[6.0] Make swift-syntax build in Swift 6 language mode

CodeGeneration/Sources/generate-swift-syntax/templates/swiftparser/TokenSpecStaticMembersFile.swift

@@ -16,7 +16,15 @@ import SyntaxSupport
 import Utils
 
 let tokenSpecStaticMembersFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
-  DeclSyntax("@_spi(RawSyntax) import SwiftSyntax")
+  DeclSyntax(
+    """
+    #if swift(>=6)
+    @_spi(RawSyntax) internal import SwiftSyntax
+    #else
+    @_spi(RawSyntax) import SwiftSyntax
+    #endif
+    """
+  )
 
   try! ExtensionDeclSyntax("extension TokenSpec") {
     for tokenSpec in Token.allCases.map(\.spec) where tokenSpec.kind != .keyword {

CodeGeneration/Sources/generate-swift-syntax/templates/swiftparserdiagnostics/ChildNameForDiagnosticsFile.swift

@@ -16,7 +16,15 @@ import SyntaxSupport
 import Utils
 
 let childNameForDiagnosticFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
-  DeclSyntax("@_spi(ExperimentalLanguageFeatures) import SwiftSyntax")
+  DeclSyntax(
+    """
+    #if swift(>=6)
+    @_spi(ExperimentalLanguageFeatures) internal import SwiftSyntax
+    #else
+    @_spi(ExperimentalLanguageFeatures) import SwiftSyntax
+    #endif
+    """
+  )
 
   try! FunctionDeclSyntax(
     "private func childNameForDiagnostics(_ keyPath: AnyKeyPath) -> String?"

CodeGeneration/Sources/generate-swift-syntax/templates/swiftparserdiagnostics/SyntaxKindNameForDiagnosticsFile.swift

@@ -16,7 +16,15 @@ import SyntaxSupport
 import Utils
 
 let syntaxKindNameForDiagnosticFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
-  DeclSyntax("@_spi(ExperimentalLanguageFeatures) import SwiftSyntax")
+  DeclSyntax(
+    """
+    #if swift(>=6)
+    @_spi(ExperimentalLanguageFeatures) internal import SwiftSyntax
+    #else
+    @_spi(ExperimentalLanguageFeatures) import SwiftSyntax
+    #endif
+    """
+  )
 
   try! ExtensionDeclSyntax("extension SyntaxKind") {
     try VariableDeclSyntax("var nameForDiagnostics: String?") {

CodeGeneration/Sources/generate-swift-syntax/templates/swiftparserdiagnostics/TokenNameForDiagnosticsFile.swift

@@ -16,7 +16,15 @@ import SyntaxSupport
 import Utils
 
 let tokenNameForDiagnosticFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
-  DeclSyntax("@_spi(RawSyntax) import SwiftSyntax")
+  DeclSyntax(
+    """
+    #if swift(>=6)
+    @_spi(RawSyntax) internal import SwiftSyntax
+    #else
+    @_spi(RawSyntax) import SwiftSyntax
+    #endif
+    """
+  )
 
   try! ExtensionDeclSyntax("extension TokenKind") {
     try! VariableDeclSyntax("var nameForDiagnostics: String") {

CodeGeneration/Sources/generate-swift-syntax/templates/swiftsyntaxbuilder/SyntaxExpressibleByStringInterpolationConformancesFile.swift

@@ -16,7 +16,15 @@ import SyntaxSupport
 import Utils
 
 let syntaxExpressibleByStringInterpolationConformancesFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
-  DeclSyntax("import SwiftSyntax")
+  DeclSyntax(
+    """
+    #if swift(>=6)
+    internal import SwiftSyntax
+    #else
+    import SwiftSyntax
+    #endif
+    """
+  )
 
