Auto merge of #75082 - Aaron1011:feature/proc-macro-backtrace, r=petrochenkov

Add `-Z proc-macro-backtrace` to allow showing proc-macro panics

Fixes #75050

Previously, we would unconditionally suppress the panic hook during
proc-macro execution. This commit adds a new flag
`-Z proc-macro-backtrace`, which allows running the panic hook for
easier debugging.

compiler/rustc_expand/src/expand.rs

@@ -1788,6 +1788,7 @@ pub struct ExpansionConfig<'feat> {
     pub should_test: bool, // If false, strip `#[test]` nodes
     pub keep_macs: bool,
     pub span_debug: bool, // If true, use verbose debugging for `proc_macro::Span`
+    pub proc_macro_backtrace: bool, // If true, show backtraces for proc-macro panics
 }
 
 impl<'feat> ExpansionConfig<'feat> {
@@ -1800,6 +1801,7 @@ impl<'feat> ExpansionConfig<'feat> {
             should_test: false,
             keep_macs: false,
             span_debug: false,
+            proc_macro_backtrace: false,
         }
     }
 

compiler/rustc_expand/src/proc_macro.rs

@@ -24,7 +24,7 @@ impl base::ProcMacro for BangProcMacro {
         input: TokenStream,
     ) -> Result<TokenStream, ErrorReported> {
         let server = proc_macro_server::Rustc::new(ecx);
-        self.client.run(&EXEC_STRATEGY, server, input).map_err(|e| {
+        self.client.run(&EXEC_STRATEGY, server, input, ecx.ecfg.proc_macro_backtrace).map_err(|e| {
             let mut err = ecx.struct_span_err(span, "proc macro panicked");
             if let Some(s) = e.as_str() {
                 err.help(&format!("message: {}", s));
@@ -48,14 +48,16 @@ impl base::AttrProcMacro for AttrProcMacro {
         annotated: TokenStream,
     ) -> Result<TokenStream, ErrorReported> {
         let server = proc_macro_server::Rustc::new(ecx);
-        self.client.run(&EXEC_STRATEGY, server, annotation, annotated).map_err(|e| {
-            let mut err = ecx.struct_span_err(span, "custom attribute panicked");
-            if let Some(s) = e.as_str() {
-                err.help(&format!("message: {}", s));
-            }
-            err.emit();
-            ErrorReported
-        })
+        self.client
+            .run(&EXEC_STRATEGY, server, annotation, annotated, ecx.ecfg.proc_macro_backtrace)
+            .map_err(|e| {
+                let mut err = ecx.struct_span_err(span, "custom attribute panicked");
+                if let Some(s) = e.as_str() {
+                    err.help(&format!("message: {}", s));
+                }
+                err.emit();
+                ErrorReported
+            })
     }
 }
 
@@ -111,17 +113,18 @@ impl MultiItemModifier for ProcMacroDerive {
         };
 
         let server = proc_macro_server::Rustc::new(ecx);
-        let stream = match self.client.run(&EXEC_STRATEGY, server, input) {
-            Ok(stream) => stream,
-            Err(e) => {
-                let mut err = ecx.struct_span_err(span, "proc-macro derive panicked");
-                if let Some(s) = e.as_str() {
-                    err.help(&format!("message: {}", s));
+        let stream =
+            match self.client.run(&EXEC_STRATEGY, server, input, ecx.ecfg.proc_macro_backtrace) {
+                Ok(stream) => stream,
+                Err(e) => {
+                    let mut err = ecx.struct_span_err(span, "proc-macro derive panicked");
+                    if let Some(s) = e.as_str() {
+                        err.help(&format!("message: {}", s));
+                    }
+                    err.emit();
+                    return ExpandResult::Ready(vec![]);
                 }
-                err.emit();
-                return ExpandResult::Ready(vec![]);
-            }
-        };
+            };
 
         let error_count_before = ecx.sess.parse_sess.span_diagnostic.err_count();
         let mut parser =

compiler/rustc_interface/src/passes.rs

@@ -291,6 +291,7 @@ fn configure_and_expand_inner<'a>(
             trace_mac: sess.opts.debugging_opts.trace_macros,
             should_test: sess.opts.test,
             span_debug: sess.opts.debugging_opts.span_debug,
+            proc_macro_backtrace: sess.opts.debugging_opts.proc_macro_backtrace,
             ..rustc_expand::expand::ExpansionConfig::default(crate_name.to_string())
         };
 

compiler/rustc_interface/src/tests.rs

@@ -502,6 +502,7 @@ fn test_debugging_options_tracking_hash() {
     untracked!(print_llvm_passes, true);
     untracked!(print_mono_items, Some(String::from("abc")));
     untracked!(print_type_sizes, true);
+    untracked!(proc_macro_backtrace, true);
     untracked!(query_dep_graph, true);
     untracked!(query_stats, true);
     untracked!(save_analysis, true);

compiler/rustc_session/src/options.rs

@@ -967,6 +967,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
         "print the result of the monomorphization collection pass"),
     print_type_sizes: bool = (false, parse_bool, [UNTRACKED],
         "print layout information for each type encountered (default: no)"),
+    proc_macro_backtrace: bool = (false, parse_bool, [UNTRACKED],
+         "show backtraces for panics during proc-macro execution (default: no)"),
     profile: bool = (false, parse_bool, [TRACKED],
         "insert profiling code (default: no)"),
     profile_emit: Option<PathBuf> = (None, parse_opt_pathbuf, [TRACKED],