Removed ignore-test-compare-mode-nll from borrowck-closures-unique.rs

by strengthening the tests there.

In almost all cases the strengthening amount to just encoding a use
that models the original lexical lifetime. A more invasive revision
was made in one case where it seems the actual issue is MIR-borrowck's
greater "knowledge" of unreachable code in the control flow...

src/test/ui/borrowck/borrowck-closures-unique.nll.stderr

@@ -0,0 +1,54 @@
+error[E0500]: closure requires unique access to `x` but it is already borrowed
+  --> $DIR/borrowck-closures-unique.rs:36:14
+   |
+LL |     let c1 = || get(x);
+   |              --     - first borrow occurs due to use of `x` in closure
+   |              |
+   |              borrow occurs here
+LL |     let c2 = || set(x); //~ ERROR closure requires unique access to `x`
+   |              ^^     - second borrow occurs due to use of `x` in closure
+   |              |
+   |              closure construction occurs here
+LL |     c1;
+   |     -- borrow later used here
+
+error[E0500]: closure requires unique access to `x` but it is already borrowed
+  --> $DIR/borrowck-closures-unique.rs:42:14
+   |
+LL |     let c1 = || get(x);
+   |              --     - first borrow occurs due to use of `x` in closure
+   |              |
+   |              borrow occurs here
+LL |     let c2 = || { get(x); set(x); }; //~ ERROR closure requires unique access to `x`
+   |              ^^       - second borrow occurs due to use of `x` in closure
+   |              |
+   |              closure construction occurs here
+LL |     c1;
+   |     -- borrow later used here
+
+error[E0524]: two closures require unique access to `x` at the same time
+  --> $DIR/borrowck-closures-unique.rs:48:14
+   |
+LL |     let c1 = || set(x);
+   |              --     - first borrow occurs due to use of `x` in closure
+   |              |
+   |              first closure is constructed here
+LL |     let c2 = || set(x); //~ ERROR two closures require unique access to `x` at the same time
+   |              ^^     - second borrow occurs due to use of `x` in closure
+   |              |
+   |              second closure is constructed here
+LL |     c1;
+   |     -- borrow later used here
+
+error[E0594]: cannot assign to `x`, as it is not declared as mutable
+  --> $DIR/borrowck-closures-unique.rs:57:38
+   |
+LL | fn e(x: &'static mut isize) {
+   |      - help: consider changing this to be mutable: `mut x`
+LL |     let c1 = |y: &'static mut isize| x = y; //~ ERROR closure cannot assign to immutable argument
+   |                                      ^^^^^ cannot assign
+
+error: aborting due to 4 previous errors
+
+Some errors occurred: E0500, E0524, E0594.
+For more information about an error, try `rustc --explain E0500`.

src/test/ui/borrowck/borrowck-closures-unique.rs

@@ -8,14 +8,14 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// ignore-compare-mode-nll
-
 // Tests that a closure which requires mutable access to the referent
 // of an `&mut` requires a "unique" borrow -- that is, the variable to
 // be borrowed (here, `x`) will not be borrowed *mutably*, but
 //  may be *immutable*, but we cannot allow
 // multiple borrows.
 
+
+
 fn get(x: &isize) -> isize {
     *x
 }
@@ -27,25 +27,40 @@ fn set(x: &mut isize) -> isize {
 fn a(x: &mut isize) {
     let c1 = || get(x);
     let c2 = || get(x);
+    c1();
+    c2();
 }
 
 fn b(x: &mut isize) {
     let c1 = || get(x);
     let c2 = || set(x); //~ ERROR closure requires unique access to `x`
+    c1;
 }
 
 fn c(x: &mut isize) {
     let c1 = || get(x);
     let c2 = || { get(x); set(x); }; //~ ERROR closure requires unique access to `x`
+    c1;
 }
 
 fn d(x: &mut isize) {
     let c1 = || set(x);
     let c2 = || set(x); //~ ERROR two closures require unique access to `x` at the same time
+    c1;
 }
 
