add lifetime extension tests for tuple struct temporaries

Author: tshepang

src/destructors.md

@@ -526,6 +526,13 @@ let x = (&*&temp(),); // Operand of tuple constructor.
 # x;
 let x = { [Some(&temp())] }; // Final expr of block.
 # x;
+let x = Some(&temp()); // Argument of tuple struct.
+# x;
+# enum Enum<'a> {
+#     Variant(&'a S),
+# }
+let x = Enum::Variant(&temp()); // Argument of tuple enum variant.
+# x;
 let x = const { &temp() }; // Final expr of `const` block.
 # x;
 let x = unsafe { &temp() }; // Final expr of `unsafe` block.