       
     buffer._bitCount = buffer._bitCount &- bitsConsumed
 
-    guard _fastPath(valid) else {
-      return .invalid(length: Int(length))
-    }
-    return .valid(encodedScalar)
+    if _fastPath(isValid) { return .valid(encodedScalar) }
+    return .invalid(length: Int(length))
   }
 }
 

  }
  
  public // @testable
  func _parseNonASCII() -> (valid: Bool, length: UInt8) {
    _sanityCheck(buffer._storage & 0x80 != 0) // this case handled elsewhere
    if buffer._storage                & 0b0__1110_0000__1100_0000
                                     == 0b0__1100_0000__1000_0000 {

    } while buffer._bitCount < 32

    // Find one unicode scalar.
    let (isValid, length) = _parseNonASCII()
    _sanityCheck(1...4 ~= length)
    _sanityCheck(length <= buffer.count)
    
