refactor(util): Unify VersionExt, VersionReqExt

For myself, I find the trait-as-a-constructor approach of
`VersionReqExt::exact` awkward and find merging it into `VersionExt` as
`VersionExt::to_exact_req` is a bit cleaner.
For example, this would make it easier to integrate with
`PartialVersion` if we want.

src/bin/cargo/commands/install.rs

@@ -6,7 +6,7 @@ use anyhow::format_err;
 use cargo::core::{GitReference, SourceId, Workspace};
 use cargo::ops;
 use cargo::util::IntoUrl;
-use cargo::util::VersionReqExt;
+use cargo::util::VersionExt;
 use cargo::CargoResult;
 use itertools::Itertools;
 use semver::VersionReq;
@@ -263,8 +263,8 @@ fn parse_semver_flag(v: &str) -> CargoResult<VersionReq> {
             ),
         }
     } else {
-        match v.trim().parse() {
-            Ok(v) => Ok(VersionReq::exact(&v)),
+        match v.trim().parse::<semver::Version>() {
+            Ok(v) => Ok(v.to_exact_req()),
             Err(e) => {
                 let mut msg = e.to_string();
 

src/cargo/util/mod.rs

@@ -22,7 +22,7 @@ pub use self::progress::{Progress, ProgressStyle};
 pub use self::queue::Queue;
 pub use self::restricted_names::validate_package_name;
 pub use self::rustc::Rustc;
-pub use self::semver_ext::{OptVersionReq, PartialVersion, RustVersion, VersionExt, VersionReqExt};
+pub use self::semver_ext::{OptVersionReq, PartialVersion, RustVersion, VersionExt};
 pub use self::vcs::{existing_vcs_repo, FossilRepo, GitRepo, HgRepo, PijulRepo};
 pub use self::workspace::{
     add_path_args, path_args, print_available_benches, print_available_binaries,

src/cargo/util/semver_ext.rs

@@ -14,42 +14,38 @@ pub enum OptVersionReq {
 
 pub trait VersionExt {
     fn is_prerelease(&self) -> bool;
-}
 
-pub trait VersionReqExt {
-    fn exact(version: &Version) -> Self;
+    fn to_exact_req(&self) -> VersionReq;
 }
 
 impl VersionExt for Version {
     fn is_prerelease(&self) -> bool {
         !self.pre.is_empty()
     }
-}
 
-impl VersionReqExt for VersionReq {
-    fn exact(version: &Version) -> Self {
+    fn to_exact_req(&self) -> VersionReq {
         VersionReq {
             comparators: vec![Comparator {
                 op: Op::Exact,
-                major: version.major,
-                minor: Some(version.minor),
-                patch: Some(version.patch),
-                pre: version.pre.clone(),
+                major: self.major,
+                minor: Some(self.minor),
+                patch: Some(self.patch),
+                pre: self.pre.clone(),
             }],
         }
     }
 }
 
 impl OptVersionReq {
     pub fn exact(version: &Version) -> Self {
-        OptVersionReq::Req(VersionReq::exact(version))
+        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(), VersionReq::exact(version))
+        OptVersionReq::Locked(version.clone(), version.to_exact_req())
     }
 
     pub fn is_exact(&self) -> bool {