tests for #[may_dangle] attribute.

Author: pnkfelix

src/test/compile-fail/auxiliary/dropck_eyepatch_extern_crate.rs

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+// Copyright 2016 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.
+
+#![feature(generic_param_attrs)]
+#![feature(dropck_eyepatch)]
+
+// The point of this test is to illustrate that the `#[may_dangle]`
+// attribute specifically allows, in the context of a type
+// implementing `Drop`, a generic parameter to be instantiated with a
+// lifetime that does not strictly outlive the owning type itself,
+// and that this attributes effects are preserved when importing
+// the type from another crate.
+//
+// See also dropck-eyepatch.rs for more information about the general
+// structure of the test.
+
+use std::fmt;
+
+pub struct Dt<A: fmt::Debug>(pub &'static str, pub A);
+pub struct Dr<'a, B:'a+fmt::Debug>(pub &'static str, pub &'a B);
+pub struct Pt<A,B: fmt::Debug>(pub &'static str, pub A, pub B);
+pub struct Pr<'a, 'b, B:'a+'b+fmt::Debug>(pub &'static str, pub &'a B, pub &'b B);
+pub struct St<A: fmt::Debug>(pub &'static str, pub A);
+pub struct Sr<'a, B:'a+fmt::Debug>(pub &'static str, pub &'a B);
+
+impl<A: fmt::Debug> Drop for Dt<A> {
+    fn drop(&mut self) { println!("drop {} {:?}", self.0, self.1); }
+}
+impl<'a, B: fmt::Debug> Drop for Dr<'a, B> {
+    fn drop(&mut self) { println!("drop {} {:?}", self.0, self.1); }
+}
+unsafe impl<#[may_dangle] A, B: fmt::Debug> Drop for Pt<A, B> {
+    // (unsafe to access self.1  due to #[may_dangle] on A)
+    fn drop(&mut self) { println!("drop {} {:?}", self.0, self.2); }
+}
+unsafe impl<#[may_dangle] 'a, 'b, B: fmt::Debug> Drop for Pr<'a, 'b, B> {
+    // (unsafe to access self.1 due to #[may_dangle] on 'a)
+    fn drop(&mut self) { println!("drop {} {:?}", self.0, self.2); }
+}

src/test/compile-fail/dropck-eyepatch-extern-crate.rs

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+// Copyright 2016 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.
+
+// aux-build:dropck_eyepatch_extern_crate.rs
+
+extern crate dropck_eyepatch_extern_crate as other;
+
+use other::{Dt,Dr,Pt,Pr,St,Sr};
+
+fn main() {
+    use std::cell::Cell;
+    let c_long;
+    let (c, mut dt, mut dr, mut pt, mut pr, st, sr)
+        : (Cell<_>, Dt<_>, Dr<_>, Pt<_, _>, Pr<_>, St<_>, Sr<_>);
+    c_long = Cell::new(1);
+    c = Cell::new(1);
+
+    // No error: sufficiently long-lived state can be referenced in dtors
+    dt = Dt("dt", &c_long);
+    dr = Dr("dr", &c_long);
+    // Error: destructor order imprecisely modelled
+    dt = Dt("dt", &c); //~ ERROR `c` does not live long enough
+    dr = Dr("dr", &c); //~ ERROR `c` does not live long enough
+
+    // No error: Drop impl asserts .1 (A and &'a _) are not accessed
+    pt = Pt("pt", &c, &c_long);
+    pr = Pr("pr", &c, &c_long);
+
+    // Error: Drop impl's assertion does not apply to `B` nor `&'b _`
+    pt = Pt("pt", &c_long, &c); //~ ERROR `c` does not live long enough
+    pr = Pr("pr", &c_long, &c); //~ ERROR `c` does not live long enough
+
+    // No error: St and Sr have no destructor.
+    st = St("st", &c);
+    sr = Sr("sr", &c);
+
+    println!("{:?}", (dt.0, dr.0, pt.0, pr.0, st.0, sr.0));
+}

