Parse the @abi attribute in SwiftSyntax

Matches work in swiftlang/swift#76878.

Author: beccadax

Diff for: CodeGeneration/Sources/SyntaxSupport/AttributeNodes.swift

@@ -141,6 +141,11 @@ public let ATTRIBUTE_NODES: [Node] = [
             name: "documentationArguments",
             kind: .node(kind: .documentationAttributeArgumentList)
           ),
+          Child(
+            name: "abiArguments",
+            kind: .node(kind: .abiAttributeArguments),
+            experimentalFeature: .abiAttribute
+          )
         ]),
         documentation: """
           The arguments of the attribute.
@@ -251,6 +256,20 @@ public let ATTRIBUTE_NODES: [Node] = [
     ]
   ),
 
+  Node(
+    kind: .abiAttributeArguments,
+    base: .syntax,
+    experimentalFeature: .abiAttribute,
+    nameForDiagnostics: "ABI-providing declaration",
+    documentation: "The arguments of the '@abi' attribute",
+    children: [
+      Child(
+        name: "provider",
+        kind: .node(kind: .decl)
+      ),
+    ]
+  ),
+
   Node(
     kind: .conventionAttributeArguments,
     base: .syntax,

Diff for: CodeGeneration/Sources/SyntaxSupport/ExperimentalFeatures.swift

@@ -19,6 +19,7 @@ public enum ExperimentalFeature: String, CaseIterable {
   case nonescapableTypes
   case trailingComma
   case coroutineAccessors
+  case abiAttribute
 
   /// The name of the feature, which is used in the doc comment.
   public var featureName: String {
@@ -35,6 +36,8 @@ public enum ExperimentalFeature: String, CaseIterable {
       return "trailing comma"
     case .coroutineAccessors:
       return "CoroutineAccessors"
+    case .abiAttribute:
+      return "@abi attribute"
     }
   }
 

Diff for: CodeGeneration/Sources/SyntaxSupport/KeywordSpec.swift

@@ -131,6 +131,7 @@ public enum Keyword: CaseIterable {
   case _underlyingVersion
   case _UnknownLayout
   case _version
+  case abi
   case accesses
   case actor
   case addressWithNativeOwner
@@ -404,6 +405,8 @@ public enum Keyword: CaseIterable {
       return KeywordSpec("_UnknownLayout")
     case ._version:
       return KeywordSpec("_version")
+    case .abi:
+      return KeywordSpec("abi", experimentalFeature: .abiAttribute)
     case .accesses:
       return KeywordSpec("accesses")
     case .actor:

Diff for: CodeGeneration/Sources/SyntaxSupport/SyntaxNodeKind.swift

@@ -22,6 +22,7 @@ public enum SyntaxNodeKind: String, CaseIterable, IdentifierConvertible, TypeCon
 
   case _canImportExpr
   case _canImportVersionInfo
+  case abiAttributeArguments
   case accessorBlock
   case accessorDecl
   case accessorDeclList
@@ -340,14 +341,23 @@ public enum SyntaxNodeKind: String, CaseIterable, IdentifierConvertible, TypeCon
     return .identifier(rawValue)
   }
 
+  public var uppercasedFirstWordRawValue: String {
+    switch self {
+    case .abiAttributeArguments:
+      "ABIAttributeArguments"
+    default:
+      rawValue.withFirstCharacterUppercased
+    }
+  }
+
   public var syntaxType: TypeSyntax {
     switch self {
     case .syntax:
       return "Syntax"
     case .syntaxCollection:
       return "SyntaxCollection"
     default:
-      return "\(raw: rawValue.withFirstCharacterUppercased)Syntax"
+      return "\(raw: uppercasedFirstWordRawValue)Syntax"
     }
   }
 

