Move const-eval/stable-metric ui tests

tests/ui/consts/const-eval/stable-metric/dominators-edge-case.rs

@@ -0,0 +1,19 @@
+// check-pass
+//
+// Exercising an edge case which was found during Stage 2 compilation.
+// Compilation would fail for this code when running the `CtfeLimit`
+// MirPass (specifically when looking up the dominators).
+#![crate_type="lib"]
+
+const DUMMY: Expr = Expr::Path(ExprPath {
+    attrs: Vec::new(),
+    path: Vec::new(),
+});
+
+pub enum Expr {
+    Path(ExprPath),
+}
+pub struct ExprPath {
+    pub attrs: Vec<()>,
+    pub path: Vec<()>,
+}