dev-check runs clippy with -D warnings against the solutions, which
flagged the nested if let Some(dir_path) = ... { if dir_path.exists() ... }
in file_cleanup as collapsible. Combined into a single if-let with a
let-chain condition (edition = "2024", so this is available).
Verified locally: compiles under --edition 2024, clippy is silent,
and the binary still runs cleanly with file size 117 and no leftover
files.
- file_io3: replace the hardcoded expected file size (117) with
SAMPLE_TEXT.len(), so the check is derived from the actual content
instead of an unexplained magic number.
- file_io3: use create_dir_all instead of create_dir, and add a
sample_file_path() helper shared by main/create_required_files/
file_cleanup to avoid three separate ad-hoc path constructions.
- file_io1/file_io2: hoist the sample text into a SAMPLE_TEXT constant
used by both the exercise and its solution, removing duplicated
literals.
No behavioral change: all three solutions were rebuilt and run
locally, producing identical output (file size still 117, permissions
still non-readonly) with no leftover files.
Adds three new exercises under exercises/24_file_io/, as proposed in rust-lang/rustlings#2233:
- file_io1: read a whole file with fs::read_to_string and handle the Result.
- file_io2: read/write a file efficiently with BufReader/BufWriter.
- file_io3: build a path with PathBuf and inspect it with .metadata().
Includes matching solutions and a README describing the learning goal of
each exercise.
