Improve recovery if variable or subscript is missing brace wrapping getter and setter

Author: ahoppen

Sources/SwiftParser/Declarations.swift

@@ -149,10 +149,10 @@ extension Parser {
   ///
   ///     declarations → declaration declarations?
   ///
-  /// If `allowMissingFuncOrVarKeywordRecovery` is `true`, this methods tries to
-  /// synthesize `func` or `var` keywords where necessary.
+  /// If `inMemberDeclList` is `true`, we know that the next item must be a
+  /// declaration and thus start with a keyword. This allows futher recovery.
   @_spi(RawSyntax)
-  public mutating func parseDeclaration(allowMissingFuncOrVarKeywordRecovery: Bool = false) -> RawDeclSyntax {
+  public mutating func parseDeclaration(inMemberDeclList: Bool = false) -> RawDeclSyntax {
     switch self.at(anyIn: PoundDeclarationStart.self) {
     case (.poundIfKeyword, _)?:
       let directive = self.parsePoundIfDirective { parser in
@@ -207,7 +207,7 @@ extension Parser {
     case (.subscriptKeyword, let handle)?:
       return RawDeclSyntax(self.parseSubscriptDeclaration(attrs, handle))
     case (.letKeyword, let handle)?, (.varKeyword, let handle)?:
-      return RawDeclSyntax(self.parseLetOrVarDeclaration(attrs, handle))
+      return RawDeclSyntax(self.parseLetOrVarDeclaration(attrs, handle, inMemberDeclList: inMemberDeclList))
     case (.initKeyword, let handle)?:
       return RawDeclSyntax(self.parseInitializerDeclaration(attrs, handle))
     case (.deinitKeyword, let handle)?:
@@ -219,7 +219,7 @@ extension Parser {
     case (.actorContextualKeyword, let handle)?:
       return RawDeclSyntax(self.parseActorDeclaration(attrs, handle))
     case nil:
-      if allowMissingFuncOrVarKeywordRecovery {
+      if inMemberDeclList {
         let isProbablyVarDecl = self.at(any: [.identifier, .wildcardKeyword]) && self.peek().tokenKind.is(any: [.colon, .equal, .comma])
         let isProbablyTupleDecl = self.at(.leftParen) && self.peek().tokenKind.is(any: [.identifier, .wildcardKeyword])
 
@@ -608,7 +608,7 @@ extension Parser {
     if self.at(.poundSourceLocationKeyword) {
       decl = RawDeclSyntax(self.parsePoundSourceLocationDirective())
     } else {
-      decl = self.parseDeclaration(allowMissingFuncOrVarKeywordRecovery: true)
+      decl = self.parseDeclaration(inMemberDeclList: true)
     }
 
     let semi = self.consume(if: .semicolon)
@@ -1690,7 +1690,7 @@ extension Parser {
 
     // Parse getter and setter.
     let accessor: RawSyntax?
-    if self.at(.leftBrace) {
+    if self.at(.leftBrace) || self.at(anyIn: AccessorKind.self) != nil {
       accessor = self.parseGetSet()
     } else {
       accessor = nil
@@ -1721,10 +1721,22 @@ extension Parser {
   ///     pattern-initializer-list → pattern-initializer | pattern-initializer ',' pattern-initializer-list
   ///     pattern-initializer → pattern initializer?
   ///     initializer → = expression
+  ///
+  /// If `inMemberDeclList` is `true`, we know that the next item needs to be a
+  /// declaration that is started by a keyword. Thus, we in the following case
+  /// we know that `set` can't start a new declaration and we can thus recover
+  /// by synthesizing a missing `{` in front of `set`.
+  /// ```
+  /// var x: Int
+  ///   set {
+  ///   }
+  /// }
+  /// ```
   @_spi(RawSyntax)
   public mutating func parseLetOrVarDeclaration(
     _ attrs: DeclAttributes,
-    _ handle: RecoveryConsumptionHandle
+    _ handle: RecoveryConsumptionHandle,
+    inMemberDeclList: Bool = false
   ) -> RawVariableDeclSyntax {
     let (unexpectedBeforeIntroducer, introducer) = self.eat(handle)
     let hasTryBeforeIntroducer = unexpectedBeforeIntroducer?.containsToken(where: { $0.tokenKind == .tryKeyword }) ?? false
@@ -1786,7 +1798,7 @@ extension Parser {
         }
 
         let accessor: RawSyntax?
-        if self.at(.leftBrace) {
+        if self.at(.leftBrace) || (inMemberDeclList && self.at(anyIn: AccessorKind.self) != nil) {
           accessor = self.parseGetSet()
         } else {
           accessor = nil
@@ -1812,21 +1824,6 @@ extension Parser {
       arena: self.arena)
   }
 
