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    use crate::core::{Dependency, PackageId, SourceId};
    use crate::util::interning::InternedString;
    use crate::util::CargoResult;
    use anyhow::bail;
    use cargo_util_schemas::manifest::FeatureName;
    use cargo_util_schemas::manifest::RustVersion;
    use semver::Version;
    use std::collections::{BTreeMap, HashMap, HashSet};
    use std::fmt;
    use std::hash::{Hash, Hasher};
    use std::mem;
    use std::rc::Rc;

    /// Subset of a `Manifest`. Contains only the most important information about
    /// a package.
    ///
    /// Summaries are cloned, and should not be mutated after creation
    #[derive(Debug, Clone)]
    pub struct Summary {
        inner: Rc<Inner>,
    }

    #[derive(Debug, Clone)]
    struct Inner {
        package_id: PackageId,
        dependencies: Vec<Dependency>,
        features: Rc<FeatureMap>,
        checksum: Option<String>,
        links: Option<InternedString>,
        rust_version: Option<RustVersion>,
    }

    impl Summary {
        pub fn new(
            pkg_id: PackageId,
            dependencies: Vec<Dependency>,
            features: &BTreeMap<InternedString, Vec<InternedString>>,
            links: Option<impl Into<InternedString>>,
            rust_version: Option<RustVersion>,
        ) -> CargoResult<Summary> {
            // ****CAUTION**** If you change anything here that may raise a new
            // error, be sure to coordinate that change with either the index
            // schema field or the SummariesCache version.
            for dep in dependencies.iter() {
                let dep_name = dep.name_in_toml();
                if dep.is_optional() && !dep.is_transitive() {
                    bail!(
                        "dev-dependencies are not allowed to be optional: `{}`",
                        dep_name
                    )
                }
            }
            let feature_map = build_feature_map(features, &dependencies)?;
            Ok(Summary {
                inner: Rc::new(Inner {
                    package_id: pkg_id,
                    dependencies,
                    features: Rc::new(feature_map),
                    checksum: None,
                    links: links.map(|l| l.into()),
                    rust_version,
                }),
            })
        }

        pub fn package_id(&self) -> PackageId {
            self.inner.package_id
        }
        pub fn name(&self) -> InternedString {
            self.package_id().name()
        }
        pub fn version(&self) -> &Version {
            self.package_id().version()
        }
        pub fn source_id(&self) -> SourceId {
            self.package_id().source_id()
        }
        pub fn dependencies(&self) -> &[Dependency] {
            &self.inner.dependencies
        }
        pub fn features(&self) -> &FeatureMap {
            &self.inner.features
        }

        pub fn checksum(&self) -> Option<&str> {
            self.inner.checksum.as_deref()
        }
        pub fn links(&self) -> Option<InternedString> {
            self.inner.links
        }

        pub fn rust_version(&self) -> Option<&RustVersion> {
            self.inner.rust_version.as_ref()
        }

        pub fn override_id(mut self, id: PackageId) -> Summary {
            Rc::make_mut(&mut self.inner).package_id = id;
            self
        }

        pub fn set_checksum(&mut self, cksum: String) {
            Rc::make_mut(&mut self.inner).checksum = Some(cksum);
        }

        pub fn map_dependencies<F>(mut self, f: F) -> Summary
        where
            F: FnMut(Dependency) -> Dependency,
        {
            {
                let slot = &mut Rc::make_mut(&mut self.inner).dependencies;
                *slot = mem::take(slot).into_iter().map(f).collect();
            }
            self
        }

        pub fn map_source(self, to_replace: SourceId, replace_with: SourceId) -> Summary {
            let me = if self.package_id().source_id() == to_replace {
                let new_id = self.package_id().with_source_id(replace_with);
                self.override_id(new_id)
            } else {
                self
            };
            me.map_dependencies(|dep| dep.map_source(to_replace, replace_with))
        }
    }

    impl PartialEq for Summary {
        fn eq(&self, other: &Summary) -> bool {
            self.inner.package_id == other.inner.package_id
        }
    }

    impl Eq for Summary {}

    impl Hash for Summary {
        fn hash<H: Hasher>(&self, state: &mut H) {
            self.inner.package_id.hash(state);
        }
    }

