Auto merge of #73265 - mark-i-m:mv-std, r=<try>tmp-nightly

mv std libs to library/

This is the first step in refactoring the directory layout of this repository, with further followup steps planned (but not done yet).

Background: currently, all crates are under src/, without nested src directories and with the unconventional `lib*` prefixes (e.g., `src/libcore/lib.rs`). This directory structures is not idiomatic and makes the `src/` directory rather overwhelming. To improve contributor experience and make things a bit more approachable, we are reorganizing the repo a bit.

In this PR, we move the standard libs (basically anything that is "runtime", as opposed to part of the compiler, build system, or one of the tools, etc). The new layout moves these libraries to a new `library/` directory in the root of the repo. Additionally, we remove the `lib*` prefixes and add nested `src/` directories.  The other crates/tools in this repo are not touched. So in summary:

```
library/<crate>/src/*.rs
src/<all the rest>     // unchanged
```

where `<crate>` is:
- core
- alloc
- std
- test
- proc_macro
- panic_abort
- panic_unwind
- profiler_builtins
- term
- unwind
- rtstartup
- backtrace
- rustc-std-workspace-*

There was a lot of discussion about this and a few rounds of compiler team approvals, FCPs, MCPs, and nominations. The original MCP is https://github.com/rust-lang/compiler-team/issues/298. The final approval of the compiler team was given here: https://github.com/rust-lang/rust/pull/73265#issuecomment-659498446.

The name `library` was chosen to complement a later move of the compiler crates to a `compiler/` directory. There was a lot of discussion around adding the nested `src/` directories. Note that this does increase the nesting depth (plausibly important for manual traversal of the tree, e.g., through GitHub's UI or `cd`), but this is deemed to be better as it fits the standard layout of Rust crates throughout most of the ecosystem, though there is some debate about how much this should apply to multi-crate projects. Overall, there seem to be more people in favor of nested `src/` than against.

After this PR, there are no dependencies out of the `library/` directory except on the `build_helper` (or crates.io crates).

1 files changed, 0 insertions, 107 deletions

diff --git a/src/libstd/sys/windows/path.rs b/src/libstd/sys/windows/path.rs
deleted file mode 100644
index dda3ed68cfc..00000000000
--- a/src/libstd/sys/windows/path.rs
+++ /dev/null
@@ -1,107 +0,0 @@
-use crate::ffi::OsStr;
-use crate::mem;
-use crate::path::Prefix;
-
-#[cfg(test)]
-mod tests;
-
-pub const MAIN_SEP_STR: &str = "\\";
-pub const MAIN_SEP: char = '\\';
-
-// The unsafety here stems from converting between `&OsStr` and `&[u8]`
-// and back. This is safe to do because (1) we only look at ASCII
-// contents of the encoding and (2) new &OsStr values are produced
-// only from ASCII-bounded slices of existing &OsStr values.
-fn os_str_as_u8_slice(s: &OsStr) -> &[u8] {
-    unsafe { mem::transmute(s) }
-}
-unsafe fn u8_slice_as_os_str(s: &[u8]) -> &OsStr {
-    mem::transmute(s)
-}
-
-#[inline]
-pub fn is_sep_byte(b: u8) -> bool {
-    b == b'/' || b == b'\\'
-}
-
-#[inline]
-pub fn is_verbatim_sep(b: u8) -> bool {
-    b == b'\\'
-}
-
-// In most DOS systems, it is not possible to have more than 26 drive letters.
-// See <https://en.wikipedia.org/wiki/Drive_letter_assignment#Common_assignments>.
-pub fn is_valid_drive_letter(disk: u8) -> bool {
-    disk.is_ascii_alphabetic()
-}
-
-pub fn parse_prefix(path: &OsStr) -> Option<Prefix<'_>> {
-    use Prefix::{DeviceNS, Disk, Verbatim, VerbatimDisk, VerbatimUNC, UNC};
-
-    let path = os_str_as_u8_slice(path);
-
-    // \\
-    if let Some(path) = path.strip_prefix(br"\\") {
-        // \\?\
-        if let Some(path) = path.strip_prefix(br"?\") {
-            // \\?\UNC\server\share
-            if let Some(path) = path.strip_prefix(br"UNC\") {
-                let (server, share) = match get_first_two_components(path, is_verbatim_sep) {
-                    Some((server, share)) => unsafe {
-                        (u8_slice_as_os_str(server), u8_slice_as_os_str(share))
-                    },
-                    None => (unsafe { u8_slice_as_os_str(path) }, OsStr::new("")),
-                };
-                return Some(VerbatimUNC(server, share));
-            } else {
-                // \\?\path
-                match path {
-                    // \\?\C:\path
-                    [c, b':', b'\\', ..] if is_valid_drive_letter(*c) => {
-                        return Some(VerbatimDisk(c.to_ascii_uppercase()));
-                    }
-                    // \\?\cat_pics
-                    _ => {
-                        let idx = path.iter().position(|&b| b == b'\\').unwrap_or(path.len());
-                        let slice = &path[..idx];
-                        return Some(Verbatim(unsafe { u8_slice_as_os_str(slice) }));
-                    }
-                }
-            }
-        } else if let Some(path) = path.strip_prefix(b".\\") {
-            // \\.\COM42
-            let idx = path.iter().position(|&b| b == b'\\').unwrap_or(path.len());
-            let slice = &path[..idx];
-            return Some(DeviceNS(unsafe { u8_slice_as_os_str(slice) }));
-        }
-        match get_first_two_components(path, is_sep_byte) {
-            Some((server, share)) if !server.is_empty() && !share.is_empty() => {
-                // \\server\share
-                return Some(unsafe { UNC(u8_slice_as_os_str(server), u8_slice_as_os_str(share)) });
-            }
-            _ => {}
-        }
-    } else if let [c, b':', ..] = path {
-        // C:
-        if is_valid_drive_letter(*c) {
-            return Some(Disk(c.to_ascii_uppercase()));
-        }
-    }
-    None
-}
-
-/// Returns the first two path components with predicate `f`.
-///
-/// The two components returned will be use by caller
-/// to construct `VerbatimUNC` or `UNC` Windows path prefix.
-///
-/// Returns [`None`] if there are no separators in path.
-fn get_first_two_components(path: &[u8], f: fn(u8) -> bool) -> Option<(&[u8], &[u8])> {
-    let idx = path.iter().position(|&x| f(x))?;
-    // Panic safe
-    // The max `idx+1` is `path.len()` and `path[path.len()..]` is a valid index.
-    let (first, path) = (&path[..idx], &path[idx + 1..]);
-    let idx = path.iter().position(|&x| f(x)).unwrap_or(path.len());
-    let second = &path[..idx];
-    Some((first, second))
-}