Fix retroactive conformance warnings for 6.0+ compilers (#7605)

`#if swift(<6.0)` is a wrong check to apply, since it has no effect with 6.0 compiler versions, unlike `#if compiler(<6.0)`.

(cherry picked from commit 067136b)

Author: MaxDesiatov

Sources/Commands/PackageCommands/Init.swift

@@ -80,7 +80,7 @@ extension SwiftPackageCommand {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension InitPackage.PackageType: ExpressibleByArgument {}
 #else
 extension InitPackage.PackageType: @retroactive ExpressibleByArgument {}

Sources/Commands/Utilities/APIDigester.swift

@@ -328,7 +328,7 @@ extension SerializedDiagnostics.SourceLocation {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension SerializedDiagnostics.SourceLocation: DiagnosticLocation {}
 #else
 extension SerializedDiagnostics.SourceLocation: @retroactive DiagnosticLocation {}

Sources/CoreCommands/Options.swift

@@ -721,7 +721,7 @@ extension URL {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension BuildConfiguration: ExpressibleByArgument {}
 extension AbsolutePath: ExpressibleByArgument {}
 extension WorkspaceConfiguration.CheckingMode: ExpressibleByArgument {}

Sources/PackageRegistryCommand/PackageRegistryCommand+Publish.swift

@@ -247,7 +247,7 @@ extension SignatureFormat {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension SignatureFormat: ExpressibleByArgument {}
 #else
 extension SignatureFormat: @retroactive ExpressibleByArgument {}

Sources/SPMTestSupport/misc.swift

@@ -488,7 +488,7 @@ extension InitPackage {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension RelativePath: ExpressibleByStringLiteral {}
 extension RelativePath: ExpressibleByStringInterpolation {}
 extension URL: ExpressibleByStringLiteral {}

Sources/Workspace/Diagnostics.swift

@@ -247,7 +247,7 @@ extension FileSystemError {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension FileSystemError: CustomStringConvertible {}
 #else
 extension FileSystemError: @retroactive CustomStringConvertible {}

Sources/Workspace/Workspace.swift

@@ -1472,7 +1472,7 @@ private func warnToStderr(_ message: String) {
 }
 
 // used for manifest validation
-#if swift(<6.0)
+#if compiler(<6.0)
 extension RepositoryManager: ManifestSourceControlValidator {}
 #else
 extension RepositoryManager: @retroactive ManifestSourceControlValidator {}

Sources/swift-bootstrap/main.swift

@@ -485,7 +485,7 @@ extension BuildConfiguration {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension AbsolutePath: ExpressibleByArgument {}
 extension BuildConfiguration: ExpressibleByArgument {}
 #else

Tests/PackageGraphPerformanceTests/DependencyResolverPerfTests.swift

@@ -201,7 +201,7 @@ extension ProductFilter {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension ProductFilter: JSONSerializable, JSONMappable {}
 #else
 extension ProductFilter: @retroactive JSONSerializable, @retroactive JSONMappable {}

Tests/PackageGraphTests/PubgrubTests.swift

@@ -3802,7 +3802,7 @@ extension PackageReference {
     }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension Term: ExpressibleByStringLiteral {}
 extension PackageReference: ExpressibleByStringLiteral {}
 #else

Tests/PackageGraphTests/TopologicalSortTests.swift

@@ -34,7 +34,7 @@ extension Int {
     public var id: Self { self }
 }
 
-#if swift(<6.0)
+#if compiler(<6.0)
 extension Int: Identifiable {}
 #else
 extension Int: @retroactive Identifiable {}