Check trivia for # and elif identifier

Author: TiagoMaiaL

Sources/SwiftParser/Directives.swift

@@ -113,13 +113,13 @@ extension Parser {
         var poundIf: Parser.Token
         let condition: RawExprSyntax?
         var atElifTypo: Bool {
-          guard self.at(.pound) else {
+          guard self.at(TokenSpec(.pound)), self.currentToken.trailingTriviaText.isEmpty else {
             return false
           }
           let identifierSpec = TokenSpec(.identifier, allowAtStartOfLine: false)
           var lookahead = self.lookahead()
           lookahead.consumeAnyToken()
-          guard lookahead.at(identifierSpec), lookahead.currentToken.tokenText == "elif" else {
+          guard lookahead.at(identifierSpec), lookahead.currentToken.tokenText == "elif", lookahead.currentToken.leadingTriviaText.isEmpty else {
             return false
           }
           lookahead.consumeAnyToken()
@@ -128,7 +128,7 @@ extension Parser {
 
         if atElifTypo {
           (unexpectedBeforePoundIf, poundIf) = self.eat(poundIfHandle)
-          guard let identifier = self.consume(if: TokenSpec(.identifier, allowAtStartOfLine: false)) else {
+          guard self.currentToken.leadingTriviaText.isEmpty, let identifier = self.consume(if: TokenSpec(.identifier, allowAtStartOfLine: false)) else {
             preconditionFailure("The current token should be an identifier, guaranteed by the previous if statement")
           }
           unexpectedBeforePoundIf = RawUnexpectedNodesSyntax(combining: unexpectedBeforePoundIf, poundIf, identifier, arena: self.arena)