Rollup merge of #126013 - nnethercote:unreachable_pub, r=Urgau

Add `#[warn(unreachable_pub)]` to a bunch of compiler crates

By default `unreachable_pub` identifies things that need not be `pub` and tells you to make them `pub(crate)`. But sometimes those things don't need any kind of visibility. So they way I did these was to remove the visibility entirely for each thing the lint identifies, and then add `pub(crate)` back in everywhere the compiler said it was necessary. (Or occasionally `pub(super)` when context suggested that was appropriate.) Tedious, but results in more `pub` removal.

There are plenty more crates to do but this seems like enough for a first PR.

r? `@compiler-errors`

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1207,7 +1207,7 @@ mod win {
 
     /// Get the Windows system OEM code page. This is most notably the code page
     /// used for link.exe's output.
-    pub fn oem_code_page() -> u32 {
+    pub(super) fn oem_code_page() -> u32 {
         unsafe {
             let mut cp: u32 = 0;
             // We're using the `LOCALE_RETURN_NUMBER` flag to return a u32.
@@ -1230,7 +1230,7 @@ mod win {
     ///
     /// It will fail if the multi-byte string is longer than `i32::MAX` or if it contains
     /// any invalid bytes for the expected encoding.
-    pub fn locale_byte_str_to_string(s: &[u8], code_page: u32) -> Option<String> {
+    pub(super) fn locale_byte_str_to_string(s: &[u8], code_page: u32) -> Option<String> {
         // `MultiByteToWideChar` requires a length to be a "positive integer".
         if s.len() > isize::MAX as usize {
             return None;

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -754,7 +754,7 @@ pub(crate) enum WorkItem<B: WriteBackendMethods> {
 }
 
 impl<B: WriteBackendMethods> WorkItem<B> {
-    pub fn module_kind(&self) -> ModuleKind {
+    fn module_kind(&self) -> ModuleKind {
         match *self {
             WorkItem::Optimize(ref m) => m.kind,
             WorkItem::CopyPostLtoArtifacts(_) | WorkItem::LTO(_) => ModuleKind::Regular,

compiler/rustc_codegen_ssa/src/lib.rs

@@ -12,6 +12,7 @@
 #![feature(rustdoc_internals)]
 #![feature(strict_provenance)]
 #![feature(try_blocks)]
+#![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
 //! This crate contains codegen code that is used by all codegen backends (LLVM and others).

compiler/rustc_codegen_ssa/src/mir/analyze.rs

@@ -13,7 +13,7 @@ use tracing::debug;
 use super::FunctionCx;
 use crate::traits::*;
 
-pub fn non_ssa_locals<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
+pub(crate) fn non_ssa_locals<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     fx: &FunctionCx<'a, 'tcx, Bx>,
 ) -> BitSet<mir::Local> {
     let mir = fx.mir;
@@ -251,14 +251,14 @@ impl<'mir, 'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> Visitor<'tcx>
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
-pub enum CleanupKind {
+pub(crate) enum CleanupKind {
     NotCleanup,
     Funclet,
     Internal { funclet: mir::BasicBlock },
 }
 
 impl CleanupKind {
-    pub fn funclet_bb(self, for_bb: mir::BasicBlock) -> Option<mir::BasicBlock> {
+    pub(crate) fn funclet_bb(self, for_bb: mir::BasicBlock) -> Option<mir::BasicBlock> {
         match self {
             CleanupKind::NotCleanup => None,
             CleanupKind::Funclet => Some(for_bb),
@@ -270,7 +270,7 @@ impl CleanupKind {
 /// MSVC requires unwinding code to be split to a tree of *funclets*, where each funclet can only
 /// branch to itself or to its parent. Luckily, the code we generates matches this pattern.
 /// Recover that structure in an analyze pass.
-pub fn cleanup_kinds(mir: &mir::Body<'_>) -> IndexVec<mir::BasicBlock, CleanupKind> {
+pub(crate) fn cleanup_kinds(mir: &mir::Body<'_>) -> IndexVec<mir::BasicBlock, CleanupKind> {
     fn discover_masters<'tcx>(
         result: &mut IndexSlice<mir::BasicBlock, CleanupKind>,
         mir: &mir::Body<'tcx>,