From debf305d9e0a21244339820923bbbc1f8589a39d Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 20 Apr 2023 18:01:59 +0200
Subject: [PATCH 1/8] Don't reexport core::fmt::rt from alloc::fmt.

---
 library/alloc/src/fmt.rs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/library/alloc/src/fmt.rs b/library/alloc/src/fmt.rs
index 1da86e1a46a57..e03b501ae4d23 100644
--- a/library/alloc/src/fmt.rs
+++ b/library/alloc/src/fmt.rs
@@ -551,8 +551,6 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#[unstable(feature = "fmt_internals", issue = "none")]
-pub use core::fmt::rt;
 #[stable(feature = "fmt_flags_align", since = "1.28.0")]
 pub use core::fmt::Alignment;
 #[stable(feature = "rust1", since = "1.0.0")]

From a77159341e12e02d7f738c709b9798e68bc4af04 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 20 Apr 2023 18:03:47 +0200
Subject: [PATCH 2/8] Use fmt::Alignment instead of fmt::rt::v1::Alignment.

---
 library/core/src/fmt/mod.rs | 24 ++++++++++++------------
 library/core/src/time.rs    |  2 +-
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index fcda097f01fce..af40dcdc5f0de 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -1451,7 +1451,7 @@ impl<'a> Formatter<'a> {
                 let old_fill = crate::mem::replace(&mut self.fill, '0');
                 let old_align = crate::mem::replace(&mut self.align, rt::v1::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 +1460,7 @@ 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)
@@ -1535,7 +1535,7 @@ 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 +1550,19 @@ 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::v1::Alignment::Left => Alignment::Left,
+            rt::v1::Alignment::Right => Alignment::Right,
+            rt::v1::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 {
@@ -1580,7 +1582,6 @@ impl<'a> Formatter<'a> {
             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;
@@ -1589,9 +1590,8 @@ 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.
@@ -1600,7 +1600,7 @@ impl<'a> Formatter<'a> {
                 // no padding
                 self.write_formatted_parts(&formatted)
             } else {
-                let post_padding = self.padding(width - len, align)?;
+                let post_padding = self.padding(width - len, Alignment::Right)?;
                 self.write_formatted_parts(&formatted)?;
                 post_padding.write(self)
             };
diff --git a/library/core/src/time.rs b/library/core/src/time.rs
index b74fe01366594..b08d5782ab6f4 100644
--- a/library/core/src/time.rs
+++ b/library/core/src/time.rs
@@ -1172,7 +1172,7 @@ impl fmt::Debug for Duration {
                         emit_without_padding(f)
                     } else {
                         // We need to add padding. Use the `Formatter::padding` helper function.
-                        let default_align = crate::fmt::rt::v1::Alignment::Left;
+                        let default_align = fmt::Alignment::Left;
                         let post_padding = f.padding(requested_w - actual_w, default_align)?;
                         emit_without_padding(f)?;
                         post_padding.write(f)

From bc11b459af451e4c35bf611a0baacba2b7919629 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 20 Apr 2023 18:04:28 +0200
Subject: [PATCH 3/8] Turn core::fmt::rt::v1 into a private module.

---
 library/core/src/fmt/mod.rs              | 47 +++++++++++-------------
 library/core/src/fmt/{rt/v1.rs => rt.rs} |  8 ++--
 2 files changed, 24 insertions(+), 31 deletions(-)
 rename library/core/src/fmt/{rt/v1.rs => rt.rs} (82%)

diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index af40dcdc5f0de..6988411095f0d 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,
@@ -433,9 +428,9 @@ impl<'a> Arguments<'a> {
     /// An `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
+    /// 2. Every [`rt::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
+    /// 3. Every [`rt::Count::Param`] within `fmt` must contain a valid index of
     ///    `args`.
     #[doc(hidden)]
     #[inline]
@@ -443,7 +438,7 @@ impl<'a> Arguments<'a> {
     pub fn new_v1_formatted(
         pieces: &'a [&'static str],
         args: &'a [ArgumentV1<'a>],
-        fmt: &'a [rt::v1::Argument],
+        fmt: &'a [rt::Argument],
         _unsafe_arg: UnsafeArg,
     ) -> Arguments<'a> {
         Arguments { pieces, fmt: Some(fmt), args }
@@ -505,7 +500,7 @@ pub struct Arguments<'a> {
     pieces: &'a [&'static str],
 
     // Placeholder specs, or `None` if all specs are default (as in "{}{}").
-    fmt: Option<&'a [rt::v1::Argument]>,
+    fmt: Option<&'a [rt::Argument]>,
 
     // Dynamic arguments for interpolation, to be interleaved with string
     // pieces. (Every argument is preceded by a string piece.)
@@ -1281,7 +1276,7 @@ pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
     Ok(())
 }
 
-unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::v1::Argument, args: &[ArgumentV1<'_>]) -> Result {
+unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::Argument, args: &[ArgumentV1<'_>]) -> Result {
     fmt.fill = arg.format.fill;
     fmt.align = arg.format.align;
     fmt.flags = arg.format.flags;
@@ -1302,11 +1297,11 @@ unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::v1::Argument, args: &[ArgumentV
     (value.formatter)(value.value, fmt)
 }
 
-unsafe fn getcount(args: &[ArgumentV1<'_>], cnt: &rt::v1::Count) -> Option<usize> {
+unsafe fn getcount(args: &[ArgumentV1<'_>], 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.
@@ -1449,7 +1444,7 @@ 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, Alignment::Right)?;
                 self.buf.write_str(buf)?;
@@ -1553,10 +1548,10 @@ impl<'a> Formatter<'a> {
         default: Alignment,
     ) -> result::Result<PostPadding, Error> {
         let align = match self.align {
-            rt::v1::Alignment::Unknown => default,
-            rt::v1::Alignment::Left => Alignment::Left,
-            rt::v1::Alignment::Right => Alignment::Right,
-            rt::v1::Alignment::Center => Alignment::Center,
+            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 {
@@ -1788,10 +1783,10 @@ 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,
         }
     }
 
diff --git a/library/core/src/fmt/rt/v1.rs b/library/core/src/fmt/rt.rs
similarity index 82%
rename from library/core/src/fmt/rt/v1.rs
rename to library/core/src/fmt/rt.rs
index 6d70796f70718..58dbe314d08be 100644
--- a/library/core/src/fmt/rt/v1.rs
+++ b/library/core/src/fmt/rt.rs
@@ -1,9 +1,7 @@
-//! 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)]
+#![unstable(feature = "fmt_internals", issue = "none")]
+
+//! These are the lang items used by format_args!().
 
 #[lang = "format_placeholder"]
 #[derive(Copy, Clone)]

From 938efe6f498b24734e68647aefb1e17459ef49b2 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 20 Apr 2023 18:05:35 +0200
Subject: [PATCH 4/8] Rename fmt::rt::Argument to Placeholder.

---
 library/core/src/fmt/mod.rs | 8 ++++----
 library/core/src/fmt/rt.rs  | 5 ++---
 2 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index 6988411095f0d..bbbfe06656cd7 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -428,7 +428,7 @@ impl<'a> Arguments<'a> {
     /// An `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::Argument::position`] value within `fmt` must be a
+    /// 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`.
@@ -438,7 +438,7 @@ impl<'a> Arguments<'a> {
     pub fn new_v1_formatted(
         pieces: &'a [&'static str],
         args: &'a [ArgumentV1<'a>],
-        fmt: &'a [rt::Argument],
+        fmt: &'a [rt::Placeholder],
         _unsafe_arg: UnsafeArg,
     ) -> Arguments<'a> {
         Arguments { pieces, fmt: Some(fmt), args }
@@ -500,7 +500,7 @@ pub struct Arguments<'a> {
     pieces: &'a [&'static str],
 
     // Placeholder specs, or `None` if all specs are default (as in "{}{}").
-    fmt: Option<&'a [rt::Argument]>,
+    fmt: Option<&'a [rt::Placeholder]>,
 
     // Dynamic arguments for interpolation, to be interleaved with string
     // pieces. (Every argument is preceded by a string piece.)
@@ -1276,7 +1276,7 @@ pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
     Ok(())
 }
 
-unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::Argument, args: &[ArgumentV1<'_>]) -> Result {
+unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::Placeholder, args: &[ArgumentV1<'_>]) -> Result {
     fmt.fill = arg.format.fill;
     fmt.align = arg.format.align;
     fmt.flags = arg.format.flags;
diff --git a/library/core/src/fmt/rt.rs b/library/core/src/fmt/rt.rs
index 58dbe314d08be..497b2e27739f9 100644
--- a/library/core/src/fmt/rt.rs
+++ b/library/core/src/fmt/rt.rs
@@ -5,8 +5,7 @@
 
 #[lang = "format_placeholder"]
 #[derive(Copy, Clone)]
-// FIXME: Rename this to Placeholder
-pub struct Argument {
+pub struct Placeholder {
     pub position: usize,
     pub format: FormatSpec,
 }
@@ -20,7 +19,7 @@ pub struct FormatSpec {
     pub width: Count,
 }
 
-impl Argument {
+impl Placeholder {
     #[inline(always)]
     pub const fn new(
         position: usize,

From bca80d811c44998e99014c4f85c1130c26cd9dd3 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 20 Apr 2023 18:07:34 +0200
Subject: [PATCH 5/8] Get rid of core::fmt::FormatSpec.

