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    use std::fmt::{self, Display};

    use semver::{Comparator, Op, Version, VersionReq};

    pub trait VersionExt {
        fn is_prerelease(&self) -> bool;

        fn to_exact_req(&self) -> VersionReq;
    }

    impl VersionExt for Version {
        fn is_prerelease(&self) -> bool {
            !self.pre.is_empty()
        }

        fn to_exact_req(&self) -> VersionReq {
            VersionReq {
                comparators: vec![Comparator {
                    op: Op::Exact,
                    major: self.major,
                    minor: Some(self.minor),
                    patch: Some(self.patch),
                    pre: self.pre.clone(),
                }],
            }
        }
    }

    #[derive(PartialEq, Eq, Hash, Clone, Debug)]
    pub enum OptVersionReq {
        Any,
        Req(VersionReq),
        /// The exact locked version and the original version requirement.
        Locked(Version, VersionReq),
        /// The exact requested version and the original version requirement.
        UpdatePrecise(Version, VersionReq),
    }

    impl OptVersionReq {
        pub fn exact(version: &Version) -> Self {
            OptVersionReq::Req(version.to_exact_req())
        }

        // Since some registries have allowed crate versions to differ only by build metadata,
        // A query using OptVersionReq::exact return nondeterministic results.
        // So we `lock_to` the exact version were interested in.
        pub fn lock_to_exact(version: &Version) -> Self {
            OptVersionReq::Locked(version.clone(), version.to_exact_req())
        }

        pub fn is_exact(&self) -> bool {
            match self {
                OptVersionReq::Any => false,
                OptVersionReq::Req(req) | OptVersionReq::UpdatePrecise(_, req) => {
                    req.comparators.len() == 1 && {
                        let cmp = &req.comparators[0];
                        cmp.op == Op::Exact && cmp.minor.is_some() && cmp.patch.is_some()
                    }
                }
                OptVersionReq::Locked(..) => true,
            }
        }

        pub fn lock_to(&mut self, version: &Version) {
            assert!(self.matches(version), "cannot lock {} to {}", self, version);
            use OptVersionReq::*;
            let version = version.clone();
            *self = match self {
                Any => Locked(version, VersionReq::STAR),
                Req(req) | Locked(_, req) | UpdatePrecise(_, req) => Locked(version, req.clone()),
            };
        }

        pub fn update_precise(&mut self, version: &Version) {
            use OptVersionReq::*;
            let version = version.clone();
            *self = match self {
                Any => UpdatePrecise(version, VersionReq::STAR),
                Req(req) | Locked(_, req) | UpdatePrecise(_, req) => {
                    UpdatePrecise(version, req.clone())
                }
            };
        }

        pub fn is_locked(&self) -> bool {
            matches!(self, OptVersionReq::Locked(..))
        }

        /// Gets the version to which this req is locked, if any.
        pub fn locked_version(&self) -> Option<&Version> {
            match self {
                OptVersionReq::Locked(version, _) => Some(version),
                _ => None,
            }
        }

        pub fn matches(&self, version: &Version) -> bool {
            match self {
                OptVersionReq::Any => true,
                OptVersionReq::Req(req) => req.matches(version),
                OptVersionReq::Locked(v, _) => {
                    // Generally, cargo is of the opinion that semver metadata should be ignored.
                    // If your registry has two versions that only differing metadata you get the bugs you deserve.
                    // We also believe that lock files should ensure reproducibility
                    // and protect against mutations from the registry.
                    // In this circumstance these two goals are in conflict, and we pick reproducibility.
                    // If the lock file tells us that there is a version called `1.0.0+bar` then
                    // we should not silently use `1.0.0+foo` even though they have the same version.
                    v == version
                }
                OptVersionReq::UpdatePrecise(v, _) => {
                    // This is used for the `--precise` field of cargo update.
                    //
                    // Unfortunately crates.io allowed versions to differ only
                    // by build metadata. This shouldn't be allowed, but since
                    // it is, this will honor it if requested.
                    //
                    // In that context we treat a requirement that does not have
                    // build metadata as allowing any metadata. But, if a requirement
                    // has build metadata, then we only allow it to match the exact
                    // metadata.
                    v.major == version.major
                        && v.minor == version.minor
                        && v.patch == version.patch
                        && v.pre == version.pre
                        && (v.build == version.build || v.build.is_empty())
                }
            }
        }
    }

    impl Display for OptVersionReq {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            match self {
                OptVersionReq::Any => f.write_str("*"),
                OptVersionReq::Req(req)
                | OptVersionReq::Locked(_, req)
                | OptVersionReq::UpdatePrecise(_, req) => Display::fmt(req, f),
            }
        }
    }

    impl From<VersionReq> for OptVersionReq {
        fn from(req: VersionReq) -> Self {
            OptVersionReq::Req(req)
        }
    }