coverage: Migrate tests/run-coverage into tests/coverage

tests/coverage/sort_groups.rs

@@ -0,0 +1,23 @@
+// compile-flags: --edition=2021
+
+// Demonstrate that `sort_subviews.py` can sort instantiation groups into a
+// predictable order, while preserving their heterogeneous contents.
+
+fn main() {
+    let cond = std::env::args().len() > 1;
+    generic_fn::<()>(cond);
+    generic_fn::<&'static str>(!cond);
+    if std::hint::black_box(false) {
+        generic_fn::<char>(cond);
+    }
+    generic_fn::<i32>(cond);
+    other_fn();
+}
+
+fn generic_fn<T>(cond: bool) {
+    if cond {
+        println!("{}", std::any::type_name::<T>());
+    }
+}
+
+fn other_fn() {}