-    arg_new!(new_octal, Octal);
-    arg_new!(new_lower_hex, LowerHex);
-    arg_new!(new_upper_hex, UpperHex);
-    arg_new!(new_pointer, Pointer);
-    arg_new!(new_binary, Binary);
-    arg_new!(new_lower_exp, LowerExp);
-    arg_new!(new_upper_exp, UpperExp);
+pub struct Arguments<'a> {
+    // Format string pieces to print.
+    pieces: &'a [&'static str],
 
-    #[doc(hidden)]
-    #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-    pub fn from_usize(x: &usize) -> ArgumentV1<'_> {
-        ArgumentV1::new(x, USIZE_MARKER)
-    }
-
-    fn as_usize(&self) -> Option<usize> {
-        // We are type punning a bit here: USIZE_MARKER only takes an &usize but
-        // formatter takes an &Opaque. Rust understandably doesn't think we should compare
-        // the function pointers if they don't have the same signature, so we cast to
-        // usizes to tell it that we just want to compare addresses.
-        if self.formatter as usize == USIZE_MARKER as usize {
-            // SAFETY: The `formatter` field is only set to USIZE_MARKER if
-            // the value is a usize, so this is safe
-            Some(unsafe { *(self.value as *const _ as *const usize) })
-        } else {
-            None
-        }
-    }
-}
+    // Placeholder specs, or `None` if all specs are default (as in "{}{}").
+    fmt: Option<&'a [rt::Placeholder]>,
 
-// flags available in the v1 format of format_args
-#[derive(Copy, Clone)]
-enum FlagV1 {
-    SignPlus,
-    SignMinus,
-    Alternate,
-    SignAwareZeroPad,
-    DebugLowerHex,
-    DebugUpperHex,
+    // Dynamic arguments for interpolation, to be interleaved with string
+    // pieces. (Every argument is preceded by a string piece.)
+    args: &'a [rt::Argument<'a>],
 }
 
+/// Used by the format_args!() macro to create a fmt::Arguments object.
+#[doc(hidden)]
+#[unstable(feature = "fmt_internals", issue = "none")]
 impl<'a> Arguments<'a> {
-    #[doc(hidden)]
     #[inline]
-    #[unstable(feature = "fmt_internals", issue = "none")]
     #[rustc_const_unstable(feature = "const_fmt_arguments_new", issue = "none")]
     pub const fn new_const(pieces: &'a [&'static str]) -> Self {
         if pieces.len() > 1 {
@@ -405,23 +303,8 @@ impl<'a> Arguments<'a> {
 
     /// When using the format_args!() macro, this function is used to generate the
     /// Arguments structure.
-    #[cfg(not(bootstrap))]
-    #[doc(hidden)]
     #[inline]
-    #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-    pub fn new_v1(pieces: &'a [&'static str], args: &'a [ArgumentV1<'a>]) -> Arguments<'a> {
-        if pieces.len() < args.len() || pieces.len() > args.len() + 1 {
-            panic!("invalid args");
-        }
-        Arguments { pieces, fmt: None, args }
-    }
-
-    #[cfg(bootstrap)]
-    #[doc(hidden)]
-    #[inline]
-    #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
-    #[rustc_const_unstable(feature = "const_fmt_arguments_new", issue = "none")]
-    pub const fn new_v1(pieces: &'a [&'static str], args: &'a [ArgumentV1<'a>]) -> Arguments<'a> {
+    pub fn new_v1(pieces: &'a [&'static str], args: &'a [rt::Argument<'a>]) -> Arguments<'a> {
         if pieces.len() < args.len() || pieces.len() > args.len() + 1 {
             panic!("invalid args");
         }
@@ -430,21 +313,17 @@ impl<'a> Arguments<'a> {
 
     /// This function is used to specify nonstandard formatting parameters.
     ///
-    /// An `UnsafeArg` is required because the following invariants must be held
+    /// An `rt::UnsafeArg` is required because the following invariants must be held
     /// in order for this function to be safe:
     /// 1. The `pieces` slice must be at least as long as `fmt`.
-    /// 2. Every [`rt::v1::Argument::position`] value within `fmt` must be a
-    ///    valid index of `args`.
-    /// 3. Every [`rt::v1::Count::Param`] within `fmt` must contain a valid index of
-    ///    `args`.
-    #[doc(hidden)]
+    /// 2. Every `rt::Placeholder::position` value within `fmt` must be a valid index of `args`.
+    /// 3. Every `rt::Count::Param` within `fmt` must contain a valid index of `args`.
     #[inline]
-    #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
     pub fn new_v1_formatted(
         pieces: &'a [&'static str],
-        args: &'a [ArgumentV1<'a>],
-        fmt: &'a [rt::v1::Argument],
-        _unsafe_arg: UnsafeArg,
+        args: &'a [rt::Argument<'a>],
+        fmt: &'a [rt::Placeholder],
+        _unsafe_arg: rt::UnsafeArg,
     ) -> Arguments<'a> {
         Arguments { pieces, fmt: Some(fmt), args }
     }
@@ -453,9 +332,7 @@ impl<'a> Arguments<'a> {
     ///
     /// This is intended to be used for setting initial `String` capacity
     /// when using `format!`. Note: this is neither the lower nor upper bound.
-    #[doc(hidden)]
     #[inline]
-    #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
     pub fn estimated_capacity(&self) -> usize {
         let pieces_length: usize = self.pieces.iter().map(|x| x.len()).sum();
 
