improve tidy to give you file that failed

the current tidy panics give you no idea why it failed

src/tools/tidy/src/bins.rs

@@ -35,7 +35,7 @@ pub fn check(path: &Path, bad: &mut bool) {
             return
         }
 
-        let metadata = t!(fs::metadata(&file));
+        let metadata = t!(fs::metadata(&file), &file);
         if metadata.mode() & 0o111 != 0 {
             println!("binary checked into source: {}", file.display());
             *bad = true;

src/tools/tidy/src/cargo.rs

@@ -20,7 +20,7 @@ use std::fs::File;
 use std::path::Path;
 
 pub fn check(path: &Path, bad: &mut bool) {
-    for entry in t!(path.read_dir()).map(|e| t!(e)) {
+    for entry in t!(path.read_dir(), path).map(|e| t!(e)) {
         // Look for `Cargo.toml` with a sibling `src/lib.rs` or `lib.rs`
         if entry.file_name().to_str() == Some("Cargo.toml") {
             if path.join("src/lib.rs").is_file() {

src/tools/tidy/src/main.rs

@@ -19,6 +19,11 @@ use std::path::{PathBuf, Path};
 use std::env;
 
 macro_rules! t {
+    ($e:expr, $p:expr) => (match $e {
+        Ok(e) => e,
+        Err(e) => panic!("{} failed on {} with {}", stringify!($e), ($p).display(), e),
+    });
+
     ($e:expr) => (match $e {
         Ok(e) => e,
         Err(e) => panic!("{} failed with {}", stringify!($e), e),
@@ -63,7 +68,7 @@ fn filter_dirs(path: &Path) -> bool {
 
 
 fn walk(path: &Path, skip: &mut FnMut(&Path) -> bool, f: &mut FnMut(&Path)) {
-    for entry in t!(fs::read_dir(path)) {
+    for entry in t!(fs::read_dir(path), path) {
         let entry = t!(entry);
         let kind = t!(entry.file_type());
         let path = entry.path();

src/tools/tidy/src/style.rs

@@ -52,7 +52,7 @@ pub fn check(path: &Path, bad: &mut bool) {
         }
 
         contents.truncate(0);
-        t!(t!(File::open(file)).read_to_string(&mut contents));
+        t!(t!(File::open(file), file).read_to_string(&mut contents));
         let skip_cr = contents.contains("ignore-tidy-cr");
         let skip_tab = contents.contains("ignore-tidy-tab");
         let skip_length = contents.contains("ignore-tidy-linelength");