Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

9 files changed, 2118 insertions, 0 deletions

diff --git a/third_party/rust/semver/src/backport.rs b/third_party/rust/semver/src/backport.rs
new file mode 100644
index 0000000000..b5e1d02be5
--- /dev/null
+++ b/third_party/rust/semver/src/backport.rs
@@ -0,0 +1,23 @@
+#[cfg(no_str_strip_prefix)] // rustc <1.45
+pub(crate) trait StripPrefixExt {
+    fn strip_prefix(&self, ch: char) -> Option<&str>;
+}
+
+#[cfg(no_str_strip_prefix)]
+impl StripPrefixExt for str {
+    fn strip_prefix(&self, ch: char) -> Option<&str> {
+        if self.starts_with(ch) {
+            Some(&self[ch.len_utf8()..])
+        } else {
+            None
+        }
+    }
+}
+
+pub(crate) use crate::alloc::vec::Vec;
+
+#[cfg(no_alloc_crate)] // rustc <1.36
+pub(crate) mod alloc {
+    pub use std::alloc;
+    pub use std::vec;
+}
diff --git a/third_party/rust/semver/src/display.rs b/third_party/rust/semver/src/display.rs
new file mode 100644
index 0000000000..3c2871bb97
--- /dev/null
+++ b/third_party/rust/semver/src/display.rs
@@ -0,0 +1,165 @@
+use crate::{BuildMetadata, Comparator, Op, Prerelease, Version, VersionReq};
+use core::fmt::{self, Alignment, Debug, Display, Write};
+
+impl Display for Version {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let do_display = |formatter: &mut fmt::Formatter| -> fmt::Result {
+            write!(formatter, "{}.{}.{}", self.major, self.minor, self.patch)?;
+            if !self.pre.is_empty() {
+                write!(formatter, "-{}", self.pre)?;
+            }
+            if !self.build.is_empty() {
+                write!(formatter, "+{}", self.build)?;
+            }
+            Ok(())
+        };
+
+        let do_len = || -> usize {
+            digits(self.major)
+                + 1
+                + digits(self.minor)
+                + 1
+                + digits(self.patch)
+                + !self.pre.is_empty() as usize
+                + self.pre.len()
+                + !self.build.is_empty() as usize
+                + self.build.len()
+        };
+
+        pad(formatter, do_display, do_len)
+    }
+}
+
+impl Display for VersionReq {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        if self.comparators.is_empty() {
+            return formatter.write_str("*");
+        }
+        for (i, comparator) in self.comparators.iter().enumerate() {
+            if i > 0 {
+                formatter.write_str(", ")?;
+            }
+            write!(formatter, "{}", comparator)?;
+        }
+        Ok(())
+    }
+}
+
+impl Display for Comparator {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let op = match self.op {
+            Op::Exact => "=",
+            Op::Greater => ">",
+            Op::GreaterEq => ">=",
+            Op::Less => "<",
+            Op::LessEq => "<=",
+            Op::Tilde => "~",
+            Op::Caret => "^",
+            Op::Wildcard => "",
+            #[cfg(no_non_exhaustive)]
+            Op::__NonExhaustive => unreachable!(),
+        };
+        formatter.write_str(op)?;
+        write!(formatter, "{}", self.major)?;
+        if let Some(minor) = &self.minor {
+            write!(formatter, ".{}", minor)?;
+            if let Some(patch) = &self.patch {
+                write!(formatter, ".{}", patch)?;
+                if !self.pre.is_empty() {
+                    write!(formatter, "-{}", self.pre)?;
+                }
+            } else if self.op == Op::Wildcard {
+                formatter.write_str(".*")?;
+            }
+        } else if self.op == Op::Wildcard {
+            formatter.write_str(".*")?;
+        }
+        Ok(())
+    }
+}
+
+impl Display for Prerelease {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str(self.as_str())
+    }
+}
+
+impl Display for BuildMetadata {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str(self.as_str())
+    }
+}
+
+impl Debug for Version {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        let mut debug = formatter.debug_struct("Version");
+        debug
+            .field("major", &self.major)
+            .field("minor", &self.minor)
+            .field("patch", &self.patch);
+        if !self.pre.is_empty() {
+            debug.field("pre", &self.pre);
+        }
+        if !self.build.is_empty() {
+            debug.field("build", &self.build);
+        }
+        debug.finish()
+    }
+}
+
+impl Debug for Prerelease {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "Prerelease(\"{}\")", self)
+    }
+}
+
+impl Debug for BuildMetadata {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        write!(formatter, "BuildMetadata(\"{}\")", self)
+    }
+}
+
+fn pad(
+    formatter: &mut fmt::Formatter,
+    do_display: impl FnOnce(&mut fmt::Formatter) -> fmt::Result,
+    do_len: impl FnOnce() -> usize,
+) -> fmt::Result {
+    let min_width = match formatter.width() {
+        Some(min_width) => min_width,
+        None => return do_display(formatter),
+    };
+
+    let len = do_len();
+    if len >= min_width {
+        return do_display(formatter);
+    }
+
+    let default_align = Alignment::Left;
+    let align = formatter.align().unwrap_or(default_align);
+    let padding = min_width - len;
+    let (pre_pad, post_pad) = match align {
+        Alignment::Left => (0, padding),
+        Alignment::Right => (padding, 0),
+        Alignment::Center => (padding / 2, (padding + 1) / 2),
+    };
+
+    let fill = formatter.fill();
+    for _ in 0..pre_pad {
+        formatter.write_char(fill)?;
+    }
+
+    do_display(formatter)?;
+
+    for _ in 0..post_pad {
+        formatter.write_char(fill)?;
+    }
+    Ok(())
+}
+
+fn digits(val: u64) -> usize {
+    if val < 10 {
+        1
+    } else {
+        1 + digits(val / 10)
+    }
+}
diff --git a/third_party/rust/semver/src/error.rs b/third_party/rust/semver/src/error.rs
new file mode 100644
index 0000000000..a514e3f11e
--- /dev/null
+++ b/third_party/rust/semver/src/error.rs
@@ -0,0 +1,124 @@
+use crate::parse::Error;
+use core::fmt::{self, Debug, Display};
+
+pub(crate) enum ErrorKind {
+    UnexpectedEnd(Position),
+    UnexpectedChar(Position, char),
+    UnexpectedCharAfter(Position, char),
+    ExpectedCommaFound(Position, char),
+    LeadingZero(Position),
+    Overflow(Position),
+    EmptySegment(Position),
+    IllegalCharacter(Position),
+    WildcardNotTheOnlyComparator(char),
+    UnexpectedAfterWildcard,
+    ExcessiveComparators,
+}
+
+#[derive(Copy, Clone, Eq, PartialEq)]
+pub(crate) enum Position {
+    Major,
+    Minor,
+    Patch,
+    Pre,
+    Build,
+}
+
+#[cfg(feature = "std")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+impl std::error::Error for Error {}
+
+impl Display for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        match &self.kind {
+            ErrorKind::UnexpectedEnd(pos) => {
+                write!(formatter, "unexpected end of input while parsing {}", pos)
+            }
+            ErrorKind::UnexpectedChar(pos, ch) => {
+                write!(
+                    formatter,
+                    "unexpected character {} while parsing {}",
+                    QuotedChar(*ch),
+                    pos,
+                )
+            }
+            ErrorKind::UnexpectedCharAfter(pos, ch) => {
+                write!(
+                    formatter,
+                    "unexpected character {} after {}",
+                    QuotedChar(*ch),
+                    pos,
+                )
+            }
+            ErrorKind::ExpectedCommaFound(pos, ch) => {
+                write!(
+                    formatter,
+                    "expected comma after {}, found {}",
+                    pos,
+                    QuotedChar(*ch),
+                )
+            }
+            ErrorKind::LeadingZero(pos) => {
+                write!(formatter, "invalid leading zero in {}", pos)
+            }
+            ErrorKind::Overflow(pos) => {
+                write!(formatter, "value of {} exceeds u64::MAX", pos)
+            }
+            ErrorKind::EmptySegment(pos) => {
+                write!(formatter, "empty identifier segment in {}", pos)
+            }
+            ErrorKind::IllegalCharacter(pos) => {
+                write!(formatter, "unexpected character in {}", pos)
+            }
+            ErrorKind::WildcardNotTheOnlyComparator(ch) => {
+                write!(
+                    formatter,
+                    "wildcard req ({}) must be the only comparator in the version req",
+                    ch,
+                )
+            }
+            ErrorKind::UnexpectedAfterWildcard => {
+                formatter.write_str("unexpected character after wildcard in version req")
+            }
+            ErrorKind::ExcessiveComparators => {
+                formatter.write_str("excessive number of version comparators")
+            }
+        }
+    }
+}
+
+impl Display for Position {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str(match self {
+            Position::Major => "major version number",
+            Position::Minor => "minor version number",
+            Position::Patch => "patch version number",
+            Position::Pre => "pre-release identifier",
+            Position::Build => "build metadata",
+        })
+    }
+}
+
+impl Debug for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("Error(\"")?;
+        Display::fmt(self, formatter)?;
+        formatter.write_str("\")")?;
+        Ok(())
+    }
+}
+
+struct QuotedChar(char);
+
+impl Display for QuotedChar {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        // Standard library versions prior to https://github.com/rust-lang/rust/pull/95345
+        // print character 0 as '\u{0}'. We prefer '\0' to keep error messages
+        // the same across all supported Rust versions.
