simulator WIP: use petgraph for topological sort over assignments

Cargo.lock

@@ -315,6 +315,7 @@ dependencies = [
  "num-bigint",
  "num-traits",
  "os_pipe",
+ "petgraph",
  "serde",
  "serde_json",
  "tempfile",
@@ -358,6 +359,12 @@ dependencies = [
  "thiserror",
 ]
 
+[[package]]
+name = "fixedbitset"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0ce7134b9999ecaf8bcd65542e436736ef32ddca1b3e06094cb6ec5755203b80"
+
 [[package]]
 name = "funty"
 version = "2.0.0"
@@ -515,6 +522,16 @@ dependencies = [
  "windows-sys 0.59.0",
 ]
 
+[[package]]
+name = "petgraph"
+version = "0.6.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4c5cc86750666a3ed20bdaf5ca2a0344f9c67674cae0515bec2da16fbaa47db"
+dependencies = [
+ "fixedbitset",
+ "indexmap",
+]
+
 [[package]]
 name = "prettyplease"
 version = "0.2.20"