@@ -475,43 +352,6 @@ impl<'a> Arguments<'a> {
     }
 }
 
-/// This structure represents a safely precompiled version of a format string
-/// and its arguments. This cannot be generated at runtime because it cannot
-/// safely be done, so no constructors are given and the fields are private
-/// to prevent modification.
-///
-/// The [`format_args!`] macro will safely create an instance of this structure.
-/// The macro validates the format string at compile-time so usage of the
-/// [`write()`] and [`format()`] functions can be safely performed.
-///
-/// You can use the `Arguments<'a>` that [`format_args!`] returns in `Debug`
-/// and `Display` contexts as seen below. The example also shows that `Debug`
-/// and `Display` format to the same thing: the interpolated format string
-/// in `format_args!`.
-///
-/// ```rust
-/// let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2));
-/// let display = format!("{}", format_args!("{} foo {:?}", 1, 2));
-/// assert_eq!("1 foo 2", display);
-/// assert_eq!(display, debug);
-/// ```
-///
-/// [`format()`]: ../../std/fmt/fn.format.html
-#[lang = "format_arguments"]
-#[stable(feature = "rust1", since = "1.0.0")]
-#[derive(Copy, Clone)]
-pub struct Arguments<'a> {
-    // Format string pieces to print.
-    pieces: &'a [&'static str],
-
-    // Placeholder specs, or `None` if all specs are default (as in "{}{}").
-    fmt: Option<&'a [rt::v1::Argument]>,
-
-    // Dynamic arguments for interpolation, to be interleaved with string
-    // pieces. (Every argument is preceded by a string piece.)
-    args: &'a [ArgumentV1<'a>],
-}
-
 impl<'a> Arguments<'a> {
     /// Get the formatted string, if it has no arguments to be formatted at runtime.
     ///
@@ -541,7 +381,7 @@ impl<'a> Arguments<'a> {
     ///
     /// fn write_str(_: &str) { /* ... */ }
     ///
-    /// fn write_fmt(args: &Arguments) {
+    /// fn write_fmt(args: &Arguments<'_>) {
     ///     if let Some(s) = args.as_str() {
     ///         write_str(s)
     ///     } else {
@@ -1251,7 +1091,7 @@ pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
                 if !piece.is_empty() {
                     formatter.buf.write_str(*piece)?;
                 }
-                (arg.formatter)(arg.value, &mut formatter)?;
+                arg.fmt(&mut formatter)?;
                 idx += 1;
             }
         }
@@ -1281,15 +1121,15 @@ pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
     Ok(())
 }
 
-unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::v1::Argument, args: &[ArgumentV1<'_>]) -> Result {
-    fmt.fill = arg.format.fill;
-    fmt.align = arg.format.align;
-    fmt.flags = arg.format.flags;
+unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::Placeholder, args: &[rt::Argument<'_>]) -> Result {
+    fmt.fill = arg.fill;
+    fmt.align = arg.align;
+    fmt.flags = arg.flags;
     // SAFETY: arg and args come from the same Arguments,
     // which guarantees the indexes are always within bounds.
     unsafe {
-        fmt.width = getcount(args, &arg.format.width);
-        fmt.precision = getcount(args, &arg.format.precision);
+        fmt.width = getcount(args, &arg.width);
+        fmt.precision = getcount(args, &arg.precision);
     }
 
     // Extract the correct argument
@@ -1299,14 +1139,14 @@ unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::v1::Argument, args: &[ArgumentV
     let value = unsafe { args.get_unchecked(arg.position) };
 
     // Then actually do some printing
-    (value.formatter)(value.value, fmt)
+    value.fmt(fmt)
 }
 
