Tweak output of const panic diagnostic

compiler/rustc_const_eval/messages.ftl

@@ -109,6 +109,8 @@ const_eval_frame_note_inner = inside {$where_ ->
     *[other] {""}
 }
 
+const_eval_frame_note_last = the failure occurred here
+
 const_eval_in_bounds_test = out-of-bounds pointer use
 const_eval_incompatible_calling_conventions =
     calling a function with calling convention {$callee_conv} using calling convention {$caller_conv}
@@ -300,8 +302,7 @@ const_eval_overflow_arith =
 const_eval_overflow_shift =
     overflowing shift by {$shift_amount} in `{$intrinsic}`
 
-const_eval_panic =
-    the evaluated program panicked at '{$msg}', {$file}:{$line}:{$col}
+const_eval_panic = evaluation panicked: {$msg}
 
 const_eval_panic_non_str = argument to `panic!()` in a const context must have type `&str`
 

compiler/rustc_const_eval/src/const_eval/error.rs

@@ -48,11 +48,8 @@ impl MachineStopType for ConstEvalErrKind {
             | ModifiedGlobal
             | WriteThroughImmutablePointer => {}
             AssertFailure(kind) => kind.add_args(adder),
-            Panic { msg, line, col, file } => {
+            Panic { msg, .. } => {
                 adder("msg".into(), msg.into_diag_arg(&mut None));
-                adder("file".into(), file.into_diag_arg(&mut None));
-                adder("line".into(), line.into_diag_arg(&mut None));
-                adder("col".into(), col.into_diag_arg(&mut None));
             }
         }
     }
@@ -72,7 +69,7 @@ pub fn get_span_and_frames<'tcx>(
     let mut stacktrace = Frame::generate_stacktrace_from_stack(stack);
     // Filter out `requires_caller_location` frames.
     stacktrace.retain(|frame| !frame.instance.def.requires_caller_location(*tcx));
-    let span = stacktrace.first().map(|f| f.span).unwrap_or(tcx.span);
+    let span = stacktrace.last().map(|f| f.span).unwrap_or(tcx.span);
 
     let mut frames = Vec::new();
 
@@ -115,6 +112,20 @@ pub fn get_span_and_frames<'tcx>(
         }
     }
 
+    // In `rustc`, we present const-eval errors from the outer-most place first to the inner-most.
+    // So we reverse the frames here. The first frame will be the same as the span from the current
+    // `TyCtxtAt<'_>`, so we remove it as it would be redundant.
+    frames.reverse();
+    if frames.len() > 0 {
+        frames.remove(0);
+    }
+    if let Some(last) = frames.last_mut()
+        // If the span is not going to be printed, we don't want the span label for `is_last`.
+        && tcx.sess.source_map().span_to_snippet(last.span.source_callsite()).is_ok()
+    {
+        last.has_label = true;
+    }
+
     (span, frames)
 }
 

compiler/rustc_const_eval/src/errors.rs

@@ -6,6 +6,7 @@ use rustc_abi::WrappingRange;
 use rustc_errors::codes::*;
 use rustc_errors::{
     Diag, DiagArgValue, DiagCtxtHandle, DiagMessage, Diagnostic, EmissionGuarantee, Level,
+    MultiSpan, SubdiagMessageOp, Subdiagnostic,
 };
 use rustc_hir::ConstContext;
 use rustc_macros::{Diagnostic, LintDiagnostic, Subdiagnostic};
@@ -17,6 +18,7 @@ use rustc_middle::mir::interpret::{
 use rustc_middle::ty::{self, Mutability, Ty};
 use rustc_span::{Span, Symbol};
 
+use crate::fluent_generated as fluent;
 use crate::interpret::InternKind;
 
 #[derive(Diagnostic)]
@@ -278,14 +280,31 @@ pub(crate) struct NonConstImplNote {
     pub span: Span,
 }
 
