remove all residual state from previous lock files

Author: Eh2406

src/cargo/core/registry.rs

@@ -195,6 +195,12 @@ impl<'cfg> PackageRegistry<'cfg> {
         self.yanked_whitelist.extend(pkgs);
     }
 
+    /// remove all residual state from previous lock files.
+    pub fn clear_lock(&mut self) {
+        trace!("clear_lock");
+        self.locked = HashMap::new();
+    }
+
     pub fn register_lock(&mut self, id: PackageId, deps: Vec<PackageId>) {
         trace!("register_lock: {}", id);
         for dep in deps.iter() {

src/cargo/ops/resolve.rs

@@ -584,6 +584,7 @@ fn register_previous_locks(
     // the registry as a locked dependency.
     let keep = |id: &PackageId| keep(id) && !avoid_locking.contains(id);
 
+    registry.clear_lock();
     for node in resolve.iter().filter(keep) {
         let deps = resolve
             .deps_not_replaced(node)

tests/testsuite/build.rs

@@ -4934,6 +4934,7 @@ use cargo_test_support::registry::Dependency;
 
 #[cargo_test]
 fn reduced_reproduction_8249() {
+    // https://github.com/rust-lang/cargo/issues/8249
     Package::new("a-src", "0.1.0").links("a").publish();
     Package::new("a-src", "0.2.0").links("a").publish();
 
@@ -4966,10 +4967,6 @@ fn reduced_reproduction_8249() {
 
     p.cargo("generate-lockfile").run();
     cargo::util::paths::append(&p.root().join("Cargo.toml"), b"c = \"*\"").unwrap();
-    p.cargo("check")
-        .with_status(101)
-        .with_stderr_contains("[..]links to the native library `a`[..]")
-        .run();
-    // This passes, what!?
+    p.cargo("check").run();
     p.cargo("check").run();
 }