-unsafe fn getcount(args: &[ArgumentV1<'_>], cnt: &rt::v1::Count) -> Option<usize> {
+unsafe fn getcount(args: &[rt::Argument<'_>], cnt: &rt::Count) -> Option<usize> {
     match *cnt {
-        rt::v1::Count::Is(n) => Some(n),
-        rt::v1::Count::Implied => None,
-        rt::v1::Count::Param(i) => {
+        rt::Count::Is(n) => Some(n),
+        rt::Count::Implied => None,
+        rt::Count::Param(i) => {
             debug_assert!(i < args.len());
             // SAFETY: cnt and args come from the same Arguments,
             // which guarantees this index is always within bounds.
@@ -1388,7 +1228,7 @@ impl<'a> Formatter<'a> {
     /// }
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         // We need to remove "-" from the number output.
     ///         let tmp = self.nb.abs().to_string();
     ///
@@ -1449,9 +1289,9 @@ impl<'a> Formatter<'a> {
             // is zero
             Some(min) if self.sign_aware_zero_pad() => {
                 let old_fill = crate::mem::replace(&mut self.fill, '0');
-                let old_align = crate::mem::replace(&mut self.align, rt::v1::Alignment::Right);
+                let old_align = crate::mem::replace(&mut self.align, rt::Alignment::Right);
                 write_prefix(self, sign, prefix)?;
-                let post_padding = self.padding(min - width, rt::v1::Alignment::Right)?;
+                let post_padding = self.padding(min - width, Alignment::Right)?;
                 self.buf.write_str(buf)?;
                 post_padding.write(self)?;
                 self.fill = old_fill;
@@ -1460,7 +1300,7 @@ impl<'a> Formatter<'a> {
             }
             // Otherwise, the sign and prefix goes after the padding
             Some(min) => {
-                let post_padding = self.padding(min - width, rt::v1::Alignment::Right)?;
+                let post_padding = self.padding(min - width, Alignment::Right)?;
                 write_prefix(self, sign, prefix)?;
                 self.buf.write_str(buf)?;
                 post_padding.write(self)
@@ -1488,7 +1328,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo;
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         formatter.pad("Foo")
     ///     }
     /// }
@@ -1535,7 +1375,7 @@ impl<'a> Formatter<'a> {
                 // If we're under both the maximum and the minimum width, then fill
                 // up the minimum width with the specified string + some alignment.
                 else {
-                    let align = rt::v1::Alignment::Left;
+                    let align = Alignment::Left;
                     let post_padding = self.padding(width - chars_count, align)?;
                     self.buf.write_str(s)?;
                     post_padding.write(self)
@@ -1550,17 +1390,19 @@ impl<'a> Formatter<'a> {
     pub(crate) fn padding(
         &mut self,
         padding: usize,
-        default: rt::v1::Alignment,
+        default: Alignment,
     ) -> result::Result<PostPadding, Error> {
         let align = match self.align {
-            rt::v1::Alignment::Unknown => default,
-            _ => self.align,
+            rt::Alignment::Unknown => default,
+            rt::Alignment::Left => Alignment::Left,
+            rt::Alignment::Right => Alignment::Right,
+            rt::Alignment::Center => Alignment::Center,
         };
 
         let (pre_pad, post_pad) = match align {
-            rt::v1::Alignment::Left => (0, padding),
-            rt::v1::Alignment::Right | rt::v1::Alignment::Unknown => (padding, 0),
-            rt::v1::Alignment::Center => (padding / 2, (padding + 1) / 2),
+            Alignment::Left => (0, padding),
+            Alignment::Right => (padding, 0),
+            Alignment::Center => (padding / 2, (padding + 1) / 2),
         };
 
         for _ in 0..pre_pad {
@@ -1573,14 +1415,17 @@ impl<'a> Formatter<'a> {
     /// Takes the formatted parts and applies the padding.
     /// Assumes that the caller already has rendered the parts with required precision,
     /// so that `self.precision` can be ignored.
-    fn pad_formatted_parts(&mut self, formatted: &numfmt::Formatted<'_>) -> Result {
+    ///
+    /// # Safety
+    ///
+    /// Any `numfmt::Part::Copy` parts in `formatted` must contain valid UTF-8.
+    unsafe fn pad_formatted_parts(&mut self, formatted: &numfmt::Formatted<'_>) -> Result {
         if let Some(mut width) = self.width {
             // for the sign-aware zero padding, we render the sign first and
             // behave as if we had no sign from the beginning.
             let mut formatted = formatted.clone();
             let old_fill = self.fill;
             let old_align = self.align;
-            let mut align = old_align;
             if self.sign_aware_zero_pad() {
                 // a sign always goes first
                 let sign = formatted.sign;
@@ -1589,19 +1434,22 @@ impl<'a> Formatter<'a> {
                 // remove the sign from the formatted parts
                 formatted.sign = "";
                 width = width.saturating_sub(sign.len());
-                align = rt::v1::Alignment::Right;
                 self.fill = '0';
-                self.align = rt::v1::Alignment::Right;
+                self.align = rt::Alignment::Right;
             }
 
