Simplify _GlueClassHook to work around Linux crash

Fixes #6

Author: kabiroberai

Sources/Orion/ClassHook+Glue.swift

@@ -27,7 +27,8 @@ public final class _GlueClassHookStorage {
 /// used to satisfy the compiler until the actual glue is provided.
 ///
 /// :nodoc:
-public enum _GlueClassHookPlaceholder<HookType: ClassHookProtocol>: _GlueClassHook {
+public enum _GlueClassHookPlaceholder: _GlueClassHook {
+    public class HookType: ClassHook<NSObject> {}
     public typealias OrigType = HookType
     public typealias SuprType = HookType
 
@@ -75,8 +76,8 @@ public struct _GlueClassHookBuilder {
 /// :nodoc:
 public protocol _GlueClassHook: _GlueAnyHook {
     associatedtype HookType: ClassHookProtocol
-    associatedtype OrigType: ClassHookProtocol where OrigType.Target == HookType.Target
-    associatedtype SuprType: ClassHookProtocol where SuprType.Target == HookType.Target
+    associatedtype OrigType: ClassHookProtocol
+    associatedtype SuprType: ClassHookProtocol
 
     static var storage: _GlueClassHookStorage { get }
     static func activate(withClassHookBuilder builder: inout _GlueClassHookBuilder)

Sources/Orion/ClassHook.swift

@@ -31,8 +31,7 @@ public protocol ClassHookProtocol: class, AnyHook {
     /// - See: `_GlueAnyHook`
     ///
     /// :nodoc:
-    associatedtype _Glue: _GlueClassHook = _GlueClassHookPlaceholder<Self>
-        where _Glue.HookType == Self
+    associatedtype _Glue: _GlueClassHook = _GlueClassHookPlaceholder
 
     /// The name of the target class, or the empty string to use `Target.self`.
     ///
@@ -259,7 +258,7 @@ extension ClassHookProtocol {
     @_transparent
     public var orig: Self {
         disableRecursionCheck()
-        guard let unwrapped = _Glue.OrigType(target: target) as? Self
+        guard let target = target as? _Glue.OrigType.Target, let unwrapped = _Glue.OrigType(target: target) as? Self
             else { orionError("Could not get orig") }
         return unwrapped
     }
@@ -277,7 +276,7 @@ extension ClassHookProtocol {
     @_transparent
     public var supr: Self {
         disableRecursionCheck()
-        guard let unwrapped = _Glue.SuprType(target: target) as? Self
+        guard let target = target as? _Glue.SuprType.Target, let unwrapped = _Glue.SuprType(target: target) as? Self
             else { orionError("Could not get supr") }
         return unwrapped
     }

Sources/OrionProcessor/OrionDiagnosticEngine.swift

@@ -32,7 +32,9 @@ public enum OrionDiagnosticConsumer {
 public class OrionDiagnosticEngine {
     private class MUXConsumer: DiagnosticConsumer {
         // this type pipes messages from many `DiagnosticEngine`s
-        // to one OrionDiagnosticEngine
+        // to one OrionDiagnosticEngine. We maintain a strong ref
+        // to the Orion engine to ensure that it isn't deinit'd
+        // until all of its child `DiagnosticEngine`s are.
         let engine: OrionDiagnosticEngine
         init(engine: OrionDiagnosticEngine) {
             self.engine = engine