From 9678751a880bc87a9beae7585ace926306a291e6 Mon Sep 17 00:00:00 2001
From: yukang <moorekang@gmail.com>
Date: Mon, 22 Aug 2022 21:45:05 +0800
Subject: [PATCH 1/2] pretty printing give proper erro message without panic

---
 compiler/rustc_driver/src/pretty.rs | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_driver/src/pretty.rs b/compiler/rustc_driver/src/pretty.rs
index f66b1a2976f1c..21a3a077a10c4 100644
--- a/compiler/rustc_driver/src/pretty.rs
+++ b/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(())
 }

From 77eb1aef52c3ec99220347dc56f87911fb3c0198 Mon Sep 17 00:00:00 2001
From: yukang <moorekang@gmail.com>
Date: Tue, 30 Aug 2022 09:31:52 +0800
Subject: [PATCH 2/2] add UI test for unpretty

---
 compiler/rustc_driver/src/pretty.rs                    | 10 +++++-----
 compiler/rustc_driver/src/session_diagnostics.rs       |  7 +++++++
 compiler/rustc_error_messages/locales/en-US/driver.ftl |  2 ++
 src/test/ui/unpretty/avoid-crash.rs                    |  4 ++++
 src/test/ui/unpretty/avoid-crash.stderr                |  4 ++++
 5 files changed, 22 insertions(+), 5 deletions(-)
 create mode 100644 src/test/ui/unpretty/avoid-crash.rs
 create mode 100644 src/test/ui/unpretty/avoid-crash.stderr

diff --git a/compiler/rustc_driver/src/pretty.rs b/compiler/rustc_driver/src/pretty.rs
index 21a3a077a10c4..faeacd3e41040 100644
--- a/compiler/rustc_driver/src/pretty.rs
+++ b/compiler/rustc_driver/src/pretty.rs
@@ -1,5 +1,6 @@
 //! The various pretty-printing routines.
 
+use crate::session_diagnostics::UnprettyDumpFail;
 use rustc_ast as ast;
 use rustc_ast_pretty::pprust;
 use rustc_errors::ErrorGuaranteed;
@@ -362,11 +363,10 @@ fn write_or_print(out: &str, ofile: Option<&Path>, sess: &Session) {
         None => print!("{}", out),
         Some(p) => {
             if let Err(e) = std::fs::write(p, out) {
-                let mut err = sess.struct_fatal(&format!(
-                    "pretty-print failed to write {} due to error `{e}`",
-                    p.display()
-                ));
-                err.emit();
+                sess.emit_fatal(UnprettyDumpFail {
+                    path: p.display().to_string(),
+                    err: e.to_string(),
+                });
             }
         }
     }
diff --git a/compiler/rustc_driver/src/session_diagnostics.rs b/compiler/rustc_driver/src/session_diagnostics.rs
index fe64d0fca9b20..e9696792d051f 100644
--- a/compiler/rustc_driver/src/session_diagnostics.rs
+++ b/compiler/rustc_driver/src/session_diagnostics.rs
@@ -31,3 +31,10 @@ pub(crate) struct RLinkRustcVersionMismatch<'a> {
 #[derive(SessionDiagnostic)]
 #[diag(driver::rlink_no_a_file)]
 pub(crate) struct RlinkNotAFile;
+
+#[derive(SessionDiagnostic)]
+#[diag(driver::unpretty_dump_fail)]
+pub(crate) struct UnprettyDumpFail {
+    pub path: String,
+    pub err: String,
+}
diff --git a/compiler/rustc_error_messages/locales/en-US/driver.ftl b/compiler/rustc_error_messages/locales/en-US/driver.ftl
index 73f084cf3290b..8ad198c86c933 100644
--- a/compiler/rustc_error_messages/locales/en-US/driver.ftl
+++ b/compiler/rustc_error_messages/locales/en-US/driver.ftl
@@ -9,3 +9,5 @@ driver_rlink_encoding_version_mismatch = .rlink file was produced with encoding
 driver_rlink_rustc_version_mismatch = .rlink file was produced by rustc version `{$rustc_version}`, but the current version is `{$current_version}`
 
 driver_rlink_no_a_file = rlink must be a file
+
+driver_unpretty_dump_fail = pretty-print failed to write `{$path}` due to error `{$err}`
diff --git a/src/test/ui/unpretty/avoid-crash.rs b/src/test/ui/unpretty/avoid-crash.rs
new file mode 100644
index 0000000000000..fd84b70d944ca
--- /dev/null
+++ b/src/test/ui/unpretty/avoid-crash.rs
@@ -0,0 +1,4 @@
+// normalize-stderr-test "error `.*`" -> "$$ERROR_MESSAGE"
+// compile-flags: -o/tmp/ -Zunpretty=ast-tree
+
+fn main() {}
diff --git a/src/test/ui/unpretty/avoid-crash.stderr b/src/test/ui/unpretty/avoid-crash.stderr
new file mode 100644
index 0000000000000..11cd3866fa869
--- /dev/null
+++ b/src/test/ui/unpretty/avoid-crash.stderr
@@ -0,0 +1,4 @@
+error: pretty-print failed to write `/tmp/` due to $ERROR_MESSAGE
+
+error: aborting due to previous error
+