Auto merge of #138379 - estebank:macro-backtrace-note, r=petrochenkov

Do not suggest using `-Zmacro-backtrace` for builtin macros

For macros that are implemented on the compiler, or that are annotated with `rustc_diagnostic_item`, which have arbitrary implementations from the point of view of the user and might as well be intrinsics, we do *not* mention the `-Zmacro-backtrace` flag. This includes `derive`s and standard macros like `panic!` and `format!`.

This PR adds a field to every `Span`'s `ExpnData` stating whether it comes from a builtin macro. This is determined by the macro being annotated with either `#[rustc_builtin_macro]` or `#[rustc_diagnostic_item]`. An alternative to using these attributes that already exist for other uses would be to introduce another attribute like `#[rustc_no_backtrace]` to have finer control on which macros are affected (for example, an error within `vec![]` now doesn't mention the backtrace, but one could make the case that it should). Ideally, instead of carrying this information in the `ExpnData` we'd instead try to query the `DefId` of the macro (that is already stored) to see if it is annotated in some way, but we do not have access to the `TyCtxt` from `rustc_errors`.

r? `@petrochenkov`

1 files changed, 10 insertions, 4 deletions

diff --git a/compiler/rustc_errors/src/emitter.rs b/compiler/rustc_errors/src/emitter.rs
index 21255fcca96..fe01e289334 100644
--- a/compiler/rustc_errors/src/emitter.rs
+++ b/compiler/rustc_errors/src/emitter.rs
@@ -297,7 +297,9 @@ pub trait Emitter: Translate {
                     // are some which do actually involve macros.
                     ExpnKind::Desugaring(..) | ExpnKind::AstPass(..) => None,
 
-                    ExpnKind::Macro(macro_kind, name) => Some((macro_kind, name)),
+                    ExpnKind::Macro(macro_kind, name) => {
+                        Some((macro_kind, name, expn_data.hide_backtrace))
+                    }
                 }
             })
             .collect();
@@ -309,13 +311,17 @@ pub trait Emitter: Translate {
         self.render_multispans_macro_backtrace(span, children, backtrace);
 
         if !backtrace {
-            if let Some((macro_kind, name)) = has_macro_spans.first() {
+            // Skip builtin macros, as their expansion isn't relevant to the end user. This includes
+            // actual intrinsics, like `asm!`.
+            if let Some((macro_kind, name, _)) = has_macro_spans.first()
+                && let Some((_, _, false)) = has_macro_spans.last()
+            {
                 // Mark the actual macro this originates from
-                let and_then = if let Some((macro_kind, last_name)) = has_macro_spans.last()
+                let and_then = if let Some((macro_kind, last_name, _)) = has_macro_spans.last()
                     && last_name != name
                 {
                     let descr = macro_kind.descr();
-                    format!(" which comes from the expansion of the {descr} `{last_name}`",)
+                    format!(" which comes from the expansion of the {descr} `{last_name}`")
                 } else {
                     "".to_string()
                 };