tests: Move run-pass tests without naming conflicts to ui

src/test/ui/structs-enums/enum-nullable-const-null-with-fields.rs

@@ -0,0 +1,13 @@
+// run-pass
+
+use std::result::Result;
+use std::result::Result::Ok;
+
+static C: Result<(), Box<isize>> = Ok(());
+
+// This is because of yet another bad assertion (ICE) about the null side of a nullable enum.
+// So we won't actually compile if the bug is present, but we check the value in main anyway.
+
+pub fn main() {
+    assert!(C.is_ok());
+}