---
 library/core/src/fmt/mod.rs | 10 +++++-----
 library/core/src/fmt/rt.rs  |  7 +------
 2 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index bbbfe06656cd7..de958a82d9640 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -1277,14 +1277,14 @@ pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
 }
 
 unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::Placeholder, args: &[ArgumentV1<'_>]) -> Result {
-    fmt.fill = arg.format.fill;
-    fmt.align = arg.format.align;
-    fmt.flags = arg.format.flags;
+    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
diff --git a/library/core/src/fmt/rt.rs b/library/core/src/fmt/rt.rs
index 497b2e27739f9..a431ee54d9508 100644
--- a/library/core/src/fmt/rt.rs
+++ b/library/core/src/fmt/rt.rs
@@ -7,11 +7,6 @@
 #[derive(Copy, Clone)]
 pub struct Placeholder {
     pub position: usize,
-    pub format: FormatSpec,
-}
-
-#[derive(Copy, Clone)]
-pub struct FormatSpec {
     pub fill: char,
     pub align: Alignment,
     pub flags: u32,
@@ -29,7 +24,7 @@ impl Placeholder {
         precision: Count,
         width: Count,
     ) -> Self {
-        Self { position, format: FormatSpec { fill, align, flags, precision, width } }
+        Self { position, fill, align, flags, precision, width }
     }
 }
 

From 441682cca9a32314835a88fa981a3bf13ffb0aa8 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 20 Apr 2023 18:09:32 +0200
Subject: [PATCH 6/8] Update comments in format args lowering.

These lang items have been moved/renamed.
---
 compiler/rustc_ast_lowering/src/format.rs | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/format.rs b/compiler/rustc_ast_lowering/src/format.rs
index c41bdc440935c..ccf481cb9b39d 100644
--- a/compiler/rustc_ast_lowering/src/format.rs
+++ b/compiler/rustc_ast_lowering/src/format.rs
@@ -220,19 +220,19 @@ fn make_argument<'hir>(
 /// Generates:
 ///
 /// ```text
-///     <core::fmt::rt::v1::Count>::Is(…)
+///     <core::fmt::rt::Count>::Is(…)
 /// ```
 ///
 /// or
 ///
 /// ```text
-///     <core::fmt::rt::v1::Count>::Param(…)
+///     <core::fmt::rt::Count>::Param(…)
 /// ```
 ///
 /// or
 ///
 /// ```text
-///     <core::fmt::rt::v1::Count>::Implied
+///     <core::fmt::rt::Count>::Implied
 /// ```
 fn make_count<'hir>(
     ctx: &mut LoweringContext<'_, 'hir>,
@@ -278,13 +278,13 @@ fn make_count<'hir>(
 /// Generates
 ///
 /// ```text
-///     <core::fmt::rt::v1::Argument::new(
+///     <core::fmt::rt::Placeholder::new(
 ///         …usize, // position
 ///         '…', // fill
-///         <core::fmt::rt::v1::Alignment>::…, // alignment
+///         <core::fmt::rt::Alignment>::…, // alignment
 ///         …u32, // flags
-///         <core::fmt::rt::v1::Count::…>, // width
-///         <core::fmt::rt::v1::Count::…>, // precision
+///         <core::fmt::rt::Count::…>, // width
+///         <core::fmt::rt::Count::…>, // precision
 ///     )
 /// ```
 fn make_format_spec<'hir>(

From 687b3fa4396ed45eee967e223750e9aa3b4b5ee9 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 20 Apr 2023 18:47:47 +0200
Subject: [PATCH 7/8] Remove doc link to private item.

---
 library/core/src/fmt/mod.rs | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index de958a82d9640..a901ae726698a 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -428,10 +428,8 @@ impl<'a> Arguments<'a> {
     /// An `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::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`.
+    /// 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`.
     #[doc(hidden)]
     #[inline]
     #[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]

From bd917bbcd272c3f9b02bb07a6231860448c8d530 Mon Sep 17 00:00:00 2001
From: Mara Bos <m-ou.se@m-ou.se>
Date: Thu, 20 Apr 2023 19:38:33 +0200
Subject: [PATCH 8/8] Add reason to #![unstable] tag.

Co-authored-by: jyn <github@jyn.dev>
---
 library/core/src/fmt/rt.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/core/src/fmt/rt.rs b/library/core/src/fmt/rt.rs
index a431ee54d9508..2c1a767691b8b 100644
--- a/library/core/src/fmt/rt.rs
+++ b/library/core/src/fmt/rt.rs
@@ -1,5 +1,5 @@
 #![allow(missing_debug_implementations)]
-#![unstable(feature = "fmt_internals", issue = "none")]
+#![unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
 
 //! These are the lang items used by format_args!().