    /// Checks features for errors, bailing out a CargoResult:Err if invalid,
    /// and creates FeatureValues for each feature.
    fn build_feature_map(
        features: &BTreeMap<InternedString, Vec<InternedString>>,
        dependencies: &[Dependency],
    ) -> CargoResult<FeatureMap> {
        use self::FeatureValue::*;
        let mut dep_map = HashMap::new();
        for dep in dependencies.iter() {
            dep_map
                .entry(dep.name_in_toml())
                .or_insert_with(Vec::new)
                .push(dep);
        }

        let mut map: FeatureMap = features
            .iter()
            .map(|(feature, list)| {
                let fvs: Vec<_> = list
                    .iter()
                    .map(|feat_value| FeatureValue::new(*feat_value))
                    .collect();
                (*feature, fvs)
            })
            .collect();

        // Add implicit features for optional dependencies if they weren't
        // explicitly listed anywhere.
        let explicitly_listed: HashSet<_> = map
            .values()
            .flatten()
            .filter_map(|fv| match fv {
                Dep { dep_name } => Some(*dep_name),
                _ => None,
            })
            .collect();
        for dep in dependencies {
            if !dep.is_optional() {
                continue;
            }
            let dep_name_in_toml = dep.name_in_toml();
            if features.contains_key(&dep_name_in_toml) || explicitly_listed.contains(&dep_name_in_toml)
            {
                continue;
            }
            let fv = Dep {
                dep_name: dep_name_in_toml,
            };
            map.insert(dep_name_in_toml, vec![fv]);
        }

        // Validate features are listed properly.
        for (feature, fvs) in &map {
            FeatureName::new(feature)?;
            for fv in fvs {
                // Find data for the referenced dependency...
                let dep_data = {
                    match fv {
                        Feature(dep_name) | Dep { dep_name, .. } | DepFeature { dep_name, .. } => {
                            dep_map.get(dep_name)
                        }
                    }
                };
                let is_optional_dep = dep_data
                    .iter()
                    .flat_map(|d| d.iter())
                    .any(|d| d.is_optional());
                let is_any_dep = dep_data.is_some();
                match fv {
                    Feature(f) => {
                        if !features.contains_key(f) {
                            if !is_any_dep {
                                bail!(
                                    "feature `{}` includes `{}` which is neither a dependency \
                                     nor another feature",
                                    feature,
                                    fv
                                );
                            }
                            if is_optional_dep {
                                if !map.contains_key(f) {
                                    bail!(
                                        "feature `{}` includes `{}`, but `{}` is an \
                                         optional dependency without an implicit feature\n\
                                         Use `dep:{}` to enable the dependency.",
                                        feature,
                                        fv,
                                        f,
                                        f
                                    );
                                }
                            } else {
                                bail!("feature `{}` includes `{}`, but `{}` is not an optional dependency\n\
                                    A non-optional dependency of the same name is defined; \
                                    consider adding `optional = true` to its definition.",
                                    feature, fv, f);
                            }
                        }
                    }
                    Dep { dep_name } => {
                        if !is_any_dep {
                            bail!(
                                "feature `{}` includes `{}`, but `{}` is not listed as a dependency",
                                feature,
                                fv,
                                dep_name
                            );
                        }
                        if !is_optional_dep {
                            bail!(
                                "feature `{}` includes `{}`, but `{}` is not an optional dependency\n\
                                 A non-optional dependency of the same name is defined; \
                                 consider adding `optional = true` to its definition.",
                                feature,
                                fv,
                                dep_name
                            );
                        }
                    }
                    DepFeature {
                        dep_name,
                        dep_feature,
                        weak,
                        ..
                    } => {
                        // Early check for some unlikely syntax.
                        if dep_feature.contains('/') {
                            bail!(
                                "multiple slashes in feature `{}` (included by feature `{}`) are not allowed",
                                fv,
                                feature
                            );
                        }

