Structured suggestion for "missing `feature` intrinsic"

```
error: `size_of_val` is not yet stable as a const intrinsic
  --> $DIR/const-unstable-intrinsic.rs:17:9
   |
LL |         unstable_intrinsic::size_of_val(&x);
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add `#![feature(unstable)]` to the crate attributes to enable
help: add `#![feature(unstable)]` to the crate attributes to enable
   |
LL + #![feature("unstable")]
   |
```

1 files changed, 7 insertions, 0 deletions

diff --git a/compiler/rustc_const_eval/src/check_consts/check.rs b/compiler/rustc_const_eval/src/check_consts/check.rs
index 94fb039512a..844dc2aa593 100644
--- a/compiler/rustc_const_eval/src/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/check_consts/check.rs
@@ -819,10 +819,17 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                             feature,
                             ..
                         }) => {
+                            let suggestion =
+                                tcx.hir_crate_items(()).definitions().next().and_then(|id| {
+                                    tcx.crate_level_attribute_injection_span(
+                                        tcx.local_def_id_to_hir_id(id),
+                                    )
+                                });
                             self.check_op(ops::IntrinsicUnstable {
                                 name: intrinsic.name,
                                 feature,
                                 const_stable_indirect: is_const_stable,
+                                suggestion,
                             });
                         }
                         Some(ConstStability { level: StabilityLevel::Stable { .. }, .. }) => {