1 files changed, 22 insertions, 0 deletions
diff --git a/compiler/rustc_mir_transform/src/required_consts.rs b/compiler/rustc_mir_transform/src/required_consts.rs
new file mode 100644
index 000000000..827ce0c02
--- /dev/null
+++ b/compiler/rustc_mir_transform/src/required_consts.rs
@@ -0,0 +1,22 @@
+use rustc_middle::mir::visit::Visitor;
+use rustc_middle::mir::{Constant, Location};
+use rustc_middle::ty::ConstKind;
+
+pub struct RequiredConstsVisitor<'a, 'tcx> {
+    required_consts: &'a mut Vec<Constant<'tcx>>,
+}
+
+impl<'a, 'tcx> RequiredConstsVisitor<'a, 'tcx> {
+    pub fn new(required_consts: &'a mut Vec<Constant<'tcx>>) -> Self {
+        RequiredConstsVisitor { required_consts }
+    }
+}
+
+impl<'tcx> Visitor<'tcx> for RequiredConstsVisitor<'_, 'tcx> {
+    fn visit_constant(&mut self, constant: &Constant<'tcx>, _: Location) {
+        let literal = constant.literal;
+        if let Some(ct) = literal.const_for_ty() && let ConstKind::Unevaluated(_) = ct.kind() {
+            self.required_consts.push(*constant);
+        }
+    }
+}