-#[derive(Subdiagnostic, Clone)]
-#[note(const_eval_frame_note)]
+#[derive(Clone)]
 pub struct FrameNote {
-    #[primary_span]
     pub span: Span,
     pub times: i32,
     pub where_: &'static str,
     pub instance: String,
+    pub has_label: bool,
+}
+
+impl Subdiagnostic for FrameNote {
+    fn add_to_diag_with<G: EmissionGuarantee, F: SubdiagMessageOp<G>>(
+        self,
+        diag: &mut Diag<'_, G>,
+        f: &F,
+    ) {
+        diag.arg("times", self.times);
+        diag.arg("where_", self.where_);
+        diag.arg("instance", self.instance);
+        let mut span: MultiSpan = self.span.into();
+        if self.has_label && !self.span.is_dummy() {
+            span.push_span_label(self.span, fluent::const_eval_frame_note_last);
+        }
+        let msg = f(diag, fluent::const_eval_frame_note.into());
+        diag.span_note(span, msg);
+    }
 }
 
 #[derive(Subdiagnostic)]

compiler/rustc_const_eval/src/interpret/stack.rs

@@ -231,13 +231,19 @@ impl<'tcx> FrameInfo<'tcx> {
     pub fn as_note(&self, tcx: TyCtxt<'tcx>) -> errors::FrameNote {
         let span = self.span;
         if tcx.def_key(self.instance.def_id()).disambiguated_data.data == DefPathData::Closure {
-            errors::FrameNote { where_: "closure", span, instance: String::new(), times: 0 }
+            errors::FrameNote {
+                where_: "closure",
+                span,
+                instance: String::new(),
+                times: 0,
+                has_label: false,
+            }
         } else {
             let instance = format!("{}", self.instance);
             // Note: this triggers a `must_produce_diag` state, which means that if we ever get
             // here we must emit a diagnostic. We should never display a `FrameInfo` unless we
             // actually want to emit a warning or error to the user.
-            errors::FrameNote { where_: "instance", span, instance, times: 0 }
+            errors::FrameNote { where_: "instance", span, instance, times: 0, has_label: false }
         }
     }
 }

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

@@ -2,7 +2,7 @@ error[E0080]: evaluation of `PrintName::<i32>::VOID` failed
   --> tests/fail/erroneous_const.rs:LL:CC
    |
 LL |     const VOID: ! = panic!();
-   |                     ^^^^^^^^ the evaluated program panicked at 'explicit panic', tests/fail/erroneous_const.rs:LL:CC
+   |                     ^^^^^^^^ evaluation panicked: explicit 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)
 

tests/ui/borrowck/issue-81899.rs

@@ -1,15 +1,14 @@
 // Regression test for #81899.
 // The `panic!()` below is important to trigger the fixed ICE.
 
-const _CONST: &[u8] = &f(&[], |_| {});
+const _CONST: &[u8] = &f(&[], |_| {}); //~ ERROR evaluation of constant value failed
 //~^ constant
 
 const fn f<F>(_: &[u8], _: F) -> &[u8]
 where
     F: FnMut(&u8),
 {
-    panic!() //~ ERROR evaluation of constant value failed
-    //~^ panic
+    panic!() //~ inside `f
 }
 
 fn main() {}

tests/ui/borrowck/issue-81899.stderr

@@ -1,19 +1,14 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/issue-81899.rs:11:5
+  --> $DIR/issue-81899.rs:4:24
    |
-LL |     panic!()
-   |     ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/issue-81899.rs:11:5
+LL | const _CONST: &[u8] = &f(&[], |_| {});
+   |                        ^^^^^^^^^^^^^^ evaluation panicked: explicit panic
    |
 note: inside `f::<{closure@$DIR/issue-81899.rs:4:31: 4:34}>`
   --> $DIR/issue-81899.rs:11:5
    |
 LL |     panic!()
-   |     ^^^^^^^^
-note: inside `_CONST`
-  --> $DIR/issue-81899.rs:4:24
-   |
-LL | const _CONST: &[u8] = &f(&[], |_| {});
-   |                        ^^^^^^^^^^^^^^
+   |     ^^^^^^^^ the failure occurred here
    = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered

tests/ui/borrowck/issue-88434-minimal-example.rs

@@ -1,14 +1,13 @@
 // Regression test related to issue 88434
 
-const _CONST: &() = &f(&|_| {});
+const _CONST: &() = &f(&|_| {}); //~ ERROR evaluation of constant value failed
 //~^ constant
 
 const fn f<F>(_: &F)
 where
     F: FnMut(&u8),
 {
-    panic!() //~ ERROR evaluation of constant value failed
-    //~^ panic
+    panic!() //~ inside `f
 }
 
 fn main() { }

tests/ui/borrowck/issue-88434-minimal-example.stderr

@@ -1,19 +1,14 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/issue-88434-minimal-example.rs:10:5
+  --> $DIR/issue-88434-minimal-example.rs:3:22
    |
-LL |     panic!()
-   |     ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/issue-88434-minimal-example.rs:10:5
+LL | const _CONST: &() = &f(&|_| {});
+   |                      ^^^^^^^^^^ evaluation panicked: explicit panic
    |
 note: inside `f::<{closure@$DIR/issue-88434-minimal-example.rs:3:25: 3:28}>`
   --> $DIR/issue-88434-minimal-example.rs:10:5
    |
 LL |     panic!()
-   |     ^^^^^^^^
-note: inside `_CONST`
-  --> $DIR/issue-88434-minimal-example.rs:3:22
-   |
-LL | const _CONST: &() = &f(&|_| {});
-   |                      ^^^^^^^^^^
+   |     ^^^^^^^^ the failure occurred here
    = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered

tests/ui/borrowck/issue-88434-removal-index-should-be-less.rs

@@ -1,14 +1,13 @@
 // Regression test for issue 88434
 
-const _CONST: &[u8] = &f(&[], |_| {});
+const _CONST: &[u8] = &f(&[], |_| {}); //~ ERROR evaluation of constant value failed
 //~^ constant
 
 const fn f<F>(_: &[u8], _: F) -> &[u8]
 where
     F: FnMut(&u8),
 {
-    panic!() //~ ERROR evaluation of constant value failed
-    //~^ panic
+    panic!() //~ inside `f
 }
 
 fn main() { }

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

@@ -1,19 +1,14 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/issue-88434-removal-index-should-be-less.rs:10:5
+  --> $DIR/issue-88434-removal-index-should-be-less.rs:3:24
    |
-LL |     panic!()
-   |     ^^^^^^^^ the evaluated program panicked at 'explicit panic', $DIR/issue-88434-removal-index-should-be-less.rs:10:5
+LL | const _CONST: &[u8] = &f(&[], |_| {});
+   |                        ^^^^^^^^^^^^^^ evaluation panicked: explicit panic
    |
 note: inside `f::<{closure@$DIR/issue-88434-removal-index-should-be-less.rs:3:31: 3:34}>`
   --> $DIR/issue-88434-removal-index-should-be-less.rs:10:5
    |
 LL |     panic!()
-   |     ^^^^^^^^
-note: inside `_CONST`
-  --> $DIR/issue-88434-removal-index-should-be-less.rs:3:24
-   |
-LL | const _CONST: &[u8] = &f(&[], |_| {});
-   |                        ^^^^^^^^^^^^^^
+   |     ^^^^^^^^ the failure occurred here
    = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 note: erroneous constant encountered

tests/ui/coherence/const-errs-dont-conflict-103369.rs

@@ -2,13 +2,12 @@
 
 pub trait ConstGenericTrait<const N: u32> {}
 
-impl ConstGenericTrait<{my_fn(1)}> for () {}
+impl ConstGenericTrait<{my_fn(1)}> for () {} //~ ERROR E0080
 