             // remaining parts go through the ordinary padding process.
             let len = formatted.len();
             let ret = if width <= len {
                 // no padding
-                self.write_formatted_parts(&formatted)
+                // SAFETY: Per the precondition.
+                unsafe { self.write_formatted_parts(&formatted) }
             } else {
-                let post_padding = self.padding(width - len, align)?;
-                self.write_formatted_parts(&formatted)?;
+                let post_padding = self.padding(width - len, Alignment::Right)?;
+                // SAFETY: Per the precondition.
+                unsafe {
+                    self.write_formatted_parts(&formatted)?;
+                }
                 post_padding.write(self)
             };
             self.fill = old_fill;
@@ -1609,20 +1457,20 @@ impl<'a> Formatter<'a> {
             ret
         } else {
             // this is the common case and we take a shortcut
-            self.write_formatted_parts(formatted)
+            // SAFETY: Per the precondition.
+            unsafe { self.write_formatted_parts(formatted) }
         }
     }
 
-    fn write_formatted_parts(&mut self, formatted: &numfmt::Formatted<'_>) -> Result {
-        fn write_bytes(buf: &mut dyn Write, s: &[u8]) -> Result {
+    /// # Safety
+    ///
+    /// Any `numfmt::Part::Copy` parts in `formatted` must contain valid UTF-8.
+    unsafe fn write_formatted_parts(&mut self, formatted: &numfmt::Formatted<'_>) -> Result {
+        unsafe fn write_bytes(buf: &mut dyn Write, s: &[u8]) -> Result {
             // SAFETY: This is used for `numfmt::Part::Num` and `numfmt::Part::Copy`.
             // It's safe to use for `numfmt::Part::Num` since every char `c` is between
-            // `b'0'` and `b'9'`, which means `s` is valid UTF-8.
-            // It's also probably safe in practice to use for `numfmt::Part::Copy(buf)`
-            // since `buf` should be plain ASCII, but it's possible for someone to pass
-            // in a bad value for `buf` into `numfmt::to_shortest_str` since it is a
-            // public function.
-            // FIXME: Determine whether this could result in UB.
+            // `b'0'` and `b'9'`, which means `s` is valid UTF-8. It's safe to use for
+            // `numfmt::Part::Copy` due to this function's precondition.
             buf.write_str(unsafe { str::from_utf8_unchecked(s) })
         }
 
@@ -1649,11 +1497,15 @@ impl<'a> Formatter<'a> {
                         *c = b'0' + (v % 10) as u8;
                         v /= 10;
                     }
-                    write_bytes(self.buf, &s[..len])?;
+                    // SAFETY: Per the precondition.
+                    unsafe {
+                        write_bytes(self.buf, &s[..len])?;
+                    }
                 }
-                numfmt::Part::Copy(buf) => {
+                // SAFETY: Per the precondition.
+                numfmt::Part::Copy(buf) => unsafe {
                     write_bytes(self.buf, buf)?;
-                }
+                },
             }
         }
         Ok(())
@@ -1670,7 +1522,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo;
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         formatter.write_str("Foo")
     ///         // This is equivalent to:
     ///         // write!(formatter, "Foo")
@@ -1695,7 +1547,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(i32);
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         formatter.write_fmt(format_args!("Foo {}", self.0))
     ///     }
     /// }
@@ -1730,7 +1582,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo;
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         let c = formatter.fill();
     ///         if let Some(width) = formatter.width() {
     ///             for _ in 0..width {
@@ -1758,14 +1610,12 @@ impl<'a> Formatter<'a> {
     /// # Examples
     ///
     /// ```
-    /// extern crate core;
-    ///
     /// use std::fmt::{self, Alignment};
     ///
     /// struct Foo;
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         let s = if let Some(s) = formatter.align() {
     ///             match s {
     ///                 Alignment::Left    => "left",
@@ -1788,10 +1638,10 @@ impl<'a> Formatter<'a> {
     #[stable(feature = "fmt_flags_align", since = "1.28.0")]
     pub fn align(&self) -> Option<Alignment> {
         match self.align {
-            rt::v1::Alignment::Left => Some(Alignment::Left),
-            rt::v1::Alignment::Right => Some(Alignment::Right),
-            rt::v1::Alignment::Center => Some(Alignment::Center),
-            rt::v1::Alignment::Unknown => None,
+            rt::Alignment::Left => Some(Alignment::Left),
+            rt::Alignment::Right => Some(Alignment::Right),
+            rt::Alignment::Center => Some(Alignment::Center),
+            rt::Alignment::Unknown => None,
         }
     }
 
@@ -1805,7 +1655,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(i32);
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         if let Some(width) = formatter.width() {
     ///             // If we received a width, we use it
     ///             write!(formatter, "{:width$}", format!("Foo({})", self.0), width = width)
@@ -1836,7 +1686,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(f32);
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         if let Some(precision) = formatter.precision() {
     ///             // If we received a precision, we use it.
     ///             write!(formatter, "Foo({1:.*})", precision, self.0)
@@ -1866,7 +1716,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(i32);
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         if formatter.sign_plus() {
     ///             write!(formatter,
     ///                    "Foo({}{})",
@@ -1885,7 +1735,7 @@ impl<'a> Formatter<'a> {
     #[must_use]
     #[stable(feature = "fmt_flags", since = "1.5.0")]
     pub fn sign_plus(&self) -> bool {
-        self.flags & (1 << FlagV1::SignPlus as u32) != 0
+        self.flags & (1 << rt::Flag::SignPlus as u32) != 0
     }
 