+        if self.0 == '\0' {
+            formatter.write_str("'\\0'")
+        } else {
+            write!(formatter, "{:?}", self.0)
+        }
+    }
+}
diff --git a/third_party/rust/semver/src/eval.rs b/third_party/rust/semver/src/eval.rs
new file mode 100644
index 0000000000..e6e38949a9
--- /dev/null
+++ b/third_party/rust/semver/src/eval.rs
@@ -0,0 +1,181 @@
+use crate::{Comparator, Op, Version, VersionReq};
+
+pub(crate) fn matches_req(req: &VersionReq, ver: &Version) -> bool {
+    for cmp in &req.comparators {
+        if !matches_impl(cmp, ver) {
+            return false;
+        }
+    }
+
+    if ver.pre.is_empty() {
+        return true;
+    }
+
+    // If a version has a prerelease tag (for example, 1.2.3-alpha.3) then it
+    // will only be allowed to satisfy req if at least one comparator with the
+    // same major.minor.patch also has a prerelease tag.
+    for cmp in &req.comparators {
+        if pre_is_compatible(cmp, ver) {
+            return true;
+        }
+    }
+
+    false
+}
+
+pub(crate) fn matches_comparator(cmp: &Comparator, ver: &Version) -> bool {
+    matches_impl(cmp, ver) && (ver.pre.is_empty() || pre_is_compatible(cmp, ver))
+}
+
+fn matches_impl(cmp: &Comparator, ver: &Version) -> bool {
+    match cmp.op {
+        Op::Exact | Op::Wildcard => matches_exact(cmp, ver),
+        Op::Greater => matches_greater(cmp, ver),
+        Op::GreaterEq => matches_exact(cmp, ver) || matches_greater(cmp, ver),
+        Op::Less => matches_less(cmp, ver),
+        Op::LessEq => matches_exact(cmp, ver) || matches_less(cmp, ver),
+        Op::Tilde => matches_tilde(cmp, ver),
+        Op::Caret => matches_caret(cmp, ver),
+        #[cfg(no_non_exhaustive)]
+        Op::__NonExhaustive => unreachable!(),
+    }
+}
+
+fn matches_exact(cmp: &Comparator, ver: &Version) -> bool {
+    if ver.major != cmp.major {
+        return false;
+    }
+
+    if let Some(minor) = cmp.minor {
+        if ver.minor != minor {
+            return false;
+        }
+    }
+
+    if let Some(patch) = cmp.patch {
+        if ver.patch != patch {
+            return false;
+        }
+    }
+
+    ver.pre == cmp.pre
+}
+
+fn matches_greater(cmp: &Comparator, ver: &Version) -> bool {
+    if ver.major != cmp.major {
+        return ver.major > cmp.major;
+    }
+
+    match cmp.minor {
+        None => return false,
+        Some(minor) => {
+            if ver.minor != minor {
+                return ver.minor > minor;
+            }
+        }
+    }
+
+    match cmp.patch {
+        None => return false,
+        Some(patch) => {
+            if ver.patch != patch {
+                return ver.patch > patch;
+            }
+        }
+    }
+
+    ver.pre > cmp.pre
+}
+
+fn matches_less(cmp: &Comparator, ver: &Version) -> bool {
+    if ver.major != cmp.major {
+        return ver.major < cmp.major;
+    }
+
+    match cmp.minor {
+        None => return false,
+        Some(minor) => {
+            if ver.minor != minor {
+                return ver.minor < minor;
+            }
+        }
+    }
+
+    match cmp.patch {
+        None => return false,
+        Some(patch) => {
+            if ver.patch != patch {
+                return ver.patch < patch;
+            }
+        }
+    }
+
+    ver.pre < cmp.pre
+}
+
+fn matches_tilde(cmp: &Comparator, ver: &Version) -> bool {
+    if ver.major != cmp.major {
+        return false;
+    }
+
+    if let Some(minor) = cmp.minor {
+        if ver.minor != minor {
+            return false;
+        }
+    }
+
+    if let Some(patch) = cmp.patch {
+        if ver.patch != patch {
+            return ver.patch > patch;
+        }
+    }
+
+    ver.pre >= cmp.pre
+}
+
+fn matches_caret(cmp: &Comparator, ver: &Version) -> bool {
+    if ver.major != cmp.major {
+        return false;
+    }
+
+    let minor = match cmp.minor {
+        None => return true,
+        Some(minor) => minor,
+    };
+
+    let patch = match cmp.patch {
+        None => {
+            if cmp.major > 0 {
+                return ver.minor >= minor;
+            } else {
+                return ver.minor == minor;
+            }
+        }
+        Some(patch) => patch,
+    };
+
+    if cmp.major > 0 {
+        if ver.minor != minor {
+            return ver.minor > minor;
+        } else if ver.patch != patch {
+            return ver.patch > patch;
+        }
+    } else if minor > 0 {
+        if ver.minor != minor {
+            return false;
+        } else if ver.patch != patch {
+            return ver.patch > patch;
+        }
+    } else if ver.minor != minor || ver.patch != patch {
+        return false;
+    }
+
+    ver.pre >= cmp.pre
+}
+
+fn pre_is_compatible(cmp: &Comparator, ver: &Version) -> bool {
+    cmp.major == ver.major
+        && cmp.minor == Some(ver.minor)
+        && cmp.patch == Some(ver.patch)
+        && !cmp.pre.is_empty()
+}
diff --git a/third_party/rust/semver/src/identifier.rs b/third_party/rust/semver/src/identifier.rs
new file mode 100644
index 0000000000..0273ae62a8
--- /dev/null
+++ b/third_party/rust/semver/src/identifier.rs
@@ -0,0 +1,422 @@
+// This module implements Identifier, a short-optimized string allowed to
+// contain only the ASCII characters hyphen, dot, 0-9, A-Z, a-z.
+//
+// As of mid-2021, the distribution of pre-release lengths on crates.io is:
+//
+//     length  count         length  count         length  count
+//        0  355929            11      81            24       2
+//        1     208            12      48            25       6
+//        2     236            13      55            26      10
+//        3    1909            14      25            27       4
+//        4    1284            15      15            28       1
+//        5    1742            16      35            30       1
+//        6    3440            17       9            31       5
+//        7    5624            18       6            32       1
+//        8    1321            19      12            36       2
+//        9     179            20       2            37     379
+//       10      65            23      11
+//
+// and the distribution of build metadata lengths is:
+//
+//     length  count         length  count         length  count
+//        0  364445             8    7725            18       1
+//        1      72             9      16            19       1
+//        2       7            10      85            20       1
+//        3      28            11      17            22       4
+//        4       9            12      10            26       1
+//        5      68            13       9            27       1
+//        6      73            14      10            40       5
+//        7      53            15       6
+//
+// Therefore it really behooves us to be able to use the entire 8 bytes of a
+// pointer for inline storage. For both pre-release and build metadata there are
+// vastly more strings with length exactly 8 bytes than the sum over all lengths
+// longer than 8 bytes.
+//
+// To differentiate the inline representation from the heap allocated long
+// representation, we'll allocate heap pointers with 2-byte alignment so that
+// they are guaranteed to have an unset least significant bit. Then in the repr
+// we store for pointers, we rotate a 1 into the most significant bit of the
+// most significant byte, which is never set for an ASCII byte.
+//
+// Inline repr:
+//
+//     0xxxxxxx 0xxxxxxx 0xxxxxxx 0xxxxxxx 0xxxxxxx 0xxxxxxx 0xxxxxxx 0xxxxxxx
+//
+// Heap allocated repr:
+//
+//     1ppppppp pppppppp pppppppp pppppppp pppppppp pppppppp pppppppp pppppppp 0
+//     ^ most significant bit   least significant bit of orig ptr, rotated out ^
+//
+// Since the most significant bit doubles as a sign bit for the similarly sized
+// signed integer type, the CPU has an efficient instruction for inspecting it,
+// meaning we can differentiate between an inline repr and a heap allocated repr
+// in one instruction. Effectively an inline repr always looks like a positive
+// i64 while a heap allocated repr always looks like a negative i64.
+//
+// For the inline repr, we store \0 padding on the end of the stored characters,
+// and thus the string length is readily determined efficiently by a cttz (count
+// trailing zeros) or bsf (bit scan forward) instruction.
+//
+// For the heap allocated repr, the length is encoded as a base-128 varint at
+// the head of the allocation.
+//
+// Empty strings are stored as an all-1 bit pattern, corresponding to -1i64.
+// Consequently the all-0 bit pattern is never a legal representation in any
+// repr, leaving it available as a niche for downstream code. For example this
+// allows size_of::<Version>() == size_of::<Option<Version>>().
+
+use crate::alloc::alloc::{alloc, dealloc, handle_alloc_error, Layout};
+use core::isize;
+use core::mem;
+use core::num::{NonZeroU64, NonZeroUsize};
+use core::ptr::{self, NonNull};
+use core::slice;
+use core::str;
+use core::usize;
+
+const PTR_BYTES: usize = mem::size_of::<NonNull<u8>>();
+
+// If pointers are already 8 bytes or bigger, then 0. If pointers are smaller
+// than 8 bytes, then Identifier will contain a byte array to raise its size up
+// to 8 bytes total.
+const TAIL_BYTES: usize = 8 * (PTR_BYTES < 8) as usize - PTR_BYTES * (PTR_BYTES < 8) as usize;
+
+#[repr(C, align(8))]
+pub(crate) struct Identifier {
+    head: NonNull<u8>,
+    tail: [u8; TAIL_BYTES],
+}
+
+impl Identifier {
+    pub(crate) const fn empty() -> Self {
+        // This is a separate constant because unsafe function calls are not
+        // allowed in a const fn body, only in a const, until later rustc than
+        // what we support.
+        const HEAD: NonNull<u8> = unsafe { NonNull::new_unchecked(!0 as *mut u8) };
+
+        // `mov rax, -1`
+        Identifier {
+            head: HEAD,
+            tail: [!0; TAIL_BYTES],
+        }
+    }
+
+    // SAFETY: string must be ASCII and not contain \0 bytes.
