Ci/set up test pipeline

.github/workflows/pull_request.yml

@@ -0,0 +1,16 @@
+name: Pull Request
+
+on: [pull_request]
+
+jobs:
+  test-ubuntu-latest:
+    name: Test Swift ${{ matrix.swift }} Ubuntu Latest
+    strategy:
+      matrix:
+        swift: ["6.0", "6.0.1", "6.0.2"]
+    runs-on: ubuntu-latest
+    container: swift:${{ matrix.swift }}
+    steps:
+      - uses: actions/checkout@v4
+      - name: Run Tests
+        run: swift test -Xswiftc -warnings-as-errors -Xcc -Werror

Sources/Differentiation/Dictionary+Differentiation.swift

@@ -7,7 +7,7 @@ import _Differentiation
 // and
 // https://bugs.swift.org/browse/TF-1193
 
-extension Dictionary: Differentiable where Value: Differentiable {
+extension Dictionary: @retroactive Differentiable where Value: Differentiable {
     public typealias TangentVector = [Key: Value.TangentVector]
     public mutating func move(by direction: TangentVector) {
         for (componentKey, componentDirection) in direction {
@@ -28,7 +28,7 @@ extension Dictionary: Differentiable where Value: Differentiable {
 }
 
 /// Implements the `AdditiveArithmetic` requirements.
-extension Dictionary: AdditiveArithmetic where Value: AdditiveArithmetic {
+extension Dictionary: @retroactive AdditiveArithmetic where Value: AdditiveArithmetic {
     public static func + (_ lhs: Self, _ rhs: Self) -> Self {
         lhs.merging(rhs, uniquingKeysWith: +)
     }

Tests/DifferentiationTests/Optional+DifferentiableMapTests.swift

@@ -1,5 +1,3 @@
-// Copyright (c) 2024 PassiveLogic, Inc.
-
 #if canImport(_Differentiation)
 
 import Differentiation
@@ -13,7 +11,7 @@ struct OptionalDifferentiableMapTests {
         func testFunc(_ x: Double?) -> Double? {
             x.differentiableMap { $0 * $0 * $0 }
         }
-        #expect(pullback(at: 1.0, of: testFunc)(.init(1.0)) == 3.0)
+        #expect(pullback(at: 1.0, of: testFunc)(.init(1.0)) == .init(3.0))
         #expect(pullback(at: nil, of: testFunc)(.init(1.0)) == .init(0.0))
         #expect(pullback(at: 0.0, of: testFunc)(.init(1.0)) == .init(0.0))
     }