Auto merge of rust-lang#138379 - estebank:macro-backtrace-note, r=<try>

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`

Author: bors

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.builtin_macro))
+                    }
                 }
             })
             .collect();
@@ -309,13 +311,18 @@ 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!`, as well as macros by example, like `println!`, which
+            // might as well be an intrinsic as far as the user is concerned.
+            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()
                 };

compiler/rustc_expand/src/base.rs

@@ -757,6 +757,11 @@ pub struct SyntaxExtension {
     /// Built-in macros have a couple of special properties like availability
     /// in `#[no_implicit_prelude]` modules, so we have to keep this flag.
     pub builtin_name: Option<Symbol>,
+    /// Whether this macro is either a compiler intrinsic (implied by the above field) or a macro
+    /// provided by the standard library where the specific of its implementation are not relevant
+    /// to the end user, like for `format!` or `println!`, which are normal macros by example, but
+    /// that is an implementation detail.
+    pub builtin: bool,
     /// Suppresses the `unsafe_code` lint for code produced by this macro.
     pub allow_internal_unsafe: bool,
     /// Enables the macro helper hack (`ident!(...)` -> `$crate::ident!(...)`) for this macro.
@@ -792,6 +797,7 @@ impl SyntaxExtension {
             helper_attrs: Vec::new(),
             edition,
             builtin_name: None,
+            builtin: false,
             kind,
             allow_internal_unsafe: false,
             local_inner_macros: false,
@@ -888,17 +894,19 @@ impl SyntaxExtension {
                 )
             })
             .unwrap_or_else(|| (None, helper_attrs));
+        let builtin = builtin_name.is_some()
+            || ast::attr::find_by_name(attrs, sym::rustc_diagnostic_item).is_some();
 
-        let stability = find_attr!(attrs, AttributeKind::Stability{stability, ..} => *stability);
+        let stability = find_attr!(attrs, AttributeKind::Stability { stability, .. } => *stability);
 
         // FIXME(jdonszelmann): make it impossible to miss the or_else in the typesystem
-        if let Some(sp) = find_attr!(attrs, AttributeKind::ConstStability{span, ..} => *span) {
+        if let Some(sp) = find_attr!(attrs, AttributeKind::ConstStability { span, .. } => *span) {
             sess.dcx().emit_err(errors::MacroConstStability {
                 span: sp,
                 head_span: sess.source_map().guess_head_span(span),
             });
         }
-        if let Some(sp) = find_attr!(attrs, AttributeKind::BodyStability{span, ..} => *span) {
+        if let Some(sp) = find_attr!(attrs, AttributeKind::BodyStability{ span, .. } => *span) {
             sess.dcx().emit_err(errors::MacroBodyStability {
                 span: sp,
                 head_span: sess.source_map().guess_head_span(span),
@@ -912,10 +920,14 @@ impl SyntaxExtension {
                 // FIXME(jdonszelmann): avoid the into_iter/collect?
                 .then(|| allow_internal_unstable.iter().map(|i| i.0).collect::<Vec<_>>().into()),
             stability,
-            deprecation: find_attr!(attrs, AttributeKind::Deprecation{deprecation, ..} => *deprecation),
+            deprecation: find_attr!(
+                attrs,
+                AttributeKind::Deprecation { deprecation, .. } => *deprecation
+            ),
             helper_attrs,
             edition,
             builtin_name,
+            builtin,
             allow_internal_unsafe,
             local_inner_macros,
             collapse_debuginfo,
@@ -1000,6 +1012,7 @@ impl SyntaxExtension {
             self.allow_internal_unsafe,
             self.local_inner_macros,
             self.collapse_debuginfo,
+            self.builtin,
         )
     }
 }

compiler/rustc_span/src/hygiene.rs

@@ -982,6 +982,11 @@ pub struct ExpnData {
     /// Should debuginfo for the macro be collapsed to the outermost expansion site (in other
     /// words, was the macro definition annotated with `#[collapse_debuginfo]`)?
     pub(crate) collapse_debuginfo: bool,
+    /// Whether this macro expansion came from a compiler implemented macro (`rustc_builtin_macro`)
+    /// or a macro by example provided by the standard library (marked with
+    /// `rustc_diagnostic_item`). If this is true, then we do not display the standard note telling
+    /// people to use the `-Zmacro-backtrace` flag.
+    pub builtin_macro: bool,
 }
 
 impl !PartialEq for ExpnData {}
@@ -1000,6 +1005,7 @@ impl ExpnData {
         allow_internal_unsafe: bool,
         local_inner_macros: bool,
         collapse_debuginfo: bool,
+        builtin_macro: bool,
     ) -> ExpnData {
         ExpnData {
             kind,
@@ -1014,6 +1020,7 @@ impl ExpnData {
             allow_internal_unsafe,
             local_inner_macros,
             collapse_debuginfo,
+            builtin_macro,
         }
     }
 
@@ -1038,6 +1045,7 @@ impl ExpnData {
             allow_internal_unsafe: false,
             local_inner_macros: false,
             collapse_debuginfo: false,
+            builtin_macro: false,
         }
     }
 