+    pub(crate) unsafe fn new_unchecked(string: &str) -> Self {
+        let len = string.len();
+        debug_assert!(len <= isize::MAX as usize);
+        match len as u64 {
+            0 => Self::empty(),
+            1..=8 => {
+                let mut bytes = [0u8; mem::size_of::<Identifier>()];
+                // SAFETY: string is big enough to read len bytes, bytes is big
+                // enough to write len bytes, and they do not overlap.
+                unsafe { ptr::copy_nonoverlapping(string.as_ptr(), bytes.as_mut_ptr(), len) };
+                // SAFETY: the head field is nonzero because the input string
+                // was at least 1 byte of ASCII and did not contain \0.
+                unsafe { mem::transmute::<[u8; mem::size_of::<Identifier>()], Identifier>(bytes) }
+            }
+            9..=0xff_ffff_ffff_ffff => {
+                // SAFETY: len is in a range that does not contain 0.
+                let size = bytes_for_varint(unsafe { NonZeroUsize::new_unchecked(len) }) + len;
+                let align = 2;
+                // On 32-bit and 16-bit architecture, check for size overflowing
+                // isize::MAX. Making an allocation request bigger than this to
+                // the allocator is considered UB. All allocations (including
+                // static ones) are limited to isize::MAX so we're guaranteed
+                // len <= isize::MAX, and we know bytes_for_varint(len) <= 5
+                // because 128**5 > isize::MAX, which means the only problem
+                // that can arise is when isize::MAX - 5 <= len <= isize::MAX.
+                // This is pretty much guaranteed to be malicious input so we
+                // don't need to care about returning a good error message.
+                if mem::size_of::<usize>() < 8 {
+                    let max_alloc = usize::MAX / 2 - align;
+                    assert!(size <= max_alloc);
+                }
+                // SAFETY: align is not zero, align is a power of two, and
+                // rounding size up to align does not overflow isize::MAX.
+                let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
+                // SAFETY: layout's size is nonzero.
+                let ptr = unsafe { alloc(layout) };
+                if ptr.is_null() {
+                    handle_alloc_error(layout);
+                }
+                let mut write = ptr;
+                let mut varint_remaining = len;
+                while varint_remaining > 0 {
+                    // SAFETY: size is bytes_for_varint(len) bytes + len bytes.
+                    // This is writing the first bytes_for_varint(len) bytes.
+                    unsafe { ptr::write(write, varint_remaining as u8 | 0x80) };
+                    varint_remaining >>= 7;
+                    // SAFETY: still in bounds of the same allocation.
+                    write = unsafe { write.add(1) };
+                }
+                // SAFETY: size is bytes_for_varint(len) bytes + len bytes. This
+                // is writing to the last len bytes.
+                unsafe { ptr::copy_nonoverlapping(string.as_ptr(), write, len) };
+                Identifier {
+                    head: ptr_to_repr(ptr),
+                    tail: [0; TAIL_BYTES],
+                }
+            }
+            0x100_0000_0000_0000..=0xffff_ffff_ffff_ffff => {
+                unreachable!("please refrain from storing >64 petabytes of text in semver version");
+            }
+            #[cfg(no_exhaustive_int_match)] // rustc <1.33
+            _ => unreachable!(),
+        }
+    }
+
+    pub(crate) fn is_empty(&self) -> bool {
+        // `cmp rdi, -1` -- basically: `repr as i64 == -1`
+        let empty = Self::empty();
+        let is_empty = self.head == empty.head && self.tail == empty.tail;
+        // The empty representation does nothing on Drop. We can't let this one
+        // drop normally because `impl Drop for Identifier` calls is_empty; that
+        // would be an infinite recursion.
+        mem::forget(empty);
+        is_empty
+    }
+
+    fn is_inline(&self) -> bool {
+        // `test rdi, rdi` -- basically: `repr as i64 >= 0`
+        self.head.as_ptr() as usize >> (PTR_BYTES * 8 - 1) == 0
+    }
+
+    fn is_empty_or_inline(&self) -> bool {
+        // `cmp rdi, -2` -- basically: `repr as i64 > -2`
+        self.is_empty() || self.is_inline()
+    }
+
+    pub(crate) fn as_str(&self) -> &str {
+        if self.is_empty() {
+            ""
+        } else if self.is_inline() {
+            // SAFETY: repr is in the inline representation.
+            unsafe { inline_as_str(self) }
+        } else {
+            // SAFETY: repr is in the heap allocated representation.
+            unsafe { ptr_as_str(&self.head) }
+        }
+    }
+}
+
+impl Clone for Identifier {
+    fn clone(&self) -> Self {
+        if self.is_empty_or_inline() {
+            Identifier {
+                head: self.head,
+                tail: self.tail,
+            }
+        } else {
+            let ptr = repr_to_ptr(self.head);
+            // SAFETY: ptr is one of our own heap allocations.
+            let len = unsafe { decode_len(ptr) };
+            let size = bytes_for_varint(len) + len.get();
+            let align = 2;
+            // SAFETY: align is not zero, align is a power of two, and rounding
+            // size up to align does not overflow isize::MAX. This is just
+            // duplicating a previous allocation where all of these guarantees
+            // were already made.
+            let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
+            // SAFETY: layout's size is nonzero.
+            let clone = unsafe { alloc(layout) };
+            if clone.is_null() {
+                handle_alloc_error(layout);
+            }
+            // SAFETY: new allocation cannot overlap the previous one (this was
+            // not a realloc). The argument ptrs are readable/writeable
+            // respectively for size bytes.
+            unsafe { ptr::copy_nonoverlapping(ptr, clone, size) }
+            Identifier {
+                head: ptr_to_repr(clone),
+                tail: [0; TAIL_BYTES],
+            }
+        }
+    }
+}
+
+impl Drop for Identifier {
+    fn drop(&mut self) {
+        if self.is_empty_or_inline() {
+            return;
+        }
+        let ptr = repr_to_ptr_mut(self.head);
+        // SAFETY: ptr is one of our own heap allocations.
+        let len = unsafe { decode_len(ptr) };
+        let size = bytes_for_varint(len) + len.get();
+        let align = 2;
+        // SAFETY: align is not zero, align is a power of two, and rounding
+        // size up to align does not overflow usize::MAX. These guarantees were
+        // made when originally allocating this memory.
+        let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
+        // SAFETY: ptr was previously allocated by the same allocator with the
+        // same layout.
+        unsafe { dealloc(ptr, layout) }
+    }
+}
+
+impl PartialEq for Identifier {
+    fn eq(&self, rhs: &Self) -> bool {
+        if self.is_empty_or_inline() {
+            // Fast path (most common)
+            self.head == rhs.head && self.tail == rhs.tail
+        } else if rhs.is_empty_or_inline() {
+            false
+        } else {
+            // SAFETY: both reprs are in the heap allocated representation.
+            unsafe { ptr_as_str(&self.head) == ptr_as_str(&rhs.head) }
+        }
+    }
+}
+
+unsafe impl Send for Identifier {}
+unsafe impl Sync for Identifier {}
+
+// We use heap pointers that are 2-byte aligned, meaning they have an
+// insignificant 0 in the least significant bit. We take advantage of that
+// unneeded bit to rotate a 1 into the most significant bit to make the repr
+// distinguishable from ASCII bytes.
+fn ptr_to_repr(original: *mut u8) -> NonNull<u8> {
+    // `mov eax, 1`
+    // `shld rax, rdi, 63`
+    let modified = (original as usize | 1).rotate_right(1);
+
+    // `original + (modified - original)`, but being mindful of provenance.
+    let diff = modified.wrapping_sub(original as usize);
+    let modified = original.wrapping_add(diff);
+
+    // SAFETY: the most significant bit of repr is known to be set, so the value
+    // is not zero.
+    unsafe { NonNull::new_unchecked(modified) }
+}
+
+// Shift out the 1 previously placed into the most significant bit of the least
+// significant byte. Shift in a low 0 bit to reconstruct the original 2-byte
+// aligned pointer.
+fn repr_to_ptr(modified: NonNull<u8>) -> *const u8 {
+    // `lea rax, [rdi + rdi]`
+    let modified = modified.as_ptr();
+    let original = (modified as usize) << 1;
+
+    // `modified + (original - modified)`, but being mindful of provenance.
+    let diff = original.wrapping_sub(modified as usize);
+    modified.wrapping_add(diff)
+}
+
+fn repr_to_ptr_mut(repr: NonNull<u8>) -> *mut u8 {
+    repr_to_ptr(repr) as *mut u8
+}
+
+// Compute the length of the inline string, assuming the argument is in short
+// string representation. Short strings are stored as 1 to 8 nonzero ASCII
+// bytes, followed by \0 padding for the remaining bytes.
+//
+// SAFETY: the identifier must indeed be in the inline representation.
+unsafe fn inline_len(repr: &Identifier) -> NonZeroUsize {
+    // SAFETY: Identifier's layout is align(8) and at least size 8. We're doing
+    // an aligned read of the first 8 bytes from it. The bytes are not all zero
+    // because inline strings are at least 1 byte long and cannot contain \0.
+    let repr = unsafe { ptr::read(repr as *const Identifier as *const NonZeroU64) };
+
+    // Rustc >=1.53 has intrinsics for counting zeros on a non-zeroable integer.
+    // On many architectures these are more efficient than counting on ordinary
+    // zeroable integers (bsf vs cttz). On rustc <1.53 without those intrinsics,
+    // we count zeros in the u64 rather than the NonZeroU64.
+    #[cfg(no_nonzero_bitscan)]
+    let repr = repr.get();
+
+    #[cfg(target_endian = "little")]
+    let zero_bits_on_string_end = repr.leading_zeros();
+    #[cfg(target_endian = "big")]
+    let zero_bits_on_string_end = repr.trailing_zeros();
+
+    let nonzero_bytes = 8 - zero_bits_on_string_end as usize / 8;
+
+    // SAFETY: repr is nonzero, so it has at most 63 zero bits on either end,
+    // thus at least one nonzero byte.
