review comment: Remove FrameInfo.is_last

Author: estebank

compiler/rustc_const_eval/src/const_eval/error.rs

@@ -89,8 +89,8 @@ pub fn get_span_and_frames<'tcx>(
         };
 
         let mut last_frame: Option<errors::FrameNote> = None;
-        for frame_info in &stacktrace {
-            let frame = frame_info.as_note(*tcx);
+        for (i, frame_info) in stacktrace.iter().enumerate() {
+            let frame = frame_info.as_note(*tcx, i + 1 == stacktrace.len());
             match last_frame.as_mut() {
                 Some(last_frame)
                     if last_frame.span == frame.span

compiler/rustc_const_eval/src/interpret/stack.rs

@@ -209,7 +209,6 @@ impl<'tcx, Prov: Provenance> LocalState<'tcx, Prov> {
 pub struct FrameInfo<'tcx> {
     pub instance: ty::Instance<'tcx>,
     pub span: Span,
-    pub is_last: bool,
 }
 
 // FIXME: only used by miri, should be removed once translatable.
@@ -229,28 +228,22 @@ impl<'tcx> fmt::Display for FrameInfo<'tcx> {
 }
 
 impl<'tcx> FrameInfo<'tcx> {
-    pub fn as_note(&self, tcx: TyCtxt<'tcx>) -> errors::FrameNote {
+    pub fn as_note(&self, tcx: TyCtxt<'tcx>, is_last: bool) -> 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,
-                is_last: self.is_last,
+                is_last,
             }
         } 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,
-                is_last: self.is_last,
-            }
+            errors::FrameNote { where_: "instance", span, instance, times: 0, is_last }
         }
     }
 }
@@ -335,15 +328,15 @@ impl<'tcx, Prov: Provenance, Extra> Frame<'tcx, Prov, Extra> {
                     let mir::SourceInfo { mut span, scope } = *frame.body.source_info(loc);
                     let mut scope_data = &frame.body.source_scopes[scope];
                     while let Some((instance, call_span)) = scope_data.inlined {
-                        frames.push(FrameInfo { span, instance, is_last: false });
+                        frames.push(FrameInfo { span, instance });
                         span = call_span;
                         scope_data = &frame.body.source_scopes[scope_data.parent_scope.unwrap()];
                     }
                     span
                 }
                 Right(span) => span,
             };
-            frames.push(FrameInfo { span, instance: frame.instance, is_last: false });
+            frames.push(FrameInfo { span, instance: frame.instance });
         }
         trace!("generate stacktrace: {:#?}", frames);
         frames