Incorporate edition flag testing into tests of `-Z borrowck=migrate`.

src/test/ui/borrowck/borrowck-feature-nll-overrides-migrate.edition.stderr

@@ -1,5 +1,5 @@
 error[E0507]: cannot move out of borrowed content
-  --> $DIR/borrowck-feature-nll-overrides-migrate.rs:30:17
+  --> $DIR/borrowck-feature-nll-overrides-migrate.rs:32:17
    |
 LL |                 (|| { let bar = foo; bar.take() })();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of borrowed content

src/test/ui/borrowck/borrowck-feature-nll-overrides-migrate.rs

@@ -18,7 +18,9 @@
 // NLL checks will be emitted as errors *even* in the presence of `-Z
 // borrowck=migrate`.
 
-// compile-flags: -Z borrowck=migrate
+// revisions: zflag edition
+// [zflag]compile-flags: -Z borrowck=migrate
+// [edition]compile-flags: --edition 2018
 
 #![feature(nll)]
 
@@ -28,7 +30,8 @@ fn main() {
         ref mut foo
             if {
                 (|| { let bar = foo; bar.take() })();
-                //~^ ERROR cannot move out of borrowed content [E0507]
+                //[zflag]~^ ERROR cannot move out of borrowed content [E0507]
+                //[edition]~^^ ERROR cannot move out of borrowed content [E0507]
                 false
             } => {},
         Some(ref _s) => println!("Note this arm is bogus; the `Some` became `None` in the guard."),

src/test/ui/borrowck/borrowck-feature-nll-overrides-migrate.zflag.stderr

@@ -0,0 +1,9 @@
+error[E0507]: cannot move out of borrowed content
+  --> $DIR/borrowck-feature-nll-overrides-migrate.rs:32:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of borrowed content
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0507`.

src/test/ui/borrowck/borrowck-migrate-to-nll.edition.stderr

@@ -1,5 +1,5 @@
 warning[E0507]: cannot move out of borrowed content
-  --> $DIR/borrowck-migrate-to-nll.rs:26:17
+  --> $DIR/borrowck-migrate-to-nll.rs:35:17
    |
 LL |                 (|| { let bar = foo; bar.take() })();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of borrowed content
@@ -9,7 +9,7 @@ LL |                 (|| { let bar = foo; bar.take() })();
            This warning will become a hard error in the future.
 
 warning[E0507]: cannot move out of `foo`, as it is immutable for the pattern guard
-  --> $DIR/borrowck-migrate-to-nll.rs:26:17
+  --> $DIR/borrowck-migrate-to-nll.rs:35:17
    |
 LL |                 (|| { let bar = foo; bar.take() })();
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/borrowck/borrowck-migrate-to-nll.rs

@@ -15,8 +15,17 @@
 // Therefore, for backwards-compatiblity, under borrowck=migrate the
 // NLL checks will be emitted as *warnings*.
 
-// compile-flags: -Z borrowck=migrate
-// run-pass
+// NLL mode makes this compile-fail; we cannot currently encode a
+// test that is run-pass or compile-fail based on compare-mode. So
+// just ignore it instead:
+
+// ignore-compare-mode-nll
+
+// revisions: zflag edition
+//[zflag]compile-flags: -Z borrowck=migrate
+//[edition]compile-flags: --edition 2018
+//[zflag] run-pass
+//[edition] run-pass
 
 fn main() {
     match Some(&4) {

src/test/ui/borrowck/borrowck-migrate-to-nll.zflag.stderr

@@ -0,0 +1,24 @@
+warning[E0507]: cannot move out of borrowed content
+  --> $DIR/borrowck-migrate-to-nll.rs:35:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cannot move out of borrowed content
+   |
+   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
+           It represents potential unsoundness in your code.
+           This warning will become a hard error in the future.
+
+warning[E0507]: cannot move out of `foo`, as it is immutable for the pattern guard
+  --> $DIR/borrowck-migrate-to-nll.rs:35:17
+   |
+LL |                 (|| { let bar = foo; bar.take() })();
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                 |
+   |                 cannot move out of `foo`, as it is immutable for the pattern guard
+   |                 cannot move
+   |
+   = note: variables bound in patterns are immutable until the end of the pattern guard
+   = warning: This error has been downgraded to a warning for backwards compatibility with previous releases.
+           It represents potential unsoundness in your code.
+           This warning will become a hard error in the future.
+