chain source errors

Author: DebugSteven

library/core/src/panicking.rs

@@ -62,7 +62,7 @@ pub const fn panic_fmt(fmt: fmt::Arguments<'_>) -> ! {
 #[track_caller]
 #[rustc_do_not_const_check] // hooked by const-eval
 #[rustc_const_unstable(feature = "core_panic", issue = "none")]
-pub const fn panic_source(fmt: fmt::Arguments<'_>, source: Option<& (dyn Error + 'static)>) -> ! {
+pub const fn panic_source(fmt: fmt::Arguments<'_>, source: Option<&(dyn Error + 'static)>) -> ! {
     if cfg!(feature = "panic_immediate_abort") {
         super::intrinsics::abort()
     }

library/std/src/panicking.rs

@@ -13,7 +13,7 @@ use crate::panic::BacktraceStyle;
 use core::panic::{BoxMeUp, Location, PanicInfo};
 
 use crate::any::Any;
-use crate::error::Error;
+use crate::error::{Error, Report};
 use crate::fmt;
 use crate::intrinsics;
 use crate::mem::{self, ManuallyDrop};
@@ -259,8 +259,9 @@ fn default_hook(info: &PanicInfo<'_>) {
 
     let write = |err: &mut dyn crate::io::Write| {
         let _ = writeln!(err, "thread '{name}' panicked at '{msg}', {location}");
-        if info.source().is_some() {
-            writeln!(err, "fun is not allowed");
+        if let Some(source) = info.source() {
+            let report = Report::new(source).pretty(true);
+            let _ = writeln!(err, "Source: {report}");
         }
         static FIRST_PANIC: AtomicBool = AtomicBool::new(true);
 
@@ -581,7 +582,13 @@ pub fn begin_panic_handler(info: &PanicInfo<'_>) -> ! {
     let msg = info.message().unwrap(); // The current implementation always returns Some
     crate::sys_common::backtrace::__rust_end_short_backtrace(move || {
         if let Some(msg) = msg.as_str() {
-            rust_panic_with_hook(&mut StrPanicPayload(msg), info.message(), loc, source, info.can_unwind());
+            rust_panic_with_hook(
+                &mut StrPanicPayload(msg),
+                info.message(),
+                loc,
+                source,
+                info.can_unwind(),
+            );
         } else {
             rust_panic_with_hook(
                 &mut PanicPayload::new(msg),
@@ -658,7 +665,7 @@ fn rust_panic_with_hook(
     payload: &mut dyn BoxMeUp,
     message: Option<&fmt::Arguments<'_>>,
     location: &Location<'_>,
-    source: Option<& (dyn Error + 'static)>,
+    source: Option<&(dyn Error + 'static)>,
     can_unwind: bool,
 ) -> ! {
     let (must_abort, panics) = panic_count::increase();

src/test/ui/error-trait/error-in-panic.rs

@@ -10,8 +10,15 @@ extern crate core;
 use core::panicking::panic_source;
 use core::error;
 
+use std::error::Error;
+
+#[derive (Debug)]
+struct MyErr {
+    super_source: SourceError,
+}
+
 #[derive (Debug)]
-struct MyErr;
+struct SourceError {}
 
 use std::fmt;
 impl fmt::Display for MyErr {
@@ -21,12 +28,25 @@ impl fmt::Display for MyErr {
 }
 
 impl error::Error for MyErr {
+    fn source(&self) -> Option<& (dyn Error + 'static)> {
+        Some(&self.super_source)
+    }
+}
+
+impl fmt::Display for SourceError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), std::fmt::Error> {
+        write!(f, "my source's source error message")
+    }
+}
+
+impl error::Error for SourceError {
 
 }
 
 fn main() {
     std::env::set_var("RUST_BACKTRACE", "full");
-    let source = MyErr;
+    let source_error = SourceError {};
+    let source = MyErr {super_source: source_error};
     //FIXME make the function do the Some wrapping for us
     panic_source(format_args!("here's my panic error message"), Some(&source));
 

src/test/ui/error-trait/error-in-panic.run.stderr

@@ -0,0 +1,25 @@
+thread 'main' panicked at 'here's my panic error message', $DIR/error-in-panic.rs:51:5
+Source: my source error message
+
+Caused by:
+      my source's source error message
+stack backtrace:
+   0:        0x10347e5cc - <std::sys_common::backtrace::_print::DisplayBacktrace as core::fmt::Display>::fmt::h739002e9033ecbde
+   1:        0x1034c1ef4 - core::fmt::write::h7ee3c88f1a3812c3
+   2:        0x103467ad8 - std::io::Write::write_fmt::h46e675c7a43a1dc6
+   3:        0x10347e494 - std::sys_common::backtrace::print::h2db63c69899aa986
+   4:        0x103441588 - std::panicking::default_hook::{{closure}}::hbf1cbfed6089b966
+   5:        0x103441348 - std::panicking::default_hook::h394fc36f8066489c
+   6:        0x103441a3c - std::panicking::rust_panic_with_hook::h022616bb2ba4e178
+   7:        0x10344907c - std::panicking::begin_panic_handler::{{closure}}::h3128246bc073fcbe
+   8:        0x103448fdc - std::sys_common::backtrace::__rust_end_short_backtrace::hbb524939a68ed8b5
+   9:        0x103441660 - _rust_begin_unwind
+  10:        0x1034dd910 - core::panicking::panic_source::hf14287b3ee2e7392
+  11:        0x102aeb728 - error_in_panic::main::hf4bbb2ae489ce4fd
+  12:        0x102aeb404 - core::ops::function::FnOnce::call_once::h0f54538c8c239b20
+  13:        0x102aeafd8 - std::sys_common::backtrace::__rust_begin_short_backtrace::h2b8f58dd23d62fa6
+  14:        0x102aeb074 - std::rt::lang_start::{{closure}}::h6d7fe7ddaa109f16
+  15:        0x10344478c - std::panicking::try::h0286e30fd7b2d786
+  16:        0x103452248 - std::rt::lang_start_internal::hc2ec5a7105141124
+  17:        0x102aeb048 - std::rt::lang_start::h8ea75b901d46518a
+  18:        0x102aeb7f0 - _main