refactor: replace InternedString with Cow in IndexPackage (#15559)

### What does this PR try to resolve?

ref #14834

As described in the issue, we want to move IndexPackage into
cargo-util-schemas. However, it contains InternedString fields, which we
don't want to expose as part of the public API.
This PR replaces InternedString with Cow.

And also, as @weihanglo's suggested, I implemented the From/Into trait
to simplify code.

From Cow tarit implementation: [`42f593f`
(#15559)](42f593f)

Replace InternedString with `into()` across the whole codebase:
[`5f90098`
(#15559)](5f90098)
I am unsure if it worsens the readability. Feel free to comment.

### How should we test and review this PR?

It shouldn't change or break any tests.

Benchmark 1:
#15559 (comment)
Benchmark 2:
#15559 (comment)

### Additional information

None

Author: weihanglo

benches/benchsuite/src/bin/capture-last-use.rs

@@ -14,7 +14,6 @@
 
 use cargo::core::global_cache_tracker::{self, DeferredGlobalLastUse, GlobalCacheTracker};
 use cargo::util::cache_lock::CacheLockMode;
-use cargo::util::interning::InternedString;
 use cargo::GlobalContext;
 use rand::prelude::*;
 use std::collections::HashMap;
@@ -57,7 +56,7 @@ fn main() {
     let cache_dir = real_home.join("registry/cache");
     for dir_ent in fs::read_dir(cache_dir).unwrap() {
         let registry = dir_ent.unwrap();
-        let encoded_registry_name = InternedString::new(&registry.file_name().to_string_lossy());
+        let encoded_registry_name = registry.file_name().to_string_lossy().into();
         for krate in fs::read_dir(registry.path()).unwrap() {
             let krate = krate.unwrap();
             let meta = krate.metadata().unwrap();
@@ -77,7 +76,7 @@ fn main() {
     let cache_dir = real_home.join("registry/src");
     for dir_ent in fs::read_dir(cache_dir).unwrap() {
         let registry = dir_ent.unwrap();
-        let encoded_registry_name = InternedString::new(&registry.file_name().to_string_lossy());
+        let encoded_registry_name = registry.file_name().to_string_lossy().into();
         for krate in fs::read_dir(registry.path()).unwrap() {
             let krate = krate.unwrap();
             let meta = krate.metadata().unwrap();
@@ -95,7 +94,7 @@ fn main() {
     let git_co_dir = real_home.join("git/checkouts");
     for dir_ent in fs::read_dir(git_co_dir).unwrap() {
         let git_source = dir_ent.unwrap();
-        let encoded_git_name = InternedString::new(&git_source.file_name().to_string_lossy());
+        let encoded_git_name = git_source.file_name().to_string_lossy().into();
         for co in fs::read_dir(git_source.path()).unwrap() {
             let co = co.unwrap();
             let meta = co.metadata().unwrap();

src/bin/cargo/commands/add.rs

@@ -10,7 +10,6 @@ use cargo::ops::cargo_add::AddOptions;
 use cargo::ops::cargo_add::DepOp;
 use cargo::ops::resolve_ws;
 use cargo::util::command_prelude::*;
-use cargo::util::interning::InternedString;
 use cargo::util::toml_mut::manifest::DepTable;
 use cargo::CargoResult;
 
@@ -287,7 +286,7 @@ fn parse_dependencies(gctx: &GlobalContext, matches: &ArgMatches) -> CargoResult
         .map(String::as_str)
         .flat_map(parse_feature)
     {
-        let parsed_value = FeatureValue::new(InternedString::new(feature));
+        let parsed_value = FeatureValue::new(feature.into());
         match parsed_value {
             FeatureValue::Feature(_) => {
                 if 1 < crates.len() {

src/bin/cargo/commands/rustc.rs

@@ -1,6 +1,5 @@
 use crate::command_prelude::*;
 use cargo::ops;
-use cargo::util::interning::InternedString;
 
 const PRINT_ARG_NAME: &str = "print";
 const CRATE_TYPE_ARG_NAME: &str = "crate-type";
@@ -77,7 +76,7 @@ pub fn exec(gctx: &mut GlobalContext, args: &ArgMatches) -> CliResult {
         ProfileChecking::LegacyRustc,
     )?;
     if compile_opts.build_config.requested_profile == "check" {
-        compile_opts.build_config.requested_profile = InternedString::new("dev");
+        compile_opts.build_config.requested_profile = "dev".into();
     }
     let target_args = values(args, "args");
     compile_opts.target_rustc_args = if target_args.is_empty() {

src/cargo/core/compiler/build_config.rs

@@ -116,7 +116,7 @@ impl BuildConfig {
             requested_kinds,
             jobs,
             keep_going,
-            requested_profile: InternedString::new("dev"),
+            requested_profile: "dev".into(),
             intent,
             message_format: MessageFormat::Human,
             force_rebuild: false,

