Added revisions: ast mir template to tests that this PR sync'ed ast+mir borrowcks.

(There are other tests that this PR also improves, but were not
completely synchronized. I chose to wait until later to pull those
into the `revisions: ast mir` testing pattern; later being either when
they *are* synchronized, or in some PR where we migrate all borrowck
tests, regardless of whether MIR-borrowck is "finished" for them or
not.)

src/test/compile-fail/borrowck/borrowck-init-in-fru.rs

@@ -8,6 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// revisions: ast mir
+//[mir]compile-flags: -Z emit-end-regions -Z borrowck-mir
+
 #[derive(Clone)]
 struct point {
     x: isize,
@@ -16,6 +19,9 @@ struct point {
 
 fn main() {
     let mut origin: point;
-    origin = point {x: 10,.. origin}; //~ ERROR use of possibly uninitialized variable: `origin.y`
+    origin = point {x: 10,.. origin};
+    //[ast]~^ ERROR use of possibly uninitialized variable: `origin.y` [E0381]
+    //[mir]~^^ ERROR (Ast) [E0381]
+    //[mir]~|  ERROR (Mir) [E0381]
     origin.clone();
 }

src/test/compile-fail/borrowck/borrowck-use-in-index-lvalue.rs

@@ -8,12 +8,19 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// revisions: ast mir
+//[mir]compile-flags: -Z emit-end-regions -Z borrowck-mir
+
 fn test() {
     let w: &mut [isize];
-    w[5] = 0; //~ ERROR use of possibly uninitialized variable: `*w`
+    w[5] = 0; //[ast]~ ERROR use of possibly uninitialized variable: `*w` [E0381]
+              //[mir]~^ ERROR (Ast) [E0381]
+              //[mir]~| ERROR (Mir) [E0381]
 
     let mut w: &mut [isize];
-    w[5] = 0; //~ ERROR use of possibly uninitialized variable: `*w`
+    w[5] = 0; //[ast]~ ERROR use of possibly uninitialized variable: `*w` [E0381]
+              //[mir]~^ ERROR (Ast) [E0381]
+              //[mir]~| ERROR (Mir) [E0381]
 }
 
 fn main() { test(); }

src/test/compile-fail/borrowck/borrowck-use-uninitialized-in-cast-trait.rs

@@ -8,6 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// revisions: ast mir
+//[mir]compile-flags: -Z emit-end-regions -Z borrowck-mir
+
 // Variation on `borrowck-use-uninitialized-in-cast` in which we do a
 // trait cast from an uninitialized source. Issue #20791.
 
@@ -16,5 +19,7 @@ impl Foo for i32 { }
 
 fn main() {
     let x: &i32;
-    let y = x as *const Foo; //~ ERROR use of possibly uninitialized variable: `*x`
+    let y = x as *const Foo; //[ast]~ ERROR use of possibly uninitialized variable: `*x`
+                             //[mir]~^ ERROR (Ast) [E0381]
+                             //[mir]~| ERROR (Mir) [E0381]
 }

src/test/compile-fail/borrowck/borrowck-use-uninitialized-in-cast.rs

@@ -8,11 +8,16 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// revisions: ast mir
+//[mir]compile-flags: -Z emit-end-regions -Z borrowck-mir
+
 // Check that we detect unused values that are cast to other things.
 // The problem was specified to casting to `*`, as creating unsafe
 // pointers was not being fully checked. Issue #20791.
 
 fn main() {
     let x: &i32;
-    let y = x as *const i32; //~ ERROR use of possibly uninitialized variable: `*x`
+    let y = x as *const i32; //[ast]~ ERROR use of possibly uninitialized variable: `*x` [E0381]
+                             //[mir]~^ ERROR (Ast) [E0381]
+                             //[mir]~| ERROR (Mir) [E0381]
 }