[Parser] Always enable abiAttribute feature

`ABIAttributeArgumentsSyntax` is still under
`@_spi(ExperimentalLanguageFeatures)`.
Not parsing the interior of `@abi` attribute causes catastrophic breakage
to the tree. Having "unknown" syntax kind in the tree is better than
dealing with structually broken trees.

Author: rintaro

CodeGeneration/Sources/SyntaxSupport/ExperimentalFeatures.swift

@@ -76,6 +76,17 @@ public enum ExperimentalFeature: String, CaseIterable {
     }
   }
 
+  public var isAlwaysEnabledInParser: Bool {
+    switch self {
+    case .abiAttribute:
+      // `@abi` attributes should be always parsed because not parsing its interior
+      // breaks the tree catastrophically.
+      return true
+    default:
+      return false
+    }
+  }
+
   /// The token that represents the experimental feature case name.
   public var token: TokenSyntax {
     .identifier(rawValue)

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

@@ -40,6 +40,19 @@ let experimentalFeaturesFile = SourceFileSyntax(leadingTrivia: copyrightHeader)
       )
     }
 
+    try! VariableDeclSyntax(
+      """
+      /// Set of features always enabled.
+      static var alwaysEnabledFeatures: Self
+      """
+    ) {
+      ArrayExprSyntax {
+        for feature in ExperimentalFeature.allCases where feature.isAlwaysEnabledInParser {
+          ArrayElementSyntax(expression: ExprSyntax(".\(feature.token)"))
+        }
+      }
+    }
+
     try! InitializerDeclSyntax(
       """
       /// Creates a new value representing the experimental feature with the

Sources/SwiftParser/Parser.swift

@@ -237,7 +237,7 @@ public struct Parser {
 
     self.maximumNestingLevel = maximumNestingLevel ?? Self.defaultMaximumNestingLevel
     self.swiftVersion = swiftVersion ?? Self.defaultSwiftVersion
-    self.experimentalFeatures = experimentalFeatures
+    self.experimentalFeatures = experimentalFeatures.union(.alwaysEnabledFeatures)
     self.lookaheadTrackerOwner = LookaheadTrackerOwner()
 
     self.lexemes = Lexer.tokenize(input, lookaheadTracker: lookaheadTrackerOwner.lookaheadTracker)

Sources/SwiftParser/generated/ExperimentalFeatures.swift

@@ -1007,74 +1007,64 @@ final class AttributeTests: ParserTestCase {
           parameterClause: FunctionParameterClauseSyntax {},
           returnClause: ReturnClauseSyntax(type: TypeSyntax("Int"))
         )
-      ) {},
-      experimentalFeatures: [.abiAttribute]
+      ) {}
     )
 
     assertParse(
       """
       @abi(associatedtype AssocTy)
       associatedtype AssocTy
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(deinit)
       deinit {}
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       enum EnumCaseDeclNotParsedAtTopLevel {
         @abi(case someCase)
         case someCase
       }
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(func fn())
       func fn()
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(init())
       init() {}
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(subscript(i: Int) -> Element)
       subscript(i: Int) -> Element {}
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(typealias Typealias = @escaping () -> Void)
       typealias Typealias = () -> Void
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(let c1, c2)
       let c1, c2
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(var v1, v2)
       var v1, v2
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
 
     assertParse(
@@ -1089,8 +1079,7 @@ final class AttributeTests: ParserTestCase {
       ),
       diagnostics: [
         DiagnosticSpec(locationMarker: "1️⃣", message: "editor placeholder in source file")
-      ],
-      experimentalFeatures: [.abiAttribute]
+      ]
     )
 
     assertParse(
@@ -1114,8 +1103,7 @@ final class AttributeTests: ParserTestCase {
       ),
       diagnostics: [
         DiagnosticSpec(locationMarker: "1️⃣", message: "import is not permitted as ABI-providing declaration")
-      ],
-      experimentalFeatures: [.abiAttribute]
+      ]
     )
 
     //
@@ -1126,66 +1114,57 @@ final class AttributeTests: ParserTestCase {
       """
       @abi(associatedtype AssocTy = T)
       associatedtype AssocTy
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(deinit {})
       deinit {}
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       enum EnumCaseDeclNotParsedAtTopLevel {
         @abi(case someCase = 42)
         case someCase
       }
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(func fn() {})
       func fn()
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(init() {})
       init() {}
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(subscript(i: Int) -> Element { get {} set {} })
       subscript(i: Int) -> Element {}
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(let c1 = 1, c2 = 2)
       let c1, c2
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(var v1 = 1, v2 = 2)
       var v1, v2
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
     assertParse(
       """
       @abi(var v3 { get {} set {} })
       var v3
-      """,
-      experimentalFeatures: [.abiAttribute]
+      """
     )
 
     //
@@ -1207,8 +1186,7 @@ final class AttributeTests: ParserTestCase {
       fixedSource: """
         @abi(var <#pattern#>)
         var v1
-        """,
-      experimentalFeatures: [.abiAttribute]
+        """
     )
     assertParse(
       """
@@ -1231,8 +1209,7 @@ final class AttributeTests: ParserTestCase {
       fixedSource: """
         @abi(var v2)
         var v2
-        """,
-      experimentalFeatures: [.abiAttribute]
+        """
     )
     assertParse(
       """
@@ -1250,8 +1227,7 @@ final class AttributeTests: ParserTestCase {
       fixedSource: """
         @abi(<#declaration#>)
         func fn2() {}
-        """,
-      experimentalFeatures: [.abiAttribute]
+        """
     )
     assertParse(
       """
@@ -1268,8 +1244,7 @@ final class AttributeTests: ParserTestCase {
       fixedSource: """
         @abi(<#declaration#>)
         func fn3() {}
-        """,
-      experimentalFeatures: [.abiAttribute]
+        """
     )
     assertParse(
       """
@@ -1291,8 +1266,7 @@ final class AttributeTests: ParserTestCase {
       fixedSource: """
         @abi(<#declaration#>) func fn4_abi())
         func fn4() {}
-        """,
-      experimentalFeatures: [.abiAttribute]
+        """
     )
 
     // `#if` is banned inside an `@abi` attribute.
@@ -1325,8 +1299,7 @@ final class AttributeTests: ParserTestCase {
           func _fn<E: Error>() throws(E)
         )
         func fn<E: Error>() throws(E) {}
-        """,
-      experimentalFeatures: [.abiAttribute]
+        """
     )
   }