     /// Determines if the `-` flag was specified.
@@ -1898,7 +1748,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(i32);
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         if formatter.sign_minus() {
     ///             // You want a minus sign? Have one!
     ///             write!(formatter, "-Foo({})", self.0)
@@ -1914,7 +1764,7 @@ impl<'a> Formatter<'a> {
     #[must_use]
     #[stable(feature = "fmt_flags", since = "1.5.0")]
     pub fn sign_minus(&self) -> bool {
-        self.flags & (1 << FlagV1::SignMinus as u32) != 0
+        self.flags & (1 << rt::Flag::SignMinus as u32) != 0
     }
 
     /// Determines if the `#` flag was specified.
@@ -1927,7 +1777,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(i32);
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         if formatter.alternate() {
     ///             write!(formatter, "Foo({})", self.0)
     ///         } else {
@@ -1942,7 +1792,7 @@ impl<'a> Formatter<'a> {
     #[must_use]
     #[stable(feature = "fmt_flags", since = "1.5.0")]
     pub fn alternate(&self) -> bool {
-        self.flags & (1 << FlagV1::Alternate as u32) != 0
+        self.flags & (1 << rt::Flag::Alternate as u32) != 0
     }
 
     /// Determines if the `0` flag was specified.
@@ -1955,7 +1805,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(i32);
     ///
     /// impl fmt::Display for Foo {
-    ///     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         assert!(formatter.sign_aware_zero_pad());
     ///         assert_eq!(formatter.width(), Some(4));
     ///         // We ignore the formatter's options.
@@ -1968,17 +1818,17 @@ impl<'a> Formatter<'a> {
     #[must_use]
     #[stable(feature = "fmt_flags", since = "1.5.0")]
     pub fn sign_aware_zero_pad(&self) -> bool {
-        self.flags & (1 << FlagV1::SignAwareZeroPad as u32) != 0
+        self.flags & (1 << rt::Flag::SignAwareZeroPad as u32) != 0
     }
 
     // FIXME: Decide what public API we want for these two flags.
     // https://github.com/rust-lang/rust/issues/48584
     fn debug_lower_hex(&self) -> bool {
-        self.flags & (1 << FlagV1::DebugLowerHex as u32) != 0
+        self.flags & (1 << rt::Flag::DebugLowerHex as u32) != 0
     }
 
     fn debug_upper_hex(&self) -> bool {
-        self.flags & (1 << FlagV1::DebugUpperHex as u32) != 0
+        self.flags & (1 << rt::Flag::DebugUpperHex as u32) != 0
     }
 
     /// Creates a [`DebugStruct`] builder designed to assist with creation of
@@ -1999,7 +1849,7 @@ impl<'a> Formatter<'a> {
     /// }
     ///
     /// impl fmt::Debug for Foo {
-    ///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         fmt.debug_struct("Foo")
     ///             .field("bar", &self.bar)
     ///             .field("baz", &self.baz)
@@ -2157,7 +2007,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo<T>(i32, String, PhantomData<T>);
     ///
     /// impl<T> fmt::Debug for Foo<T> {
-    ///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         fmt.debug_tuple("Foo")
     ///             .field(&self.0)
     ///             .field(&self.1)
@@ -2289,7 +2139,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(Vec<i32>);
     ///
     /// impl fmt::Debug for Foo {
-    ///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         fmt.debug_list().entries(self.0.iter()).finish()
     ///     }
     /// }
@@ -2312,7 +2162,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(Vec<i32>);
     ///
     /// impl fmt::Debug for Foo {
-    ///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         fmt.debug_set().entries(self.0.iter()).finish()
     ///     }
     /// }
@@ -2328,14 +2178,14 @@ impl<'a> Formatter<'a> {
     /// ```rust
     /// use std::fmt;
     ///
-    /// struct Arm<'a, L: 'a, R: 'a>(&'a (L, R));
-    /// struct Table<'a, K: 'a, V: 'a>(&'a [(K, V)], V);
+    /// struct Arm<'a, L, R>(&'a (L, R));
+    /// struct Table<'a, K, V>(&'a [(K, V)], V);
     ///
     /// impl<'a, L, R> fmt::Debug for Arm<'a, L, R>
     /// where
     ///     L: 'a + fmt::Debug, R: 'a + fmt::Debug
     /// {
-    ///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         L::fmt(&(self.0).0, fmt)?;
     ///         fmt.write_str(" => ")?;
     ///         R::fmt(&(self.0).1, fmt)
@@ -2346,7 +2196,7 @@ impl<'a> Formatter<'a> {
     /// where
     ///     K: 'a + fmt::Debug, V: 'a + fmt::Debug
     /// {
-    ///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         fmt.debug_set()
     ///         .entries(self.0.iter().map(Arm))
     ///         .entry(&Arm(&(format_args!("_"), &self.1)))
@@ -2370,7 +2220,7 @@ impl<'a> Formatter<'a> {
     /// struct Foo(Vec<(String, i32)>);
     ///
     /// impl fmt::Debug for Foo {
-    ///     fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+    ///     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
     ///         fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
     ///     }
     /// }
@@ -2429,6 +2279,7 @@ fmt_refs! { Debug, Display, Octal, Binary, LowerHex, UpperHex, LowerExp, UpperEx
 
