Add regression tests to ensure stable drop order

src/test/run-pass/rfc1857-drop-order.rs

@@ -0,0 +1,231 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(dead_code, unreachable_code)]
+
+use std::cell::RefCell;
+use std::rc::Rc;
+use std::panic::{self, AssertUnwindSafe, UnwindSafe};
+
+// This struct is used to record the order in which elements are dropped
+struct PushOnDrop {
+    vec: Rc<RefCell<Vec<u32>>>,
+    val: u32
+}
+
+impl PushOnDrop {
+    fn new(val: u32, vec: Rc<RefCell<Vec<u32>>>) -> PushOnDrop {
+        PushOnDrop { vec, val }
+    }
+}
+
+impl Drop for PushOnDrop {
+    fn drop(&mut self) {
+        self.vec.borrow_mut().push(self.val)
+    }
+}
+
+impl UnwindSafe for PushOnDrop { }
+
+// Structs
+struct TestStruct {
+    x: PushOnDrop,
+    y: PushOnDrop,
+    z: PushOnDrop
+}
+
+// Tuple structs
+struct TestTupleStruct(PushOnDrop, PushOnDrop, PushOnDrop);
+
+// Enum variants
+enum TestEnum {
+    Tuple(PushOnDrop, PushOnDrop, PushOnDrop),
+    Struct { x: PushOnDrop, y: PushOnDrop, z: PushOnDrop }
+}
+
+fn test_drop_tuple() {
+    // Tuple fields are dropped in the same order they are declared
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let test_tuple = (PushOnDrop::new(1, dropped_fields.clone()),
+                      PushOnDrop::new(2, dropped_fields.clone()));
+    drop(test_tuple);
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+
+    // Panic during construction means that fields are treated as local variables
+    // Therefore they are dropped in reverse order of initialization
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        (PushOnDrop::new(2, cloned.clone()),
+         PushOnDrop::new(1, cloned.clone()),
+         panic!("this panic is catched :D"));
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+}
+
+fn test_drop_struct() {
+    // Struct fields are dropped in the same order they are declared
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let test_struct = TestStruct {
+        x: PushOnDrop::new(1, dropped_fields.clone()),
+        y: PushOnDrop::new(2, dropped_fields.clone()),
+        z: PushOnDrop::new(3, dropped_fields.clone()),
+    };
+    drop(test_struct);
+    assert_eq!(*dropped_fields.borrow(), &[1, 2, 3]);
+
+    // The same holds for tuple structs
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let test_tuple_struct = TestTupleStruct(PushOnDrop::new(1, dropped_fields.clone()),
+                                            PushOnDrop::new(2, dropped_fields.clone()),
+                                            PushOnDrop::new(3, dropped_fields.clone()));
+    drop(test_tuple_struct);
+    assert_eq!(*dropped_fields.borrow(), &[1, 2, 3]);
+
+    // Panic during struct construction means that fields are treated as local variables
+    // Therefore they are dropped in reverse order of initialization
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        TestStruct {
+            x: PushOnDrop::new(2, cloned.clone()),
+            y: PushOnDrop::new(1, cloned.clone()),
+            z: panic!("this panic is catched :D")
+        };
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+
+    // Test with different initialization order
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        TestStruct {
+            y: PushOnDrop::new(2, cloned.clone()),
+            x: PushOnDrop::new(1, cloned.clone()),
+            z: panic!("this panic is catched :D")
+        };
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+
+    // The same holds for tuple structs
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        TestTupleStruct(PushOnDrop::new(2, cloned.clone()),
+                        PushOnDrop::new(1, cloned.clone()),
+                        panic!("this panic is catched :D"));
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+}
+
+fn test_drop_enum() {
+    // Enum variants are dropped in the same order they are declared
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let test_struct_enum = TestEnum::Struct {
+        x: PushOnDrop::new(1, dropped_fields.clone()),
+        y: PushOnDrop::new(2, dropped_fields.clone()),
+        z: PushOnDrop::new(3, dropped_fields.clone())
+    };
+    drop(test_struct_enum);
+    assert_eq!(*dropped_fields.borrow(), &[1, 2, 3]);
+
+    // The same holds for tuple enum variants
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let test_tuple_enum = TestEnum::Tuple(PushOnDrop::new(1, dropped_fields.clone()),
+                                          PushOnDrop::new(2, dropped_fields.clone()),
+                                          PushOnDrop::new(3, dropped_fields.clone()));
+    drop(test_tuple_enum);
+    assert_eq!(*dropped_fields.borrow(), &[1, 2, 3]);
+
+    // Panic during enum construction means that fields are treated as local variables
+    // Therefore they are dropped in reverse order of initialization
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        TestEnum::Struct {
+            x: PushOnDrop::new(2, cloned.clone()),
+            y: PushOnDrop::new(1, cloned.clone()),
+            z: panic!("this panic is catched :D")
+        };
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+
+    // Test with different initialization order
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        TestEnum::Struct {
+            y: PushOnDrop::new(2, cloned.clone()),
+            x: PushOnDrop::new(1, cloned.clone()),
+            z: panic!("this panic is catched :D")
+        };
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+
+    // The same holds for tuple enum variants
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        TestEnum::Tuple(PushOnDrop::new(2, cloned.clone()),
+                        PushOnDrop::new(1, cloned.clone()),
+                        panic!("this panic is catched :D"));
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+}
+
+fn test_drop_list() {
+    // Elements in a Vec are dropped in the same order they are pushed
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let xs = vec![PushOnDrop::new(1, dropped_fields.clone()),
+                  PushOnDrop::new(2, dropped_fields.clone()),
+                  PushOnDrop::new(3, dropped_fields.clone())];
+    drop(xs);
+    assert_eq!(*dropped_fields.borrow(), &[1, 2, 3]);
+
+    // The same holds for arrays
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let xs = [PushOnDrop::new(1, dropped_fields.clone()),
+              PushOnDrop::new(2, dropped_fields.clone()),
+              PushOnDrop::new(3, dropped_fields.clone())];
+    drop(xs);
+    assert_eq!(*dropped_fields.borrow(), &[1, 2, 3]);
+
+    // Panic during vec construction means that fields are treated as local variables
+    // Therefore they are dropped in reverse order of initialization
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        vec![
+            PushOnDrop::new(2, cloned.clone()),
+            PushOnDrop::new(1, cloned.clone()),
+            panic!("this panic is catched :D")
+        ];
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+
+    // The same holds for arrays
+    let dropped_fields = Rc::new(RefCell::new(Vec::new()));
+    let cloned = AssertUnwindSafe(dropped_fields.clone());
+    panic::catch_unwind(|| {
+        [
+            PushOnDrop::new(2, cloned.clone()),
+            PushOnDrop::new(1, cloned.clone()),
+            panic!("this panic is catched :D")
+        ];
+    }).err().unwrap();
+    assert_eq!(*dropped_fields.borrow(), &[1, 2]);
+}
+
+fn main() {
+    test_drop_tuple();
+    test_drop_struct();
+    test_drop_enum();
+    test_drop_list();
+}