+    unsafe { NonZeroUsize::new_unchecked(nonzero_bytes) }
+}
+
+// SAFETY: repr must be in the inline representation, i.e. at least 1 and at
+// most 8 nonzero ASCII bytes padded on the end with \0 bytes.
+unsafe fn inline_as_str(repr: &Identifier) -> &str {
+    let ptr = repr as *const Identifier as *const u8;
+    let len = unsafe { inline_len(repr) }.get();
+    // SAFETY: we are viewing the nonzero ASCII prefix of the inline repr's
+    // contents as a slice of bytes. Input/output lifetimes are correctly
+    // associated.
+    let slice = unsafe { slice::from_raw_parts(ptr, len) };
+    // SAFETY: the string contents are known to be only ASCII bytes, which are
+    // always valid UTF-8.
+    unsafe { str::from_utf8_unchecked(slice) }
+}
+
+// Decode varint. Varints consist of between one and eight base-128 digits, each
+// of which is stored in a byte with most significant bit set. Adjacent to the
+// varint in memory there is guaranteed to be at least 9 ASCII bytes, each of
+// which has an unset most significant bit.
+//
+// SAFETY: ptr must be one of our own heap allocations, with the varint header
+// already written.
+unsafe fn decode_len(ptr: *const u8) -> NonZeroUsize {
+    // SAFETY: There is at least one byte of varint followed by at least 9 bytes
+    // of string content, which is at least 10 bytes total for the allocation,
+    // so reading the first two is no problem.
+    let [first, second] = unsafe { ptr::read(ptr as *const [u8; 2]) };
+    if second < 0x80 {
+        // SAFETY: the length of this heap allocated string has been encoded as
+        // one base-128 digit, so the length is at least 9 and at most 127. It
+        // cannot be zero.
+        unsafe { NonZeroUsize::new_unchecked((first & 0x7f) as usize) }
+    } else {
+        return unsafe { decode_len_cold(ptr) };
+
+        // Identifiers 128 bytes or longer. This is not exercised by any crate
+        // version currently published to crates.io.
+        #[cold]
+        #[inline(never)]
+        unsafe fn decode_len_cold(mut ptr: *const u8) -> NonZeroUsize {
+            let mut len = 0;
+            let mut shift = 0;
+            loop {
+                // SAFETY: varint continues while there are bytes having the
+                // most significant bit set, i.e. until we start hitting the
+                // ASCII string content with msb unset.
+                let byte = unsafe { *ptr };
+                if byte < 0x80 {
+                    // SAFETY: the string length is known to be 128 bytes or
+                    // longer.
+                    return unsafe { NonZeroUsize::new_unchecked(len) };
+                }
+                // SAFETY: still in bounds of the same allocation.
+                ptr = unsafe { ptr.add(1) };
+                len += ((byte & 0x7f) as usize) << shift;
+                shift += 7;
+            }
+        }
+    }
+}
+
+// SAFETY: repr must be in the heap allocated representation, with varint header
+// and string contents already written.
+unsafe fn ptr_as_str(repr: &NonNull<u8>) -> &str {
+    let ptr = repr_to_ptr(*repr);
+    let len = unsafe { decode_len(ptr) };
+    let header = bytes_for_varint(len);
+    let slice = unsafe { slice::from_raw_parts(ptr.add(header), len.get()) };
+    // SAFETY: all identifier contents are ASCII bytes, which are always valid
+    // UTF-8.
+    unsafe { str::from_utf8_unchecked(slice) }
+}
+
+// Number of base-128 digits required for the varint representation of a length.
+fn bytes_for_varint(len: NonZeroUsize) -> usize {
+    #[cfg(no_nonzero_bitscan)] // rustc <1.53
+    let len = len.get();
+
+    let usize_bits = mem::size_of::<usize>() * 8;
+    let len_bits = usize_bits - len.leading_zeros() as usize;
+    (len_bits + 6) / 7
+}
diff --git a/third_party/rust/semver/src/impls.rs b/third_party/rust/semver/src/impls.rs
new file mode 100644
index 0000000000..c3b6c60133
--- /dev/null
+++ b/third_party/rust/semver/src/impls.rs
@@ -0,0 +1,156 @@
+use crate::backport::*;
+use crate::identifier::Identifier;
+use crate::{BuildMetadata, Comparator, Prerelease, VersionReq};
+use core::cmp::Ordering;
+use core::hash::{Hash, Hasher};
+use core::iter::FromIterator;
+use core::ops::Deref;
+
+impl Default for Identifier {
+    fn default() -> Self {
+        Identifier::empty()
+    }
+}
+
+impl Eq for Identifier {}
+
+impl Hash for Identifier {
+    fn hash<H: Hasher>(&self, hasher: &mut H) {
+        self.as_str().hash(hasher);
+    }
+}
+
+impl Deref for Prerelease {
+    type Target = str;
+
+    fn deref(&self) -> &Self::Target {
+        self.identifier.as_str()
+    }
+}
+
+impl Deref for BuildMetadata {
+    type Target = str;
+
+    fn deref(&self) -> &Self::Target {
+        self.identifier.as_str()
+    }
+}
+
+impl PartialOrd for Prerelease {
+    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
+        Some(Ord::cmp(self, rhs))
+    }
+}
+
+impl PartialOrd for BuildMetadata {
+    fn partial_cmp(&self, rhs: &Self) -> Option<Ordering> {
+        Some(Ord::cmp(self, rhs))
+    }
+}
+
+impl Ord for Prerelease {
+    fn cmp(&self, rhs: &Self) -> Ordering {
+        match self.is_empty() {
+            true if rhs.is_empty() => return Ordering::Equal,
+            // A real release compares greater than prerelease.
+            true => return Ordering::Greater,
+            // Prerelease compares less than the real release.
+            false if rhs.is_empty() => return Ordering::Less,
+            false => {}
+        }
+
+        let lhs = self.as_str().split('.');
+        let mut rhs = rhs.as_str().split('.');
+
+        for lhs in lhs {
+            let rhs = match rhs.next() {
+                // Spec: "A larger set of pre-release fields has a higher
+                // precedence than a smaller set, if all of the preceding
+                // identifiers are equal."
+                None => return Ordering::Greater,
+                Some(rhs) => rhs,
+            };
+
+            let string_cmp = || Ord::cmp(lhs, rhs);
+            let is_ascii_digit = |b: u8| b.is_ascii_digit();
+            let ordering = match (
+                lhs.bytes().all(is_ascii_digit),
+                rhs.bytes().all(is_ascii_digit),
+            ) {
+                // Respect numeric ordering, for example 99 < 100. Spec says:
+                // "Identifiers consisting of only digits are compared
+                // numerically."
+                (true, true) => Ord::cmp(&lhs.len(), &rhs.len()).then_with(string_cmp),
+                // Spec: "Numeric identifiers always have lower precedence than
+                // non-numeric identifiers."
+                (true, false) => return Ordering::Less,
+                (false, true) => return Ordering::Greater,
+                // Spec: "Identifiers with letters or hyphens are compared
+                // lexically in ASCII sort order."
+                (false, false) => string_cmp(),
+            };
+
+            if ordering != Ordering::Equal {
+                return ordering;
+            }
+        }
+
+        if rhs.next().is_none() {
+            Ordering::Equal
+        } else {
+            Ordering::Less
+        }
+    }
+}
+
+impl Ord for BuildMetadata {
+    fn cmp(&self, rhs: &Self) -> Ordering {
+        let lhs = self.as_str().split('.');
+        let mut rhs = rhs.as_str().split('.');
+
+        for lhs in lhs {
+            let rhs = match rhs.next() {
+                None => return Ordering::Greater,
+                Some(rhs) => rhs,
+            };
+
+            let is_ascii_digit = |b: u8| b.is_ascii_digit();
+            let ordering = match (
+                lhs.bytes().all(is_ascii_digit),
+                rhs.bytes().all(is_ascii_digit),
+            ) {
+                (true, true) => {
+                    // 0 < 00 < 1 < 01 < 001 < 2 < 02 < 002 < 10
+                    let lhval = lhs.trim_start_matches('0');
+                    let rhval = rhs.trim_start_matches('0');
+                    Ord::cmp(&lhval.len(), &rhval.len())
+                        .then_with(|| Ord::cmp(lhval, rhval))
+                        .then_with(|| Ord::cmp(&lhs.len(), &rhs.len()))
+                }
+                (true, false) => return Ordering::Less,
+                (false, true) => return Ordering::Greater,
+                (false, false) => Ord::cmp(lhs, rhs),
+            };
+
+            if ordering != Ordering::Equal {
+                return ordering;
+            }
+        }
+
+        if rhs.next().is_none() {
+            Ordering::Equal
+        } else {
+            Ordering::Less
+        }
+    }
+}
+
+impl FromIterator<Comparator> for VersionReq {
+    fn from_iter<I>(iter: I) -> Self
+    where
+        I: IntoIterator<Item = Comparator>,
+    {
+        let comparators = Vec::from_iter(iter);
+        VersionReq { comparators }
+    }
+}
diff --git a/third_party/rust/semver/src/lib.rs b/third_party/rust/semver/src/lib.rs
new file mode 100644
index 0000000000..32ed96d1ca
--- /dev/null
+++ b/third_party/rust/semver/src/lib.rs
@@ -0,0 +1,533 @@
+//! [![github]](https://github.com/dtolnay/semver)&ensp;[![crates-io]](https://crates.io/crates/semver)&ensp;[![docs-rs]](https://docs.rs/semver)
+//!
+//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
+//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
+//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
+//!
+//! <br>
+//!
+//! A parser and evaluator for Cargo's flavor of Semantic Versioning.
+//!