   let typesExpressibleByStringInterpolation =
     SYNTAX_NODES

Package.swift

@@ -297,7 +297,13 @@ let package = Package(
       dependencies: ["_InstructionCounter", "_SwiftSyntaxTestSupport", "SwiftIDEUtils", "SwiftParser", "SwiftSyntax"],
       exclude: ["Inputs"]
     ),
-  ]
+  ],
+  // Disable Swift 6 mode when the `SWIFTSYNTAX_DISABLE_SWIFT_6_MODE` environment variable is set. This works around the following
+  // issue: The self-hosted SwiftPM job has Xcode 15.3 (Swift 5.10) installed and builds a Swift 6 SwiftPM from source.
+  // It then tries to build itself as a fat binary using the just-built Swift 6 SwiftPM, which uses xcbuild from Xcode
+  // as the build system. But the xcbuild in the installed Xcode is too old and doesn't know about Swift 6 mode, so it
+  // fails with: SWIFT_VERSION '6' is unsupported, supported versions are: 4.0, 4.2, 5.0 (rdar://126952308)
+  swiftLanguageVersions: hasEnvironmentVariable("SWIFTSYNTAX_DISABLE_SWIFT_6_MODE") ? [.v5] : [.v5, .version("6")]
 )
 
 // This is a fake target that depends on all targets in the package.

Sources/SwiftCompilerPluginMessageHandling/Diagnostics.swift

@@ -10,8 +10,13 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+internal import SwiftDiagnostics
+internal import SwiftSyntax
+#else
 import SwiftDiagnostics
 import SwiftSyntax
+#endif
 
 /// Errors in macro handing.
 enum MacroExpansionError {

Sources/SwiftCompilerPluginMessageHandling/JSON/JSONEncoding.swift

@@ -17,7 +17,7 @@ func encodeToJSON(value: some Encodable) throws -> [UInt8] {
 }
 
 /// Intermediate representation for serializing JSON structure.
-private class JSONReference {
+private final class JSONReference {
   enum Backing {
     case null
     case trueKeyword
@@ -60,9 +60,17 @@ private class JSONReference {
     backing = .array(arr)
   }
 
+  #if swift(>=6)
+  // nonisolated(unsafe) is fine for these properties because they represent primitives
+  // that are never modified.
+  nonisolated(unsafe) static let null: JSONReference = .init(backing: .null)
+  nonisolated(unsafe) static let trueKeyword: JSONReference = .init(backing: .trueKeyword)
+  nonisolated(unsafe) static let falseKeyword: JSONReference = .init(backing: .falseKeyword)
+  #else
   static let null: JSONReference = .init(backing: .null)
   static let trueKeyword: JSONReference = .init(backing: .trueKeyword)
   static let falseKeyword: JSONReference = .init(backing: .falseKeyword)
+  #endif
 
   @inline(__always)
   static func newArray() -> JSONReference {

Sources/SwiftCompilerPluginMessageHandling/Macros.swift

@@ -10,12 +10,21 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+internal import SwiftBasicFormat
+internal import SwiftDiagnostics
+internal import SwiftOperators
+internal import SwiftSyntax
+@_spi(MacroExpansion) @_spi(ExperimentalLanguageFeature) internal import SwiftSyntaxMacroExpansion
+@_spi(ExperimentalLanguageFeature) internal import SwiftSyntaxMacros
+#else
 import SwiftBasicFormat
 import SwiftDiagnostics
 import SwiftOperators
 import SwiftSyntax
 @_spi(MacroExpansion) @_spi(ExperimentalLanguageFeature) import SwiftSyntaxMacroExpansion
 @_spi(ExperimentalLanguageFeature) import SwiftSyntaxMacros
+#endif
 
 extension CompilerPluginMessageHandler {
   /// Get concrete macro type from a pair of module name and type name.

Sources/SwiftCompilerPluginMessageHandling/PluginMacroExpansionContext.swift

@@ -10,11 +10,19 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+internal import SwiftDiagnostics
+internal import SwiftOperators
+internal import SwiftParser
+internal import SwiftSyntax
+internal import SwiftSyntaxMacros
+#else
 import SwiftDiagnostics
 import SwiftOperators
 import SwiftParser
 import SwiftSyntax
 import SwiftSyntaxMacros
+#endif
 
 /// Manages known source code combined with their filename/fileID. This can be
 /// used to get line/column from a syntax node in the managed source code.

