Remove scoped_tls dependency

This is causing [conflicts] with rebuilding upstream in rust-lang/rust, so
remove this for now until we figure out a better solution.

[conflicts]: https://github.com/rust-lang/rust/pull/49053#issuecomment-375906970

Cargo.toml

@@ -41,7 +41,6 @@ libgit2-sys = "0.7"
 log = "0.4"
 num_cpus = "1.0"
 same-file = "1"
-scoped-tls = "0.1"
 semver = { version = "0.9.0", features = ["serde"] }
 serde = "1.0"
 serde_derive = "1.0"

src/cargo/lib.rs

@@ -31,8 +31,6 @@ extern crate libgit2_sys;
 extern crate log;
 extern crate num_cpus;
 extern crate same_file;
-#[macro_use]
-extern crate scoped_tls;
 extern crate semver;
 extern crate serde;
 #[macro_use]

src/cargo/sources/registry/index.rs

@@ -148,8 +148,11 @@ impl<'cfg> RegistryIndex<'cfg> {
             features,
             yanked,
             links,
-        } = super::DEFAULT_ID.set(&self.source_id, || {
-            serde_json::from_str::<RegistryPackage>(line)
+        } = super::DEFAULT_ID.with(|slot| {
+            *slot.borrow_mut() = Some(self.source_id.clone());
+            let res = serde_json::from_str::<RegistryPackage>(line);
+            drop(slot.borrow_mut().take());
+            res
         })?;
         let pkgid = PackageId::new(&name, &vers, &self.source_id)?;
         let summary = Summary::new(pkgid, deps.inner, features, links)?;

src/cargo/sources/registry/mod.rs

@@ -159,6 +159,7 @@
 //! ```
 
 use std::borrow::Cow;
+use std::cell::RefCell;
 use std::collections::BTreeMap;
 use std::fmt;
 use std::fs::File;
@@ -454,7 +455,7 @@ impl<'cfg> Source for RegistrySource<'cfg> {
 //
 // If you're reading this and find this thread local funny, check to see if that
 // PR is merged. If it is then let's ditch this thread local!
-scoped_thread_local!(static DEFAULT_ID: SourceId);
+thread_local!(static DEFAULT_ID: RefCell<Option<SourceId>> = Default::default());
 
 impl<'de> de::Deserialize<'de> for DependencyList {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
@@ -506,7 +507,7 @@ fn parse_registry_dependency(dep: RegistryDependency) -> CargoResult<Dependency>
     let id = if let Some(registry) = registry {
         SourceId::for_registry(&registry.to_url()?)?
     } else {
-        DEFAULT_ID.with(|id| id.clone())
+        DEFAULT_ID.with(|id| id.borrow().as_ref().unwrap().clone())
     };
 
     let mut dep = Dependency::parse_no_deprecated(&name, Some(&req), &id)?;