Update synthetic locked version_req to real locked

Previously we use exact semver version req to synthesize locked version
req. Now we make those need a truly locked to be `OptVersionReq::Locked`.

Author: weihanglo

src/cargo/core/dependency.rs

@@ -320,7 +320,6 @@ impl Dependency {
     /// Locks this dependency to depending on the specified package ID.
     pub fn lock_to(&mut self, id: PackageId) -> &mut Dependency {
         assert_eq!(self.inner.source_id, id.source_id());
-        assert!(self.inner.req.matches(id.version()));
         trace!(
             "locking dep from `{}` with `{}` at {} to {}",
             self.package_name(),
@@ -329,7 +328,7 @@ impl Dependency {
             id
         );
         let me = Rc::make_mut(&mut self.inner);
-        me.req = OptVersionReq::exact(id.version());
+        me.req.lock_to(id.version());
 
         // Only update the `precise` of this source to preserve other
         // information about dependency's source which may not otherwise be
@@ -340,10 +339,10 @@ impl Dependency {
         self
     }
 
-    /// Returns `true` if this is a "locked" dependency, basically whether it has
-    /// an exact version req.
+    /// Returns `true` if this is a "locked" dependency. Basically a locked
+    /// dependency has an exact version req, but not vice versa.
     pub fn is_locked(&self) -> bool {
-        self.inner.req.is_exact()
+        self.inner.req.is_locked()
     }
 
     /// Returns `false` if the dependency is only used to build the local package.

src/cargo/core/registry.rs

@@ -5,10 +5,9 @@ use crate::core::{Dependency, PackageId, Source, SourceId, SourceMap, Summary};
 use crate::sources::config::SourceConfigMap;
 use crate::util::errors::CargoResult;
 use crate::util::interning::InternedString;
-use crate::util::{profile, CanonicalUrl, Config, VersionReqExt};
+use crate::util::{profile, CanonicalUrl, Config};
 use anyhow::{bail, Context as _};
 use log::{debug, trace};
-use semver::VersionReq;
 use url::Url;
 
 /// Source of information about a group of packages.
@@ -765,8 +764,7 @@ fn lock(
                 if locked.source_id() == dep.source_id() {
                     dep.lock_to(locked);
                 } else {
-                    let req = VersionReq::exact(locked.version());
-                    dep.set_version_req(req);
+                    dep.lock_version(locked.version());
                 }
                 return dep;
             }

src/cargo/ops/cargo_install.rs

@@ -681,7 +681,7 @@ fn installed_exact_package<T>(
 where
     T: Source,
 {
-    if !dep.is_locked() {
+    if !dep.version_req().is_exact() {
         // If the version isn't exact, we may need to update the registry and look for a newer
         // version - we can't know if the package is installed without doing so.
         return Ok(None);