Auto merge of #46268 - arielb1:union-borrow, r=nikomatsakis

MIR borrowck: implement union-and-array-compatible semantics

Fixes #44831.
Fixes #44834.
Fixes #45537.
Fixes #45696 (by implementing DerefPure semantics, which is what we want going forward).

r? @nikomatsakis

src/test/compile-fail/borrowck/borrowck-local-borrow-outlives-fn.rs

@@ -13,7 +13,7 @@
 
 fn cplusplus_mode(x: isize) -> &'static isize {
     &x //[ast]~ ERROR `x` does not live long enough
-       //[mir]~^ ERROR borrowed value does not live long enough
 }
+//[mir]~^ ERROR borrowed value does not live long enough
 
 fn main() {}

src/test/compile-fail/borrowck/borrowck-local-borrow-with-panic-outlives-fn.rs

@@ -14,9 +14,9 @@
 fn cplusplus_mode_exceptionally_unsafe(x: &mut Option<&'static mut isize>) {
     let mut z = (0, 0);
     *x = Some(&mut z.1); //[ast]~ ERROR [E0597]
-                         //[mir]~^ ERROR [E0597]
     panic!("catch me for a dangling pointer!")
 }
+//[mir]~^ ERROR [E0597]
 
 fn main() {
     cplusplus_mode_exceptionally_unsafe(&mut None);

src/test/compile-fail/borrowck/borrowck-move-moved-value-into-closure.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 borrowck=mir
+
 #![feature(box_syntax)]
 
 fn call_f<F:FnOnce() -> isize>(f: F) -> isize {
@@ -18,5 +21,6 @@ fn main() {
     let t: Box<_> = box 3;
 
     call_f(move|| { *t + 1 });
-    call_f(move|| { *t + 1 }); //~ ERROR capture of moved value
+    call_f(move|| { *t + 1 }); //[ast]~ ERROR capture of moved value
+    //[mir]~^ ERROR use of moved value
 }

src/test/compile-fail/borrowck/borrowck-mut-borrow-linear-errors.rs

@@ -23,15 +23,9 @@ fn main() {
             1 => { addr = &mut x; } //[ast]~ ERROR [E0499]
             //[mir]~^ ERROR [E0499]
             2 => { addr = &mut x; } //[ast]~ ERROR [E0499]
-            //[mir]~^ ERROR [E0506]
-            //[mir]~| ERROR [E0499]
-            //[mir]~| ERROR [E0499]
+            //[mir]~^ ERROR [E0499]
             _ => { addr = &mut x; } //[ast]~ ERROR [E0499]
-            //[mir]~^ ERROR [E0506]
-            //[mir]~| ERROR [E0499]
-            //[mir]~| ERROR [E0499]
+            //[mir]~^ ERROR [E0499]
         }
     }
 }
-
-

src/test/compile-fail/borrowck/borrowck-thread-local-static-borrow-outlives-fn.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-test will be fixed later
 // revisions: ast mir
 //[mir]compile-flags: -Z borrowck=mir
 

