Replace offset(of: ) with getOffsetToStart

Author: StevenWong12

Sources/SwiftParser/Lexer/LexemeSequence.swift

@@ -122,20 +122,6 @@ extension Lexer {
         return remainingText
       }
     }
-
-    #if SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION
-    /// If `pointer` is in the source buffer of this ``LexemeSequence``, return
-    /// its offset, otherwise `nil`. Should only be used for the parser's
-    /// alternate token introspection
-    func offset(of pointer: UnsafePointer<UInt8>) -> Int? {
-      let offset = pointer - self.sourceBufferStart.input.baseAddress!
-      if offset <= self.sourceBufferStart.input.count {
-        return offset
-      } else {
-        return nil
-      }
-    }
-    #endif
   }
 
   @_spi(Testing)

Sources/SwiftParser/Parser.swift

@@ -250,11 +250,7 @@ public struct Parser {
   public var alternativeTokenChoices: [Int: [TokenSpec]] = [:]
 
   mutating func recordAlternativeTokenChoice(for lexeme: Lexer.Lexeme, choices: [TokenSpec]) {
-    guard let lexemeBaseAddress = lexeme.tokenText.baseAddress,
-      let offset = lexemes.offset(of: lexemeBaseAddress)
-    else {
-      return
-    }
+    let offset = lexemes.getOffsetToStart(lexeme)
     alternativeTokenChoices[offset, default: []].append(contentsOf: choices)
   }
   #endif