inform constraint generation using maybe-init

In particular, if we see a variable is DROP-LIVE, but it is not
MAYBE-INIT, then we can ignore the drop. This leavess attempt to use
more complex refinements of the idea (e.g., for subpaths or subfields)
to future work.

10 files changed, 197 insertions, 0 deletions

diff --git a/src/test/ui/nll/maybe-initialized-drop-implicit-fragment-drop.rs b/src/test/ui/nll/maybe-initialized-drop-implicit-fragment-drop.rs
new file mode 100644
index 00000000000..0047f6d5923
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop-implicit-fragment-drop.rs
@@ -0,0 +1,33 @@
+// 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.
+
+//compile-flags: -Z emit-end-regions -Zborrowck=mir -Z nll
+
+#![allow(warnings)]
+
+struct Wrap<'p> { p: &'p mut i32 }
+
+impl<'p> Drop for Wrap<'p> {
+    fn drop(&mut self) {
+        *self.p += 1;
+    }
+}
+
+struct Foo<'p> { a: String, b: Wrap<'p> }
+
+fn main() {
+    let mut x = 0;
+    let wrap = Wrap { p: &mut x };
+    let s = String::from("str");
+    let foo = Foo { a: s, b: wrap };
+    std::mem::drop(foo.b);
+    x = 1; //~ ERROR cannot assign to `x` because it is borrowed [E0506]
+    // FIXME ^ Should not error in the future with implicit dtors, only manually implemented ones
+}
diff --git a/src/test/ui/nll/maybe-initialized-drop-implicit-fragment-drop.stderr b/src/test/ui/nll/maybe-initialized-drop-implicit-fragment-drop.stderr
new file mode 100644
index 00000000000..389334f9c1d
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop-implicit-fragment-drop.stderr
@@ -0,0 +1,11 @@
+error[E0506]: cannot assign to `x` because it is borrowed
+  --> $DIR/maybe-initialized-drop-implicit-fragment-drop.rs:31:5
+   |
+27 |     let wrap = Wrap { p: &mut x };
+   |                          ------ borrow of `x` occurs here
+...
+31 |     x = 1; //~ ERROR cannot assign to `x` because it is borrowed [E0506]
+   |     ^^^^^ assignment to borrowed `x` occurs here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/nll/maybe-initialized-drop-uninitialized.rs b/src/test/ui/nll/maybe-initialized-drop-uninitialized.rs
new file mode 100644
index 00000000000..64a4d391000
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop-uninitialized.rs
@@ -0,0 +1,28 @@
+// 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.
+
+//compile-flags: -Z emit-end-regions -Zborrowck=mir -Z nll
+
+#![allow(warnings)]
+
+struct Wrap<'p> { p: &'p mut i32 }
+
+impl<'p> Drop for Wrap<'p> {
+    fn drop(&mut self) {
+        *self.p += 1;
+    }
+}
+
+fn main() {
+    let mut x = 0;
+    let wrap = Wrap { p: &mut x };
+    std::mem::drop(wrap);
+    x = 1; // OK, drop is inert
+}
diff --git a/src/test/ui/nll/maybe-initialized-drop-uninitialized.stderr b/src/test/ui/nll/maybe-initialized-drop-uninitialized.stderr
new file mode 100644
index 00000000000..e69de29bb2d
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop-uninitialized.stderr
diff --git a/src/test/ui/nll/maybe-initialized-drop-with-fragment.rs b/src/test/ui/nll/maybe-initialized-drop-with-fragment.rs
new file mode 100644
index 00000000000..3242136f005
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop-with-fragment.rs
@@ -0,0 +1,32 @@
+// 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.
+
+//compile-flags: -Z emit-end-regions -Zborrowck=mir -Z nll
+
+#![allow(warnings)]
+
+struct Wrap<'p> { p: &'p mut i32 }
+
+impl<'p> Drop for Wrap<'p> {
+    fn drop(&mut self) {
+        *self.p += 1;
+    }
+}
+
+struct Foo<'p> { a: String, b: Wrap<'p> }
+
+fn main() {
+    let mut x = 0;
+    let wrap = Wrap { p: &mut x };
+    let s = String::from("str");
+    let foo = Foo { a: s, b: wrap };
+    std::mem::drop(foo.a);