src/test/compile-fail/dropck-eyepatch.rs

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+// Copyright 2016 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.
+
+#![feature(generic_param_attrs)]
+#![feature(dropck_eyepatch)]
+
+// The point of this test is to illustrate that the `#[may_dangle]`
+// attribute specifically allows, in the context of a type
+// implementing `Drop`, a generic parameter to be instantiated with a
+// lifetime that does not strictly outlive the owning type itself.
+//
+// Here we test that only the expected errors are issued.
+//
+// The illustration is made concrete by comparison with two variations
+// on the type with `#[may_dangle]`:
+//
+//   1. an analogous type that does not implement `Drop` (and thus
+//      should exhibit maximal flexibility with respect to dropck), and
+//
+//   2. an analogous type that does not use `#[may_dangle]` (and thus
+//      should exhibit the standard limitations imposed by dropck.
+//
+// The types in this file follow a pattern, {D,P,S}{t,r}, where:
+//
+// - D means "I implement Drop"
+//
+// - P means "I implement Drop but guarantee my (first) parameter is
+//     pure, i.e. not accessed from the destructor"; no other parameters
+//     are pure.
+//
+// - S means "I do not implement Drop"
+//
+// - t suffix is used when the first generic is a type
+//
+// - r suffix is used when the first generic is a lifetime.
+
+use std::fmt;
+
+struct Dt<A: fmt::Debug>(&'static str, A);
+struct Dr<'a, B:'a+fmt::Debug>(&'static str, &'a B);
+struct Pt<A,B: fmt::Debug>(&'static str, A, B);
+struct Pr<'a, 'b, B:'a+'b+fmt::Debug>(&'static str, &'a B, &'b B);
+struct St<A: fmt::Debug>(&'static str, A);
+struct Sr<'a, B:'a+fmt::Debug>(&'static str, &'a B);
+
+impl<A: fmt::Debug> Drop for Dt<A> {
+    fn drop(&mut self) { println!("drop {} {:?}", self.0, self.1); }
+}
+impl<'a, B: fmt::Debug> Drop for Dr<'a, B> {
+    fn drop(&mut self) { println!("drop {} {:?}", self.0, self.1); }
+}
+unsafe impl<#[may_dangle] A, B: fmt::Debug> Drop for Pt<A, B> {
+    // (unsafe to access self.1  due to #[may_dangle] on A)
+    fn drop(&mut self) { println!("drop {} {:?}", self.0, self.2); }
+}
+unsafe impl<#[may_dangle] 'a, 'b, B: fmt::Debug> Drop for Pr<'a, 'b, B> {
+    // (unsafe to access self.1 due to #[may_dangle] on 'a)
+    fn drop(&mut self) { println!("drop {} {:?}", self.0, self.2); }
+}
+
+fn main() {
+    use std::cell::Cell;
+    let c_long;
+    let (c, mut dt, mut dr, mut pt, mut pr, st, sr)
+        : (Cell<_>, Dt<_>, Dr<_>, Pt<_, _>, Pr<_>, St<_>, Sr<_>);
+    c_long = Cell::new(1);
+    c = Cell::new(1);
+
+    // No error: sufficiently long-lived state can be referenced in dtors
+    dt = Dt("dt", &c_long);
+    dr = Dr("dr", &c_long);
+    // Error: destructor order imprecisely modelled
+    dt = Dt("dt", &c); //~ ERROR `c` does not live long enough
+    dr = Dr("dr", &c); //~ ERROR `c` does not live long enough
+
+    // No error: Drop impl asserts .1 (A and &'a _) are not accessed
+    pt = Pt("pt", &c, &c_long);
+    pr = Pr("pr", &c, &c_long);
+
+    // Error: Drop impl's assertion does not apply to `B` nor `&'b _`
+    pt = Pt("pt", &c_long, &c); //~ ERROR `c` does not live long enough
+    pr = Pr("pr", &c_long, &c); //~ ERROR `c` does not live long enough
+
+    // No error: St and Sr have no destructor.
+    st = St("st", &c);
+    sr = Sr("sr", &c);
+
+    println!("{:?}", (dt.0, dr.0, pt.0, pr.0, st.0, sr.0));
+}

src/test/compile-fail/feature-gate-may-dangle.rs

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+// Copyright 2016 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.
+
+// Check that `may_dangle` is rejected if `dropck_eyepatch` feature gate is absent.
+
+#![feature(generic_param_attrs)]
+
+struct Pt<A>(A);
+impl<#[may_dangle] A> Drop for Pt<A> {
+    //~^ ERROR may_dangle has unstable semantics and may be removed in the future
+    //~| HELP add #![feature(dropck_eyepatch)] to the crate attributes to enable
+    fn drop(&mut self) { }
+}

