start enforcing closure types

src/test/ui/nll/user-annotations/closure-substs.rs

@@ -0,0 +1,29 @@
+// 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.
+
+#![feature(nll)]
+
+// Test that we enforce user-provided type annotations on closures.
+
+fn foo<'a>() {
+    |x: &'a i32| -> &'static i32 {
+        return x; //~ ERROR
+    };
+}
+
+fn bar<'a>() {
+    |x: &i32, b: fn(&'static i32)| {
+        b(x); //~ ERROR
+        //~^ ERROR borrowed data escapes outside of closure
+        //~| ERROR unsatisfied lifetime constraints
+    };
+}
+
+fn main() { }

src/test/ui/nll/user-annotations/closure-substs.stderr

@@ -0,0 +1,42 @@
+error: unsatisfied lifetime constraints
+  --> $DIR/closure-substs.rs:17:16
+   |
+LL | fn foo<'a>() {
+   |        -- lifetime `'a` defined here
+LL |     |x: &'a i32| -> &'static i32 {
+LL |         return x; //~ ERROR
+   |                ^ returning this value requires that `'a` must outlive `'static`
+
+error: borrowed data escapes outside of closure
+  --> $DIR/closure-substs.rs:23:9
+   |
+LL |     |x: &i32, b: fn(&'static i32)| {
+   |      - `x` is a reference that is only valid in the closure body
+LL |         b(x); //~ ERROR
+   |         ^^^^ `x` escapes the closure body here
+
+error: borrowed data escapes outside of closure
+  --> $DIR/closure-substs.rs:23:9
+   |
+LL |     |x: &i32, b: fn(&'static i32)| {
+   |      -        - `b` is declared here, outside of the closure body
+   |      |
+   |      `x` is a reference that is only valid in the closure body
+LL |         b(x); //~ ERROR
+   |         ^^^^ `x` escapes the closure body here
+
+error: unsatisfied lifetime constraints
+  --> $DIR/closure-substs.rs:23:9
+   |
+LL |     |x: &i32, b: fn(&'static i32)| {
+   |     ------------------------------
+   |     |   |
+   |     |   let's call the lifetime of this reference `'1`
+   |     lifetime `'2` represents this closure's body
+LL |         b(x); //~ ERROR
+   |         ^^^^ argument requires that `'1` must outlive `'2`
+   |
+   = note: closure implements `Fn`, so references to captured variables can't escape the closure
+
+error: aborting due to 4 previous errors
+