 #[unstable(feature = "never_type", issue = "35121")]
 impl Debug for ! {
+    #[inline]
     fn fmt(&self, _: &mut Formatter<'_>) -> Result {
         *self
     }
@@ -2436,6 +2287,7 @@ impl Debug for ! {
 
 #[unstable(feature = "never_type", issue = "35121")]
 impl Display for ! {
+    #[inline]
     fn fmt(&self, _: &mut Formatter<'_>) -> Result {
         *self
     }
@@ -2538,13 +2390,13 @@ pub(crate) fn pointer_fmt_inner(ptr_addr: usize, f: &mut Formatter<'_>) -> Resul
     // or not to zero extend, and then unconditionally set it to get the
     // prefix.
     if f.alternate() {
-        f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
+        f.flags |= 1 << (rt::Flag::SignAwareZeroPad as u32);
 
         if f.width.is_none() {
             f.width = Some((usize::BITS / 4) as usize + 2);
         }
     }
-    f.flags |= 1 << (FlagV1::Alternate as u32);
+    f.flags |= 1 << (rt::Flag::Alternate as u32);
 
     let ret = LowerHex::fmt(&ptr_addr, f);
 
diff --git a/library/core/src/fmt/num.rs b/library/core/src/fmt/num.rs
index d8365ae9b..4f42f73eb 100644
--- a/library/core/src/fmt/num.rs
+++ b/library/core/src/fmt/num.rs
@@ -52,8 +52,12 @@ impl_int! { i8 i16 i32 i64 i128 isize }
 impl_uint! { u8 u16 u32 u64 u128 usize }
 
 /// A type that represents a specific radix
+///
+/// # Safety
+///
+/// `digit` must return an ASCII character.
 #[doc(hidden)]
-trait GenericRadix: Sized {
+unsafe trait GenericRadix: Sized {
     /// The number of digits.
     const BASE: u8;
 
@@ -129,7 +133,7 @@ struct UpperHex;
 
 macro_rules! radix {
     ($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
-        impl GenericRadix for $T {
+        unsafe impl GenericRadix for $T {
             const BASE: u8 = $base;
             const PREFIX: &'static str = $prefix;
             fn digit(x: u8) -> u8 {
@@ -407,7 +411,7 @@ macro_rules! impl_Exp {
             let parts = &[
                 numfmt::Part::Copy(buf_slice),
                 numfmt::Part::Zero(added_precision),
-                numfmt::Part::Copy(exp_slice)
+                numfmt::Part::Copy(exp_slice),
             ];
             let sign = if !is_nonnegative {
                 "-"
@@ -416,8 +420,9 @@ macro_rules! impl_Exp {
             } else {
                 ""
             };
-            let formatted = numfmt::Formatted{sign, parts};
-            f.pad_formatted_parts(&formatted)
+            let formatted = numfmt::Formatted { sign, parts };
+            // SAFETY: `buf_slice` and `exp_slice` contain only ASCII characters.
+            unsafe { f.pad_formatted_parts(&formatted) }
         }
 
