Recipe for headache (UB in my Nim code)

code.nim

#This code was written in an attempt to solve 2022 Advent of Code Day 7 [https://adventofcode.com/2022/day/7]
import strutils, sequtils, math

# const data = readfile("data.txt").splitLines()

type
    Efile = tuple #Elf file type
        fsize: int
        fname: string

    Edir = object #Elf directory type
        files: seq[Efile]
        dirs: seq[Edir]



proc touchfile(main: var Edir, file: Efile) = #proc to help add  a single file to an elf directory
    main.files.add(file)
proc mkdir(main: var Edir, dir: Edir) = #proc to help add a child_directory into a given elf directory
    main.dirs.add(dir)

proc newDir(files: seq[(int, string)]): Edir = #proc to help turn any sequence of files into an elf directory
    Edir(files: files)


proc dirSize(dir: Edir): int =
    # This is the proc giving me a lot of headache
    # My plan was for this proc to go through a given directory, add all the file_sizes to the `temp` sequence
    # and return the sum of the values in the `temp` sequence.
    # To do this, I planned to recursively call `dirSize` on any child_directory I found in the parent directory
    # However, when I call the recursive `dirsize` on the `folder` variable on line 42, the compiler complains
    # saying that `folder` is of type <Efile>, instead of it being of type <Edir>.
    #`Similarly, if `temp` was a seq[int], the compiler would complain that `val` was a string meanwhile it isn't.
    var
        #temp: seq[int] ---> when temp was a seq[int]
        temp: seq[string] # This should have been seq[int] but due to similar issues,
                            # I had to use seq[string] as a workaround.
    for fieldName, fieldValue in dir.fieldPairs:
        if fieldName == "files":
            for file in fieldValue:
                for n, val in file.fieldPairs:
                    if n == "fsize":
                        #echo typeof(val) -----> returns int
                        #temp.add(val) ----> complained that `val` was a string (which is not true), and `temp` was a seq[int] (which was true at that moment)
                        temp.add($val) #similar problem was occuring but I was able to solve it by casting val to string,
                            #then mapping over temp and parsing to seq[int] before summation
        else:
            for folder in fieldValue:
                #echo typeof(folder)   #-----> This returns Edir
                #================================================
                temp.add($dirSize(folder)) # -----> Line 51, fails with "type mismatch: got <Efile> instead of <Edir>"
                #================================================

    result = sum temp.mapIt(parseInt(it)) #Just summing the values of `temp`


runnableExamples:
    var root: Edir #make a new elf directory
    root.touchfile((12, "hi")) #add a new file to the root directory
    root.touchfile((14, "hi5"))# add another file to the directory

    root.mkdir(root)#add another directory under root which contains the same thing as root

    echo root.dirSize