Add context to i/o errors
diff --git a/gen/src/fs.rs b/gen/src/fs.rs
new file mode 100644
index 0000000..6ad92f8
--- /dev/null
+++ b/gen/src/fs.rs
@@ -0,0 +1,121 @@
+#![allow(dead_code)]
+
+use std::error::Error as StdError;
+use std::fmt::{self, Display};
+use std::io;
+use std::path::{Path, PathBuf};
+
+type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug)]
+pub(crate) struct Error {
+    source: io::Error,
+    message: String,
+}
+
+impl Display for Error {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str(&self.message)
+    }
+}
+
+impl StdError for Error {
+    fn source(&self) -> Option<&(dyn StdError + 'static)> {
+        Some(&self.source)
+    }
+}
+
+macro_rules! err {
+    ($io_error:expr, $fmt:expr $(, $path:expr)* $(,)?) => {
+        Err(Error {
+            source: $io_error,
+            message: format!($fmt $(, $path.display())*),
+        })
+    }
+}
+
+pub(crate) fn canonicalize(path: impl AsRef<Path>) -> Result<PathBuf> {
+    let path = path.as_ref();
+    match std::fs::canonicalize(path) {
+        Ok(string) => Ok(string),
+        Err(e) => err!(e, "Unable to canonicalize path: `{}`", path),
+    }
+}
+
+pub(crate) fn copy(from: impl AsRef<Path>, to: impl AsRef<Path>) -> Result<u64> {
+    let from = from.as_ref();
+    let to = to.as_ref();
+    match std::fs::copy(from, to) {
+        Ok(n) => Ok(n),
+        Err(e) => err!(e, "Failed to copy `{}` -> `{}`", from, to),
+    }
+}
+
+pub(crate) fn create_dir_all(path: impl AsRef<Path>) -> Result<()> {
+    let path = path.as_ref();
+    match std::fs::create_dir_all(path) {
+        Ok(()) => Ok(()),
+        Err(e) => err!(e, "Failed to create directory `{}`", path),
+    }
+}
+
+pub(crate) fn current_dir() -> Result<PathBuf> {
+    match std::env::current_dir() {
+        Ok(dir) => Ok(dir),
+        Err(e) => err!(e, "Failed to determine current directory"),
+    }
+}
+
+pub(crate) fn read_to_string(path: impl AsRef<Path>) -> Result<String> {
+    let path = path.as_ref();
+    match std::fs::read_to_string(path) {
+        Ok(string) => Ok(string),
+        Err(e) => err!(e, "Failed to read file `{}`", path),
+    }
+}
+
+pub(crate) fn remove_file(path: impl AsRef<Path>) -> Result<()> {
+    let path = path.as_ref();
+    match std::fs::remove_file(path) {
+        Ok(()) => Ok(()),
+        Err(e) => err!(e, "Failed to remove file `{}`", path),
+    }
+}
+
+#[cfg(unix)]
+pub(crate) fn symlink(src: impl AsRef<Path>, dst: impl AsRef<Path>) -> Result<()> {
+    let src = src.as_ref();
+    let dst = dst.as_ref();
+    match std::os::unix::fs::symlink(src, dst) {
+        Ok(()) => Ok(()),
+        Err(e) => err!(
+            e,
+            "Failed to create symlink `{}` pointing to `{}`",
+            dst,
+            src,
+        ),
+    }
+}
+
+#[cfg(windows)]
+pub(crate) fn symlink_file(src: impl AsRef<Path>, dst: impl AsRef<Path>) -> Result<()> {
+    let src = src.as_ref();
+    let dst = dst.as_ref();
+    match std::os::windows::fs::symlink_file(src, dst) {
+        Ok(()) => Ok(()),
+        Err(e) => err!(
+            e,
+            "Failed to create symlink `{}` pointing to `{}`",
+            dst,
+            src,
+        ),
+    }
+}
+
+pub(crate) fn write(path: impl AsRef<Path>, contents: impl AsRef<[u8]>) -> Result<()> {
+    let path = path.as_ref();
+    match std::fs::write(path, contents) {
+        Ok(()) => Ok(()),
+        Err(e) => err!(e, "Failed to write file `{}`", path),
+    }
+}