Add swift-syntax 510 support; matrix testing for swift-syntax versions

- Implement matrix strategy for macOS job to test against multiple versions of swift-syntax
- Configure SWIFT_SYNTAX_VERSION environment variable to dictate swift-syntax version per test run
- Add explicit dependency resolution step to macOS job to ensure correct versions are used
- Maintain existing setup for Linux CI without changes

.github/workflows/ci.yml

@@ -17,10 +17,18 @@ jobs:
   macos:
     name: macOS
     runs-on: macos-13
+    strategy:
+      matrix:
+        swift-syntax-version: ['509.0.0..<510.0.0', '510.0.0..<511.0.0']
+
     steps:
       - uses: actions/checkout@v4
       - name: Select Xcode 15
         run: sudo xcode-select -s /Applications/Xcode_15.0.app
+      - name: Set SWIFT_SYNTAX_VERSION environment variable
+        run: echo "SWIFT_SYNTAX_VERSION=${{ matrix.swift-syntax-version }}" >> $GITHUB_ENV
+      - name: Resolve Dependencies
+        run: swift package resolve
       - name: Run tests
         run: swift test
 

Package.resolved

@@ -5,17 +5,17 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/pointfreeco/swift-snapshot-testing",
       "state" : {
-        "revision" : "59b663f68e69f27a87b45de48cb63264b8194605",
-        "version" : "1.15.1"
+        "revision" : "625ccca8570773dd84a34ee51a81aa2bc5a4f97a",
+        "version" : "1.16.0"
       }
     },
     {
       "identity" : "swift-syntax",
       "kind" : "remoteSourceControl",
-      "location" : "https://github.com/apple/swift-syntax.git",
+      "location" : "https://github.com/apple/swift-syntax",
       "state" : {
-        "revision" : "6ad4ea24b01559dde0773e3d091f1b9e36175036",
-        "version" : "509.0.2"
+        "revision" : "fa8f95c2d536d6620cc2f504ebe8a6167c9fc2dd",
+        "version" : "510.0.1"
       }
     }
   ],

Package.swift

@@ -1,6 +1,7 @@
 // swift-tools-version: 5.9
 
 import CompilerPluginSupport
+import Foundation
 import PackageDescription
 
 let package = Package(
@@ -23,7 +24,8 @@ let package = Package(
   ],
   dependencies: [
     .package(url: "https://github.com/pointfreeco/swift-snapshot-testing", from: "1.15.0"),
-    .package(url: "https://github.com/apple/swift-syntax", from: "509.0.0"),
+//    .conditionalPackage(url: "https://github.com/apple/swift-syntax", envVar: "SWIFT_SYNTAX_VERSION", default: "509.0.0..<510.0.0")
+    .conditionalPackage(url: "https://github.com/apple/swift-syntax", envVar: "SWIFT_SYNTAX_VERSION", default: "509.0.0..<511.0.0")
   ],
   targets: [
     .macro(
@@ -68,3 +70,34 @@ let package = Package(
     ),
   ]
 )
+
+extension Package.Dependency {
+  /// Creates a package dependency based on an environment variable or uses a default version expression.
+  static func conditionalPackage(url: String, envVar: String, default versionExpression: String) -> Package.Dependency {
+    let versionRangeString = ProcessInfo.processInfo.environment[envVar] ?? versionExpression
+    let (lower, op, upper) = parseVersionExpression(from: versionRangeString)
+    if op == "..<" {
+      return .package(url: url, lower..<upper)
+    } else if op == "..." {
+      return .package(url: url, lower...upper)
+    } else {
+      fatalError("Unsupported version range operator: \(op)")
+    }
+  }
+
+  private static func parseVersionExpression(from expression: String) -> (Version, String, Version) {
+    let rangeOperators = ["..<", "..."]
+    for op in rangeOperators {
+      if expression.contains(op) {
+        let parts = expression.split(separator: op, maxSplits: 1, omittingEmptySubsequences: true).map(String.init)
+        guard parts.count == 2,
+              let lower = Version(parts[0]),
+              let upper = Version(parts[1]) else {
+          fatalError("Invalid version expression format: \(expression)")
+        }
+        return (lower, op, upper)
+      }
+    }
+    fatalError("No valid range operator found in expression: \(expression)")
+  }
+}

Sources/MemberwiseInitMacros/Macros/Support/ExprTypeInference.swift

@@ -256,6 +256,11 @@ extension ExprSyntax {
       else { return nil }
       return .tuple(elementTypes)
 
+#if canImport(SwiftSyntax510)
+    case .thenStmt:
+      return nil
+#endif
+
     case .token, .accessorBlock, .accessorDeclList, .accessorDecl, .accessorEffectSpecifiers,
       .accessorParameters, .actorDecl, .arrayElementList, .arrayElement, .arrayType, .arrowExpr,
       .assignmentExpr, .associatedTypeDecl, .attributeList, .attribute, .attributedType,