Auto merge of rust-lang#134286 - Urgau:unreach_pub-std, r=ibraheemdev

Enable `unreachable_pub` lint in core

This PR enables the [`unreachable_pub`](https://doc.rust-lang.org/rustc/lints/listing/allowed-by-default.html#unreachable-pub) as warn in `core`, `rtstartup` and `panic_unwind`.

The motivation is similar to the compiler [MCP: Enable deny(unreachable_pub) on `rustc_*` crates](rust-lang/compiler-team#773 (comment)) :

> "Where is this thing used?" is a question I ask all the time when reading unfamiliar code. Because of this, I generally find it annoying when things are marked with a more permissive visibility than necessary. "This thing marked pub, which other crates is it used in? Oh, it's not used in any other crates."

Another motivation is to help to lint by utilizing it in-tree and seeing it's limitation in more complex scenarios.

The diff was mostly generated with `./x.py fix --stage 1 library/core/ -- --broken-code`, as well as manual edits for code in macros, generated code and other targets.

r? libs

library/core/src/arch.rs

@@ -1,6 +1,14 @@
 #![doc = include_str!("../../stdarch/crates/core_arch/src/core_arch_docs.md")]
 
-#[allow(unused_imports)]
+#[allow(
+    // some targets don't have anything to reexport, which
+    // makes the `pub use` unused and unreachable, allow
+    // both lints as to not have `#[cfg]`s
+    //
+    // cf. https://github.com/rust-lang/rust/pull/116033#issuecomment-1760085575
+    unused_imports,
+    unreachable_pub
+)]
 #[stable(feature = "simd_arch", since = "1.27.0")]
 pub use crate::core_arch::arch::*;
 

library/core/src/array/mod.rs

@@ -893,7 +893,7 @@ impl<T> Guard<'_, T> {
     ///
     /// No more than N elements must be initialized.
     #[inline]
-    pub unsafe fn push_unchecked(&mut self, item: T) {
+    pub(crate) unsafe fn push_unchecked(&mut self, item: T) {
         // SAFETY: If `initialized` was correct before and the caller does not
         // invoke this method more than N times then writes will be in-bounds
         // and slots will not be initialized more than once.

library/core/src/escape.rs

@@ -163,63 +163,63 @@ pub(crate) struct EscapeIterInner<const N: usize> {
 }
 
 impl<const N: usize> EscapeIterInner<N> {
-    pub const fn backslash(c: ascii::Char) -> Self {
+    pub(crate) const fn backslash(c: ascii::Char) -> Self {
         let (data, range) = backslash(c);
         Self { data, alive: range }
     }
 
-    pub const fn ascii(c: u8) -> Self {
+    pub(crate) const fn ascii(c: u8) -> Self {
         let (data, range) = escape_ascii(c);
         Self { data, alive: range }
     }
 
-    pub const fn unicode(c: char) -> Self {
+    pub(crate) const fn unicode(c: char) -> Self {
         let (data, range) = escape_unicode(c);
         Self { data, alive: range }
     }
 
     #[inline]
-    pub const fn empty() -> Self {
+    pub(crate) const fn empty() -> Self {
         Self { data: [ascii::Char::Null; N], alive: 0..0 }
     }
 
     #[inline]
-    pub fn as_ascii(&self) -> &[ascii::Char] {
+    pub(crate) fn as_ascii(&self) -> &[ascii::Char] {
         // SAFETY: `self.alive` is guaranteed to be a valid range for indexing `self.data`.
         unsafe {
             self.data.get_unchecked(usize::from(self.alive.start)..usize::from(self.alive.end))
         }
     }
 
     #[inline]
-    pub fn as_str(&self) -> &str {
+    pub(crate) fn as_str(&self) -> &str {
         self.as_ascii().as_str()
     }
 
     #[inline]
-    pub fn len(&self) -> usize {
+    pub(crate) fn len(&self) -> usize {
         usize::from(self.alive.end - self.alive.start)
     }
 
-    pub fn next(&mut self) -> Option<u8> {
+    pub(crate) fn next(&mut self) -> Option<u8> {
         let i = self.alive.next()?;
 
         // SAFETY: `i` is guaranteed to be a valid index for `self.data`.
         unsafe { Some(self.data.get_unchecked(usize::from(i)).to_u8()) }
     }
 
-    pub fn next_back(&mut self) -> Option<u8> {
+    pub(crate) fn next_back(&mut self) -> Option<u8> {
         let i = self.alive.next_back()?;
 
         // SAFETY: `i` is guaranteed to be a valid index for `self.data`.
         unsafe { Some(self.data.get_unchecked(usize::from(i)).to_u8()) }
     }
 
-    pub fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
+    pub(crate) fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
         self.alive.advance_by(n)
     }
 