         $(
diff --git a/library/core/src/fmt/rt.rs b/library/core/src/fmt/rt.rs
new file mode 100644
index 000000000..d37888c27
--- /dev/null
+++ b/library/core/src/fmt/rt.rs
@@ -0,0 +1,212 @@
+#![allow(missing_debug_implementations)]
+#![unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
+
+//! These are the lang items used by format_args!().
+
+use super::*;
+
+#[lang = "format_placeholder"]
+#[derive(Copy, Clone)]
+pub struct Placeholder {
+    pub position: usize,
+    pub fill: char,
+    pub align: Alignment,
+    pub flags: u32,
+    pub precision: Count,
+    pub width: Count,
+}
+
+impl Placeholder {
+    #[inline(always)]
+    pub const fn new(
+        position: usize,
+        fill: char,
+        align: Alignment,
+        flags: u32,
+        precision: Count,
+        width: Count,
+    ) -> Self {
+        Self { position, fill, align, flags, precision, width }
+    }
+}
+
+#[lang = "format_alignment"]
+#[derive(Copy, Clone, PartialEq, Eq)]
+pub enum Alignment {
+    Left,
+    Right,
+    Center,
+    Unknown,
+}
+
+/// Used by [width](https://doc.rust-lang.org/std/fmt/#width)
+/// and [precision](https://doc.rust-lang.org/std/fmt/#precision) specifiers.
+#[lang = "format_count"]
+#[derive(Copy, Clone)]
+pub enum Count {
+    /// Specified with a literal number, stores the value
+    Is(usize),
+    /// Specified using `$` and `*` syntaxes, stores the index into `args`
+    Param(usize),
+    /// Not specified
+    Implied,
+}
+
+// This needs to match the order of flags in compiler/rustc_ast_lowering/src/format.rs.
+#[derive(Copy, Clone)]
+pub(super) enum Flag {
+    SignPlus,
+    SignMinus,
+    Alternate,
+    SignAwareZeroPad,
+    DebugLowerHex,
+    DebugUpperHex,
+}
+
+/// This struct represents the generic "argument" which is taken by format_args!().
+/// It contains a function to format the given value. At compile time it is ensured that the
+/// function and the value have the correct types, and then this struct is used to canonicalize
+/// arguments to one type.
+///
+/// Argument is essentially an optimized partially applied formatting function,
+/// equivalent to `exists T.(&T, fn(&T, &mut Formatter<'_>) -> Result`.
+#[lang = "format_argument"]
+#[derive(Copy, Clone)]
+pub struct Argument<'a> {
+    value: &'a Opaque,
+    formatter: fn(&Opaque, &mut Formatter<'_>) -> Result,
+}
+
+#[rustc_diagnostic_item = "ArgumentMethods"]
+impl<'a> Argument<'a> {
+    #[inline(always)]
+    fn new<'b, T>(x: &'b T, f: fn(&T, &mut Formatter<'_>) -> Result) -> Argument<'b> {
+        // SAFETY: `mem::transmute(x)` is safe because
+        //     1. `&'b T` keeps the lifetime it originated with `'b`
+        //              (so as to not have an unbounded lifetime)
+        //     2. `&'b T` and `&'b Opaque` have the same memory layout
+        //              (when `T` is `Sized`, as it is here)
+        // `mem::transmute(f)` is safe since `fn(&T, &mut Formatter<'_>) -> Result`
+        // and `fn(&Opaque, &mut Formatter<'_>) -> Result` have the same ABI
+        // (as long as `T` is `Sized`)
+        unsafe { Argument { formatter: mem::transmute(f), value: mem::transmute(x) } }
+    }
+
+    #[inline(always)]
+    pub fn new_display<'b, T: Display>(x: &'b T) -> Argument<'_> {
+        Self::new(x, Display::fmt)
+    }
+    #[inline(always)]
+    pub fn new_debug<'b, T: Debug>(x: &'b T) -> Argument<'_> {
+        Self::new(x, Debug::fmt)
+    }
+    #[inline(always)]
+    pub fn new_octal<'b, T: Octal>(x: &'b T) -> Argument<'_> {
+        Self::new(x, Octal::fmt)
+    }
+    #[inline(always)]
+    pub fn new_lower_hex<'b, T: LowerHex>(x: &'b T) -> Argument<'_> {
+        Self::new(x, LowerHex::fmt)
+    }
+    #[inline(always)]
+    pub fn new_upper_hex<'b, T: UpperHex>(x: &'b T) -> Argument<'_> {
+        Self::new(x, UpperHex::fmt)
+    }
+    #[inline(always)]
+    pub fn new_pointer<'b, T: Pointer>(x: &'b T) -> Argument<'_> {
+        Self::new(x, Pointer::fmt)
+    }
+    #[inline(always)]
+    pub fn new_binary<'b, T: Binary>(x: &'b T) -> Argument<'_> {
+        Self::new(x, Binary::fmt)
+    }
+    #[inline(always)]
+    pub fn new_lower_exp<'b, T: LowerExp>(x: &'b T) -> Argument<'_> {
+        Self::new(x, LowerExp::fmt)
+    }
+    #[inline(always)]
+    pub fn new_upper_exp<'b, T: UpperExp>(x: &'b T) -> Argument<'_> {
+        Self::new(x, UpperExp::fmt)
+    }
+    #[inline(always)]
+    pub fn from_usize(x: &usize) -> Argument<'_> {
+        Self::new(x, USIZE_MARKER)
+    }
+
+    #[inline(always)]
+    pub(super) fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+        (self.formatter)(self.value, f)
+    }
+
+    #[inline(always)]
+    pub(super) fn as_usize(&self) -> Option<usize> {
+        // We are type punning a bit here: USIZE_MARKER only takes an &usize but