src/tools/clippy/tests/ui/derive_ord_xor_partial_ord.stderr

@@ -11,7 +11,6 @@ LL | impl PartialOrd for DeriveOrd {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: `-D clippy::derive-ord-xor-partial-ord` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::derive_ord_xor_partial_ord)]`
-   = note: this error originates in the derive macro `Ord` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: you are deriving `Ord` but have implemented `PartialOrd` explicitly
   --> tests/ui/derive_ord_xor_partial_ord.rs:33:10
@@ -24,7 +23,6 @@ note: `PartialOrd` implemented here
    |
 LL | impl PartialOrd<DeriveOrdWithExplicitTypeVariable> for DeriveOrdWithExplicitTypeVariable {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: this error originates in the derive macro `Ord` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: you are implementing `Ord` explicitly but have derived `PartialOrd`
   --> tests/ui/derive_ord_xor_partial_ord.rs:47:1
@@ -42,7 +40,6 @@ note: `PartialOrd` implemented here
    |
 LL | #[derive(PartialOrd, PartialEq, Eq)]
    |          ^^^^^^^^^^
-   = note: this error originates in the derive macro `PartialOrd` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: you are implementing `Ord` explicitly but have derived `PartialOrd`
   --> tests/ui/derive_ord_xor_partial_ord.rs:69:5
@@ -60,7 +57,6 @@ note: `PartialOrd` implemented here
    |
 LL |     #[derive(PartialOrd, PartialEq, Eq)]
    |              ^^^^^^^^^^
-   = note: this error originates in the derive macro `PartialOrd` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 4 previous errors
 

src/tools/clippy/tests/ui/derived_hash_with_manual_eq.stderr

@@ -10,7 +10,6 @@ note: `PartialEq` implemented here
 LL | impl PartialEq for Bar {
    | ^^^^^^^^^^^^^^^^^^^^^^
    = note: `#[deny(clippy::derived_hash_with_manual_eq)]` on by default
-   = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: you are deriving `Hash` but have implemented `PartialEq` explicitly
   --> tests/ui/derived_hash_with_manual_eq.rs:23:10
@@ -23,7 +22,6 @@ note: `PartialEq` implemented here
    |
 LL | impl PartialEq<Baz> for Baz {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
 

src/tools/clippy/tests/ui/diverging_sub_expression.stderr

@@ -36,8 +36,6 @@ error: sub-expression diverges
    |
 LL |                 _ => true || panic!("boo"),
    |                              ^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: sub-expression diverges
   --> tests/ui/diverging_sub_expression.rs:52:29

src/tools/clippy/tests/ui/fallible_impl_from.stderr

@@ -38,7 +38,6 @@ note: potential failure(s)
    |
 LL |             panic!();
    |             ^^^^^^^^
-   = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: consider implementing `TryFrom` instead
   --> tests/ui/fallible_impl_from.rs:40:1
@@ -64,7 +63,6 @@ LL |         } else if s.parse::<u32>().unwrap() != 42 {
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |             panic!("{:?}", s);
    |             ^^^^^^^^^^^^^^^^^
-   = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: consider implementing `TryFrom` instead
   --> tests/ui/fallible_impl_from.rs:60:1
@@ -85,7 +83,6 @@ LL |         if s.parse::<u32>().ok().unwrap() != 42 {
    |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 LL |             panic!("{:?}", s);
    |             ^^^^^^^^^^^^^^^^^
-   = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 4 previous errors
 

src/tools/clippy/tests/ui/impl_hash_with_borrow_str_and_bytes.stderr

@@ -23,7 +23,6 @@ LL | #[derive(Hash)]
    = note: ... as (`hash("abc") != hash("abc".as_bytes())`
    = help: consider either removing one of the  `Borrow` implementations (`Borrow<str>` or `Borrow<[u8]>`) ...
    = help: ... or not implementing `Hash` for this type
-   = note: this error originates in the derive macro `Hash` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: the semantics of `Borrow<T>` around `Hash` can't be satisfied when both `Borrow<str>` and `Borrow<[u8]>` are implemented
   --> tests/ui/impl_hash_with_borrow_str_and_bytes.rs:117:6

src/tools/clippy/tests/ui/issue-7447.stderr

@@ -6,15 +6,12 @@ LL |     byte_view(panic!());
    |
    = note: `-D clippy::diverging-sub-expression` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::diverging_sub_expression)]`
-   = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: sub-expression diverges
   --> tests/ui/issue-7447.rs:29:19
    |
 LL |     group_entries(panic!());
    |                   ^^^^^^^^
-   |
-   = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
 

src/tools/clippy/tests/ui/recursive_format_impl.stderr

@@ -12,72 +12,54 @@ error: using `self` as `Display` in `impl Display` will cause infinite recursion
    |
 LL |         write!(f, "{}", self)
    |         ^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: using `self` as `Display` in `impl Display` will cause infinite recursion
   --> tests/ui/recursive_format_impl.rs:86:9
    |
 LL |         write!(f, "{}", &self)
    |         ^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: using `self` as `Debug` in `impl Debug` will cause infinite recursion
   --> tests/ui/recursive_format_impl.rs:93:9
    |
 LL |         write!(f, "{:?}", &self)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: using `self` as `Display` in `impl Display` will cause infinite recursion
   --> tests/ui/recursive_format_impl.rs:103:9
    |
 LL |         write!(f, "{}", &&&self)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: using `self` as `Display` in `impl Display` will cause infinite recursion
   --> tests/ui/recursive_format_impl.rs:178:9
    |
 LL |         write!(f, "{}", &*self)
    |         ^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: using `self` as `Debug` in `impl Debug` will cause infinite recursion
   --> tests/ui/recursive_format_impl.rs:185:9
    |
 LL |         write!(f, "{:?}", &*self)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: using `self` as `Display` in `impl Display` will cause infinite recursion
   --> tests/ui/recursive_format_impl.rs:202:9
    |
 LL |         write!(f, "{}", *self)
    |         ^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: using `self` as `Display` in `impl Display` will cause infinite recursion
   --> tests/ui/recursive_format_impl.rs:219:9
    |
 LL |         write!(f, "{}", **&&*self)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: using `self` as `Display` in `impl Display` will cause infinite recursion
   --> tests/ui/recursive_format_impl.rs:236:9
    |
 LL |         write!(f, "{}", &&**&&*self)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `write` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 10 previous errors