+//! Semantic Versioning (see <https://semver.org>) is a guideline for how
+//! version numbers are assigned and incremented. It is widely followed within
+//! the Cargo/crates.io ecosystem for Rust.
+//!
+//! <br>
+//!
+//! # Example
+//!
+//! ```
+//! use semver::{BuildMetadata, Prerelease, Version, VersionReq};
+//!
+//! fn main() {
+//!     let req = VersionReq::parse(">=1.2.3, <1.8.0").unwrap();
+//!
+//!     // Check whether this requirement matches version 1.2.3-alpha.1 (no)
+//!     let version = Version {
+//!         major: 1,
+//!         minor: 2,
+//!         patch: 3,
+//!         pre: Prerelease::new("alpha.1").unwrap(),
+//!         build: BuildMetadata::EMPTY,
+//!     };
+//!     assert!(!req.matches(&version));
+//!
+//!     // Check whether it matches 1.3.0 (yes it does)
+//!     let version = Version::parse("1.3.0").unwrap();
+//!     assert!(req.matches(&version));
+//! }
+//! ```
+//!
+//! <br><br>
+//!
+//! # Scope of this crate
+//!
+//! Besides Cargo, several other package ecosystems and package managers for
+//! other languages also use SemVer:&ensp;RubyGems/Bundler for Ruby, npm for
+//! JavaScript, Composer for PHP, CocoaPods for Objective-C...
+//!
+//! The `semver` crate is specifically intended to implement Cargo's
+//! interpretation of Semantic Versioning.
+//!
+//! Where the various tools differ in their interpretation or implementation of
+//! the spec, this crate follows the implementation choices made by Cargo. If
+//! you are operating on version numbers from some other package ecosystem, you
+//! will want to use a different semver library which is appropriate to that
+//! ecosystem.
+//!
+//! The extent of Cargo's SemVer support is documented in the *[Specifying
+//! Dependencies]* chapter of the Cargo reference.
+//!
+//! [Specifying Dependencies]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html
+
+#![doc(html_root_url = "https://docs.rs/semver/1.0.16")]
+#![cfg_attr(doc_cfg, feature(doc_cfg))]
+#![cfg_attr(all(not(feature = "std"), not(no_alloc_crate)), no_std)]
+#![cfg_attr(not(no_unsafe_op_in_unsafe_fn_lint), deny(unsafe_op_in_unsafe_fn))]
+#![cfg_attr(no_unsafe_op_in_unsafe_fn_lint, allow(unused_unsafe))]
+#![cfg_attr(no_str_strip_prefix, allow(unstable_name_collisions))]
+#![allow(
+    clippy::cast_lossless,
+    clippy::cast_possible_truncation,
+    clippy::doc_markdown,
+    clippy::items_after_statements,
+    clippy::manual_map,
+    clippy::match_bool,
+    clippy::missing_errors_doc,
+    clippy::must_use_candidate,
+    clippy::needless_doctest_main,
+    clippy::option_if_let_else,
+    clippy::ptr_as_ptr,
+    clippy::redundant_else,
+    clippy::semicolon_if_nothing_returned, // https://github.com/rust-lang/rust-clippy/issues/7324
+    clippy::similar_names,
+    clippy::unnested_or_patterns,
+    clippy::unseparated_literal_suffix,
+    clippy::wildcard_imports
+)]
+
+#[cfg(not(no_alloc_crate))]
+extern crate alloc;
+
+mod backport;
+mod display;
+mod error;
+mod eval;
+mod identifier;
+mod impls;
+mod parse;
+
+#[cfg(feature = "serde")]
+mod serde;
+
+use crate::alloc::vec::Vec;
+use crate::identifier::Identifier;
+use core::str::FromStr;
+
+#[allow(unused_imports)]
+use crate::backport::*;
+
+pub use crate::parse::Error;
+
+/// **SemVer version** as defined by <https://semver.org>.
+///
+/// # Syntax
+///
+/// - The major, minor, and patch numbers may be any integer 0 through u64::MAX.
+///   When representing a SemVer version as a string, each number is written as
+///   a base 10 integer. For example, `1.0.119`.
+///
+/// - Leading zeros are forbidden in those positions. For example `1.01.00` is
+///   invalid as a SemVer version.
+///
+/// - The pre-release identifier, if present, must conform to the syntax
+///   documented for [`Prerelease`].
+///
+/// - The build metadata, if present, must conform to the syntax documented for
+///   [`BuildMetadata`].
+///
+/// - Whitespace is not allowed anywhere in the version.
+///
+/// # Total ordering
+///
+/// Given any two SemVer versions, one is less than, greater than, or equal to
+/// the other. Versions may be compared against one another using Rust's usual
+/// comparison operators.
+///
+/// - The major, minor, and patch number are compared numerically from left to
+/// right, lexicographically ordered as a 3-tuple of integers. So for example
+/// version `1.5.0` is less than version `1.19.0`, despite the fact that
+/// "1.19.0" &lt; "1.5.0" as ASCIIbetically compared strings and 1.19 &lt; 1.5
+/// as real numbers.
+///
+/// - When major, minor, and patch are equal, a pre-release version is
+///   considered less than the ordinary release:&ensp;version `1.0.0-alpha.1` is
+///   less than version `1.0.0`.
+///
+/// - Two pre-releases of the same major, minor, patch are compared by
+///   lexicographic ordering of dot-separated components of the pre-release
+///   string.
+///
+///   - Identifiers consisting of only digits are compared
+///     numerically:&ensp;`1.0.0-pre.8` is less than `1.0.0-pre.12`.
+///
+///   - Identifiers that contain a letter or hyphen are compared in ASCII sort
+///     order:&ensp;`1.0.0-pre12` is less than `1.0.0-pre8`.
+///
+///   - Any numeric identifier is always less than any non-numeric
+///     identifier:&ensp;`1.0.0-pre.1` is less than `1.0.0-pre.x`.
+///
+/// Example:&ensp;`1.0.0-alpha`&ensp;&lt;&ensp;`1.0.0-alpha.1`&ensp;&lt;&ensp;`1.0.0-alpha.beta`&ensp;&lt;&ensp;`1.0.0-beta`&ensp;&lt;&ensp;`1.0.0-beta.2`&ensp;&lt;&ensp;`1.0.0-beta.11`&ensp;&lt;&ensp;`1.0.0-rc.1`&ensp;&lt;&ensp;`1.0.0`
+#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
+pub struct Version {
+    pub major: u64,
+    pub minor: u64,
+    pub patch: u64,
+    pub pre: Prerelease,
+    pub build: BuildMetadata,
+}
+
+/// **SemVer version requirement** describing the intersection of some version
+/// comparators, such as `>=1.2.3, <1.8`.
+///
+/// # Syntax
+///
+/// - Either `*` (meaning "any"), or one or more comma-separated comparators.
+///
+/// - A [`Comparator`] is an operator ([`Op`]) and a partial version, separated
+///   by optional whitespace. For example `>=1.0.0` or `>=1.0`.
+///
+/// - Build metadata is syntactically permitted on the partial versions, but is
+///   completely ignored, as it's never relevant to whether any comparator
+///   matches a particular version.
+///
+/// - Whitespace is permitted around commas and around operators. Whitespace is
+///   not permitted within a partial version, i.e. anywhere between the major
+///   version number and its minor, patch, pre-release, or build metadata.
+#[derive(Clone, Eq, PartialEq, Hash, Debug)]
+#[cfg_attr(no_const_vec_new, derive(Default))]
+pub struct VersionReq {
+    pub comparators: Vec<Comparator>,
+}
+
+/// A pair of comparison operator and partial version, such as `>=1.2`. Forms
+/// one piece of a VersionReq.
+#[derive(Clone, Eq, PartialEq, Hash, Debug)]
+pub struct Comparator {
+    pub op: Op,
+    pub major: u64,
+    pub minor: Option<u64>,
+    /// Patch is only allowed if minor is Some.
+    pub patch: Option<u64>,
+    /// Non-empty pre-release is only allowed if patch is Some.
+    pub pre: Prerelease,
+}
+
+/// SemVer comparison operator: `=`, `>`, `>=`, `<`, `<=`, `~`, `^`, `*`.