Diff for: CodeGeneration/Sources/Utils/SyntaxBuildableType.swift

@@ -151,7 +151,7 @@ public struct SyntaxBuildableType: Hashable {
   public var resultBuilderType: TypeSyntax {
     switch kind {
     case .node(kind: let kind):
-      return TypeSyntax("\(raw: kind.rawValue.withFirstCharacterUppercased)Builder")
+      return TypeSyntax("\(raw: kind.uppercasedFirstWordRawValue)Builder")
     case .token:
       preconditionFailure("Tokens cannot be constructed using result builders")
     }

Diff for: CodeGeneration/Sources/generate-swift-syntax/templates/swiftsyntax/SyntaxEnumFile.swift

@@ -60,7 +60,7 @@ let syntaxEnumFile = SourceFileSyntax(leadingTrivia: copyrightHeader) {
 
   for base in SYNTAX_NODES where base.kind.isBase {
     let baseKind = base.kind
-    let baseName = baseKind.rawValue.withFirstCharacterUppercased
+    let baseName = baseKind.uppercasedFirstWordRawValue
     let enumType: TypeSyntax = "\(raw: baseName)SyntaxEnum"
 
     try! EnumDeclSyntax(

Diff for: Sources/SwiftParser/Attributes.swift

@@ -11,9 +11,9 @@
 //===----------------------------------------------------------------------===//
 
 #if swift(>=6)
-@_spi(RawSyntax) internal import SwiftSyntax
+@_spi(ExperimentalLanguageFeatures) @_spi(RawSyntax) internal import SwiftSyntax
 #else
-@_spi(RawSyntax) import SwiftSyntax
+@_spi(ExperimentalLanguageFeatures) @_spi(RawSyntax) import SwiftSyntax
 #endif
 
 extension Parser {
@@ -58,6 +58,7 @@ extension Parser {
     case _typeEraser
     case _unavailableFromAsync
     case `rethrows`
+    case abi
     case attached
     case available
     case backDeployed
@@ -95,6 +96,7 @@ extension Parser {
       case TokenSpec(._typeEraser): self = ._typeEraser
       case TokenSpec(._unavailableFromAsync): self = ._unavailableFromAsync
       case TokenSpec(.`rethrows`): self = .rethrows
+      case TokenSpec(.abi) where experimentalFeatures.contains(.abiAttribute): self = .abi
       case TokenSpec(.attached): self = .attached
       case TokenSpec(.available): self = .available
       case TokenSpec(.backDeployed): self = .backDeployed
@@ -136,6 +138,7 @@ extension Parser {
       case ._typeEraser: return .keyword(._typeEraser)
       case ._unavailableFromAsync: return .keyword(._unavailableFromAsync)
       case .`rethrows`: return .keyword(.rethrows)
+      case .abi: return .keyword(.abi)
       case .attached: return .keyword(.attached)
       case .available: return .keyword(.available)
       case .backDeployed: return .keyword(.backDeployed)
@@ -176,9 +179,16 @@ extension Parser {
     case noArgument
   }
 
+  /// Parse the argument of an attribute, if it has one.
+  ///
+  /// - Parameters:
+  ///   - argumentMode: Indicates whether the attribute must, may, or may not have an argument.
+  ///   - parseArguments: Called to parse the argument list. If there is an opening parenthesis, it will have already been consumed.
+  ///   - parseMissingArguments: If provided, called instead of `parseArgument` when an argument list was required but no opening parenthesis was present.
   mutating func parseAttribute(
     argumentMode: AttributeArgumentMode,
-    parseArguments: (inout Parser) -> RawAttributeSyntax.Arguments
+    parseArguments: (inout Parser) -> RawAttributeSyntax.Arguments,
+    parseMissingArguments: ((inout Parser) -> RawAttributeSyntax.Arguments)? = nil
   ) -> RawAttributeListSyntax.Element {
     var (unexpectedBeforeAtSign, atSign) = self.expect(.atSign)
     if atSign.trailingTriviaByteLength > 0 || self.currentToken.leadingTriviaByteLength > 0 {
@@ -213,7 +223,11 @@ extension Parser {
         )
         leftParen = leftParen.tokenView.withTokenDiagnostic(tokenDiagnostic: diagnostic, arena: self.arena)
       }
-      let argument = parseArguments(&self)
+      let argument = if let parseMissingArguments, leftParen.presence == .missing {
+        parseMissingArguments(&self)
+      } else {
+        parseArguments(&self)
+      }
       let (unexpectedBeforeRightParen, rightParen) = self.expect(.rightParen)
       return .attribute(
         RawAttributeSyntax(
@@ -255,6 +269,12 @@ extension Parser {
     }
 
