guard nonisolated(unsafe) by experimental feature

Author: sophiapoirier

CodeGeneration/Sources/SyntaxSupport/ExperimentalFeatures.swift

@@ -17,6 +17,7 @@ public enum ExperimentalFeature: String, CaseIterable {
   case thenStatements
   case typedThrows
   case doExpressions
+  case globalConcurrency
 
   /// The name of the feature, which is used in the doc comment.
   public var featureName: String {
@@ -29,6 +30,8 @@ public enum ExperimentalFeature: String, CaseIterable {
       return "typed throws"
     case .doExpressions:
       return "'do' expressions"
+    case .globalConcurrency:
+      return "strict concurrency for globals"
     }
   }
 

Sources/SwiftParser/Modifiers.swift

@@ -61,7 +61,12 @@ extension Parser {
       case (.declarationModifier(.unowned), let handle)?:
         elements.append(self.parseUnownedModifier(handle))
       case (.declarationModifier(.nonisolated), let handle)?:
-        elements.append(parseNonisolatedModifier(handle))
+        if experimentalFeatures.contains(.globalConcurrency) {
+          elements.append(parseNonisolatedModifier(handle))
+        } else {
+          let (unexpectedBeforeKeyword, keyword) = self.eat(handle)
+          elements.append(RawDeclModifierSyntax(unexpectedBeforeKeyword, name: keyword, detail: nil, arena: self.arena))
+        }
       case (.declarationModifier(.final), let handle)?,
         (.declarationModifier(.required), let handle)?,
         (.declarationModifier(.optional), let handle)?,

Sources/SwiftParser/generated/ExperimentalFeatures.swift

@@ -35,4 +35,7 @@ extension Parser.ExperimentalFeatures {
 
   /// Whether to enable the parsing of 'do' expressions.
   public static let doExpressions = Self (rawValue: 1 << 3)
+  
+  /// Whether to enable the parsing of strict concurrency for globals.
+  public static let globalConcurrency = Self (rawValue: 1 << 4)
 }

Tests/SwiftParserTest/DeclarationTests.swift

@@ -265,7 +265,8 @@ final class DeclarationTests: ParserTestCase {
           nonisolated(unsafe) var c: Int { 0 }
           nonisolated(unsafe) let d = 0
         }
-        """
+        """,
+      experimentalFeatures: [.globalConcurrency]
     )
   }