src/cargo/core/compiler/fingerprint/mod.rs

@@ -694,7 +694,7 @@ impl<'de> Deserialize<'de> for DepFingerprint {
         let (pkg_id, name, public, hash) = <(u64, String, bool, u64)>::deserialize(d)?;
         Ok(DepFingerprint {
             pkg_id,
-            name: InternedString::new(&name),
+            name: name.into(),
             public,
             fingerprint: Arc::new(Fingerprint {
                 memoized_hash: Mutex::new(Some(hash)),

src/cargo/core/dependency.rs

@@ -632,7 +632,7 @@ impl ArtifactKind {
             _ => {
                 return kind
                     .strip_prefix("bin:")
-                    .map(|bin_name| ArtifactKind::SelectedBinary(InternedString::new(bin_name)))
+                    .map(|bin_name| ArtifactKind::SelectedBinary(bin_name.into()))
                     .ok_or_else(|| anyhow::anyhow!("'{}' is not a valid artifact specifier", kind))
             }
         })

src/cargo/core/package.rs

@@ -208,14 +208,7 @@ impl Package {
         let crate_features = summary
             .features()
             .iter()
-            .map(|(k, v)| {
-                (
-                    *k,
-                    v.iter()
-                        .map(|fv| InternedString::new(&fv.to_string()))
-                        .collect(),
-                )
-            })
+            .map(|(k, v)| (*k, v.iter().map(|fv| fv.to_string().into()).collect()))
             .collect();
 
         SerializedPackage {
@@ -443,7 +436,7 @@ impl<'gctx> PackageSet<'gctx> {
             ))),
             downloads_finished: 0,
             downloaded_bytes: 0,
-            largest: (0, InternedString::new("")),
+            largest: (0, "".into()),
             success: false,
             updated_at: Cell::new(Instant::now()),
             timeout,

src/cargo/core/package_id.rs

@@ -78,7 +78,7 @@ impl<'de> de::Deserialize<'de> for PackageId {
         let (field, rest) = string
             .split_once(' ')
             .ok_or_else(|| de::Error::custom("invalid serialized PackageId"))?;
-        let name = InternedString::new(field);
+        let name = field.into();
 
         let (field, rest) = rest
             .split_once(' ')

src/cargo/core/profiles.rs

@@ -93,7 +93,7 @@ impl Profiles {
         // Merge with predefined profiles.
         use std::collections::btree_map::Entry;
         for (predef_name, mut predef_prof) in Self::predefined_profiles().into_iter() {
-            match profiles.entry(InternedString::new(predef_name)) {
+            match profiles.entry(predef_name.into()) {
                 Entry::Vacant(vac) => {
                     vac.insert(predef_prof);
                 }
@@ -119,9 +119,9 @@ impl Profiles {
     /// Returns the hard-coded directory names for built-in profiles.
     fn predefined_dir_names() -> HashMap<InternedString, InternedString> {
         [
-            (InternedString::new("dev"), InternedString::new("debug")),
-            (InternedString::new("test"), InternedString::new("debug")),
-            (InternedString::new("bench"), InternedString::new("release")),
+            ("dev".into(), "debug".into()),
+            ("test".into(), "debug".into()),
+            ("bench".into(), "release".into()),
         ]
         .into()
     }
@@ -134,12 +134,12 @@ impl Profiles {
         trim_paths_enabled: bool,
     ) {
         profile_makers.by_name.insert(
-            InternedString::new("dev"),
+            "dev".into(),
             ProfileMaker::new(Profile::default_dev(), profiles.get("dev").cloned()),
         );
 
         profile_makers.by_name.insert(
-            InternedString::new("release"),
+            "release".into(),
             ProfileMaker::new(
                 Profile::default_release(trim_paths_enabled),
                 profiles.get("release").cloned(),
@@ -185,7 +185,7 @@ impl Profiles {
         match &profile.dir_name {
             None => {}
             Some(dir_name) => {
-                self.dir_names.insert(name, InternedString::new(dir_name));
+                self.dir_names.insert(name, dir_name.into());
             }
         }
 
@@ -230,7 +230,7 @@ impl Profiles {
                 self.get_profile_maker(&inherits_name).unwrap().clone()
             }
             Some(inherits_name) => {
-                let inherits_name = InternedString::new(&inherits_name);
+                let inherits_name = inherits_name.into();
                 if !set.insert(inherits_name) {
                     bail!(
                         "profile inheritance loop detected with profile `{}` inheriting `{}`",
@@ -297,7 +297,7 @@ impl Profiles {
                 CompileKind::Target(target) => target.short_name(),
             };
             if target.contains("-apple-") {
-                profile.split_debuginfo = Some(InternedString::new("unpacked"));
+                profile.split_debuginfo = Some("unpacked".into());
             }
         }
 
@@ -455,7 +455,7 @@ impl ProfileMaker {
             // basically turning down the optimization level and avoid limiting
             // codegen units. This ensures that we spend little time optimizing as
             // well as enabling parallelism by not constraining codegen units.
-            profile.opt_level = InternedString::new("0");
+            profile.opt_level = "0".into();
             profile.codegen_units = None;
 
