Use the default hasher

src/app_state.rs

@@ -1,6 +1,7 @@
 use anyhow::{bail, Context, Error, Result};
 use crossterm::{cursor, terminal, QueueableCommand};
 use std::{
+    collections::HashSet,
     env,
     fs::{File, OpenOptions},
     io::{Read, Seek, StdoutLock, Write},
@@ -16,7 +17,6 @@ use std::{
 use crate::{
     clear_terminal,
     cmd::CmdRunner,
-    collections::hash_set_with_capacity,
     embedded::EMBEDDED_FILES,
     exercise::{Exercise, RunnableExercise},
     info_file::ExerciseInfo,
@@ -146,7 +146,7 @@ impl AppState {
                 break 'block StateFileStatus::NotRead;
             }
 
-            let mut done_exercises = hash_set_with_capacity(exercises.len());
+            let mut done_exercises = HashSet::with_capacity(exercises.len());
 
             for done_exercise_name in lines {
                 if done_exercise_name.is_empty() {

src/collections.rs

@@ -1,9 +0,0 @@
-use foldhash::fast::FixedState;
-
-/// DOS attacks aren't a concern for Rustlings. Therefore, we use `foldhash` with a fixed state.
-pub type HashSet<T> = std::collections::HashSet<T, FixedState>;
-
-#[inline]
-pub fn hash_set_with_capacity<T>(capacity: usize) -> HashSet<T> {
-    HashSet::with_capacity_and_hasher(capacity, FixedState::default())
-}

src/dev/check.rs

@@ -1,6 +1,7 @@
 use anyhow::{anyhow, bail, Context, Error, Result};
 use std::{
     cmp::Ordering,
+    collections::HashSet,
     fs::{self, read_dir, OpenOptions},
     io::{self, Read, Write},
     path::{Path, PathBuf},
@@ -11,7 +12,6 @@ use std::{
 use crate::{
     cargo_toml::{append_bins, bins_start_end_ind, BINS_BUFFER_CAPACITY},
     cmd::CmdRunner,
-    collections::{hash_set_with_capacity, HashSet},
     exercise::{RunnableExercise, OUTPUT_CAPACITY},
     info_file::{ExerciseInfo, InfoFile},
     CURRENT_FORMAT_VERSION,
@@ -53,8 +53,8 @@ fn check_cargo_toml(
 
 // Check the info of all exercises and return their paths in a set.
 fn check_info_file_exercises(info_file: &InfoFile) -> Result<HashSet<PathBuf>> {
-    let mut names = hash_set_with_capacity(info_file.exercises.len());
-    let mut paths = hash_set_with_capacity(info_file.exercises.len());
+    let mut names = HashSet::with_capacity(info_file.exercises.len());
+    let mut paths = HashSet::with_capacity(info_file.exercises.len());
 
     let mut file_buf = String::with_capacity(1 << 14);
     for exercise_info in &info_file.exercises {
@@ -282,7 +282,7 @@ fn check_solutions(
         .collect::<Result<Vec<_>, _>>()
         .context("Failed to spawn a thread to check a solution")?;
 
-    let mut sol_paths = hash_set_with_capacity(info_file.exercises.len());
+    let mut sol_paths = HashSet::with_capacity(info_file.exercises.len());
     let mut fmt_cmd = Command::new("rustfmt");
     fmt_cmd
         .arg("--check")

src/main.rs

@@ -13,7 +13,6 @@ use self::{app_state::AppState, dev::DevCommands, info_file::InfoFile};
 mod app_state;
 mod cargo_toml;
 mod cmd;
-mod collections;
 mod dev;
 mod embedded;
 mod exercise;