Resolve issue where standalone return statemente incorrectly expected an expression

Author: ahoppen

Sources/SwiftParser/Declarations.swift

@@ -13,7 +13,7 @@
 @_spi(RawSyntax) import SwiftSyntax
 
 extension TokenConsumer {
-  func atStartOfDeclaration(isAtTopLevel: Bool = false, allowRecovery: Bool = false) -> Bool {
+  func atStartOfDeclaration(isAtTopLevel: Bool = false, allowRecovery: Bool = false, allowCase: Bool = false) -> Bool {
     if self.at(anyIn: PoundDeclarationStart.self) != nil {
       return true
     }

Sources/SwiftParser/Statements.swift

@@ -828,8 +828,8 @@ extension Parser {
     // followed by a '}', '', statement or decl start keyword sequence.
     let expr: RawExprSyntax?
     if
-      self.at(any: [
-        RawTokenKind.rightBrace, .semicolon, .eof,
+      !self.at(any: [
+        .rightBrace, .caseKeyword, .semicolon, .eof,
         .poundIfKeyword, .poundErrorKeyword, .poundWarningKeyword,
         .poundEndifKeyword, .poundElseKeyword, .poundElseifKeyword
       ])

Tests/SwiftParserTest/Statements.swift

@@ -227,4 +227,15 @@ final class StatementTests: XCTestCase {
       ]
     )
   }
+
+  func testReturnBeforeCase() {
+    AssertParse("""
+    switch value {
+    case 1:
+      return
+    case 2:
+      return
+    }
+    """)
+  }
 }