filterIt not working

grade_school.nim

import unittest

import algorithm, sequtils

type
  Student* = tuple[name: string, grade: int]
  School* = object
    students*: seq[Student]

proc roster*(s: School): seq[string] =
  s.students
    .sortedByIt((it.grade, it.name))
    .mapIt(it.name)

proc grade*(s: School, g: int): seq[string] =
  s.students
    .filter(proc(i: Student): bool = i.grade == g)
    .sortedByIt((it.grade, it.name))
    .mapIt(it.name)
  # Doesn't work - s.students.filterIt(it.grade == g).sortedByIt((it.grade, it.name)).mapIt(it.name)

# Given students' names along with the grade that they are in,
# create a roster for the school.

suite "Grade School":

  test "Adding a student adds them to the sorted roster":
    let school = School(students: @[("Aimee", 2)])

    check school.roster() == @["Aimee"]

  test "Adding more student adds them to the sorted roster":
    let school = School(students: @[("Blair", 2), ("James", 2), ("Paul", 2)])

    check school.roster() == @["Blair", "James", "Paul"]

  test "Adding students to different grades adds them to the same sorted roster":
    let school = School(students: @[("Chelsea", 3), ("Logan", 7)])
    
    check school.roster() == @["Chelsea", "Logan"]

  test "Roster returns an empty list if there are no students enrolled":
    let school = School(students: @[])
    let expected: seq[string] = @[]

    check school.roster() == expected


  test "Student names with grades are displayed in the same sorted roster":
    let school = School(students: @[
      ("Peter", 2),
      ("Anna", 1),
      ("Barb", 1),
      ("Zoe", 2),
      ("Alex", 2),
      ("Jim", 3),
      ("Charlie", 1)
    ])
  
    check school.roster() == @["Anna", "Barb", "Charlie", "Alex", "Peter", "Zoe", "Jim"]

  test "Grade returns the students in that grade in alphabetical order":
    let school = School(students: @[("Franklin", 5), ("Bradley", 5), ("Jeff", 1)])
  
    check school.grade(5) == @["Bradley", "Franklin"]

  test "Grade returns an empty list if there are no students in that grade":
    let school = School(students: @[])
    let expected: seq[string] = @[]

    check school.grade(1) == expected

Logs from the build,

nimble build --verbose
Setting Nim stdlib prefix to
Setting Nim stdlib path to /Users/ascotti/.choosenim/toolchains/nim-0.18.0/lib
Verifying dependencies for grade_school@0.1.0
Building grade_school/grade_school using c backend
Error: Build failed for package: grade_school
... Details:
... Execution failed with exit code 1
... Command: "/Users/ascotti/.nimble/bin/nim" c --noBabelPath -o:"/Users/ascotti/Documents/code/nim/grade_school/grade_school" "/Users/ascotti/Documents/code/nim/grade_school/src/grade_school.nim"
... Output: Hint: used config file '/Users/ascotti/.choosenim/toolchains/nim-0.18.0/config/nim.cfg' [Conf]
... Hint: system [Processing]
... Hint: grade_school [Processing]
... Hint: unittest [Processing]
... Hint: macros [Processing]
... Hint: strutils [Processing]
... Hint: parseutils [Processing]
... Hint: math [Processing]
... Hint: algorithm [Processing]
... Hint: streams [Processing]
... Hint: times [Processing]
... Hint: posix [Processing]
... Hint: sets [Processing]
... Hint: hashes [Processing]
... Hint: os [Processing]
... Hint: ospaths [Processing]
... Hint: terminal [Processing]
... Hint: strformat [Processing]
... Hint: unicode [Processing]
... Hint: colors [Processing]
... Hint: tables [Processing]
... Hint: termios [Processing]
... Hint: sequtils [Processing]
... lib/pure/collections/sequtils.nim(398, 7) Error: internal error: environment misses: result