-    pub fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
+    pub(crate) fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
         self.alive.advance_back_by(n)
     }
 }

library/core/src/ffi/mod.rs

@@ -172,35 +172,35 @@ mod c_char_definition {
                 target_arch = "xtensa",
             )
         ))] {
-            pub type c_char = u8;
+            pub(super) type c_char = u8;
         } else {
             // On every other target, c_char is signed.
-            pub type c_char = i8;
+            pub(super) type c_char = i8;
         }
     }
 }
 
 mod c_int_definition {
     cfg_if! {
         if #[cfg(any(target_arch = "avr", target_arch = "msp430"))] {
-            pub type c_int = i16;
-            pub type c_uint = u16;
+            pub(super) type c_int = i16;
+            pub(super) type c_uint = u16;
         } else {
-            pub type c_int = i32;
-            pub type c_uint = u32;
+            pub(super) type c_int = i32;
+            pub(super) type c_uint = u32;
         }
     }
 }
 
 mod c_long_definition {
     cfg_if! {
         if #[cfg(all(target_pointer_width = "64", not(windows)))] {
-            pub type c_long = i64;
-            pub type c_ulong = u64;
+            pub(super) type c_long = i64;
+            pub(super) type c_ulong = u64;
         } else {
             // The minimal size of `long` in the C standard is 32 bits
-            pub type c_long = i32;
-            pub type c_ulong = u32;
+            pub(super) type c_long = i32;
+            pub(super) type c_ulong = u32;
         }
     }
 }

library/core/src/lib.rs

@@ -101,6 +101,7 @@
 #![warn(multiple_supertrait_upcastable)]
 #![allow(internal_features)]
 #![deny(ffi_unwind_calls)]
+#![warn(unreachable_pub)]
 // Do not check link redundancy on bootstraping phase
 #![allow(rustdoc::redundant_explicit_links)]
 #![warn(rustdoc::unescaped_backticks)]
@@ -396,7 +397,8 @@ pub mod primitive;
     unused_imports,
     unsafe_op_in_unsafe_fn,
     ambiguous_glob_reexports,
-    deprecated_in_future
+    deprecated_in_future,
+    unreachable_pub
 )]
 #[allow(rustdoc::bare_urls)]
 mod core_arch;

library/core/src/net/display_buffer.rs

@@ -2,19 +2,19 @@ use crate::mem::MaybeUninit;
 use crate::{fmt, str};
 
 /// Used for slow path in `Display` implementations when alignment is required.
-pub struct DisplayBuffer<const SIZE: usize> {
+pub(super) struct DisplayBuffer<const SIZE: usize> {
     buf: [MaybeUninit<u8>; SIZE],
     len: usize,
 }
 
 impl<const SIZE: usize> DisplayBuffer<SIZE> {
     #[inline]
-    pub const fn new() -> Self {
+    pub(super) const fn new() -> Self {
         Self { buf: [MaybeUninit::uninit(); SIZE], len: 0 }
     }
 
     #[inline]
-    pub fn as_str(&self) -> &str {
+    pub(super) fn as_str(&self) -> &str {
         // SAFETY: `buf` is only written to by the `fmt::Write::write_str` implementation
         // which writes a valid UTF-8 string to `buf` and correctly sets `len`.
         unsafe {

library/core/src/num/dec2flt/decimal.rs

@@ -12,7 +12,7 @@
 use crate::num::dec2flt::common::{ByteSlice, is_8digits};
 
 #[derive(Clone)]
-pub struct Decimal {
+pub(super) struct Decimal {
     /// The number of significant digits in the decimal.
     pub num_digits: usize,
     /// The offset of the decimal point in the significant digits.
@@ -55,21 +55,21 @@ impl Decimal {
     ///
     /// In Python:
     ///     `-emin + p2 + math.floor((emin+ 1)*math.log(2, b)-math.log(1-2**(-p2), b))`
-    pub const MAX_DIGITS: usize = 768;
+    pub(super) const MAX_DIGITS: usize = 768;
     /// The max digits that can be exactly represented in a 64-bit integer.
-    pub const MAX_DIGITS_WITHOUT_OVERFLOW: usize = 19;
-    pub const DECIMAL_POINT_RANGE: i32 = 2047;
+    pub(super) const MAX_DIGITS_WITHOUT_OVERFLOW: usize = 19;
+    pub(super) const DECIMAL_POINT_RANGE: i32 = 2047;
 
     /// Append a digit to the buffer.
-    pub fn try_add_digit(&mut self, digit: u8) {
+    pub(super) fn try_add_digit(&mut self, digit: u8) {
         if self.num_digits < Self::MAX_DIGITS {
             self.digits[self.num_digits] = digit;
         }
         self.num_digits += 1;
     }
 