                        // dep: cannot be combined with /
                        if let Some(stripped_dep) = dep_name.strip_prefix("dep:") {
                            let has_other_dep = explicitly_listed.contains(stripped_dep);
                            let is_optional = dep_map
                                .get(stripped_dep)
                                .iter()
                                .flat_map(|d| d.iter())
                                .any(|d| d.is_optional());
                            let extra_help = if *weak || has_other_dep || !is_optional {
                                // In this case, the user should just remove dep:.
                                // Note that "hiding" an optional dependency
                                // wouldn't work with just a single `dep:foo?/bar`
                                // because there would not be any way to enable
                                // `foo`.
                                String::new()
                            } else {
                                format!(
                                    "\nIf the intent is to avoid creating an implicit feature \
                                     `{stripped_dep}` for an optional dependency, \
                                     then consider replacing this with two values:\n    \
                                     \"dep:{stripped_dep}\", \"{stripped_dep}/{dep_feature}\""
                                )
                            };
                            bail!(
                                "feature `{feature}` includes `{fv}` with both `dep:` and `/`\n\
                                To fix this, remove the `dep:` prefix.{extra_help}"
                            )
                        }

                        // Validation of the feature name will be performed in the resolver.
                        if !is_any_dep {
                            bail!(
                                "feature `{}` includes `{}`, but `{}` is not a dependency",
                                feature,
                                fv,
                                dep_name
                            );
                        }
                        if *weak && !is_optional_dep {
                            bail!("feature `{}` includes `{}` with a `?`, but `{}` is not an optional dependency\n\
                                A non-optional dependency of the same name is defined; \
                                consider removing the `?` or changing the dependency to be optional",
                                feature, fv, dep_name);
                        }
                    }
                }
            }
        }

        // Make sure every optional dep is mentioned at least once.
        let used: HashSet<_> = map
            .values()
            .flatten()
            .filter_map(|fv| match fv {
                Dep { dep_name } | DepFeature { dep_name, .. } => Some(dep_name),
                _ => None,
            })
            .collect();
        if let Some(dep) = dependencies
            .iter()
            .find(|dep| dep.is_optional() && !used.contains(&dep.name_in_toml()))
        {
            bail!(
                "optional dependency `{}` is not included in any feature\n\
                Make sure that `dep:{}` is included in one of features in the [features] table.",
                dep.name_in_toml(),
                dep.name_in_toml(),
            );
        }

        Ok(map)
    }

    /// FeatureValue represents the types of dependencies a feature can have.
    #[derive(Clone, Debug, Ord, PartialOrd, Eq, PartialEq, Hash)]
    pub enum FeatureValue {
        /// A feature enabling another feature.
        Feature(InternedString),
        /// A feature enabling a dependency with `dep:dep_name` syntax.
        Dep { dep_name: InternedString },
        /// A feature enabling a feature on a dependency with `crate_name/feat_name` syntax.
        DepFeature {
            dep_name: InternedString,
            dep_feature: InternedString,
            /// If `true`, indicates the `?` syntax is used, which means this will
            /// not automatically enable the dependency unless the dependency is
            /// activated through some other means.
            weak: bool,
        },
    }

    impl FeatureValue {
        pub fn new(feature: InternedString) -> FeatureValue {
            match feature.find('/') {
                Some(pos) => {
                    let (dep, dep_feat) = feature.split_at(pos);
                    let dep_feat = &dep_feat[1..];
                    let (dep, weak) = if let Some(dep) = dep.strip_suffix('?') {
                        (dep, true)
                    } else {
                        (dep, false)
                    };
                    FeatureValue::DepFeature {
                        dep_name: InternedString::new(dep),
                        dep_feature: InternedString::new(dep_feat),
                        weak,
                    }
                }
                None => {
                    if let Some(dep_name) = feature.strip_prefix("dep:") {
                        FeatureValue::Dep {
                            dep_name: InternedString::new(dep_name),
                        }
                    } else {
                        FeatureValue::Feature(feature)
                    }
                }
            }
        }

        /// Returns `true` if this feature explicitly used `dep:` syntax.
        pub fn has_dep_prefix(&self) -> bool {
            matches!(self, FeatureValue::Dep { .. })
        }
    }

    impl fmt::Display for FeatureValue {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            use self::FeatureValue::*;
            match self {
                Feature(feat) => write!(f, "{}", feat),
                Dep { dep_name } => write!(f, "dep:{}", dep_name),
                DepFeature {
                    dep_name,
                    dep_feature,
                    weak,
                } => {
                    let weak = if *weak { "?" } else { "" };
                    write!(f, "{}{}/{}", dep_name, weak, dep_feature)
                }
            }
        }
    }

    pub type FeatureMap = BTreeMap<InternedString, Vec<FeatureValue>>;