src/test/run-pass/auxiliary/dropck_eyepatch_extern_crate.rs

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+// Copyright 2016 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.
+
+#![feature(generic_param_attrs)]
+#![feature(dropck_eyepatch)]
+
+// The point of this test is to illustrate that the `#[may_dangle]`
+// attribute specifically allows, in the context of a type
+// implementing `Drop`, a generic parameter to be instantiated with a
+// lifetime that does not strictly outlive the owning type itself,
+// and that this attributes effects are preserved when importing
+// the type from another crate.
+//
+// See also dropck-eyepatch.rs for more information about the general
+// structure of the test.
+
+use std::cell::RefCell;
+
+pub trait Foo { fn foo(&self, _: &str); }
+
+pub struct Dt<A: Foo>(pub &'static str, pub A);
+pub struct Dr<'a, B:'a+Foo>(pub &'static str, pub &'a B);
+pub struct Pt<A,B: Foo>(pub &'static str, pub A, pub B);
+pub struct Pr<'a, 'b, B:'a+'b+Foo>(pub &'static str, pub &'a B, pub &'b B);
+pub struct St<A: Foo>(pub &'static str, pub A);
+pub struct Sr<'a, B:'a+Foo>(pub &'static str, pub &'a B);
+
+impl<A: Foo> Drop for Dt<A> {
+    fn drop(&mut self) { println!("drop {}", self.0); self.1.foo(self.0); }
+}
+impl<'a, B: Foo> Drop for Dr<'a, B> {
+    fn drop(&mut self) { println!("drop {}", self.0); self.1.foo(self.0); }
+}
+unsafe impl<#[may_dangle] A, B: Foo> Drop for Pt<A, B> {
+    // (unsafe to access self.1  due to #[may_dangle] on A)
+    fn drop(&mut self) { println!("drop {}", self.0); self.2.foo(self.0); }
+}
+unsafe impl<#[may_dangle] 'a, 'b, B: Foo> Drop for Pr<'a, 'b, B> {
+    // (unsafe to access self.1 due to #[may_dangle] on 'a)
+    fn drop(&mut self) { println!("drop {}", self.0); self.2.foo(self.0); }
+}
+
+impl Foo for RefCell<String> {
+    fn foo(&self, s: &str) {
+        let s2 = format!("{}|{}", *self.borrow(), s);
+        *self.borrow_mut() = s2;
+    }
+}
+
+impl<'a, T:Foo> Foo for &'a T {
+    fn foo(&self, s: &str) {
+        (*self).foo(s);
+    }
+}

src/test/run-pass/dropck-eyepatch-extern-crate.rs

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+// Copyright 2016 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.
+
+// aux-build:dropck_eyepatch_extern_crate.rs
+
+extern crate dropck_eyepatch_extern_crate as other;
+
+use other::{Dt,Dr,Pt,Pr,St,Sr};
+
+fn main() {
+    use std::cell::RefCell;
+
+    struct CheckOnDrop(RefCell<String>, &'static str);
+    impl Drop for CheckOnDrop {
+        fn drop(&mut self) { assert_eq!(*self.0.borrow(), self.1); }
+    }
+
+    let c_long;
+    let (c, dt, dr, pt, pr, st, sr)
+        : (CheckOnDrop, Dt<_>, Dr<_>, Pt<_, _>, Pr<_>, St<_>, Sr<_>);
+    c_long = CheckOnDrop(RefCell::new("c_long".to_string()),
+                         "c_long|pr|pt|dr|dt");
+    c = CheckOnDrop(RefCell::new("c".to_string()),
+                    "c");
+
+    // No error: sufficiently long-lived state can be referenced in dtors
+    dt = Dt("dt", &c_long.0);
+    dr = Dr("dr", &c_long.0);
+
+    // No error: Drop impl asserts .1 (A and &'a _) are not accessed
+    pt = Pt("pt", &c.0, &c_long.0);
+    pr = Pr("pr", &c.0, &c_long.0);
+
+    // No error: St and Sr have no destructor.
+    st = St("st", &c.0);
+    sr = Sr("sr", &c.0);
+
+    println!("{:?}", (dt.0, dr.0, pt.0, pr.0, st.0, sr.0));
+    assert_eq!(*c_long.0.borrow(), "c_long");
+    assert_eq!(*c.0.borrow(), "c");
+}