Mention first and last macro in backtrace

compiler/rustc_errors/src/emitter.rs

@@ -389,11 +389,11 @@ pub trait Emitter {
     ) {
         // Check for spans in macros, before `fix_multispans_in_extern_macros`
         // has a chance to replace them.
-        let has_macro_spans = iter::once(&*span)
+        let has_macro_spans: Vec<_> = iter::once(&*span)
             .chain(children.iter().map(|child| &child.span))
             .flat_map(|span| span.primary_spans())
             .flat_map(|sp| sp.macro_backtrace())
-            .find_map(|expn_data| {
+            .filter_map(|expn_data| {
                 match expn_data.kind {
                     ExpnKind::Root => None,
 
@@ -403,7 +403,8 @@ pub trait Emitter {
 
                     ExpnKind::Macro(macro_kind, name) => Some((macro_kind, name)),
                 }
-            });
+            })
+            .collect();
 
         if !backtrace {
             self.fix_multispans_in_extern_macros(source_map, span, children);
@@ -412,11 +413,23 @@ pub trait Emitter {
         self.render_multispans_macro_backtrace(span, children, backtrace);
 
         if !backtrace {
-            if let Some((macro_kind, name)) = has_macro_spans {
-                let descr = macro_kind.descr();
+            if let Some((macro_kind, name)) = has_macro_spans.last() {
+                // Mark the actual macro this originates from
+                let and_then = if let Some((macro_kind, first_name)) = has_macro_spans.first()
+                    && first_name != name
+                {
+                    let descr = macro_kind.descr();
+                    format!(
+                        " which{} expands to {descr} `{first_name}`",
+                        if has_macro_spans.len() > 2 { " eventually" } else { "" }
+                    )
+                } else {
+                    "".to_string()
+                };
 
+                let descr = macro_kind.descr();
                 let msg = format!(
-                    "this {level} originates in the {descr} `{name}` \
+                    "this {level} originates in the {descr} `{name}`{and_then} \
                     (in Nightly builds, run with -Z macro-backtrace for more info)",
                 );
 

compiler/rustc_errors/src/lib.rs

@@ -6,6 +6,7 @@
 #![feature(drain_filter)]
 #![feature(backtrace)]
 #![feature(if_let_guard)]
+#![feature(let_chains)]
 #![feature(let_else)]
 #![feature(never_type)]
 #![feature(adt_const_params)]

src/test/ui/borrowck/borrowck-and-init.stderr

@@ -4,7 +4,7 @@ error[E0381]: borrow of possibly-uninitialized variable: `i`
 LL |     println!("{}", i);
    |                    ^ use of possibly-uninitialized `i`
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/borrowck/borrowck-break-uninit-2.stderr

@@ -4,7 +4,7 @@ error[E0381]: borrow of possibly-uninitialized variable: `x`
 LL |     println!("{}", x);
    |                    ^ use of possibly-uninitialized `x`
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/borrowck/borrowck-break-uninit.stderr

@@ -4,7 +4,7 @@ error[E0381]: borrow of possibly-uninitialized variable: `x`
 LL |     println!("{}", x);
    |                    ^ use of possibly-uninitialized `x`
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/borrowck/borrowck-or-init.stderr

@@ -4,7 +4,7 @@ error[E0381]: borrow of possibly-uninitialized variable: `i`
 LL |     println!("{}", i);
    |                    ^ use of possibly-uninitialized `i`
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/borrowck/borrowck-while-break.stderr

@@ -4,7 +4,7 @@ error[E0381]: borrow of possibly-uninitialized variable: `v`
 LL |     println!("{}", v);
    |                    ^ use of possibly-uninitialized `v`
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/borrowck/issue-24267-flow-exit.stderr

@@ -4,15 +4,15 @@ error[E0381]: borrow of possibly-uninitialized variable: `x`
 LL |     println!("{}", x);
    |                    ^ use of possibly-uninitialized `x`
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0381]: borrow of possibly-uninitialized variable: `x`
   --> $DIR/issue-24267-flow-exit.rs:18:20
    |
 LL |     println!("{}", x);
    |                    ^ use of possibly-uninitialized `x`
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 2 previous errors
 

src/test/ui/borrowck/issue-64453.stderr

@@ -5,7 +5,7 @@ LL | static settings_dir: String = format!("");
    |                               ^^^^^^^^^^^
    |
    = help: add `#![feature(const_fmt_arguments_new)]` to the crate attributes to enable
-   = note: this error originates in the macro `$crate::__export::format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `format` which expands to macro `$crate::__export::format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0015]: cannot call non-const fn `format` in statics
   --> $DIR/issue-64453.rs:4:31

src/test/ui/borrowck/issue-81899.stderr

@@ -10,7 +10,7 @@ LL |     panic!()
    |     the evaluated program panicked at 'explicit panic', $DIR/issue-81899.rs:12:5
    |     inside `f::<[closure@$DIR/issue-81899.rs:4:31: 4:37]>` at $SRC_DIR/std/src/panic.rs:LL:COL
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: any use of this value will cause an error
   --> $DIR/issue-81899.rs:4:23

src/test/ui/borrowck/issue-88434-minimal-example.stderr

@@ -10,7 +10,7 @@ LL |     panic!()
    |     the evaluated program panicked at 'explicit panic', $DIR/issue-88434-minimal-example.rs:11:5
    |     inside `f::<[closure@$DIR/issue-88434-minimal-example.rs:3:25: 3:31]>` at $SRC_DIR/std/src/panic.rs:LL:COL
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: any use of this value will cause an error
   --> $DIR/issue-88434-minimal-example.rs:3:21

