diagnostics: hide expansion of builtin-like macros

Author: mejrs

compiler/rustc_errors/src/emitter.rs

@@ -24,7 +24,7 @@ use rustc_lexer;
 use rustc_lint_defs::pluralize;
 use rustc_span::hygiene::{ExpnKind, MacroKind};
 use rustc_span::source_map::SourceMap;
-use rustc_span::{FileLines, FileName, SourceFile, Span, char_width, str_width};
+use rustc_span::{FileLines, FileName, SourceFile, Span, char_width, str_width, sym};
 use termcolor::{Buffer, BufferWriter, Color, ColorChoice, ColorSpec, StandardStream, WriteColor};
 use tracing::{debug, instrument, trace, warn};
 
@@ -298,7 +298,17 @@ pub trait Emitter: Translate {
                     ExpnKind::Desugaring(..) | ExpnKind::AstPass(..) => None,
 
                     ExpnKind::Macro(macro_kind, name) => {
-                        Some((macro_kind, name, expn_data.hide_backtrace))
+                        // Don't recommend using `-Zmacro-backtrace` if
+                        // - hide_backtrace is true, which it is for builtin macros
+                        // - if the macro uses internal features so their expansion is unlikely to be useful
+                        let hide_macro_backtrace_suggestion = expn_data.hide_backtrace
+                            || expn_data.allow_internal_unstable.is_some_and(|aiu| {
+                                aiu.contains(&sym::fmt_internals)
+                                    || aiu.contains(&sym::print_internals)
+                                    || aiu.contains(&sym::liballoc_internals)
+                            });
+
+                        Some((macro_kind, name, hide_macro_backtrace_suggestion))
                     }
                 }
             })
@@ -311,8 +321,9 @@ pub trait Emitter: Translate {
         self.render_multispans_macro_backtrace(span, children, backtrace);
 
         if !backtrace {
-            // Skip builtin macros, as their expansion isn't relevant to the end user. This includes
-            // actual intrinsics, like `asm!`.
+            // Skip some special macros, as their expansion isn't relevant to the end user.
+            // This includes actual intrinsics and builtins like `asm!`, as well as macros
+            // that contain implementation details like the formatting macros
             if let Some((macro_kind, name, _)) = has_macro_spans.first()
                 && let Some((_, _, false)) = has_macro_spans.last()
             {

compiler/rustc_span/src/symbol.rs

@@ -1007,6 +1007,7 @@ symbols! {
         fmaf64,
         fmt,
         fmt_debug,
+        fmt_internals,
         fmul_algebraic,
         fmul_fast,
         fmuladdf128,
@@ -1240,6 +1241,7 @@ symbols! {
         let_else,
         lhs,
         lib,
+        liballoc_internals,
         libc,
         lifetime,
         lifetime_capture_rules_2024,
@@ -1623,6 +1625,7 @@ symbols! {
         prelude_import,
         preserves_flags,
         prfchw_target_feature,
+        print_internals,
         print_macro,
         println_macro,
         proc_dash_macro: "proc-macro",

src/tools/miri/tests/fail/dangling_pointers/out_of_bounds_read.stderr

@@ -13,7 +13,6 @@ LL |     let v: Vec<u16> = vec![1, 2];
    |                       ^^^^^^^^^^
    = note: BACKTRACE (of the first span):
    = note: inside `main` at tests/fail/dangling_pointers/out_of_bounds_read.rs:LL:CC
-   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

src/tools/miri/tests/fail/dangling_pointers/out_of_bounds_write.stderr

@@ -13,7 +13,6 @@ LL |     let mut v: Vec<u16> = vec![1, 2];
    |                           ^^^^^^^^^^
    = note: BACKTRACE (of the first span):
    = note: inside `main` at tests/fail/dangling_pointers/out_of_bounds_write.rs:LL:CC
-   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

src/tools/miri/tests/fail/erroneous_const2.stderr

@@ -23,8 +23,6 @@ note: erroneous constant encountered
    |
 LL |     println!("{}", FOO);
    |                    ^^^
-   |
-   = note: this note originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 1 previous error
 

src/tools/miri/tests/fail/intrinsics/simd-scatter.stderr

@@ -18,7 +18,6 @@ LL |         let mut vec: Vec<i8> = vec![10, 11, 12, 13, 14, 15, 16, 17, 18];
    |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: BACKTRACE (of the first span):
    = note: inside `main` at tests/fail/intrinsics/simd-scatter.rs:LL:CC
-   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

src/tools/miri/tests/fail/tree_borrows/protector-write-lazy.stderr

@@ -19,7 +19,6 @@ LL | }
    = help: this transition corresponds to a loss of read and write permissions
    = note: BACKTRACE (of the first span):
    = note: inside `main` at tests/fail/tree_borrows/protector-write-lazy.rs:LL:CC
-   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 

tests/rustdoc-ui/doctest/main-alongside-macro-calls.fail.stdout

@@ -13,8 +13,6 @@ error: macros that expand to items must be delimited with braces or followed by
    |
 LL | println!();
    | ^^^^^^^^^^
-   |
-   = note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: macro expansion ignores `{` and any tokens following
   --> $SRC_DIR/std/src/macros.rs:LL:COL
@@ -35,8 +33,6 @@ error: macros that expand to items must be delimited with braces or followed by
    |
 LL | println!();
    | ^^^^^^^^^^
-   |
-   = note: this error originates in the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: macro expansion ignores `{` and any tokens following
   --> $SRC_DIR/std/src/macros.rs:LL:COL

tests/ui/asm/parse-error.stderr

@@ -193,16 +193,12 @@ error: asm template must be a string literal
    |
 LL |         asm!(format!("{{{}}}", 0), in(reg) foo);
    |              ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `format` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: asm template must be a string literal
   --> $DIR/parse-error.rs:86:21
    |
 LL |         asm!("{1}", format!("{{{}}}", 0), in(reg) foo, out(reg) bar);
    |                     ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `format` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: _ cannot be used for input operands
   --> $DIR/parse-error.rs:88:28
@@ -357,16 +353,12 @@ error: asm template must be a string literal
    |
 LL | global_asm!(format!("{{{}}}", 0), const FOO);
    |             ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `format` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: asm template must be a string literal
   --> $DIR/parse-error.rs:143:20
    |
 LL | global_asm!("{1}", format!("{{{}}}", 0), const FOO, const BAR);
    |                    ^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `format` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: the `in` operand cannot be used with `global_asm!`
   --> $DIR/parse-error.rs:146:19

tests/ui/asm/x86_64/type-check-2.stderr

@@ -21,7 +21,6 @@ LL |         asm!("{}", in(reg) vec![0]);
    |                            ^^^^^^^
    |
    = note: only integers, floats, SIMD vectors, pointers and function pointers can be used as arguments for inline assembly
-   = note: this error originates in the macro `vec` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: cannot use value of type `(i32, i32, i32)` for inline assembly
   --> $DIR/type-check-2.rs:52:28