-  enum AccessorKind: SyntaxText, ContextualKeywords, Equatable {
-    case `get` = "get"
-    case `set` = "set"
-    case `didSet` = "didSet"
-    case `willSet` = "willSet"
-    case unsafeAddress = "unsafeAddress"
-    case addressWithOwner = "addressWithOwner"
-    case addressWithNativeOwner = "addressWithNativeOwner"
-    case unsafeMutableAddress = "unsafeMutableAddress"
-    case mutableAddressWithOwner = "mutableAddressWithOwner"
-    case mutableAddressWithNativeOwner = "mutableAddressWithNativeOwner"
-    case _read = "_read"
-    case _modify = "_modify"
-  }
-
   struct AccessorIntroducer {
     var attributes: RawAttributeListSyntax?
     var modifier: RawDeclModifierSyntax?
@@ -1921,7 +1918,14 @@ extension Parser {
   @_spi(RawSyntax)
   public mutating func parseGetSet() -> RawSyntax {
     // Parse getter and setter.
-    let (unexpectedBeforeLBrace, lbrace) = self.expect(.leftBrace)
+    let unexpectedBeforeLBrace: RawUnexpectedNodesSyntax?
+    let lbrace: RawTokenSyntax
+    if self.at(anyIn: AccessorKind.self) != nil {
+      unexpectedBeforeLBrace = nil
+      lbrace = missingToken(.leftBrace, text: nil)
+    } else {
+      (unexpectedBeforeLBrace, lbrace) = self.expect(.leftBrace)
+    }
     // Collect all explicit accessors to a list.
     var elements = [RawAccessorDeclSyntax]()
     do {

Sources/SwiftParser/RawTokenKindSubset.swift

@@ -72,6 +72,21 @@ extension ContextualKeywords where RawValue == SyntaxText {
 
 // MARK: - Subsets
 
+enum AccessorKind: SyntaxText, ContextualKeywords, Equatable {
+  case `get` = "get"
+  case `set` = "set"
+  case `didSet` = "didSet"
+  case `willSet` = "willSet"
+  case unsafeAddress = "unsafeAddress"
+  case addressWithOwner = "addressWithOwner"
+  case addressWithNativeOwner = "addressWithNativeOwner"
+  case unsafeMutableAddress = "unsafeMutableAddress"
+  case mutableAddressWithOwner = "mutableAddressWithOwner"
+  case mutableAddressWithNativeOwner = "mutableAddressWithNativeOwner"
+  case _read = "_read"
+  case _modify = "_modify"
+}
+
 enum BinaryOperator: RawTokenKindSubset {
   case spacedBinaryOperator
   case unspacedBinaryOperator

Tests/SwiftParserTest/Declarations.swift

@@ -1143,6 +1143,57 @@ final class DeclarationTests: XCTestCase {
       """
     )
   }
+
+  func testVariableDeclWithGetSetButNoBrace() {
+    AssertParse(
+      """
+      struct Foo {
+        var x: Int 1️⃣
+          get {
+            4
+          }
+          set {
+            x = newValue
+          }
+        }
+      }
+      """,
+      diagnostics: [
+        DiagnosticSpec(message: "expected '{' in variable")
+      ]
+    )
+  }
+
+  func testVariableDeclWithSetGetButNoBrace() {
+    AssertParse(
+      """
+      struct Foo {
+        var x: Int 1️⃣
+          set {
+            x = newValue
+          }
+          get {
+            4
+          }
+        }
+      }
+      """,
+      diagnostics: [
+        DiagnosticSpec(message: "expected '{' in variable")
+      ]
+    )
+  }
+
+  func testVariableFollowedByReferenceToSet() {
+    AssertParse(
+      """
+      func bar() {
+          let a = b
+          set.c
+      }
+      """
+    )
+  }
 }
 
 extension Parser.DeclAttributes {

Tests/SwiftParserTest/translated/SubscriptingTests.swift

@@ -362,20 +362,18 @@ final class SubscriptingTests: XCTestCase {
     AssertParse(
       """
       struct A8 {
-        subscript(i : Int) -> Int
-          1️⃣get 2️⃣{
+        subscript(i : Int) -> Int1️⃣
+          get {
             return stored
           }
-          3️⃣set 4️⃣{
+          set {
             stored = value
           }
-        }
+        }2️⃣
       """,
       diagnostics: [
-        DiagnosticSpec(locationMarker: "1️⃣", message: "expected 'func' in function"),
-        DiagnosticSpec(locationMarker: "2️⃣", message: "expected parameter clause in function signature"),
-        DiagnosticSpec(locationMarker: "3️⃣", message: "expected 'func' in function"),
-        DiagnosticSpec(locationMarker: "4️⃣", message: "expected parameter clause in function signature"),
+        DiagnosticSpec(locationMarker: "1️⃣", message: "expected '{' in subscript"),
+        DiagnosticSpec(locationMarker: "2️⃣", message: "expected '}' to end struct"),
       ]
     )
   }