-fn e(x: &mut isize) {
+// This test was originally encoded in the form shown as `fn f` below.
+// However, since MIR-borrowck and thus NLL takes more control-flow information
+// into account, it was necessary to change the test in order to witness the
+// same (expected) error under both AST-borrowck and NLL.
+fn e(x: &'static mut isize) {
+    let c1 = |y: &'static mut isize| x = y; //~ ERROR closure cannot assign to immutable argument
+    c1;
+}
+
+fn f(x: &'static mut isize) {
     let c1 = || x = panic!(); //~ ERROR closure cannot assign to immutable argument
+    c1;
 }
 
 fn main() {

src/test/ui/borrowck/borrowck-closures-unique.stderr

@@ -1,5 +1,5 @@
 error[E0500]: closure requires unique access to `x` but it is already borrowed
-  --> $DIR/borrowck-closures-unique.rs:34:14
+  --> $DIR/borrowck-closures-unique.rs:36:14
    |
 LL |     let c1 = || get(x);
    |              --     - previous borrow occurs due to use of `x` in closure
@@ -9,11 +9,12 @@ LL |     let c2 = || set(x); //~ ERROR closure requires unique access to `x`
    |              ^^     - borrow occurs due to use of `x` in closure
    |              |
    |              closure construction occurs here
+LL |     c1;
 LL | }
    | - borrow ends here
 
 error[E0500]: closure requires unique access to `x` but it is already borrowed
-  --> $DIR/borrowck-closures-unique.rs:39:14
+  --> $DIR/borrowck-closures-unique.rs:42:14
    |
 LL |     let c1 = || get(x);
    |              --     - previous borrow occurs due to use of `x` in closure
@@ -23,11 +24,12 @@ LL |     let c2 = || { get(x); set(x); }; //~ ERROR closure requires unique acce
    |              ^^       - borrow occurs due to use of `x` in closure
    |              |
    |              closure construction occurs here
+LL |     c1;
 LL | }
    | - borrow ends here
 
 error[E0524]: two closures require unique access to `x` at the same time
-  --> $DIR/borrowck-closures-unique.rs:44:14
+  --> $DIR/borrowck-closures-unique.rs:48:14
    |
 LL |     let c1 = || set(x);
    |              --     - previous borrow occurs due to use of `x` in closure
@@ -37,11 +39,22 @@ LL |     let c2 = || set(x); //~ ERROR two closures require unique access to `x`
    |              ^^     - borrow occurs due to use of `x` in closure
    |              |
    |              second closure is constructed here
+LL |     c1;
 LL | }
    | - borrow from first closure ends here
 
 error[E0595]: closure cannot assign to immutable argument `x`
-  --> $DIR/borrowck-closures-unique.rs:48:14
+  --> $DIR/borrowck-closures-unique.rs:57:14
+   |
+LL |     let c1 = |y: &'static mut isize| x = y; //~ ERROR closure cannot assign to immutable argument
+   |              ^^^^^^^^^^^^^^^^^^^^^^^ cannot borrow mutably
+help: consider removing the `&mut`, as it is an immutable binding to a mutable reference
+   |
+LL |     x //~ ERROR closure cannot assign to immutable argument
+   |     ^
+
+error[E0595]: closure cannot assign to immutable argument `x`
+  --> $DIR/borrowck-closures-unique.rs:62:14
    |
 LL |     let c1 = || x = panic!(); //~ ERROR closure cannot assign to immutable argument
    |              ^^ cannot borrow mutably
@@ -50,7 +63,7 @@ help: consider removing the `&mut`, as it is an immutable binding to a mutable r
 LL |     x //~ ERROR closure cannot assign to immutable argument
    |     ^
 
-error: aborting due to 4 previous errors
+error: aborting due to 5 previous errors
 
 Some errors occurred: E0500, E0524, E0595.
 For more information about an error, try `rustc --explain E0500`.