+    x = 1; //~ ERROR cannot assign to `x` because it is borrowed [E0506]
+}
diff --git a/src/test/ui/nll/maybe-initialized-drop-with-fragment.stderr b/src/test/ui/nll/maybe-initialized-drop-with-fragment.stderr
new file mode 100644
index 00000000000..9edeca2d188
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop-with-fragment.stderr
@@ -0,0 +1,11 @@
+error[E0506]: cannot assign to `x` because it is borrowed
+  --> $DIR/maybe-initialized-drop-with-fragment.rs:31:5
+   |
+27 |     let wrap = Wrap { p: &mut x };
+   |                          ------ borrow of `x` occurs here
+...
+31 |     x = 1; //~ ERROR cannot assign to `x` because it is borrowed [E0506]
+   |     ^^^^^ assignment to borrowed `x` occurs here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/nll/maybe-initialized-drop-with-uninitialized-fragments.rs b/src/test/ui/nll/maybe-initialized-drop-with-uninitialized-fragments.rs
new file mode 100644
index 00000000000..3e32818b8dc
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop-with-uninitialized-fragments.rs
@@ -0,0 +1,34 @@
+// 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.
+
+//compile-flags: -Z emit-end-regions -Zborrowck=mir -Z nll
+
+#![allow(warnings)]
+
+struct Wrap<'p> { p: &'p mut i32 }
+
+impl<'p> Drop for Wrap<'p> {
+    fn drop(&mut self) {
+        *self.p += 1;
+    }
+}
+
+struct Foo<'p> { a: String, b: Wrap<'p> }
+
+fn main() {
+    let mut x = 0;
+    let wrap = Wrap { p: &mut x };
+    let s = String::from("str");
+    let foo = Foo { a: s, b: wrap };
+    std::mem::drop(foo.a);
+    std::mem::drop(foo.b);
+    x = 1; //~ ERROR cannot assign to `x` because it is borrowed [E0506]
+    // FIXME ^ This currently errors and it should not.
+}
diff --git a/src/test/ui/nll/maybe-initialized-drop-with-uninitialized-fragments.stderr b/src/test/ui/nll/maybe-initialized-drop-with-uninitialized-fragments.stderr
new file mode 100644
index 00000000000..24d0d6d04c8
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop-with-uninitialized-fragments.stderr
@@ -0,0 +1,11 @@
+error[E0506]: cannot assign to `x` because it is borrowed
+  --> $DIR/maybe-initialized-drop-with-uninitialized-fragments.rs:32:5
+   |
+27 |     let wrap = Wrap { p: &mut x };
+   |                          ------ borrow of `x` occurs here
+...
+32 |     x = 1; //~ ERROR cannot assign to `x` because it is borrowed [E0506]
+   |     ^^^^^ assignment to borrowed `x` occurs here
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/nll/maybe-initialized-drop.rs b/src/test/ui/nll/maybe-initialized-drop.rs
new file mode 100644
index 00000000000..291fcbd73f3
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop.rs
@@ -0,0 +1,27 @@
+// 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.
+
+//compile-flags: -Z emit-end-regions -Zborrowck=mir -Z nll
+
+#![allow(warnings)]
+
+struct Wrap<'p> { p: &'p mut i32 }
+
+impl<'p> Drop for Wrap<'p> {
+    fn drop(&mut self) {
+        *self.p += 1;
+    }
+}
+
+fn main() {
+    let mut x = 0;
+    let wrap = Wrap { p: &mut x };
+    x = 1; //~ ERROR cannot assign to `x` because it is borrowed [E0506]
+}
diff --git a/src/test/ui/nll/maybe-initialized-drop.stderr b/src/test/ui/nll/maybe-initialized-drop.stderr
new file mode 100644
index 00000000000..7b1b55d133a
--- /dev/null
+++ b/src/test/ui/nll/maybe-initialized-drop.stderr
@@ -0,0 +1,10 @@
+error[E0506]: cannot assign to `x` because it is borrowed
+  --> $DIR/maybe-initialized-drop.rs:26:5
+   |
+25 |     let wrap = Wrap { p: &mut x };
+   |                          ------ borrow of `x` occurs here
+26 |     x = 1; //~ ERROR cannot assign to `x` because it is borrowed [E0506]
+   |     ^^^^^ assignment to borrowed `x` occurs here
+
+error: aborting due to previous error
+