Improve error message where a closure escapes fn while trying to borrow

from the current fn. Employ the new `span_suggestion` to show how you
can use `move`.

5 files changed, 54 insertions, 4 deletions

diff --git a/src/test/compile-fail/borrowck-escaping-closure-error-1.rs b/src/test/compile-fail/borrowck-escaping-closure-error-1.rs
new file mode 100644
index 00000000000..87e40df7663
--- /dev/null
+++ b/src/test/compile-fail/borrowck-escaping-closure-error-1.rs
@@ -0,0 +1,25 @@
+// Copyright 2015 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.
+
+use std::thread::spawn;
+
+// Test that we give a custom error (E0373) for the case where a
+// closure is escaping current frame, and offer a suggested code edit.
+// I refrained from including the precise message here, but the
+// original text as of the time of this writing is:
+//
+//    closure may outlive the current function, but it borrows `books`,
+//    which is owned by the current function
+
+fn main() {
+    let mut books = vec![1,2,3];
+    spawn(|| books.push(4));
+    //~^ ERROR E0373
+}
diff --git a/src/test/compile-fail/borrowck-escaping-closure-error-2.rs b/src/test/compile-fail/borrowck-escaping-closure-error-2.rs
new file mode 100644
index 00000000000..67700be890b
--- /dev/null
+++ b/src/test/compile-fail/borrowck-escaping-closure-error-2.rs
@@ -0,0 +1,25 @@
+// Copyright 2015 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.
+
+// Test that we give a custom error (E0373) for the case where a
+// closure is escaping current frame, and offer a suggested code edit.
+// I refrained from including the precise message here, but the
+// original text as of the time of this writing is:
+//
+//    closure may outlive the current function, but it borrows `books`,
+//    which is owned by the current function
+
+fn foo<'a>(x: &'a i32) -> Box<FnMut()+'a> {
+    let mut books = vec![1,2,3];
+    Box::new(|| books.push(4))
+    //~^ ERROR E0373
+}
+
+fn main() { }
diff --git a/src/test/compile-fail/issue-16747.rs b/src/test/compile-fail/issue-16747.rs
index 64334fe4392..b4abef0bd28 100644
--- a/src/test/compile-fail/issue-16747.rs
+++ b/src/test/compile-fail/issue-16747.rs
@@ -18,10 +18,10 @@ trait Collection { fn len(&self) -> usize; }
 
 struct List<'a, T: ListItem<'a>> {
 //~^ ERROR the parameter type `T` may not live long enough
-//~^^ NOTE ...so that the reference type `&'a [T]` does not outlive the data it points at
+//~| HELP consider adding an explicit lifetime bound
+//~| NOTE ...so that the reference type `&'a [T]` does not outlive the data it points at
     slice: &'a [T]
 }
-//~^ HELP consider adding an explicit lifetime bound
 impl<'a, T: ListItem<'a>> Collection for List<'a, T> {
     fn len(&self) -> usize {
         0
diff --git a/src/test/compile-fail/issue-4335.rs b/src/test/compile-fail/issue-4335.rs
index 55a793f7480..0089bff3e8f 100644
--- a/src/test/compile-fail/issue-4335.rs
+++ b/src/test/compile-fail/issue-4335.rs
@@ -15,7 +15,7 @@ fn id<T>(t: T) -> T { t }
 fn f<'r, T>(v: &'r T) -> Box<FnMut() -> T + 'r> {
     // FIXME (#22405): Replace `Box::new` with `box` here when/if possible.
     id(Box::new(|| *v))
-        //~^ ERROR `v` does not live long enough
+        //~^ ERROR E0373
         //~| ERROR cannot move out of borrowed content
 }
 
diff --git a/src/test/compile-fail/regions-nested-fns-2.rs b/src/test/compile-fail/regions-nested-fns-2.rs
index bdebadb2832..948dc8cd219 100644
--- a/src/test/compile-fail/regions-nested-fns-2.rs
+++ b/src/test/compile-fail/regions-nested-fns-2.rs
@@ -13,7 +13,7 @@ fn ignore<F>(_f: F) where F: for<'z> FnOnce(&'z isize) -> &'z isize {}
 fn nested() {
     let y = 3;
     ignore(
-        |z| { //~ ERROR `y` does not live long enough
+        |z| { //~ ERROR E0373
             if false { &y } else { z }
         });
 }