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

tests/coverage/closure_bug.rs

@@ -0,0 +1,44 @@
+// Regression test for #115930.
+// All of these closures are identical, and should produce identical output in
+// the coverage report. However, an unstable sort was causing them to be treated
+// inconsistently when preparing coverage spans.
+
+fn main() {
+    let truthy = std::env::args().len() == 1;
+
+    let a
+        =
+        |
+        |
+        if truthy { true } else { false };
+
+    a();
+    if truthy { a(); }
+
+    let b
+        =
+        |
+        |
+        if truthy { true } else { false };
+
+    b();
+    if truthy { b(); }
+
+    let c
+        =
+        |
+        |
+        if truthy { true } else { false };
+
+    c();
+    if truthy { c(); }
+
+    let d
+        =
+        |
+        |
+        if truthy { true } else { false };
+
+    d();
+    if truthy { d(); }
+}