+///
+/// # Op::Exact
+/// - &ensp;**`=I.J.K`**&emsp;&mdash;&emsp;exactly the version I.J.K
+/// - &ensp;**`=I.J`**&emsp;&mdash;&emsp;equivalent to `>=I.J.0, <I.(J+1).0`
+/// - &ensp;**`=I`**&emsp;&mdash;&emsp;equivalent to `>=I.0.0, <(I+1).0.0`
+///
+/// # Op::Greater
+/// - &ensp;**`>I.J.K`**
+/// - &ensp;**`>I.J`**&emsp;&mdash;&emsp;equivalent to `>=I.(J+1).0`
+/// - &ensp;**`>I`**&emsp;&mdash;&emsp;equivalent to `>=(I+1).0.0`
+///
+/// # Op::GreaterEq
+/// - &ensp;**`>=I.J.K`**
+/// - &ensp;**`>=I.J`**&emsp;&mdash;&emsp;equivalent to `>=I.J.0`
+/// - &ensp;**`>=I`**&emsp;&mdash;&emsp;equivalent to `>=I.0.0`
+///
+/// # Op::Less
+/// - &ensp;**`<I.J.K`**
+/// - &ensp;**`<I.J`**&emsp;&mdash;&emsp;equivalent to `<I.J.0`
+/// - &ensp;**`<I`**&emsp;&mdash;&emsp;equivalent to `<I.0.0`
+///
+/// # Op::LessEq
+/// - &ensp;**`<=I.J.K`**
+/// - &ensp;**`<=I.J`**&emsp;&mdash;&emsp;equivalent to `<I.(J+1).0`
+/// - &ensp;**`<=I`**&emsp;&mdash;&emsp;equivalent to `<(I+1).0.0`
+///
+/// # Op::Tilde&emsp;("patch" updates)
+/// *Tilde requirements allow the **patch** part of the semver version (the third number) to increase.*
+/// - &ensp;**`~I.J.K`**&emsp;&mdash;&emsp;equivalent to `>=I.J.K, <I.(J+1).0`
+/// - &ensp;**`~I.J`**&emsp;&mdash;&emsp;equivalent to `=I.J`
+/// - &ensp;**`~I`**&emsp;&mdash;&emsp;equivalent to `=I`
+///
+/// # Op::Caret&emsp;("compatible" updates)
+/// *Caret requirements allow parts that are **right of the first nonzero** part of the semver version to increase.*
+/// - &ensp;**`^I.J.K`**&ensp;(for I\>0)&emsp;&mdash;&emsp;equivalent to `>=I.J.K, <(I+1).0.0`
+/// - &ensp;**`^0.J.K`**&ensp;(for J\>0)&emsp;&mdash;&emsp;equivalent to `>=0.J.K, <0.(J+1).0`
+/// - &ensp;**`^0.0.K`**&emsp;&mdash;&emsp;equivalent to `=0.0.K`
+/// - &ensp;**`^I.J`**&ensp;(for I\>0 or J\>0)&emsp;&mdash;&emsp;equivalent to `^I.J.0`
+/// - &ensp;**`^0.0`**&emsp;&mdash;&emsp;equivalent to `=0.0`
+/// - &ensp;**`^I`**&emsp;&mdash;&emsp;equivalent to `=I`
+///
+/// # Op::Wildcard
+/// - &ensp;**`I.J.*`**&emsp;&mdash;&emsp;equivalent to `=I.J`
+/// - &ensp;**`I.*`**&ensp;or&ensp;**`I.*.*`**&emsp;&mdash;&emsp;equivalent to `=I`
+#[derive(Copy, Clone, Eq, PartialEq, Hash, Debug)]
+#[cfg_attr(not(no_non_exhaustive), non_exhaustive)]
+pub enum Op {
+    Exact,
+    Greater,
+    GreaterEq,
+    Less,
+    LessEq,
+    Tilde,
+    Caret,
+    Wildcard,
+
+    #[cfg(no_non_exhaustive)] // rustc <1.40
+    #[doc(hidden)]
+    __NonExhaustive,
+}
+
+/// Optional pre-release identifier on a version string. This comes after `-` in
+/// a SemVer version, like `1.0.0-alpha.1`
+///
+/// # Examples
+///
+/// Some real world pre-release idioms drawn from crates.io:
+///
+/// - **[mio]** <code>0.7.0-<b>alpha.1</b></code> &mdash; the most common style
+///   for numbering pre-releases.
+///
+/// - **[pest]** <code>1.0.0-<b>beta.8</b></code>,&ensp;<code>1.0.0-<b>rc.0</b></code>
+///   &mdash; this crate makes a distinction between betas and release
+///   candidates.
+///
+/// - **[sassers]** <code>0.11.0-<b>shitshow</b></code> &mdash; ???.
+///
+/// - **[atomic-utils]** <code>0.0.0-<b>reserved</b></code> &mdash; a squatted
+///   crate name.
+///
+/// [mio]: https://crates.io/crates/mio
+/// [pest]: https://crates.io/crates/pest
+/// [atomic-utils]: https://crates.io/crates/atomic-utils
+/// [sassers]: https://crates.io/crates/sassers
+///
+/// *Tip:* Be aware that if you are planning to number your own pre-releases,
+/// you should prefer to separate the numeric part from any non-numeric
+/// identifiers by using a dot in between. That is, prefer pre-releases
+/// `alpha.1`, `alpha.2`, etc rather than `alpha1`, `alpha2` etc. The SemVer
+/// spec's rule for pre-release precedence has special treatment of numeric
+/// components in the pre-release string, but only if there are no non-digit
+/// characters in the same dot-separated component. So you'd have `alpha.2` &lt;
+/// `alpha.11` as intended, but `alpha11` &lt; `alpha2`.
+///
+/// # Syntax
+///
+/// Pre-release strings are a series of dot separated identifiers immediately
+/// following the patch version. Identifiers must comprise only ASCII
+/// alphanumerics and hyphens: `0-9`, `A-Z`, `a-z`, `-`. Identifiers must not be
+/// empty. Numeric identifiers must not include leading zeros.
+///
+/// # Total ordering
+///
+/// Pre-releases have a total order defined by the SemVer spec. It uses
+/// lexicographic ordering of dot-separated components. Identifiers consisting
+/// of only digits are compared numerically. Otherwise, identifiers are compared
+/// in ASCII sort order. Any numeric identifier is always less than any
+/// non-numeric identifier.
+///
+/// Example:&ensp;`alpha`&ensp;&lt;&ensp;`alpha.85`&ensp;&lt;&ensp;`alpha.90`&ensp;&lt;&ensp;`alpha.200`&ensp;&lt;&ensp;`alpha.0a`&ensp;&lt;&ensp;`alpha.1a0`&ensp;&lt;&ensp;`alpha.a`&ensp;&lt;&ensp;`beta`
+#[derive(Default, Clone, Eq, PartialEq, Hash)]
+pub struct Prerelease {
+    identifier: Identifier,
+}
+
+/// Optional build metadata identifier. This comes after `+` in a SemVer
+/// version, as in `0.8.1+zstd.1.5.0`.
+///
+/// # Examples
+///
+/// Some real world build metadata idioms drawn from crates.io:
+///
+/// - **[libgit2-sys]** <code>0.12.20+<b>1.1.0</b></code> &mdash; for this
+///   crate, the build metadata indicates the version of the C libgit2 library
+///   that the Rust crate is built against.
+///
+/// - **[mashup]** <code>0.1.13+<b>deprecated</b></code> &mdash; just the word
+///   "deprecated" for a crate that has been superseded by another. Eventually
+///   people will take notice of this in Cargo's build output where it lists the
+///   crates being compiled.
+///
+/// - **[google-bigquery2]** <code>2.0.4+<b>20210327</b></code> &mdash; this
+///   library is automatically generated from an official API schema, and the
+///   build metadata indicates the date on which that schema was last captured.
+///
+/// - **[fbthrift-git]** <code>0.0.6+<b>c7fcc0e</b></code> &mdash; this crate is
+///   published from snapshots of a big company monorepo. In monorepo
+///   development, there is no concept of versions, and all downstream code is
+///   just updated atomically in the same commit that breaking changes to a
+///   library are landed. Therefore for crates.io purposes, every published
+///   version must be assumed to be incompatible with the previous. The build
+///   metadata provides the source control hash of the snapshotted code.
+///
+/// [libgit2-sys]: https://crates.io/crates/libgit2-sys
+/// [mashup]: https://crates.io/crates/mashup
+/// [google-bigquery2]: https://crates.io/crates/google-bigquery2
+/// [fbthrift-git]: https://crates.io/crates/fbthrift-git
+///
+/// # Syntax
+///
+/// Build metadata is a series of dot separated identifiers immediately
+/// following the patch or pre-release version. Identifiers must comprise only
+/// ASCII alphanumerics and hyphens: `0-9`, `A-Z`, `a-z`, `-`. Identifiers must
+/// not be empty. Leading zeros *are* allowed, unlike any other place in the
+/// SemVer grammar.
+///
+/// # Total ordering
+///
+/// Build metadata is ignored in evaluating `VersionReq`; it plays no role in
+/// whether a `Version` matches any one of the comparison operators.
+///
+/// However for comparing build metadatas among one another, they do have a
+/// total order which is determined by lexicographic ordering of dot-separated
+/// components. Identifiers consisting of only digits are compared numerically.
+/// Otherwise, identifiers are compared in ASCII sort order. Any numeric
+/// identifier is always less than any non-numeric identifier.
+///
+/// Example:&ensp;`demo`&ensp;&lt;&ensp;`demo.85`&ensp;&lt;&ensp;`demo.90`&ensp;&lt;&ensp;`demo.090`&ensp;&lt;&ensp;`demo.200`&ensp;&lt;&ensp;`demo.1a0`&ensp;&lt;&ensp;`demo.a`&ensp;&lt;&ensp;`memo`
+#[derive(Default, Clone, Eq, PartialEq, Hash)]
+pub struct BuildMetadata {
+    identifier: Identifier,
+}
+
+impl Version {
+    /// Create `Version` with an empty pre-release and build metadata.
+    ///
+    /// Equivalent to:
+    ///
+    /// ```
+    /// # use semver::{BuildMetadata, Prerelease, Version};
+    /// #
+    /// # const fn new(major: u64, minor: u64, patch: u64) -> Version {
+    /// Version {
+    ///     major,
+    ///     minor,
+    ///     patch,
+    ///     pre: Prerelease::EMPTY,
+    ///     build: BuildMetadata::EMPTY,
+    /// }
+    /// # }
+    /// ```
+    pub const fn new(major: u64, minor: u64, patch: u64) -> Self {
+        Version {
+            major,
+            minor,
+            patch,
+            pre: Prerelease::EMPTY,
+            build: BuildMetadata::EMPTY,
+        }
+    }
+
+    /// Create `Version` by parsing from string representation.
+    ///
+    /// # Errors
+    ///
+    /// Possible reasons for the parse to fail include:
+    ///
+    /// - `1.0` &mdash; too few numeric components. A SemVer version must have
+    ///   exactly three. If you are looking at something that has fewer than
+    ///   three numbers in it, it's possible it is a `VersionReq` instead (with
+    ///   an implicit default `^` comparison operator).
+    ///
+    /// - `1.0.01` &mdash; a numeric component has a leading zero.
+    ///
+    /// - `1.0.unknown` &mdash; unexpected character in one of the components.
+    ///
+    /// - `1.0.0-` or `1.0.0+` &mdash; the pre-release or build metadata are
+    ///   indicated present but empty.
