Auto merge of #57568 - Centril:rollup, r=Centril

Rollup of 16 pull requests

Successful merges:

 - #57351 (Don't actually create a full MIR stack frame when not needed)
 - #57353 (Optimise floating point `is_finite` (2x) and `is_infinite` (1.6x).)
 - #57412 (Improve the wording)
 - #57436 (save-analysis: use a fallback when access levels couldn't be computed)
 - #57453 (lldb_batchmode.py: try `import _thread` for Python 3)
 - #57454 (Some cleanups for core::fmt)
 - #57461 (Change `String` to `&'static str` in `ParseResult::Failure`.)
 - #57473 (std: Render large exit codes as hex on Windows)
 - #57474 (save-analysis: Get path def from parent in case there's no def for the path itself.)
 - #57494 (Speed up item_bodies for large match statements involving regions)
 - #57496 (re-do docs for core::cmp)
 - #57508 (rustdoc: Allow inlining of reexported crates and crate items)
 - #57547 (Use `ptr::eq` where applicable)
 - #57557 (resolve: Mark extern crate items as used in more cases)
 - #57560 (hygiene: Do not treat `Self` ctor as a local variable)
 - #57564 (Update the const fn tracking issue to the new metabug)

Failed merges:

r? @ghost

5 files changed, 49 insertions, 64 deletions

diff --git a/src/libcore/cmp.rs b/src/libcore/cmp.rs
index f420d0d00a4..86f28a957cd 100644
--- a/src/libcore/cmp.rs
+++ b/src/libcore/cmp.rs
@@ -1,27 +1,22 @@
 //! Functionality for ordering and comparison.
 //!
-//! This module defines both [`PartialOrd`] and [`PartialEq`] traits which are used
-//! by the compiler to implement comparison operators. Rust programs may
-//! implement [`PartialOrd`] to overload the `<`, `<=`, `>`, and `>=` operators,
-//! and may implement [`PartialEq`] to overload the `==` and `!=` operators.
+//! This module contains various tools for ordering and comparing values. In
+//! summary:
 //!
-//! [`PartialOrd`]: trait.PartialOrd.html
-//! [`PartialEq`]: trait.PartialEq.html
+//! * [`Eq`] and [`PartialEq`] are traits that allow you to define total and
+//!   partial equality between values, respectively. Implementing them overloads
+//!   the `==` and `!=` operators.
+//! * [`Ord`] and [`PartialOrd`] are traits that allow you to define total and
+//!   partial orderings between values, respectively. Implementing them overloads
+//!   the `<`, `<=`, `>`, and `>=` operators.
+//! * [`Ordering`][cmp::Ordering] is an enum returned by the
+//!   main functions of [`Ord`] and [`PartialOrd`], and describes an ordering.
+//! * [`Reverse`][cmp::Reverse] is a struct that allows you to easily reverse
+//!   an ordering.
+//! * [`max`][cmp::max] and [`min`][cmp::min] are functions that build off of
+//!   [`Ord`] and allow you to find the maximum or minimum of two values.
 //!
-//! # Examples
-//!
-//! ```
-//! let x: u32 = 0;
-//! let y: u32 = 1;
-//!
-//! // these two lines are equivalent
-//! assert_eq!(x < y, true);
-//! assert_eq!(x.lt(&y), true);
-//!
-//! // these two lines are also equivalent
-//! assert_eq!(x == y, false);
-//! assert_eq!(x.eq(&y), false);
-//! ```
+//! For more details, see the respective documentation of each item in the list.
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index ec1aeb8a7d1..214b5d3a84f 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -191,29 +191,8 @@ pub trait Write {
     /// assert_eq!(&buf, "world");
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    fn write_fmt(&mut self, args: Arguments) -> Result {
-        // This Adapter is needed to allow `self` (of type `&mut
-        // Self`) to be cast to a Write (below) without
-        // requiring a `Sized` bound.
-        struct Adapter<'a,T: ?Sized +'a>(&'a mut T);
-
-        impl<T: ?Sized> Write for Adapter<'_, T>
-            where T: Write
-        {
-            fn write_str(&mut self, s: &str) -> Result {
-                self.0.write_str(s)
-            }
-
-            fn write_char(&mut self, c: char) -> Result {
-                self.0.write_char(c)
-            }
-
-            fn write_fmt(&mut self, args: Arguments) -> Result {
-                self.0.write_fmt(args)
-            }
-        }
-
-        write(&mut Adapter(self), args)
+    fn write_fmt(mut self: &mut Self, args: Arguments) -> Result {
+        write(&mut self, args)
     }
 }
 
@@ -268,7 +247,7 @@ struct Void {
 /// 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.
-#[derive(Copy)]
+#[derive(Copy, Clone)]
 #[allow(missing_debug_implementations)]
 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
            issue = "0")]
@@ -278,14 +257,6 @@ pub struct ArgumentV1<'a> {
     formatter: fn(&Void, &mut Formatter) -> Result,
 }
 
