coverage: Clean up marker statements that aren't needed later

Some of the marker statements used by coverage are added during MIR building
for use by the InstrumentCoverage pass (during analysis), and are not needed
afterwards.

compiler/rustc_const_eval/src/transform/validate.rs

@@ -4,6 +4,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_index::bit_set::BitSet;
 use rustc_index::IndexVec;
 use rustc_infer::traits::Reveal;
+use rustc_middle::mir::coverage::CoverageKind;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::visit::{NonUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
@@ -345,11 +346,21 @@ impl<'a, 'tcx> Visitor<'tcx> for CfgChecker<'a, 'tcx> {
                     self.fail(location, format!("explicit `{kind:?}` is forbidden"));
                 }
             }
+            StatementKind::Coverage(coverage) => {
+                let kind = &coverage.kind;
+                if self.mir_phase >= MirPhase::Analysis(AnalysisPhase::PostCleanup)
+                    && let CoverageKind::BlockMarker { .. } | CoverageKind::SpanMarker { .. } = kind
+                {
+                    self.fail(
+                        location,
+                        format!("{kind:?} should have been removed after analysis"),
+                    );
+                }
+            }
             StatementKind::Assign(..)
             | StatementKind::StorageLive(_)
             | StatementKind::StorageDead(_)
             | StatementKind::Intrinsic(_)
-            | StatementKind::Coverage(_)
             | StatementKind::ConstEvalCounter
             | StatementKind::PlaceMention(..)
             | StatementKind::Nop => {}