     switch peek(isAtAnyIn: DeclarationAttributeWithSpecialSyntax.self) {
+    case .abi:
+      return parseAttribute(argumentMode: .required) { parser in
+        return .abiArguments(parser.parseABIAttributeArguments())
+      } parseMissingArguments: { parser in
+        return .abiArguments(parser.parseABIAttributeArguments(missing: true))
+      }
     case .available, ._spi_available:
       return parseAttribute(argumentMode: .required) { parser in
         return .availability(parser.parseAvailabilityArgumentSpecList())
@@ -918,6 +938,33 @@ extension Parser {
   }
 }
 
+extension Parser {
+  mutating func parseABIAttributeArguments(missing: Bool = false) -> RawABIAttributeArgumentsSyntax {
+    let providerDecl: RawDeclSyntax = if missing {
+      // There are two situations where the left paren might be missing:
+      //   1. The user just forgot the paren: `@abi var x_abi: Int) var x: Int`
+      //   2. The user forgot the whole argument list: `@abi var x: Int`
+      // Normally, we would distinguish these by seeing if whatever comes after
+      // the attribute parses as an argument. However, for @abi the argument is
+      // a decl, so in #2, we would consume the decl the attribute is attached
+      // to! This leads to a lousy diagnostic in that situation.
+      // Avoid this problem by simply returning a missing decl immediately.
+      // FIXME: Could we look ahead to find an unbalanced parenthesis?
+      RawDeclSyntax(
+        RawMissingDeclSyntax(
+          attributes: self.emptyCollection(RawAttributeListSyntax.self),
+          modifiers: self.emptyCollection(RawDeclModifierListSyntax.self),
+          arena: arena
+        )
+      )
+    } else {
+      parseDeclaration(in: .attribute)
+    }
+
+    return RawABIAttributeArgumentsSyntax(provider: providerDecl, arena: arena)
+  }
+}
+
 extension Parser {
   mutating func parseBackDeployedAttributeArguments() -> RawBackDeployedAttributeArgumentsSyntax {
     let (unexpectedBeforeLabel, label) = self.expect(.keyword(.before))

Diff for: Sources/SwiftParser/Declarations.swift

@@ -168,11 +168,24 @@ extension Parser {
     }
   }
 
+  /// Information about the syntactic position of the declaration being parsed.
+  /// Used to tweak recovery and to permit missing bodies.
+  enum DeclarationParsingContext {
+    /// The declaration is at the top level of a file.
+    case topLevelCode
+
+    /// The declaration is nested inside the member list of a DeclGroupSyntax.
+    case memberList
+
+    /// The declaration is nested inside the argument list of an attribute.
+    case attribute
+  }
+
   /// Parse a declaration.
   ///
-  /// If `inMemberDeclList` is `true`, we know that the next item must be a
+  /// If `parseContext` is `memberList`, we know that the next item must be a
   /// declaration and thus start with a keyword. This allows further recovery.
-  mutating func parseDeclaration(inMemberDeclList: Bool = false) -> RawDeclSyntax {
+  mutating func parseDeclaration(in parseContext: DeclarationParsingContext = .topLevelCode) -> RawDeclSyntax {
     // If we are at a `#if` of attributes, the `#if` directive should be
     // parsed when we're parsing the attributes.
     if self.at(.poundIf) && !self.withLookahead({ $0.consumeIfConfigOfAttributes() }) {
@@ -221,7 +234,14 @@ extension Parser {
       // to parse.
       // If we are inside a memberDecl list, we don't want to eat closing braces (which most likely close the outer context)
       // while recovering to the declaration start.
-      let recoveryPrecedence = inMemberDeclList ? TokenPrecedence.closingBrace : nil
+      let recoveryPrecedence = switch parseContext {
+      case .topLevelCode:
+        Optional<TokenPrecedence>.none
+      case .memberList:
+        Optional(TokenPrecedence.closingBrace)
+      case .attribute:
+        Optional(TokenPrecedence.weakBracketed(closingDelimiter: .rightParen))
+      }
       recoveryResult = self.canRecoverTo(anyIn: DeclarationKeyword.self, overrideRecoveryPrecedence: recoveryPrecedence)
     }
 
