Check if arrow or leftbrace can be recovered

Author: StevenWong12

Sources/SwiftParser/Declarations.swift

@@ -1375,7 +1375,7 @@ extension Parser {
     var effectSpecifiers = self.parseDeclEffectSpecifiers()
 
     let output: RawReturnClauseSyntax?
-    if self.at(.arrow) {
+    if let _ = self.canRecoverTo(TokenSpec(.arrow)) {
       output = self.parseFunctionReturnClause(effectSpecifiers: &effectSpecifiers, allowNamedOpaqueResultType: true)
     } else {
       output = nil

Sources/SwiftParser/TopLevel.swift

@@ -98,7 +98,7 @@ extension Parser {
   /// This function is used when parsing places where function bodies are
   /// optional - like the function requirements in protocol declarations.
   mutating func parseOptionalCodeBlock(allowInitDecl: Bool = true) -> RawCodeBlockSyntax? {
-    guard self.at(.leftBrace) else {
+    guard let _ = self.canRecoverTo(TokenSpec(.leftBrace)) else {
       return nil
     }
     return self.parseCodeBlock(allowInitDecl: allowInitDecl)