Update to Swift 5.9

Author: cpisciotta

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       fail-fast: false
       matrix:
         platform: [macos-latest, ubuntu-latest]
-        swift_version: [5.7, 5.8, 5.9]
+        swift_version: [5.9]
     steps:
       - uses: swift-actions/setup-swift@61a116f4030ac34fb5731aab0eff5a0aed94ba29
         with:
@@ -32,14 +32,15 @@ jobs:
     runs-on: ${{ matrix.platform }}
     strategy:
       matrix:
-        platform: [macos-latest, ubuntu-latest]
+        platform: [macos-13, ubuntu-latest]
     steps:
       - uses: actions/checkout@v4
+      - name: Load Swift Version
+        run: echo "SWIFT_VERSION=$(<.swift-version)" >> $GITHUB_ENV
       - name: Install Swift and Tools
-        if: matrix.platform == 'ubuntu-latest'
         uses: swift-actions/setup-swift@cdbe0f7f4c77929b6580e71983e8606e55ffe7e4
         with:
-          swift-version: 5.9.2
+          swift-version: ${{ env.SWIFT_VERSION }}
       - run: swift test --enable-code-coverage
       - name: Prepare Code Coverage
         run: ./tools/export_coverage

.github/workflows/release.yml

@@ -5,7 +5,7 @@ on:
 name: Release
 
 env:
-  SWIFT_VERSION: 5.7
+  SWIFT_VERSION: 5.9
 
 jobs:
   create_release:

.swift-version

@@ -1 +1 @@
-5.7.1
+5.9

Makefile

@@ -58,7 +58,7 @@ package-linux-x86_64:
 	$(eval SWIFT_BUILD_FLAGS := $(SHARED_SWIFT_BUILD_FLAGS) --triple $(TARGET_TRIPLE))
 	$(eval BUILD_DIRECTORY := $(shell swift build --show-bin-path $(SWIFT_BUILD_FLAGS)))
 	docker run --rm --volume `pwd`:/workdir --workdir /workdir \
-		swift:5.7-bionic swift build $(SWIFT_BUILD_FLAGS)
+		swift:5.9 swift build $(SWIFT_BUILD_FLAGS)
 	tar --directory "$(BUILD_DIRECTORY)" --create --xz --file \
 		"$(PRODUCT_NAME).tar.xz" "$(PRODUCT_NAME)"
 

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.7
+// swift-tools-version:5.9
 import PackageDescription
 
 let package = Package(

README.md

@@ -60,7 +60,7 @@ In that directory, create a `Package.swift` file with the following contents.
 In addition, add an empty file named `Empty.swift` to the same location.
 
 ```swift
-// swift-tools-version: 5.6
+// swift-tools-version: 5.9
 import PackageDescription
 
 let package = Package(