+    ///
+    /// - `1.0.0-alpha_123` &mdash; pre-release or build metadata have something
+    ///   outside the allowed characters, which are `0-9`, `A-Z`, `a-z`, `-`,
+    ///   and `.` (dot).
+    ///
+    /// - `23456789999999999999.0.0` &mdash; overflow of a u64.
+    pub fn parse(text: &str) -> Result<Self, Error> {
+        Version::from_str(text)
+    }
+}
+
+impl VersionReq {
+    /// A `VersionReq` with no constraint on the version numbers it matches.
+    /// Equivalent to `VersionReq::parse("*").unwrap()`.
+    ///
+    /// In terms of comparators this is equivalent to `>=0.0.0`.
+    ///
+    /// Counterintuitively a `*` VersionReq does not match every possible
+    /// version number. In particular, in order for *any* `VersionReq` to match
+    /// a pre-release version, the `VersionReq` must contain at least one
+    /// `Comparator` that has an explicit major, minor, and patch version
+    /// identical to the pre-release being matched, and that has a nonempty
+    /// pre-release component. Since `*` is not written with an explicit major,
+    /// minor, and patch version, and does not contain a nonempty pre-release
+    /// component, it does not match any pre-release versions.
+    #[cfg(not(no_const_vec_new))] // rustc <1.39
+    pub const STAR: Self = VersionReq {
+        comparators: Vec::new(),
+    };
+
+    /// Create `VersionReq` by parsing from string representation.
+    ///
+    /// # Errors
+    ///
+    /// Possible reasons for the parse to fail include:
+    ///
+    /// - `>a.b` &mdash; unexpected characters in the partial version.
+    ///
+    /// - `@1.0.0` &mdash; unrecognized comparison operator.
+    ///
+    /// - `^1.0.0, ` &mdash; unexpected end of input.
+    ///
+    /// - `>=1.0 <2.0` &mdash; missing comma between comparators.
+    ///
+    /// - `*.*` &mdash; unsupported wildcard syntax.
+    pub fn parse(text: &str) -> Result<Self, Error> {
+        VersionReq::from_str(text)
+    }
+
+    /// Evaluate whether the given `Version` satisfies the version requirement
+    /// described by `self`.
+    pub fn matches(&self, version: &Version) -> bool {
+        eval::matches_req(self, version)
+    }
+}
+
+/// The default VersionReq is the same as [`VersionReq::STAR`].
+#[cfg(not(no_const_vec_new))]
+impl Default for VersionReq {
+    fn default() -> Self {
+        VersionReq::STAR
+    }
+}
+
+impl Comparator {
+    pub fn parse(text: &str) -> Result<Self, Error> {
+        Comparator::from_str(text)
+    }
+
+    pub fn matches(&self, version: &Version) -> bool {
+        eval::matches_comparator(self, version)
+    }
+}
+
+impl Prerelease {
+    pub const EMPTY: Self = Prerelease {
+        identifier: Identifier::empty(),
+    };
+
+    pub fn new(text: &str) -> Result<Self, Error> {
+        Prerelease::from_str(text)
+    }
+
+    pub fn as_str(&self) -> &str {
+        self.identifier.as_str()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.identifier.is_empty()
+    }
+}
+
+impl BuildMetadata {
+    pub const EMPTY: Self = BuildMetadata {
+        identifier: Identifier::empty(),
+    };
+
+    pub fn new(text: &str) -> Result<Self, Error> {
+        BuildMetadata::from_str(text)
+    }
+
+    pub fn as_str(&self) -> &str {
+        self.identifier.as_str()
+    }
+
+    pub fn is_empty(&self) -> bool {
+        self.identifier.is_empty()
+    }
+}
diff --git a/third_party/rust/semver/src/parse.rs b/third_party/rust/semver/src/parse.rs
new file mode 100644
index 0000000000..6a8f6ffba4
--- /dev/null
+++ b/third_party/rust/semver/src/parse.rs
@@ -0,0 +1,405 @@
+use crate::backport::*;
+use crate::error::{ErrorKind, Position};
+use crate::identifier::Identifier;
+use crate::{BuildMetadata, Comparator, Op, Prerelease, Version, VersionReq};
+use core::str::FromStr;
+
+/// Error parsing a SemVer version or version requirement.
+///
+/// # Example
+///
+/// ```
+/// use semver::Version;
+///
+/// fn main() {
+///     let err = Version::parse("1.q.r").unwrap_err();
+///
+///     // "unexpected character 'q' while parsing minor version number"
+///     eprintln!("{}", err);
+/// }
+/// ```
+pub struct Error {
+    pub(crate) kind: ErrorKind,
+}
+
+impl FromStr for Version {
+    type Err = Error;
+
+    fn from_str(text: &str) -> Result<Self, Self::Err> {
+        let mut pos = Position::Major;
+        let (major, text) = numeric_identifier(text, pos)?;
+        let text = dot(text, pos)?;
+
+        pos = Position::Minor;
+        let (minor, text) = numeric_identifier(text, pos)?;
+        let text = dot(text, pos)?;
+
+        pos = Position::Patch;
+        let (patch, text) = numeric_identifier(text, pos)?;
+
+        if text.is_empty() {
+            return Ok(Version::new(major, minor, patch));
+        }
+
+        let (pre, text) = if let Some(text) = text.strip_prefix('-') {
+            pos = Position::Pre;
+            let (pre, text) = prerelease_identifier(text)?;
+            if pre.is_empty() {
+                return Err(Error::new(ErrorKind::EmptySegment(pos)));
+            }
+            (pre, text)
+        } else {
+            (Prerelease::EMPTY, text)
+        };
+
+        let (build, text) = if let Some(text) = text.strip_prefix('+') {
+            pos = Position::Build;
+            let (build, text) = build_identifier(text)?;
+            if build.is_empty() {
+                return Err(Error::new(ErrorKind::EmptySegment(pos)));
+            }
+            (build, text)
+        } else {
+            (BuildMetadata::EMPTY, text)
+        };
+
+        if let Some(unexpected) = text.chars().next() {
+            return Err(Error::new(ErrorKind::UnexpectedCharAfter(pos, unexpected)));
+        }
+
+        Ok(Version {
+            major,
+            minor,
+            patch,
+            pre,
+            build,
+        })
+    }
+}
+
+impl FromStr for VersionReq {
+    type Err = Error;
+
+    fn from_str(text: &str) -> Result<Self, Self::Err> {
+        let text = text.trim_start_matches(' ');
+        if let Some((ch, text)) = wildcard(text) {
+            let rest = text.trim_start_matches(' ');
+            if rest.is_empty() {
+                #[cfg(not(no_const_vec_new))]
+                return Ok(VersionReq::STAR);
+                #[cfg(no_const_vec_new)] // rustc <1.39
+                return Ok(VersionReq {
+                    comparators: Vec::new(),
+                });
+            } else if rest.starts_with(',') {
+                return Err(Error::new(ErrorKind::WildcardNotTheOnlyComparator(ch)));
+            } else {
+                return Err(Error::new(ErrorKind::UnexpectedAfterWildcard));
+            }
+        }
+
+        let depth = 0;
+        let mut comparators = Vec::new();
+        let len = version_req(text, &mut comparators, depth)?;
+        unsafe { comparators.set_len(len) }
+        Ok(VersionReq { comparators })
+    }
+}
+
+impl FromStr for Comparator {
+    type Err = Error;
+
+    fn from_str(text: &str) -> Result<Self, Self::Err> {
+        let text = text.trim_start_matches(' ');
+        let (comparator, pos, rest) = comparator(text)?;
+        if !rest.is_empty() {
+            let unexpected = rest.chars().next().unwrap();
+            return Err(Error::new(ErrorKind::UnexpectedCharAfter(pos, unexpected)));
+        }
+        Ok(comparator)
+    }
+}
+
+impl FromStr for Prerelease {
+    type Err = Error;
+
+    fn from_str(text: &str) -> Result<Self, Self::Err> {
+        let (pre, rest) = prerelease_identifier(text)?;
+        if !rest.is_empty() {
+            return Err(Error::new(ErrorKind::IllegalCharacter(Position::Pre)));
+        }
+        Ok(pre)
+    }
+}
+
+impl FromStr for BuildMetadata {
+    type Err = Error;
+
+    fn from_str(text: &str) -> Result<Self, Self::Err> {
+        let (build, rest) = build_identifier(text)?;
+        if !rest.is_empty() {
+            return Err(Error::new(ErrorKind::IllegalCharacter(Position::Build)));
+        }
+        Ok(build)
+    }
+}
+
+impl Error {
+    fn new(kind: ErrorKind) -> Self {
+        Error { kind }
+    }
+}
+
+impl Op {
+    const DEFAULT: Self = Op::Caret;
+}
+
+fn numeric_identifier(input: &str, pos: Position) -> Result<(u64, &str), Error> {
+    let mut len = 0;
+    let mut value = 0u64;
+
+    while let Some(&digit) = input.as_bytes().get(len) {
+        if digit < b'0' || digit > b'9' {
+            break;
+        }
+        if value == 0 && len > 0 {
+            return Err(Error::new(ErrorKind::LeadingZero(pos)));
+        }
+        match value
+            .checked_mul(10)
+            .and_then(|value| value.checked_add((digit - b'0') as u64))
+        {
+            Some(sum) => value = sum,
+            None => return Err(Error::new(ErrorKind::Overflow(pos))),
+        }
+        len += 1;
+    }
+
+    if len > 0 {
+        Ok((value, &input[len..]))
