pretty printing give proper erro message without panic

Author: chenyukang

compiler/rustc_driver/src/pretty.rs

@@ -357,12 +357,16 @@ fn get_source(input: &Input, sess: &Session) -> (String, FileName) {
     (src, src_name)
 }
 
-fn write_or_print(out: &str, ofile: Option<&Path>) {
+fn write_or_print(out: &str, ofile: Option<&Path>, sess: &Session) {
     match ofile {
         None => print!("{}", out),
         Some(p) => {
             if let Err(e) = std::fs::write(p, out) {
-                panic!("print-print failed to write {} due to {}", p.display(), e);
+                let mut err = sess.struct_fatal(&format!(
+                    "pretty-print failed to write {} due to error `{e}`",
+                    p.display()
+                ));
+                err.emit();
             }
         }
     }
@@ -402,7 +406,7 @@ pub fn print_after_parsing(
         _ => unreachable!(),
     };
 
-    write_or_print(&out, ofile);
+    write_or_print(&out, ofile, sess);
 }
 
 pub fn print_after_hir_lowering<'tcx>(
@@ -468,7 +472,7 @@ pub fn print_after_hir_lowering<'tcx>(
         _ => unreachable!(),
     };
 
-    write_or_print(&out, ofile);
+    write_or_print(&out, ofile, tcx.sess);
 }
 
 // In an ideal world, this would be a public function called by the driver after
@@ -512,7 +516,7 @@ fn print_with_analysis(
         _ => unreachable!(),
     };
 
-    write_or_print(&out, ofile);
+    write_or_print(&out, ofile, tcx.sess);
 
     Ok(())
 }