interpret: avoid dummy spans in the stacktrace

compiler/rustc_const_eval/src/const_eval/error.rs

@@ -110,7 +110,7 @@ pub fn get_span_and_frames<'tcx>(
     tcx: TyCtxtAt<'tcx>,
     stack: &[Frame<'tcx, impl Provenance, impl Sized>],
 ) -> (Span, Vec<errors::FrameNote>) {
-    let mut stacktrace = Frame::generate_stacktrace_from_stack(stack);
+    let mut stacktrace = Frame::generate_stacktrace_from_stack(stack, *tcx);
     // Filter out `requires_caller_location` frames.
     stacktrace.retain(|frame| !frame.instance.def.requires_caller_location(*tcx));
     let span = stacktrace.last().map(|f| f.span).unwrap_or(tcx.span);

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -635,7 +635,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
 
     #[must_use]
     pub fn generate_stacktrace(&self) -> Vec<FrameInfo<'tcx>> {
-        Frame::generate_stacktrace_from_stack(self.stack())
+        Frame::generate_stacktrace_from_stack(self.stack(), *self.tcx)
     }
 
     pub fn adjust_nan<F1, F2>(&self, f: F2, inputs: &[F1]) -> F2

compiler/rustc_const_eval/src/interpret/stack.rs

@@ -321,12 +321,15 @@ impl<'tcx, Prov: Provenance, Extra> Frame<'tcx, Prov, Extra> {
     }
 
     #[must_use]
-    pub fn generate_stacktrace_from_stack(stack: &[Self]) -> Vec<FrameInfo<'tcx>> {
+    pub fn generate_stacktrace_from_stack(
+        stack: &[Self],
+        tcx: TyCtxt<'tcx>,
+    ) -> Vec<FrameInfo<'tcx>> {
         let mut frames = Vec::new();
         // This deliberately does *not* honor `requires_caller_location` since it is used for much
         // more than just panics.
         for frame in stack.iter().rev() {
-            let span = match frame.loc {
+            let mut span = match frame.loc {
                 Left(loc) => {
                     // If the stacktrace passes through MIR-inlined source scopes, add them.
                     let mir::SourceInfo { mut span, scope } = *frame.body.source_info(loc);
@@ -340,6 +343,10 @@ impl<'tcx, Prov: Provenance, Extra> Frame<'tcx, Prov, Extra> {
                 }
                 Right(span) => span,
             };
+            if span.is_dummy() {
+                // Some statements lack a proper span; point at the function instead.
+                span = tcx.def_span(frame.instance.def_id());
+            }
             frames.push(FrameInfo { span, instance: frame.instance });
         }
         trace!("generate stacktrace: {:#?}", frames);

src/tools/miri/src/diagnostics.rs

@@ -257,7 +257,7 @@ pub fn report_result<'tcx>(
                 // The "active" thread might actually be terminated, so we ignore it.
                 let mut any_pruned = false;
                 for (thread, stack) in ecx.machine.threads.all_blocked_stacks() {
-                    let stacktrace = Frame::generate_stacktrace_from_stack(stack);
+                    let stacktrace = Frame::generate_stacktrace_from_stack(stack, *ecx.tcx);
                     let (stacktrace, was_pruned) = prune_stacktrace(stacktrace, &ecx.machine);
                     any_pruned |= was_pruned;
                     report_msg(
@@ -633,7 +633,8 @@ impl<'tcx> MiriMachine<'tcx> {
     pub fn emit_diagnostic(&self, e: NonHaltingDiagnostic) {
         use NonHaltingDiagnostic::*;
 
-        let stacktrace = Frame::generate_stacktrace_from_stack(self.threads.active_thread_stack());
+        let stacktrace =
+            Frame::generate_stacktrace_from_stack(self.threads.active_thread_stack(), self.tcx);
         let (stacktrace, _was_pruned) = prune_stacktrace(stacktrace, self);
 
         let (label, diag_level) = match &e {