-impl ConstGenericTrait<{my_fn(2)}> for () {}
+impl ConstGenericTrait<{my_fn(2)}> for () {} //~ ERROR E0080
 
 const fn my_fn(v: u32) -> u32 {
-    panic!("Some error occurred"); //~ ERROR E0080
-    //~| ERROR E0080
+    panic!("Some error occurred");
 }
 
 fn main() {}

tests/ui/coherence/const-errs-dont-conflict-103369.stderr

@@ -1,37 +1,27 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const-errs-dont-conflict-103369.rs:10:5
+  --> $DIR/const-errs-dont-conflict-103369.rs:5:25
    |
-LL |     panic!("Some error occurred");
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'Some error occurred', $DIR/const-errs-dont-conflict-103369.rs:10:5
+LL | impl ConstGenericTrait<{my_fn(1)}> for () {}
+   |                         ^^^^^^^^ evaluation panicked: Some error occurred
    |
 note: inside `my_fn`
   --> $DIR/const-errs-dont-conflict-103369.rs:10:5
    |
 LL |     panic!("Some error occurred");
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-note: inside `<() as ConstGenericTrait<{my_fn(1)}>>::{constant#0}`
-  --> $DIR/const-errs-dont-conflict-103369.rs:5:25
-   |
-LL | impl ConstGenericTrait<{my_fn(1)}> for () {}
-   |                         ^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the failure occurred here
    = note: this error originates in the macro `$crate::panic::panic_2015` which comes from the expansion of the macro `panic` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0080]: evaluation of constant value failed
-  --> $DIR/const-errs-dont-conflict-103369.rs:10:5
+  --> $DIR/const-errs-dont-conflict-103369.rs:7:25
    |
-LL |     panic!("Some error occurred");
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the evaluated program panicked at 'Some error occurred', $DIR/const-errs-dont-conflict-103369.rs:10:5
+LL | impl ConstGenericTrait<{my_fn(2)}> for () {}
+   |                         ^^^^^^^^ evaluation panicked: Some error occurred
    |
 note: inside `my_fn`
   --> $DIR/const-errs-dont-conflict-103369.rs:10:5
    |
 LL |     panic!("Some error occurred");
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-note: inside `<() as ConstGenericTrait<{my_fn(2)}>>::{constant#0}`
-  --> $DIR/const-errs-dont-conflict-103369.rs:7:25
-   |
-LL | impl ConstGenericTrait<{my_fn(2)}> for () {}
-   |                         ^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the failure occurred here
    = note: this error originates in the macro `$crate::panic::panic_2015` 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

tests/ui/const-generics/issues/issue-100313.rs

@@ -6,15 +6,14 @@ struct T<const B: &'static bool>;
 impl<const B: &'static bool> T<B> {
     const fn set_false(&self) {
         unsafe {
-            *(B as *const bool as *mut bool) = false;
-            //~^ ERROR evaluation of constant value failed [E0080]
+            *(B as *const bool as *mut bool) = false; //~ inside `T
         }
     }
 }
 
 const _: () = {
     let x = T::<{ &true }>;
-    x.set_false();
+    x.set_false(); //~ ERROR evaluation of constant value failed [E0080]
 };
 
 fn main() {}

tests/ui/const-generics/issues/issue-100313.stderr

@@ -1,19 +1,14 @@
 error[E0080]: evaluation of constant value failed
-  --> $DIR/issue-100313.rs:9:13
+  --> $DIR/issue-100313.rs:16:5
    |
-LL |             *(B as *const bool as *mut bool) = false;
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ writing to ALLOC0 which is read-only
+LL |     x.set_false();
+   |     ^^^^^^^^^^^^^ writing to ALLOC0 which is read-only
    |
 note: inside `T::<&true>::set_false`
   --> $DIR/issue-100313.rs:9:13
    |
 LL |             *(B as *const bool as *mut bool) = false;
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-note: inside `_`
-  --> $DIR/issue-100313.rs:17:5
-   |
-LL |     x.set_false();
-   |     ^^^^^^^^^^^^^
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the failure occurred here
 
 error: aborting due to 1 previous error