Add a declModifier token precedence to represent the declaration modifiers

Author: StevenWong12

Sources/SwiftParser/Declarations.swift

@@ -1695,7 +1695,7 @@ extension Parser {
   @_spi(RawSyntax)
   public mutating func parseOperatorDeclaration() -> RawOperatorDeclSyntax {
 
-    let (unexpectedBeforeModifier, modifier) = self.expect(.keyword(.infix), .keyword(.postfix), .keyword(.prefix), default: .keyword(.prefix))
+    let (unexpectedBeforeModifier, modifier) = self.expect(anyIn: OperatorModifiers.self, default: .prefix, overrideRecoveryPrecedence: .declKeyword)
 
     let (unexpectedBeforeOperator, operatorKeyword) = self.expect(.keyword(.operator))
 

Sources/SwiftParser/Parser.swift

@@ -402,11 +402,12 @@ extension Parser {
   @inline(__always)
   mutating func expect<SpecSet: TokenSpecSet>(
     anyIn specSet: SpecSet.Type,
-    default defaultKind: SpecSet
+    default defaultKind: SpecSet,
+    overrideRecoveryPrecedence: TokenPrecedence? = nil
   ) -> (unexpected: RawUnexpectedNodesSyntax?, token: RawTokenSyntax) {
     return expectImpl(
       consume: { $0.consume(ifAnyIn: specSet) },
-      canRecoverTo: { $0.canRecoverTo(anyIn: specSet)?.1 },
+      canRecoverTo: { $0.canRecoverTo(anyIn: specSet, overrideRecoveryPrecedence: overrideRecoveryPrecedence)?.1 },
       makeMissing: { $0.missingToken(defaultKind.spec) }
     )
   }

Sources/SwiftParser/TokenPrecedence.swift

@@ -38,6 +38,7 @@ public enum TokenPrecedence: Comparable {
   case strongPunctuator
   /// The closing delimiter of `strongBracketed`
   case closingBrace
+  case declModifier
   /// Tokens that start a new declaration
   case declKeyword
   case openingPoundIf
@@ -81,12 +82,14 @@ public enum TokenPrecedence: Comparable {
         return 8
       case .closingBrace:
         return 9
-      case .declKeyword:
+      case .declModifier:
         return 10
-      case .openingPoundIf:
+      case .declKeyword:
         return 11
-      case .closingPoundIf:
+      case .openingPoundIf:
         return 12
+      case .closingPoundIf:
+        return 13
       }
     }
 
@@ -210,17 +213,21 @@ public enum TokenPrecedence: Comparable {
       // Return-like statements
       .break, .continue, .fallthrough, .return, .throw, .yield:
       self = .stmtKeyword
+    // MARK: Decl Modifiers
+    case // Operator Modifiers
+    .infix, .prefix, .postfix,
+      // Access modifiers
+      .fileprivate, .internal, .private, .public, .static:
+      self = .declModifier
     // MARK: Decl keywords
     case  // Types
     .associatedtype, .class, .enum, .extension, .protocol, .struct, .typealias,
-      // Access modifiers
-      .fileprivate, .internal, .private, .public, .static,
       // Functions
       .deinit, .func, .`init`, .subscript,
       // Variables
       .let, .var,
       // Operator stuff
-      .operator, .precedencegroup, .infix, .prefix, .postfix,
+      .operator, .precedencegroup,
       // Misc
       .import:
       self = .declKeyword

Sources/SwiftParser/TokenSpecSet.swift

@@ -321,6 +321,29 @@ enum Operator: TokenSpecSet {
   }
 }
 
+enum OperatorModifiers: TokenSpecSet {
+  case `prefix`
+  case `infix`
+  case `postfix`
+
+  init?(lexeme: Lexer.Lexeme) {
+    switch PrepareForKeywordMatch(lexeme) {
+    case TokenSpec(.prefix): self = .prefix
+    case TokenSpec(.infix): self = .infix
+    case TokenSpec(.postfix): self = .postfix
+    default: return nil
+    }
+  }
+
+  var spec: TokenSpec {
+    switch self {
+    case .prefix: return .keyword(.prefix)
+    case .postfix: return .keyword(.postfix)
+    case .infix: return .keyword(.infix)
+    }
+  }
+}
+
 /// Tokens that can be used in operator declarations
 enum OperatorLike: TokenSpecSet {
   case `operator`(Operator)

Tests/SwiftParserTest/translated/OperatorDeclTests.swift

@@ -479,7 +479,7 @@ final class OperatorDeclTests: XCTestCase {
       ]
     )
   }
-  
+
   func testOperatorDecl124() {
     assertParse(
       """
@@ -491,7 +491,7 @@ final class OperatorDeclTests: XCTestCase {
       ]
     )
   }
-  
+
   func testOperatorDecl125() {
     assertParse(
       """
@@ -503,6 +503,17 @@ final class OperatorDeclTests: XCTestCase {
     )
   }
 
+  func testOperatorDecl126() {
+    assertParse(
+      """
+      1️⃣private(set) infix operator ~~~
+      """,
+      diagnostics: [
+        DiagnosticSpec(message: "unexpected code 'private(set)' before operator declaration")
+      ]
+    )
+  }
+
   func testIdentifierAsOperatorName() {
     assertParse(
       "postfix operator 1️⃣aa",