src/test/ui/borrowck/issue-88434-removal-index-should-be-less.stderr

@@ -10,7 +10,7 @@ LL |     panic!()
    |     the evaluated program panicked at 'explicit panic', $DIR/issue-88434-removal-index-should-be-less.rs:11:5
    |     inside `f::<[closure@$DIR/issue-88434-removal-index-should-be-less.rs:3:31: 3:37]>` at $SRC_DIR/std/src/panic.rs:LL:COL
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: any use of this value will cause an error
   --> $DIR/issue-88434-removal-index-should-be-less.rs:3:23

src/test/ui/borrowck/move-error-snippets.stderr

@@ -12,7 +12,7 @@ LL |         let a = $c;
 LL | sss!();
    | ------ in this macro invocation
    |
-   = note: this error originates in the macro `aaa` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `sss` which expands to macro `aaa` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/closures/2229_closure_analysis/diagnostics/arrays.stderr

@@ -82,7 +82,7 @@ LL |     println!("{}", arr[3]);
 LL |     c();
    |     - mutable borrow later used here
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0502]: cannot borrow `arr` as immutable because it is also borrowed as mutable
   --> $DIR/arrays.rs:73:24

src/test/ui/closures/2229_closure_analysis/diagnostics/box.stderr

@@ -26,7 +26,7 @@ LL |
 LL |     c();
    |     - mutable borrow later used here
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0506]: cannot assign to `e.0.0.m.x` because it is borrowed
   --> $DIR/box.rs:55:5

src/test/ui/closures/2229_closure_analysis/diagnostics/repr_packed.stderr

@@ -9,7 +9,7 @@ LL |         println!("{}", foo.x);
    = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 
@@ -25,5 +25,5 @@ LL |         println!("{}", foo.x);
    = note: for more information, see issue #82523 <https://github.com/rust-lang/rust/issues/82523>
    = note: fields of packed structs are not properly aligned, and creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 

src/test/ui/closures/2229_closure_analysis/diagnostics/simple-struct-min-capture.stderr

@@ -14,7 +14,7 @@ LL |
 LL |     c();
    |     - mutable borrow later used here
    |
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/codemap_tests/bad-format-args.stderr

@@ -4,7 +4,7 @@ error: requires at least a format string argument
 LL |     format!();
    |     ^^^^^^^^^
    |
-   = note: this error originates in the macro `$crate::__export::format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `format` which expands to macro `$crate::__export::format_args` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: expected `,`, found `1`
   --> $DIR/bad-format-args.rs:3:16

src/test/ui/codemap_tests/tab_3.stderr

@@ -14,7 +14,7 @@ note: this function takes ownership of the receiver `self`, which moves `some_ve
    |
 LL |     fn into_iter(self) -> Self::IntoIter;
    |                  ^^^^
-   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error
 

src/test/ui/consts/const-eval/conditional_array_execution.stderr

@@ -28,7 +28,7 @@ LL |     println!("{}", FOO);
    |
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
-   = note: this warning originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this warning originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to previous error; 2 warnings emitted
 
@@ -64,5 +64,5 @@ LL | #![warn(const_err)]
    |         ^^^^^^^^^
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
    = note: for more information, see issue #71800 <https://github.com/rust-lang/rust/issues/71800>
-   = note: this warning originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this warning originates in the macro `println` which expands to macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)
 

src/test/ui/consts/const-eval/const_panic.stderr

@@ -4,23 +4,23 @@ error[E0080]: evaluation of constant value failed
 LL | const Z: () = std::panic!("cheese");
    |               ^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'cheese', $DIR/const_panic.rs:6:15
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `std::panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:9:16
    |
 LL | const Z2: () = std::panic!();
    |                ^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic.rs:9:16
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `std::panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:12:15
    |
 LL | const Y: () = std::unreachable!();
    |               ^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic.rs:12:15
    |
-   = note: this error originates in the macro `$crate::panic::unreachable_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `std::unreachable` which expands to macro `$crate::panic::unreachable_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:15:15
@@ -36,39 +36,39 @@ error[E0080]: evaluation of constant value failed
 LL | const W: () = std::panic!(MSG);
    |               ^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:18:15
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `std::panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:21:16
    |
 LL | const W2: () = std::panic!("{}", MSG);
    |                ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:21:16
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `std::panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:24:20
    |
 LL | const Z_CORE: () = core::panic!("cheese");
    |                    ^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'cheese', $DIR/const_panic.rs:24:20
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `core::panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:27:21
    |
 LL | const Z2_CORE: () = core::panic!();
    |                     ^^^^^^^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/const_panic.rs:27:21
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `core::panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:30:20
    |
 LL | const Y_CORE: () = core::unreachable!();
    |                    ^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'internal error: entered unreachable code', $DIR/const_panic.rs:30:20
    |
-   = note: this error originates in the macro `$crate::panic::unreachable_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `core::unreachable` which expands to macro `$crate::panic::unreachable_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:33:20
@@ -84,15 +84,15 @@ error[E0080]: evaluation of constant value failed
 LL | const W_CORE: () = core::panic!(MSG);
    |                    ^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:36:20
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `core::panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/const_panic.rs:39:21
    |
 LL | const W2_CORE: () = core::panic!("{}", MSG);
    |                     ^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'hello', $DIR/const_panic.rs:39:21
    |
-   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `core::panic` which expands to macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 12 previous errors