Replace im_rc::OrdSet with rpds::HashTrieSet

Summary:
the `im`/`im-rc` crate contains logic bugs (we are hitting problems outlined in bodil/im-rs#124 sporadically) and appears unmaintained.

This diff switches to the `rpds` crate which offers the same kind of functionality and appears to be better maintained.

Reviewed By: CatherineGasnier

Differential Revision: D34339520

fbshipit-source-id: 5fd5eab468f46d0fcc5294d3d7142e1c8541fbd5

hphp/hack/src/depgraph/cargo/depgraph/Cargo.toml

@@ -9,6 +9,6 @@ path = "../../depgraph/lib.rs"
 crate-type = ["lib", "staticlib"]
 
 [dependencies]
-im-rc = { version = "14.2", features = ["serde"] }
 memmap = "0.7"
 ocamlrep = { path = "../../../ocamlrep" }
+rpds = "0.11.0"

hphp/hack/src/depgraph/depgraph/reader.rs

@@ -8,7 +8,7 @@ pub use crate::dep::Dep;
 
 use std::ops::Deref;
 
-use im_rc::OrdSet;
+use rpds::HashTrieSet;
 
 /// Use a `DepGraphOpener` to initialize a dependency graph from a file.
 ///
@@ -153,16 +153,16 @@ impl<'bytes> DepGraph<'bytes> {
     }
 
     /// Add the direct typing dependencies for one dependency.
-    pub fn add_typing_deps_for_dep(&self, acc: &mut OrdSet<Dep>, dep: Dep) {
+    pub fn add_typing_deps_for_dep(&self, acc: &mut HashTrieSet<Dep>, dep: Dep) {
         if let Some(dept_hash_list) = self.hash_list_for(dep) {
             for dept in self.hash_list_hashes(dept_hash_list) {
-                acc.insert(dept);
+                acc.insert_mut(dept);
             }
         }
     }
 
     /// Query the direct typing dependencies for the given set of dependencies.
-    pub fn query_typing_deps_multi(&self, deps: &OrdSet<Dep>) -> OrdSet<Dep> {
+    pub fn query_typing_deps_multi(&self, deps: &HashTrieSet<Dep>) -> HashTrieSet<Dep> {
         let mut acc = deps.clone();
         for dep in deps {
             self.add_typing_deps_for_dep(&mut acc, *dep);

hphp/hack/src/deps/cargo/deps_rust/Cargo.toml

@@ -10,10 +10,10 @@ crate-type = ["lib", "staticlib"]
 
 [dependencies]
 depgraph = { path = "../../../depgraph/cargo/depgraph" }
-im-rc = { version = "14.2", features = ["serde"] }
 ocamlrep = { path = "../../../ocamlrep" }
 ocamlrep_custom = { path = "../../../ocamlrep_custom" }
 ocamlrep_ocamlpool = { path = "../../../ocamlrep_ocamlpool" }
 once_cell = "1.8"
 oxidized = { path = "../../../oxidized" }
+rpds = "0.11.0"
 typing_deps_hash = { path = "../typing_deps_hash" }