+    } else if let Some(unexpected) = input[len..].chars().next() {
+        Err(Error::new(ErrorKind::UnexpectedChar(pos, unexpected)))
+    } else {
+        Err(Error::new(ErrorKind::UnexpectedEnd(pos)))
+    }
+}
+
+fn wildcard(input: &str) -> Option<(char, &str)> {
+    if let Some(rest) = input.strip_prefix('*') {
+        Some(('*', rest))
+    } else if let Some(rest) = input.strip_prefix('x') {
+        Some(('x', rest))
+    } else if let Some(rest) = input.strip_prefix('X') {
+        Some(('X', rest))
+    } else {
+        None
+    }
+}
+
+fn dot(input: &str, pos: Position) -> Result<&str, Error> {
+    if let Some(rest) = input.strip_prefix('.') {
+        Ok(rest)
+    } else if let Some(unexpected) = input.chars().next() {
+        Err(Error::new(ErrorKind::UnexpectedCharAfter(pos, unexpected)))
+    } else {
+        Err(Error::new(ErrorKind::UnexpectedEnd(pos)))
+    }
+}
+
+fn prerelease_identifier(input: &str) -> Result<(Prerelease, &str), Error> {
+    let (string, rest) = identifier(input, Position::Pre)?;
+    let identifier = unsafe { Identifier::new_unchecked(string) };
+    Ok((Prerelease { identifier }, rest))
+}
+
+fn build_identifier(input: &str) -> Result<(BuildMetadata, &str), Error> {
+    let (string, rest) = identifier(input, Position::Build)?;
+    let identifier = unsafe { Identifier::new_unchecked(string) };
+    Ok((BuildMetadata { identifier }, rest))
+}
+
+fn identifier(input: &str, pos: Position) -> Result<(&str, &str), Error> {
+    let mut accumulated_len = 0;
+    let mut segment_len = 0;
+    let mut segment_has_nondigit = false;
+
+    loop {
+        match input.as_bytes().get(accumulated_len + segment_len) {
+            Some(b'A'..=b'Z') | Some(b'a'..=b'z') | Some(b'-') => {
+                segment_len += 1;
+                segment_has_nondigit = true;
+            }
+            Some(b'0'..=b'9') => {
+                segment_len += 1;
+            }
+            boundary => {
+                if segment_len == 0 {
+                    if accumulated_len == 0 && boundary != Some(&b'.') {
+                        return Ok(("", input));
+                    } else {
+                        return Err(Error::new(ErrorKind::EmptySegment(pos)));
+                    }
+                }
+                if pos == Position::Pre
+                    && segment_len > 1
+                    && !segment_has_nondigit
+                    && input[accumulated_len..].starts_with('0')
+                {
+                    return Err(Error::new(ErrorKind::LeadingZero(pos)));
+                }
+                accumulated_len += segment_len;
+                if boundary == Some(&b'.') {
+                    accumulated_len += 1;
+                    segment_len = 0;
+                    segment_has_nondigit = false;
+                } else {
+                    return Ok(input.split_at(accumulated_len));
+                }
+            }
+        }
+    }
+}
+
+fn op(input: &str) -> (Op, &str) {
+    let bytes = input.as_bytes();
+    if bytes.first() == Some(&b'=') {
+        (Op::Exact, &input[1..])
+    } else if bytes.first() == Some(&b'>') {
+        if bytes.get(1) == Some(&b'=') {
+            (Op::GreaterEq, &input[2..])
+        } else {
+            (Op::Greater, &input[1..])
+        }
+    } else if bytes.first() == Some(&b'<') {
+        if bytes.get(1) == Some(&b'=') {
+            (Op::LessEq, &input[2..])
+        } else {
+            (Op::Less, &input[1..])
+        }
+    } else if bytes.first() == Some(&b'~') {
+        (Op::Tilde, &input[1..])
+    } else if bytes.first() == Some(&b'^') {
+        (Op::Caret, &input[1..])
+    } else {
+        (Op::DEFAULT, input)
+    }
+}
+
+fn comparator(input: &str) -> Result<(Comparator, Position, &str), Error> {
+    let (mut op, text) = op(input);
+    let default_op = input.len() == text.len();
+    let text = text.trim_start_matches(' ');
+
+    let mut pos = Position::Major;
+    let (major, text) = numeric_identifier(text, pos)?;
+    let mut has_wildcard = false;
+
+    let (minor, text) = if let Some(text) = text.strip_prefix('.') {
+        pos = Position::Minor;
+        if let Some((_, text)) = wildcard(text) {
+            has_wildcard = true;
+            if default_op {
+                op = Op::Wildcard;
+            }
+            (None, text)
+        } else {
+            let (minor, text) = numeric_identifier(text, pos)?;
+            (Some(minor), text)
+        }
+    } else {
+        (None, text)
+    };
+
+    let (patch, text) = if let Some(text) = text.strip_prefix('.') {
+        pos = Position::Patch;
+        if let Some((_, text)) = wildcard(text) {
+            if default_op {
+                op = Op::Wildcard;
+            }
+            (None, text)
+        } else if has_wildcard {
+            return Err(Error::new(ErrorKind::UnexpectedAfterWildcard));
+        } else {
+            let (patch, text) = numeric_identifier(text, pos)?;
+            (Some(patch), text)
+        }
+    } else {
+        (None, text)
+    };
+
+    let (pre, text) = if patch.is_some() && text.starts_with('-') {
+        pos = Position::Pre;
+        let text = &text[1..];
+        let (pre, text) = prerelease_identifier(text)?;
+        if pre.is_empty() {
+            return Err(Error::new(ErrorKind::EmptySegment(pos)));
+        }
+        (pre, text)
+    } else {
+        (Prerelease::EMPTY, text)
+    };
+
+    let text = if patch.is_some() && text.starts_with('+') {
+        pos = Position::Build;
+        let text = &text[1..];
+        let (build, text) = build_identifier(text)?;
+        if build.is_empty() {
+            return Err(Error::new(ErrorKind::EmptySegment(pos)));
+        }
+        text
+    } else {
+        text
+    };
+
+    let text = text.trim_start_matches(' ');
+
+    let comparator = Comparator {
+        op,
+        major,
+        minor,
+        patch,
+        pre,
+    };
+
+    Ok((comparator, pos, text))
+}
+
+fn version_req(input: &str, out: &mut Vec<Comparator>, depth: usize) -> Result<usize, Error> {
+    let (comparator, pos, text) = match comparator(input) {
+        Ok(success) => success,
+        Err(mut error) => {
+            if let Some((ch, mut rest)) = wildcard(input) {
+                rest = rest.trim_start_matches(' ');
+                if rest.is_empty() || rest.starts_with(',') {
+                    error.kind = ErrorKind::WildcardNotTheOnlyComparator(ch);
+                }
+            }
+            return Err(error);
+        }
+    };
+
+    if text.is_empty() {
+        out.reserve_exact(depth + 1);
+        unsafe { out.as_mut_ptr().add(depth).write(comparator) }
+        return Ok(depth + 1);
+    }
+
+    let text = if let Some(text) = text.strip_prefix(',') {
+        text.trim_start_matches(' ')
+    } else {
+        let unexpected = text.chars().next().unwrap();
+        return Err(Error::new(ErrorKind::ExpectedCommaFound(pos, unexpected)));
+    };
+
+    const MAX_COMPARATORS: usize = 32;
+    if depth + 1 == MAX_COMPARATORS {
+        return Err(Error::new(ErrorKind::ExcessiveComparators));
+    }
+
+    // Recurse to collect parsed Comparator objects on the stack. We perform a
+    // single allocation to allocate exactly the right sized Vec only once the
+    // total number of comparators is known.
+    let len = version_req(text, out, depth + 1)?;
+    unsafe { out.as_mut_ptr().add(depth).write(comparator) }
+    Ok(len)
+}
diff --git a/third_party/rust/semver/src/serde.rs b/third_party/rust/semver/src/serde.rs
new file mode 100644
index 0000000000..1fcc7d87f6
--- /dev/null
+++ b/third_party/rust/semver/src/serde.rs
@@ -0,0 +1,109 @@
+use crate::{Comparator, Version, VersionReq};
+use core::fmt;
+use serde::de::{Deserialize, Deserializer, Error, Visitor};
+use serde::ser::{Serialize, Serializer};
+
+impl Serialize for Version {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.collect_str(self)
+    }
+}
+
+impl Serialize for VersionReq {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.collect_str(self)
+    }
+}
+
+impl Serialize for Comparator {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        serializer.collect_str(self)
+    }
+}
+
+impl<'de> Deserialize<'de> for Version {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        struct VersionVisitor;
+
+        impl<'de> Visitor<'de> for VersionVisitor {
+            type Value = Version;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("semver version")
+            }
+
+            fn visit_str<E>(self, string: &str) -> Result<Self::Value, E>
+            where
+                E: Error,
+            {
+                string.parse().map_err(Error::custom)
+            }
+        }
+
+        deserializer.deserialize_str(VersionVisitor)
+    }
+}
+
+impl<'de> Deserialize<'de> for VersionReq {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        struct VersionReqVisitor;
+
+        impl<'de> Visitor<'de> for VersionReqVisitor {
+            type Value = VersionReq;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("semver version")
+            }
+
+            fn visit_str<E>(self, string: &str) -> Result<Self::Value, E>
+            where
+                E: Error,
+            {
+                string.parse().map_err(Error::custom)
+            }
+        }
+
+        deserializer.deserialize_str(VersionReqVisitor)
+    }
+}
+
+impl<'de> Deserialize<'de> for Comparator {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        struct ComparatorVisitor;
+
+        impl<'de> Visitor<'de> for ComparatorVisitor {
+            type Value = Comparator;
+
+            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+                formatter.write_str("semver comparator")
+            }
+
+            fn visit_str<E>(self, string: &str) -> Result<Self::Value, E>
+            where
+                E: Error,
+            {
+                string.parse().map_err(Error::custom)
+            }
+        }
+
+        deserializer.deserialize_str(ComparatorVisitor)
+    }
+}