[DEV-7084] TAMER: fs: impl File for BufReader

This further simplifies the POC linker.

tamer/src/fs.rs

@@ -41,7 +41,7 @@ use std::collections::HashSet;
 use std::ffi::OsString;
 use std::fs;
 use std::hash::BuildHasher;
-use std::io::Result;
+use std::io::{BufReader, Read, Result};
 use std::path::{Path, PathBuf};
 
 /// A file.
@@ -58,6 +58,13 @@ impl File for fs::File {
     }
 }
 
+impl<F: File + Read> File for BufReader<F> {
+    /// Open the file at `path` and construct a [`BufReader`] from it.
+    fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
+        Ok(BufReader::new(F::open(path)?))
+    }
+}
+
 pub struct CanonicalFile<F: File>(PathBuf, F);
 
 impl<F: File> Into<(PathBuf, F)> for CanonicalFile<F> {
@@ -178,6 +185,20 @@ mod test {
         }
     }
 
+    impl Read for DummyFile {
+        fn read(&mut self, _buf: &mut [u8]) -> Result<usize> {
+            Ok(0)
+        }
+    }
+
+    #[test]
+    fn buf_reader_file() {
+        let path: PathBuf = "buf/path".into();
+        let result: BufReader<DummyFile> = File::open(path.clone()).unwrap();
+
+        assert_eq!(DummyFile(path), result.into_inner());
+    }
+
     #[test]
     fn vist_once() {
         let mut fs = VisitOnceFilesystem::<RandomState>::new();

tamer/src/ld/poc.rs

@@ -133,15 +133,14 @@ fn load_xmlo<'a, 'i, I: Interner<'i>>(
 
     let mut found: FxHashSet<&str> = Default::default();
 
-    let cfile: CanonicalFile<fs::File> = match fs.open(path_str)? {
+    let cfile: CanonicalFile<BufReader<fs::File>> = match fs.open(path_str)? {
         VisitOnceFile::FirstVisit(file) => file,
         VisitOnceFile::Visited => return Ok(None),
     };
 
     let (path, file) = cfile.into();
 
-    let reader = BufReader::new(file);
-    let mut xmlo: XmloReader<'_, _, _> = (reader, interner).into();
+    let mut xmlo: XmloReader<'_, _, _> = (file, interner).into();
     let mut elig = None;
 
     let mut name: Option<&'i Symbol<'i>> = None;