Rollup merge of rust-lang#59082 - alexreg:cosmetic-2-doc-comments, r=Centril

A few improvements to comments in user-facing crates

Not too many this time, and all concern comments (almost all doc comments) in user-facing crates (libstd, libcore, liballoc).

r? @steveklabnik

Author: kennytm

src/libcore/iter/adapters/mod.rs

@@ -1198,7 +1198,7 @@ impl<I: Iterator> Peekable<I> {
     }
 }
 
-/// An iterator that rejects elements while `predicate` is true.
+/// An iterator that rejects elements while `predicate` returns `true`.
 ///
 /// This `struct` is created by the [`skip_while`] method on [`Iterator`]. See its
 /// documentation for more.
@@ -1286,7 +1286,7 @@ impl<I: Iterator, P> Iterator for SkipWhile<I, P>
 impl<I, P> FusedIterator for SkipWhile<I, P>
     where I: FusedIterator, P: FnMut(&I::Item) -> bool {}
 
-/// An iterator that only accepts elements while `predicate` is true.
+/// An iterator that only accepts elements while `predicate` returns `true`.
 ///
 /// This `struct` is created by the [`take_while`] method on [`Iterator`]. See its
 /// documentation for more.

src/libcore/mem.rs

@@ -1111,11 +1111,12 @@ impl<T: ?Sized> DerefMut for ManuallyDrop<T> {
 /// ```
 ///
 /// The compiler then knows to not make any incorrect assumptions or optimizations on this code.
+//
 // FIXME before stabilizing, explain how to initialize a struct field-by-field.
 #[allow(missing_debug_implementations)]
 #[unstable(feature = "maybe_uninit", issue = "53491")]
 #[derive(Copy)]
-// NOTE after stabilizing `MaybeUninit` proceed to deprecate `mem::uninitialized`.
+// NOTE: after stabilizing `MaybeUninit`, proceed to deprecate `mem::uninitialized`.
 pub union MaybeUninit<T> {
     uninit: (),
     value: ManuallyDrop<T>,
@@ -1125,13 +1126,13 @@ pub union MaybeUninit<T> {
 impl<T: Copy> Clone for MaybeUninit<T> {
     #[inline(always)]
     fn clone(&self) -> Self {
-        // Not calling T::clone(), we cannot know if we are initialized enough for that.
+        // Not calling `T::clone()`, we cannot know if we are initialized enough for that.
         *self
     }
 }
 
 impl<T> MaybeUninit<T> {
-    /// Create a new `MaybeUninit<T>` initialized with the given value.
+    /// Creates a new `MaybeUninit<T>` initialized with the given value.
     ///
     /// Note that dropping a `MaybeUninit<T>` will never call `T`'s drop code.
     /// It is your responsibility to make sure `T` gets dropped if it got initialized.
@@ -1239,6 +1240,7 @@ impl<T> MaybeUninit<T> {
     /// let x_vec = unsafe { &*x.as_ptr() };
     /// // We have created a reference to an uninitialized vector! This is undefined behavior.
     /// ```
+    ///
     /// (Notice that the rules around references to uninitialized data are not finalized yet, but
     /// until they are, it is advisable to avoid them.)
     #[unstable(feature = "maybe_uninit", issue = "53491")]
@@ -1277,6 +1279,7 @@ impl<T> MaybeUninit<T> {
     /// let x_vec = unsafe { &mut *x.as_mut_ptr() };
     /// // We have created a reference to an uninitialized vector! This is undefined behavior.
     /// ```
+    ///
     /// (Notice that the rules around references to uninitialized data are not finalized yet, but
     /// until they are, it is advisable to avoid them.)
     #[unstable(feature = "maybe_uninit", issue = "53491")]

src/libcore/num/dec2flt/algorithm.rs

@@ -326,7 +326,7 @@ pub fn algorithm_m<T: RawFloat>(f: &Big, e: i16) -> T {
     round_by_remainder(v, rem, q, z)
 }
 
-/// Skip over most Algorithm M iterations by checking the bit length.
+/// Skips over most Algorithm M iterations by checking the bit length.
 fn quick_start<T: RawFloat>(u: &mut Big, v: &mut Big, k: &mut i16) {
     // The bit length is an estimate of the base two logarithm, and log(u / v) = log(u) - log(v).
     // The estimate is off by at most 1, but always an under-estimate, so the error on log(u)

src/libcore/num/dec2flt/mod.rs

@@ -304,8 +304,8 @@ fn simplify(decimal: &mut Decimal) {
     }
 }
 
-/// Quick and dirty upper bound on the size (log10) of the largest value that Algorithm R and
-/// Algorithm M will compute while working on the given decimal.
+/// Returns a quick-an-dirty upper bound on the size (log10) of the largest value that Algorithm R
+/// and Algorithm M will compute while working on the given decimal.
 fn bound_intermediate_digits(decimal: &Decimal, e: i64) -> u64 {
     // We don't need to worry too much about overflow here thanks to trivial_cases() and the
     // parser, which filter out the most extreme inputs for us.
@@ -324,7 +324,7 @@ fn bound_intermediate_digits(decimal: &Decimal, e: i64) -> u64 {
     }
 }
 
