adopt Swift Collection's OrderedSet and OrderedDictionary

They're better optimised and tested.

Author: WowbaggersLiquidLunch

Package.swift

@@ -39,7 +39,6 @@ let package = Package(
             name: "TSCTestSupport",
             targets: ["TSCTestSupport"]),
     ],
-    dependencies: [],
     targets: [
 
         // MARK: Tools support core targets
@@ -55,11 +54,21 @@ let package = Package(
         .target(
             /** TSCBasic support library */
             name: "TSCBasic",
-            dependencies: ["TSCLibc", "TSCclibc"]),
+            dependencies: [
+                "TSCLibc",
+                "TSCclibc",
+                .product(name: "OrderedCollections", package: "swift-collections"),
+            ]
+        ),
         .target(
             /** Abstractions for common operations, should migrate to TSCBasic */
             name: "TSCUtility",
-            dependencies: ["TSCBasic", "TSCclibc"]),
+            dependencies: [
+                "TSCBasic",
+                "TSCclibc",
+                .product(name: "OrderedCollections", package: "swift-collections"),
+            ]
+        ),
 
         // MARK: Additional Test Dependencies
 
@@ -86,6 +95,19 @@ let package = Package(
     ]
 )
 
+/// When not using local dependencies, the branch to use for llbuild and TSC repositories.
+let relatedDependenciesBranch = "main"
+
+if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
+    package.dependencies += [
+        .package(url: "https://github.com/apple/swift-collections.git", .branch("main")),
+    ]
+} else {
+    package.dependencies += [
+        .package(path: "../swift-collections"),
+    ]
+}
+
 // FIXME: conditionalise these flags since SwiftPM 5.3 and earlier will crash
 // for platforms they don't know about.
 #if os(Windows)

Sources/TSCBasic/GraphAlgorithms.swift

@@ -1,13 +1,15 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+ Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See http://swift.org/LICENSE.txt for license information
  See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 */
 
+import OrderedCollections
+
 public enum GraphError: Error {
     /// A cycle was detected in the input.
     case unexpectedCycle
@@ -69,7 +71,7 @@ public func topologicalSort<T: Hashable>(
 
         // Otherwise, visit each adjacent node.
         for succ in try successors(node) {
-            guard stack.append(succ) else {
+            guard stack.append(succ).inserted else {
                 // If the successor is already in this current stack, we have found a cycle.
                 //
                 // FIXME: We could easily include information on the cycle we found here.
@@ -120,7 +122,7 @@ public func findCycle<T: Hashable>(
     // FIXME: Convert to stack.
     func visit(_ node: T, _ successors: (T) throws -> [T]) rethrows -> (path: [T], cycle: [T])? {
         // If this node is already in the current path then we have found a cycle.
-        if !path.append(node) {
+        if !path.append(node).inserted {
             let index = path.firstIndex(of: node)!
             return (Array(path[path.startIndex..<index]), Array(path[index..<path.endIndex]))
         }

Sources/TSCBasic/OrderedDictionary.swift

@@ -1,15 +1,16 @@
 /*
  This source file is part of the Swift.org open source project
 
- Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+ Copyright (c) 2014 - 2021 Apple Inc. and the Swift project authors
  Licensed under Apache License v2.0 with Runtime Library Exception
 
  See http://swift.org/LICENSE.txt for license information
  See http://swift.org/CONTRIBUTORS.txt for Swift project authors 
 */
 
-import TSCBasic
 import Foundation
+import OrderedCollections
+import TSCBasic
 
 public enum PkgConfigError: Swift.Error, CustomStringConvertible {
     case couldNotFindConfigFile(name: String)