             // For build dependencies, we usually don't need debuginfo, and
@@ -531,12 +531,12 @@ fn merge_toml_overrides(
 /// Does not merge overrides (see `merge_toml_overrides`).
 fn merge_profile(profile: &mut Profile, toml: &TomlProfile) {
     if let Some(ref opt_level) = toml.opt_level {
-        profile.opt_level = InternedString::new(&opt_level.0);
+        profile.opt_level = opt_level.0.as_str().into();
     }
     match toml.lto {
         Some(StringOrBool::Bool(b)) => profile.lto = Lto::Bool(b),
         Some(StringOrBool::String(ref n)) if is_off(n.as_str()) => profile.lto = Lto::Off,
-        Some(StringOrBool::String(ref n)) => profile.lto = Lto::Named(InternedString::new(n)),
+        Some(StringOrBool::String(ref n)) => profile.lto = Lto::Named(n.into()),
         None => {}
     }
     if toml.codegen_backend.is_some() {
@@ -552,7 +552,7 @@ fn merge_profile(profile: &mut Profile, toml: &TomlProfile) {
         profile.debug_assertions = debug_assertions;
     }
     if let Some(split_debuginfo) = &toml.split_debuginfo {
-        profile.split_debuginfo = Some(InternedString::new(split_debuginfo));
+        profile.split_debuginfo = Some(split_debuginfo.into());
     }
     if let Some(rpath) = toml.rpath {
         profile.rpath = rpath;
@@ -578,16 +578,12 @@ fn merge_profile(profile: &mut Profile, toml: &TomlProfile) {
         profile.trim_paths = Some(trim_paths.clone());
     }
     profile.strip = match toml.strip {
-        Some(StringOrBool::Bool(true)) => {
-            Strip::Resolved(StripInner::Named(InternedString::new("symbols")))
-        }
+        Some(StringOrBool::Bool(true)) => Strip::Resolved(StripInner::Named("symbols".into())),
         Some(StringOrBool::Bool(false)) => Strip::Resolved(StripInner::None),
         Some(StringOrBool::String(ref n)) if n.as_str() == "none" => {
             Strip::Resolved(StripInner::None)
         }
-        Some(StringOrBool::String(ref n)) => {
-            Strip::Resolved(StripInner::Named(InternedString::new(n)))
-        }
+        Some(StringOrBool::String(ref n)) => Strip::Resolved(StripInner::Named(n.into())),
         None => Strip::Deferred(StripInner::None),
     };
 }
@@ -635,8 +631,8 @@ pub struct Profile {
 impl Default for Profile {
     fn default() -> Profile {
         Profile {
-            name: InternedString::new(""),
-            opt_level: InternedString::new("0"),
+            name: "".into(),
+            opt_level: "0".into(),
             root: ProfileRoot::Debug,
             lto: Lto::Bool(false),
             codegen_backend: None,
@@ -710,7 +706,7 @@ impl Profile {
     /// Returns a built-in `dev` profile.
     fn default_dev() -> Profile {
         Profile {
-            name: InternedString::new("dev"),
+            name: "dev".into(),
             root: ProfileRoot::Debug,
             debuginfo: DebugInfo::Resolved(TomlDebugInfo::Full),
             debug_assertions: true,
@@ -724,9 +720,9 @@ impl Profile {
     fn default_release(trim_paths_enabled: bool) -> Profile {
         let trim_paths = trim_paths_enabled.then(|| TomlTrimPathsValue::Object.into());
         Profile {
-            name: InternedString::new("release"),
+            name: "release".into(),
             root: ProfileRoot::Release,
-            opt_level: InternedString::new("3"),
+            opt_level: "3".into(),
             trim_paths,
             ..Profile::default()
         }
@@ -1274,13 +1270,13 @@ fn merge_config_profiles(
             profile.merge(&config_profile);
         }
         if let Some(inherits) = &profile.inherits {
-            check_to_add.insert(InternedString::new(inherits));
+            check_to_add.insert(inherits.into());
         }
     }
     // Add the built-in profiles. This is important for things like `cargo
     // test` which implicitly use the "dev" profile for dependencies.
-    for name in &["dev", "release", "test", "bench"] {
-        check_to_add.insert(InternedString::new(name));
+    for name in ["dev", "release", "test", "bench"] {
+        check_to_add.insert(name.into());
     }
     // Add config-only profiles.
     // Need to iterate repeatedly to get all the inherits values.
@@ -1291,7 +1287,7 @@ fn merge_config_profiles(
             if !profiles.contains_key(name.as_str()) {
                 if let Some(config_profile) = get_config_profile(ws, &name)? {
                     if let Some(inherits) = &config_profile.inherits {
-                        check_to_add.insert(InternedString::new(inherits));
+                        check_to_add.insert(inherits.into());
                     }
                     profiles.insert(name, config_profile);
                 }

src/cargo/core/resolver/features.rs

@@ -306,7 +306,7 @@ impl CliFeatures {
             .flat_map(|s| s.split_whitespace())
             .flat_map(|s| s.split(','))
             .filter(|s| !s.is_empty())
-            .map(InternedString::new)
+            .map(|s| s.into())
             .map(FeatureValue::new)
             .collect()
     }