@@ -230,28 +250,28 @@ extension Parser {
       return RawDeclSyntax(self.parseImportDeclaration(attrs, handle))
     case (.lhs(.class), let handle)?:
       return RawDeclSyntax(
-        self.parseNominalTypeDeclaration(for: RawClassDeclSyntax.self, attrs: attrs, introucerHandle: handle)
+        self.parseNominalTypeDeclaration(for: RawClassDeclSyntax.self, attrs: attrs, introucerHandle: handle, parseContext: parseContext)
       )
     case (.lhs(.enum), let handle)?:
       return RawDeclSyntax(
-        self.parseNominalTypeDeclaration(for: RawEnumDeclSyntax.self, attrs: attrs, introucerHandle: handle)
+        self.parseNominalTypeDeclaration(for: RawEnumDeclSyntax.self, attrs: attrs, introucerHandle: handle, parseContext: parseContext)
       )
     case (.lhs(.case), let handle)?:
       return RawDeclSyntax(self.parseEnumCaseDeclaration(attrs, handle))
     case (.lhs(.struct), let handle)?:
       return RawDeclSyntax(
-        self.parseNominalTypeDeclaration(for: RawStructDeclSyntax.self, attrs: attrs, introucerHandle: handle)
+        self.parseNominalTypeDeclaration(for: RawStructDeclSyntax.self, attrs: attrs, introucerHandle: handle, parseContext: parseContext)
       )
     case (.lhs(.protocol), let handle)?:
       return RawDeclSyntax(
-        self.parseNominalTypeDeclaration(for: RawProtocolDeclSyntax.self, attrs: attrs, introucerHandle: handle)
+        self.parseNominalTypeDeclaration(for: RawProtocolDeclSyntax.self, attrs: attrs, introucerHandle: handle, parseContext: parseContext)
       )
     case (.lhs(.associatedtype), let handle)?:
       return RawDeclSyntax(self.parseAssociatedTypeDeclaration(attrs, handle))
     case (.lhs(.typealias), let handle)?:
       return RawDeclSyntax(self.parseTypealiasDeclaration(attrs, handle))
     case (.lhs(.extension), let handle)?:
-      return RawDeclSyntax(self.parseExtensionDeclaration(attrs, handle))
+      return RawDeclSyntax(self.parseExtensionDeclaration(attrs, handle, parseContext: parseContext))
     case (.lhs(.func), let handle)?:
       return RawDeclSyntax(self.parseFuncDeclaration(attrs, handle))
     case (.lhs(.subscript), let handle)?:
@@ -266,19 +286,19 @@ extension Parser {
       return RawDeclSyntax(self.parsePrecedenceGroupDeclaration(attrs, handle))
     case (.lhs(.actor), let handle)?:
       return RawDeclSyntax(
-        self.parseNominalTypeDeclaration(for: RawActorDeclSyntax.self, attrs: attrs, introucerHandle: handle)
+        self.parseNominalTypeDeclaration(for: RawActorDeclSyntax.self, attrs: attrs, introucerHandle: handle, parseContext: parseContext)
       )
     case (.lhs(.macro), let handle)?:
       return RawDeclSyntax(self.parseMacroDeclaration(attrs: attrs, introducerHandle: handle))
     case (.lhs(.pound), let handle)?:
       return RawDeclSyntax(self.parseMacroExpansionDeclaration(attrs, handle))
     case (.rhs, let handle)?:
-      return RawDeclSyntax(self.parseBindingDeclaration(attrs, handle, inMemberDeclList: inMemberDeclList))
+      return RawDeclSyntax(self.parseBindingDeclaration(attrs, handle, inMemberDeclList: parseContext != .topLevelCode))
     case nil:
       break
     }
 