+        // formatter takes an &Opaque. Rust understandably doesn't think we should compare
+        // the function pointers if they don't have the same signature, so we cast to
+        // usizes to tell it that we just want to compare addresses.
+        if self.formatter as usize == USIZE_MARKER as usize {
+            // SAFETY: The `formatter` field is only set to USIZE_MARKER if
+            // the value is a usize, so this is safe
+            Some(unsafe { *(self.value as *const _ as *const usize) })
+        } else {
+            None
+        }
+    }
+
+    /// Used by `format_args` when all arguments are gone after inlining,
+    /// when using `&[]` would incorrectly allow for a bigger lifetime.
+    ///
+    /// This fails without format argument inlining, and that shouldn't be different
+    /// when the argument is inlined:
+    ///
+    /// ```compile_fail,E0716
+    /// let f = format_args!("{}", "a");
+    /// println!("{f}");
+    /// ```
+    #[inline(always)]
+    pub fn none() -> [Self; 0] {
+        []
+    }
+}
+
+/// This struct represents the unsafety of constructing an `Arguments`.
+/// It exists, rather than an unsafe function, in order to simplify the expansion
+/// of `format_args!(..)` and reduce the scope of the `unsafe` block.
+#[lang = "format_unsafe_arg"]
+pub struct UnsafeArg {
+    _private: (),
+}
+
+impl UnsafeArg {
+    /// See documentation where `UnsafeArg` is required to know when it is safe to
+    /// create and use `UnsafeArg`.
+    #[inline(always)]
+    pub unsafe fn new() -> Self {
+        Self { _private: () }
+    }
+}
+
+extern "C" {
+    type Opaque;
+}
+
+// This guarantees a single stable value for the function pointer associated with
+// indices/counts in the formatting infrastructure.
+//
+// Note that a function defined as such would not be correct as functions are
+// always tagged unnamed_addr with the current lowering to LLVM IR, so their
+// address is not considered important to LLVM and as such the as_usize cast
+// could have been miscompiled. In practice, we never call as_usize on non-usize
+// containing data (as a matter of static generation of the formatting
+// arguments), so this is merely an additional check.
+//
+// We primarily want to ensure that the function pointer at `USIZE_MARKER` has
+// an address corresponding *only* to functions that also take `&usize` as their
+// first argument. The read_volatile here ensures that we can safely ready out a
+// usize from the passed reference and that this address does not point at a
+// non-usize taking function.
+static USIZE_MARKER: fn(&usize, &mut Formatter<'_>) -> Result = |ptr, _| {
+    // SAFETY: ptr is a reference
+    let _v: usize = unsafe { crate::ptr::read_volatile(ptr) };
+    loop {}
+};
diff --git a/library/core/src/fmt/rt/v1.rs b/library/core/src/fmt/rt/v1.rs
deleted file mode 100644
index 6d70796f7..000000000
--- a/library/core/src/fmt/rt/v1.rs
+++ /dev/null
@@ -1,63 +0,0 @@
-//! This is an internal module used by the ifmt! runtime. These structures are
-//! emitted to static arrays to precompile format strings ahead of time.
-//!
-//! These definitions are similar to their `ct` equivalents, but differ in that
-//! these can be statically allocated and are slightly optimized for the runtime
-#![allow(missing_debug_implementations)]
-
-#[lang = "format_placeholder"]
-#[derive(Copy, Clone)]
-// FIXME: Rename this to Placeholder
-pub struct Argument {
-    pub position: usize,
-    pub format: FormatSpec,
-}
-
-#[derive(Copy, Clone)]
-pub struct FormatSpec {
-    pub fill: char,
-    pub align: Alignment,
-    pub flags: u32,
-    pub precision: Count,
-    pub width: Count,
-}
-
-impl Argument {
-    #[inline(always)]
-    pub const fn new(
-        position: usize,
-        fill: char,
-        align: Alignment,
-        flags: u32,
-        precision: Count,
-        width: Count,
-    ) -> Self {
-        Self { position, format: FormatSpec { fill, align, flags, precision, width } }
-    }
-}
-
-/// Possible alignments that can be requested as part of a formatting directive.
-#[lang = "format_alignment"]
-#[derive(Copy, Clone, PartialEq, Eq)]
-pub enum Alignment {
-    /// Indication that contents should be left-aligned.
-    Left,
-    /// Indication that contents should be right-aligned.
-    Right,
-    /// Indication that contents should be center-aligned.
-    Center,
-    /// No alignment was requested.
-    Unknown,
-}
-
-/// Used by [width](https://doc.rust-lang.org/std/fmt/#width) and [precision](https://doc.rust-lang.org/std/fmt/#precision) specifiers.
-#[lang = "format_count"]
-#[derive(Copy, Clone)]
-pub enum Count {
-    /// Specified with a literal number, stores the value
-    Is(usize),
-    /// Specified using `$` and `*` syntaxes, stores the index into `args`
-    Param(usize),
-    /// Not specified
-    Implied,
-}