-#[unstable(feature = "fmt_internals", reason = "internal to format_args!",
-           issue = "0")]
-impl Clone for ArgumentV1<'_> {
-    fn clone(&self) -> Self {
-        *self
-    }
-}
-
 impl<'a> ArgumentV1<'a> {
     #[inline(never)]
     fn show_usize(x: &usize, f: &mut Formatter) -> Result {
@@ -1105,7 +1076,7 @@ impl<'a> Formatter<'a> {
                 self.args[i].as_usize()
             }
             rt::v1::Count::NextParam => {
-                self.curarg.next().and_then(|arg| arg.as_usize())
+                self.curarg.next()?.as_usize()
             }
         }
     }
@@ -1171,15 +1142,15 @@ impl<'a> Formatter<'a> {
             sign = Some('+'); width += 1;
         }
 
-        let mut prefixed = false;
-        if self.alternate() {
-            prefixed = true; width += prefix.chars().count();
+        let prefixed = self.alternate();
+        if prefixed {
+            width += prefix.chars().count();
         }
 
         // Writes the sign if it exists, and then the prefix if it was requested
         let write_prefix = |f: &mut Formatter| {
             if let Some(c) = sign {
-                f.buf.write_str(c.encode_utf8(&mut [0; 4]))?;
+                f.buf.write_char(c)?;
             }
             if prefixed { f.buf.write_str(prefix) }
             else { Ok(()) }
@@ -1341,7 +1312,7 @@ impl<'a> Formatter<'a> {
 
                 // remove the sign from the formatted parts
                 formatted.sign = b"";
-                width = if width < sign.len() { 0 } else { width - sign.len() };
+                width = width.saturating_sub(sign.len());
                 align = rt::v1::Alignment::Right;
                 self.fill = '0';
                 self.align = rt::v1::Alignment::Right;
diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs
index d1bd9755202..68da79135d3 100644
--- a/src/libcore/num/f32.rs
+++ b/src/libcore/num/f32.rs
@@ -161,6 +161,14 @@ impl f32 {
         self != self
     }
 
+    // FIXME(#50145): `abs` is publicly unavailable in libcore due to
+    // concerns about portability, so this implementation is for
+    // private use internally.
+    #[inline]
+    fn abs_private(self) -> f32 {
+        f32::from_bits(self.to_bits() & 0x7fff_ffff)
+    }
+
     /// Returns `true` if this value is positive infinity or negative infinity and
     /// false otherwise.
     ///
@@ -181,7 +189,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn is_infinite(self) -> bool {
-        self == INFINITY || self == NEG_INFINITY
+        self.abs_private() == INFINITY
     }
 
     /// Returns `true` if this number is neither infinite nor `NaN`.
@@ -203,7 +211,9 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn is_finite(self) -> bool {
-        !(self.is_nan() || self.is_infinite())
+        // There's no need to handle NaN separately: if self is NaN,
+        // the comparison is not true, exactly as desired.
+        self.abs_private() < INFINITY
     }
 
     /// Returns `true` if the number is neither zero, infinite,
diff --git a/src/libcore/num/f64.rs b/src/libcore/num/f64.rs
index 8ada5b6756c..b6773915481 100644
--- a/src/libcore/num/f64.rs
+++ b/src/libcore/num/f64.rs
@@ -161,6 +161,14 @@ impl f64 {
         self != self
     }
 
+    // FIXME(#50145): `abs` is publicly unavailable in libcore due to
+    // concerns about portability, so this implementation is for
+    // private use internally.
+    #[inline]
+    fn abs_private(self) -> f64 {
+        f64::from_bits(self.to_bits() & 0x7fff_ffff_ffff_ffff)
+    }
+
     /// Returns `true` if this value is positive infinity or negative infinity and
     /// false otherwise.
     ///
@@ -181,7 +189,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn is_infinite(self) -> bool {
-        self == INFINITY || self == NEG_INFINITY
+        self.abs_private() == INFINITY
     }
 
     /// Returns `true` if this number is neither infinite nor `NaN`.
@@ -203,7 +211,9 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn is_finite(self) -> bool {
-        !(self.is_nan() || self.is_infinite())
+        // There's no need to handle NaN separately: if self is NaN,
+        // the comparison is not true, exactly as desired.
+        self.abs_private() < INFINITY
     }
 
     /// Returns `true` if the number is neither zero, infinite,
diff --git a/src/libcore/str/pattern.rs b/src/libcore/str/pattern.rs
index b4eae4d1bb7..55a7ba181e5 100644
--- a/src/libcore/str/pattern.rs
+++ b/src/libcore/str/pattern.rs
@@ -425,8 +425,7 @@ impl<'a> Pattern<'a> for char {
     #[inline]
     fn into_searcher(self, haystack: &'a str) -> Self::Searcher {
         let mut utf8_encoded = [0; 4];
-        self.encode_utf8(&mut utf8_encoded);
-        let utf8_size = self.len_utf8();
+        let utf8_size = self.encode_utf8(&mut utf8_encoded).len();
         CharSearcher {
             haystack,
             finger: 0,