src/test/compile-fail/borrowck/borrowck-union-borrow.rs

@@ -52,12 +52,12 @@ fn main() {
         {
             let ra = &u.a;
             let rmb = &mut u.b; //[ast]~ ERROR cannot borrow `u` (via `u.b`) as mutable because `u` is also borrowed as immutable (via `u.a`)
-                                // FIXME Error for MIR (needs support for union)
+                                //[mir]~^ ERROR cannot borrow `u.b` as mutable because it is also borrowed as immutable
         }
         {
             let ra = &u.a;
             u.b = 1; //[ast]~ ERROR cannot assign to `u.b` because it is borrowed
-                     // FIXME Error for MIR (needs support for union)
+                     //[mir]~^ ERROR cannot assign to `u.b` because it is borrowed
         }
         // Mut borrow, same field
         {
@@ -84,22 +84,23 @@ fn main() {
         {
             let rma = &mut u.a;
             let rb = &u.b; //[ast]~ ERROR cannot borrow `u` (via `u.b`) as immutable because `u` is also borrowed as mutable (via `u.a`)
-                           // FIXME Error for MIR (needs support for union)
+                           //[mir]~^ ERROR cannot borrow `u.b` as immutable because it is also borrowed as mutable
         }
         {
             let ra = &mut u.a;
             let b = u.b; //[ast]~ ERROR cannot use `u.b` because it was mutably borrowed
-                         // FIXME Error for MIR (needs support for union)
+                         //[mir]~^ ERROR cannot use `u.b` because it was mutably borrowed
+
         }
         {
             let rma = &mut u.a;
             let rmb2 = &mut u.b; //[ast]~ ERROR cannot borrow `u` (via `u.b`) as mutable more than once at a time
-                                 // FIXME Error for MIR (needs support for union)
+                                 //[mir]~^ ERROR cannot borrow `u.b` as mutable more than once at a time
         }
         {
             let rma = &mut u.a;
             u.b = 1; //[ast]~ ERROR cannot assign to `u.b` because it is borrowed
-                     // FIXME Error for MIR (needs support for union)
+                     //[mir]~^ ERROR cannot assign to `u.b` because it is borrowed
         }
     }
 }

src/test/compile-fail/borrowck/borrowck-vec-pattern-move-tail.rs

@@ -1,3 +1,4 @@
+
 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
@@ -22,7 +23,7 @@ fn main() {
     println!("t[0]: {}", t[0]);
     a[2] = 0; //[ast]~ ERROR cannot assign to `a[..]` because it is borrowed
               //[cmp]~^ ERROR cannot assign to `a[..]` because it is borrowed (Ast)
-              // FIXME Error for MIR (error missed)
+              //[cmp]~| ERROR cannot assign to `a[..]` because it is borrowed (Mir)
     println!("t[0]: {}", t[0]);
     t[0];
 }

src/test/compile-fail/issue-25579.rs

@@ -20,13 +20,9 @@ fn causes_ice(mut l: &mut Sexpression) {
     loop { match l {
         &mut Sexpression::Num(ref mut n) => {},
         &mut Sexpression::Cons(ref mut expr) => { //[ast]~ ERROR [E0499]
-                                                  //[mir]~^ ERROR [E0506]
-                                                  //[mir]~| ERROR [E0499]
+                                                  //[mir]~^ ERROR [E0499]
             l = &mut **expr; //[ast]~ ERROR [E0506]
                              //[mir]~^ ERROR [E0506]
-                             //[mir]~| ERROR [E0506]
-                             //[mir]~| ERROR [E0499]
-                             //[mir]~| ERROR [E0499]
         }
     }}
 }

src/test/compile-fail/region-borrow-params-issue-29793-big.rs

@@ -16,6 +16,10 @@
 // behavior (because the improperly accepted closure was actually
 // able to be invoked).
 
+// ignore-tidy-linelength
+// revisions: ast mir
+//[mir]compile-flags: -Z borrowck=mir
+
 struct WrapA<F>(Option<F>);
 
 impl<F> WrapA<F> {
@@ -75,9 +79,11 @@ impl<F, T> WrapA<F>
 fn main() {
     let mut w = WrapA::new().set(|x: usize, y: usize| {
         WrapB::new().set(|t: bool| if t { x } else { y }) // (separate errors for `x` vs `y`)
-            //~^ ERROR `x` does not live long enough
-            //~| ERROR `y` does not live long enough
+            //[ast]~^ ERROR `x` does not live long enough
+            //[ast]~| ERROR `y` does not live long enough
     });
+    //[mir]~^ ERROR borrowed value does not live long enough
+    //[mir]~| ERROR borrowed value does not live long enough
 
     w.handle(); // This works
     // w.handle_ref(); // This doesn't

src/test/run-pass/match-pipe-binding.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// compile-flags: -Z borrowck=compare
 
 fn test1() {
     // from issue 6338