Don’t consider MattchingPattern start the start of an expression

Author: ahoppen

Sources/SwiftParser/RawTokenKindSubset.swift

@@ -773,16 +773,13 @@ enum PrimaryExpressionStart: RawTokenKindSubset {
 enum ExpressionStart: RawTokenKindSubset {
   case awaitTryMove(AwaitTryMove)
   case expressionPrefixOperator(ExpressionPrefixOperator)
-  case matchingPatternStart(MatchingPatternStart)
   case primaryExpressionStart(PrimaryExpressionStart)
 
   init?(lexeme: Lexer.Lexeme) {
     if let subset = AwaitTryMove(lexeme: lexeme) {
       self = .awaitTryMove(subset)
     } else if let subset = ExpressionPrefixOperator(lexeme: lexeme) {
       self = .expressionPrefixOperator(subset)
-    } else if let subset = MatchingPatternStart(lexeme: lexeme) {
-      self = .matchingPatternStart(subset)
     } else if let subset = PrimaryExpressionStart(lexeme: lexeme) {
       self = .primaryExpressionStart(subset)
     } else {
@@ -793,15 +790,13 @@ enum ExpressionStart: RawTokenKindSubset {
   static var allCases: [ExpressionStart] {
     return AwaitTryMove.allCases.map(Self.awaitTryMove)
       + ExpressionPrefixOperator.allCases.map(Self.expressionPrefixOperator)
-      + MatchingPatternStart.allCases.map(Self.matchingPatternStart)
       + PrimaryExpressionStart.allCases.map(Self.primaryExpressionStart)
   }
 
   var rawTokenKind: RawTokenKind {
     switch self {
     case .awaitTryMove(let underlyingKind): return underlyingKind.rawTokenKind
     case .expressionPrefixOperator(let underlyingKind): return underlyingKind.rawTokenKind
-    case .matchingPatternStart(let underlyingKind): return underlyingKind.rawTokenKind
     case .primaryExpressionStart(let underlyingKind): return underlyingKind.rawTokenKind
     }
   }
@@ -810,7 +805,6 @@ enum ExpressionStart: RawTokenKindSubset {
     switch self {
     case .awaitTryMove(let underlyingKind): return underlyingKind.contextualKeyword
     case .expressionPrefixOperator(let underlyingKind): return underlyingKind.contextualKeyword
-    case .matchingPatternStart(let underlyingKind): return underlyingKind.contextualKeyword
     case .primaryExpressionStart(let underlyingKind): return underlyingKind.contextualKeyword
     }
   }

Tests/SwiftParserTest/StatementTests.swift

@@ -603,4 +603,19 @@ final class StatementTests: XCTestCase {
       )
     )
   }
+
+  func testPatternExprInSwitchCaseItem() {
+    AssertParse(
+      """
+      switch x {
+      case a:
+      1️⃣is
+      }
+      """,
+      diagnostics: [
+        DiagnosticSpec(message: "unexpected 'is' keyword in 'switch' statement")
+      ]
+    )
+  }
+
 }