     /// Trim trailing zeros from the buffer.
-    pub fn trim(&mut self) {
+    pub(super) fn trim(&mut self) {
         // All of the following calls to `Decimal::trim` can't panic because:
         //
         //  1. `parse_decimal` sets `num_digits` to a max of `Decimal::MAX_DIGITS`.
@@ -83,7 +83,7 @@ impl Decimal {
         }
     }
 
-    pub fn round(&self) -> u64 {
+    pub(super) fn round(&self) -> u64 {
         if self.num_digits == 0 || self.decimal_point < 0 {
             return 0;
         } else if self.decimal_point > 18 {
@@ -111,7 +111,7 @@ impl Decimal {
     }
 
     /// Computes decimal * 2^shift.
-    pub fn left_shift(&mut self, shift: usize) {
+    pub(super) fn left_shift(&mut self, shift: usize) {
         if self.num_digits == 0 {
             return;
         }
@@ -152,7 +152,7 @@ impl Decimal {
     }
 
     /// Computes decimal * 2^-shift.
-    pub fn right_shift(&mut self, shift: usize) {
+    pub(super) fn right_shift(&mut self, shift: usize) {
         let mut read_index = 0;
         let mut write_index = 0;
         let mut n = 0_u64;
@@ -202,7 +202,7 @@ impl Decimal {
 }
 
 /// Parse a big integer representation of the float as a decimal.
-pub fn parse_decimal(mut s: &[u8]) -> Decimal {
+pub(super) fn parse_decimal(mut s: &[u8]) -> Decimal {
     let mut d = Decimal::default();
     let start = s;
 

library/core/src/num/dec2flt/fpu.rs

@@ -1,7 +1,7 @@
 //! Platform-specific, assembly instructions to avoid
 //! intermediate rounding on architectures with FPUs.
 
-pub use fpu_precision::set_precision;
+pub(super) use fpu_precision::set_precision;
 
 // On x86, the x87 FPU is used for float operations if the SSE/SSE2 extensions are not available.
 // The x87 FPU operates with 80 bits of precision by default, which means that operations will
@@ -42,7 +42,7 @@ mod fpu_precision {
     ///  - 0b10, double precision i.e., 64-bits
     ///  - 0b11, double extended precision i.e., 80-bits (default state)
     /// The 0b01 value is reserved and should not be used.
-    pub struct FPUControlWord(u16);
+    pub(crate) struct FPUControlWord(u16);
 
     fn set_cw(cw: u16) {
         // SAFETY: the `fldcw` instruction has been audited to be able to work correctly with
@@ -57,7 +57,7 @@ mod fpu_precision {
     }
 
     /// Sets the precision field of the FPU to `T` and returns a `FPUControlWord`.
-    pub fn set_precision<T>() -> FPUControlWord {
+    pub(crate) fn set_precision<T>() -> FPUControlWord {
         let mut cw = 0_u16;
 
         // Compute the value for the Precision Control field that is appropriate for `T`.
@@ -97,5 +97,5 @@ mod fpu_precision {
 // precision of the computation is determined on a per-operation basis.
 #[cfg(any(not(target_arch = "x86"), target_feature = "sse2"))]
 mod fpu_precision {
-    pub fn set_precision<T>() {}
+    pub(crate) fn set_precision<T>() {}
 }

library/core/src/num/dec2flt/table.rs

@@ -6,16 +6,17 @@
 //!
 //! DO NOT MODIFY: Generated by `src/etc/dec2flt_table.py`
 
-pub const SMALLEST_POWER_OF_FIVE: i32 = -342;
-pub const LARGEST_POWER_OF_FIVE: i32 = 308;
-pub const N_POWERS_OF_FIVE: usize = (LARGEST_POWER_OF_FIVE - SMALLEST_POWER_OF_FIVE + 1) as usize;
+pub(super) const SMALLEST_POWER_OF_FIVE: i32 = -342;
+pub(super) const LARGEST_POWER_OF_FIVE: i32 = 308;
+pub(super) const N_POWERS_OF_FIVE: usize =
+    (LARGEST_POWER_OF_FIVE - SMALLEST_POWER_OF_FIVE + 1) as usize;
 
 // Use static to avoid long compile times: Rust compiler errors
 // can have the entire table compiled multiple times, and then
 // emit code multiple times, even if it's stripped out in
 // the final binary.
 #[rustfmt::skip]
-pub static POWER_OF_FIVE_128: [(u64, u64); N_POWERS_OF_FIVE] = [
+pub(super) static POWER_OF_FIVE_128: [(u64, u64); N_POWERS_OF_FIVE] = [
     (0xeef453d6923bd65a, 0x113faa2906a13b3f), // 5^-342
     (0x9558b4661b6565f8, 0x4ac7ca59a424c507), // 5^-341
     (0xbaaee17fa23ebf76, 0x5d79bcf00d2df649), // 5^-340