Sources/SwiftIDEUtils/SyntaxClassification.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 public enum SyntaxClassification: Sendable {
   /// An attribute starting with an `@`.

Sources/SwiftIDEUtils/Utils.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+internal import SwiftSyntax
+#else
 import SwiftSyntax
+#endif
 
 extension Range<AbsolutePosition> {
   /// Shift the range `utf8Offset` bytes to the right, ie. add `utf8Offset` to the upper and lower bound.

Sources/SwiftOperators/OperatorError+Diagnostics.swift

@@ -12,8 +12,8 @@
 
 #if swift(>=6)
 public import SwiftDiagnostics
-import SwiftParser
-import SwiftSyntax
+internal import SwiftParser
+internal import SwiftSyntax
 #else
 import SwiftDiagnostics
 import SwiftParser

Sources/SwiftOperators/OperatorTable+Defaults.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+internal import SwiftSyntax
+#else
 import SwiftSyntax
+#endif
 
 /// Prefabricated operator precedence graphs.
 extension OperatorTable {

Sources/SwiftOperators/OperatorTable.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+internal import SwiftSyntax
+#else
 import SwiftSyntax
+#endif
 
 /// Maintains and validates information about all operators in a Swift program.
 ///

Sources/SwiftOperators/PrecedenceGraph.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+internal import SwiftSyntax
+#else
 import SwiftSyntax
+#endif
 
 /// Describes the relative precedence of two groups.
 enum Precedence: Sendable {

Sources/SwiftParser/Attributes.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 extension Parser {
   mutating func parseAttributeList() -> RawAttributeListSyntax {

Sources/SwiftParser/Availability.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 extension Parser {
   /// Parse a list of availability arguments.

Sources/SwiftParser/Declarations.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 extension DeclarationModifier {
   var canHaveParenthesizedArgument: Bool {

Sources/SwiftParser/Directives.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 extension Parser {
   private enum IfConfigContinuationClauseStartKeyword: TokenSpecSet {

Sources/SwiftParser/ExpressionInterpretedAsVersionTuple.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) public import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 extension ExprSyntax {
   /// Parse the source code of this node as a `VersionTupleSyntax`.

Sources/SwiftParser/Expressions.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 extension TokenConsumer {
   mutating func atStartOfExpression() -> Bool {

Sources/SwiftParser/IsValidIdentifier.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 /// Context in which to check if a name can be used as an identifier.
 ///

Sources/SwiftParser/Lexer/Cursor.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) @_spi(BumpPtrAllocator) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) @_spi(BumpPtrAllocator) import SwiftSyntax
+#endif
 
 extension SyntaxText {
   fileprivate func containsPlaceholderEnd() -> Bool {

Sources/SwiftParser/Lexer/LexemeSequence.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) @_spi(BumpPtrAllocator) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) @_spi(BumpPtrAllocator) import SwiftSyntax
+#endif
 
 extension Lexer {
   /// A sequence of ``Lexer/Lexeme`` tokens starting from a ``Lexer/Cursor``

Sources/SwiftParser/Lexer/RegexLiteralLexer.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) @_spi(BumpPtrAllocator) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) @_spi(BumpPtrAllocator) import SwiftSyntax
+#endif
 
 /// A separate lexer specifically for regex literals.
 fileprivate struct RegexLiteralLexer {

Sources/SwiftParser/Lookahead.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 extension Parser {
   /// Token lookahead for the parser.

Sources/SwiftParser/LoopProgressCondition.swift

@@ -10,7 +10,11 @@
 //
 //===----------------------------------------------------------------------===//
 
+#if swift(>=6)
+@_spi(RawSyntax) internal import SwiftSyntax
+#else
 @_spi(RawSyntax) import SwiftSyntax
+#endif
 
 /// A type that can be used to make sure that a loop in the parser makes process.
 ///