-    if inMemberDeclList {
+    if parseContext != .topLevelCode {
       let isProbablyVarDecl = self.at(.identifier, .wildcard) && self.peek(isAt: .colon, .equal, .comma)
       let isProbablyTupleDecl = self.at(.leftParen) && self.peek(isAt: .identifier, .wildcard)
 
@@ -377,7 +397,8 @@ extension Parser {
   /// Parse an extension declaration.
   mutating func parseExtensionDeclaration(
     _ attrs: DeclAttributes,
-    _ handle: RecoveryConsumptionHandle
+    _ handle: RecoveryConsumptionHandle,
+    parseContext: DeclarationParsingContext
   ) -> RawExtensionDeclSyntax {
     let (unexpectedBeforeExtensionKeyword, extensionKeyword) = self.eat(handle)
     let type = self.parseType()
@@ -395,7 +416,12 @@ extension Parser {
     } else {
       whereClause = nil
     }
-    let memberBlock = self.parseMemberBlock(introducer: extensionKeyword)
+    let memberBlock: RawMemberBlockSyntax?
+    if parseContext == .attribute && !self.at(.leftBrace) {
+      memberBlock = nil
+    } else {
+      memberBlock = self.parseMemberBlock(introducer: extensionKeyword)
+    }
     return RawExtensionDeclSyntax(
       attributes: attrs.attributes,
       modifiers: attrs.modifiers,
@@ -746,7 +772,7 @@ extension Parser {
     if self.at(.poundSourceLocation) {
       decl = RawDeclSyntax(self.parsePoundSourceLocationDirective())
     } else {
-      decl = self.parseDeclaration(inMemberDeclList: true)
+      decl = self.parseDeclaration(in: .memberList)
     }
 
     let semi = self.consume(if: .semicolon)

Diff for: Sources/SwiftParser/Nominals.swift

@@ -211,7 +211,8 @@ extension Parser {
   mutating func parseNominalTypeDeclaration<T>(
     for T: T.Type,
     attrs: DeclAttributes,
-    introucerHandle: RecoveryConsumptionHandle
+    introucerHandle: RecoveryConsumptionHandle,
+    parseContext: DeclarationParsingContext
   ) -> T where T: NominalTypeDeclarationTrait {
     let (unexpectedBeforeIntroducerKeyword, introducerKeyword) = self.eat(introucerHandle)
     let (unexpectedBeforeName, name) = self.expectIdentifier(keywordRecovery: true)
@@ -258,7 +259,12 @@ extension Parser {
       whereClause = nil
     }
 
-    let memberBlock = self.parseMemberBlock(introducer: introducerKeyword)
+    let memberBlock: RawMemberBlockSyntax?
+    if parseContext == .attribute && !self.at(.leftBrace) {
+      memberBlock = nil
+    } else {
+      memberBlock = self.parseMemberBlock(introducer: introducerKeyword)
+    }
     return T.init(
       attributes: attrs.attributes,
       modifiers: attrs.modifiers,

Diff for: Sources/SwiftParser/TokenPrecedence.swift

@@ -283,6 +283,7 @@ enum TokenPrecedence: Comparable {
       ._swift_native_objc_runtime_base,
       ._typeEraser,
       ._unavailableFromAsync,
+      .abi,
       .attached,
       .available,
       .backDeployed,