-/// Detect obvious overflows and underflows without even looking at the decimal digits.
+/// Detects obvious overflows and underflows without even looking at the decimal digits.
 fn trivial_cases<T: RawFloat>(decimal: &Decimal) -> Option<T> {
     // There were zeros but they were stripped by simplify()
     if decimal.integral.is_empty() && decimal.fractional.is_empty() {

src/libcore/num/dec2flt/parse.rs

@@ -78,7 +78,7 @@ pub fn parse_decimal(s: &str) -> ParseResult {
     }
 }
 
-/// Carve off decimal digits up to the first non-digit character.
+/// Carves off decimal digits up to the first non-digit character.
 fn eat_digits(s: &[u8]) -> (&[u8], &[u8]) {
     let mut i = 0;
     while i < s.len() && b'0' <= s[i] && s[i] <= b'9' {

src/libcore/num/flt2dec/decoder.rs

@@ -10,7 +10,7 @@ use num::dec2flt::rawfp::RawFloat;
 ///
 /// - Any number from `(mant - minus) * 2^exp` to `(mant + plus) * 2^exp` will
 ///   round to the original value. The range is inclusive only when
-///   `inclusive` is true.
+///   `inclusive` is `true`.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub struct Decoded {
     /// The scaled mantissa.

src/libcore/num/flt2dec/mod.rs

@@ -315,15 +315,15 @@ fn digits_to_dec_str<'a>(buf: &'a [u8], exp: i16, frac_digits: usize,
     }
 }
 
-/// Formats given decimal digits `0.<...buf...> * 10^exp` into the exponential form
-/// with at least given number of significant digits. When `upper` is true,
+/// Formats the given decimal digits `0.<...buf...> * 10^exp` into the exponential
+/// form with at least the given number of significant digits. When `upper` is `true`,
 /// the exponent will be prefixed by `E`; otherwise that's `e`. The result is
 /// stored to the supplied parts array and a slice of written parts is returned.
 ///
 /// `min_digits` can be less than the number of actual significant digits in `buf`;
 /// it will be ignored and full digits will be printed. It is only used to print
-/// additional zeroes after rendered digits. Thus `min_digits` of 0 means that
-/// it will only print given digits and nothing else.
+/// additional zeroes after rendered digits. Thus, `min_digits == 0` means that
+/// it will only print the given digits and nothing else.
 fn digits_to_exp_str<'a>(buf: &'a [u8], exp: i16, min_ndigits: usize, upper: bool,
                          parts: &'a mut [Part<'a>]) -> &'a [Part<'a>] {
     assert!(!buf.is_empty());
@@ -384,7 +384,7 @@ fn determine_sign(sign: Sign, decoded: &FullDecoded, negative: bool) -> &'static
     }
 }
 
-/// Formats given floating point number into the decimal form with at least
+/// Formats the given floating point number into the decimal form with at least
 /// given number of fractional digits. The result is stored to the supplied parts
 /// array while utilizing given byte buffer as a scratch. `upper` is currently
 /// unused but left for the future decision to change the case of non-finite values,
@@ -438,7 +438,7 @@ pub fn to_shortest_str<'a, T, F>(mut format_shortest: F, v: T,
     }
 }
 
-/// Formats given floating point number into the decimal form or
+/// Formats the given floating point number into the decimal form or
 /// the exponential form, depending on the resulting exponent. The result is
 /// stored to the supplied parts array while utilizing given byte buffer
 /// as a scratch. `upper` is used to determine the case of non-finite values
@@ -497,7 +497,7 @@ pub fn to_shortest_exp_str<'a, T, F>(mut format_shortest: F, v: T,
     }
 }
 
-/// Returns rather crude approximation (upper bound) for the maximum buffer size
+/// Returns a rather crude approximation (upper bound) for the maximum buffer size
 /// calculated from the given decoded exponent.
 ///
 /// The exact limit is:

src/libcore/pin.rs

@@ -1,4 +1,4 @@
-//! Types which pin data to its location in memory
+//! Types that pin data to its location in memory.
 //!
 //! It is sometimes useful to have objects that are guaranteed to not move,
 //! in the sense that their placement in memory does not change, and can thus be relied upon.

src/libcore/str/mod.rs

@@ -2968,7 +2968,7 @@ impl str {
     ///
     /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
     /// allows a reverse search and forward/reverse search yields the same
-    /// elements. This is true for, eg, [`char`] but not for `&str`.
+    /// elements. This is true for, e.g., [`char`], but not for `&str`.
     ///
     /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
     ///
@@ -3143,7 +3143,7 @@ impl str {
     ///
     /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
     /// allows a reverse search and forward/reverse search yields the same
-    /// elements. This is true for, eg, [`char`] but not for `&str`.
+    /// elements. This is true for, e.g., [`char`], but not for `&str`.
     ///
     /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
     ///
@@ -3326,7 +3326,7 @@ impl str {
     ///
     /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
     /// allows a reverse search and forward/reverse search yields the same
-    /// elements. This is true for, eg, [`char`] but not for `&str`.
+    /// elements. This is true for, e.g., [`char`], but not for `&str`.
     ///
     /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
     ///
@@ -3402,7 +3402,7 @@ impl str {
     ///
     /// The returned iterator will be a [`DoubleEndedIterator`] if the pattern
     /// allows a reverse search and forward/reverse search yields the same
-    /// elements. This is true for, eg, [`char`] but not for `&str`.
+    /// elements. This is true for, e.g., [`char`], but not for `&str`.
     ///
     /// [`DoubleEndedIterator`]: iter/trait.DoubleEndedIterator.html
     ///

src/libcore/task/wake.rs

@@ -108,7 +108,7 @@ impl Waker {
         unsafe { (self.waker.vtable.wake)(self.waker.data) }
     }
 
-    /// Returns whether or not this `Waker` and other `Waker` have awaken the same task.
+    /// Returns `true` if this `Waker` and another `Waker` have awoken the same task.
     ///
     /// This function works on a best-effort basis, and may return false even
     /// when the `Waker`s would awaken the same task. However, if this function