Auto merge of #44922 - zilbuz:issue-44596/E0594, r=pnkfelix

MIR borrowck: move span_label to `borrowck_errors.rs`

The calls to `span_label` are moved and factorized for:
* E0503 (`cannot_use_when_mutably_borrowed()`)
* E0506 (`cannot_assign_to_borrowed()`)

Additionnally, the error E0594 (`cannot_assign_static()`) has been factorized between `check_loan.rs` and `borrowc_check.rs`.

Part of #44596

src/test/compile-fail/E0594.rs

@@ -0,0 +1,20 @@
+// 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.
+
+// revisions: ast mir
+//[mir]compile-flags: -Z emit-end-regions -Z borrowck-mir
+
+static NUM: i32 = 18;
+
+fn main() {
+    NUM = 20; //[ast]~ ERROR E0594
+              //[mir]~^ ERROR cannot assign to immutable static item (Ast)
+              //[mir]~| ERROR cannot assign to immutable static item `NUM` (Mir)
+}

src/test/compile-fail/borrowck/borrowck-assign-to-constants.rs

@@ -8,9 +8,14 @@
 // 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
+
 static foo: isize = 5;
 
 fn main() {
     // assigning to various global constants
-    foo = 6; //~ ERROR cannot assign to immutable static item
+    foo = 6; //[ast]~ ERROR cannot assign to immutable static item
+             //[mir]~^ ERROR cannot assign to immutable static item (Ast)
+             //[mir]~| ERROR cannot assign to immutable static item `foo` (Mir)
 }

src/test/compile-fail/borrowck/borrowck-overloaded-index-ref-index.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
+
 use std::ops::{Index, IndexMut};
 
 struct Foo {
@@ -57,12 +60,18 @@ fn main() {
     let mut s = "hello".to_string();
     let rs = &mut s;
     println!("{}", f[&s]);
-    //~^ ERROR cannot borrow `s` as immutable because it is also borrowed as mutable
+    //[ast]~^ ERROR cannot borrow `s` as immutable because it is also borrowed as mutable
+    //[mir]~^^ ERROR cannot borrow `s` as immutable because it is also borrowed as mutable (Ast)
+    //[mir]~| ERROR cannot borrow `s` as immutable because it is also borrowed as mutable (Mir)
     f[&s] = 10;
-    //~^ ERROR cannot borrow `s` as immutable because it is also borrowed as mutable
+    //[ast]~^ ERROR cannot borrow `s` as immutable because it is also borrowed as mutable
+    //[mir]~^^ ERROR cannot borrow `s` as immutable because it is also borrowed as mutable (Ast)
+    //[mir]~| ERROR cannot borrow `s` as immutable because it is also borrowed as mutable (Mir)
     let s = Bar {
         x: 1,
     };
     s[2] = 20;
-    //~^ ERROR cannot assign to immutable indexed content
+    //[ast]~^ ERROR cannot assign to immutable indexed content
+    //[mir]~^^ ERROR cannot assign to immutable indexed content
+    // FIXME Error for MIR
 }

src/test/compile-fail/issue-5500-1.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
+
 struct TrieMapIterator<'a> {
     node: &'a usize
 }
@@ -15,6 +18,8 @@ struct TrieMapIterator<'a> {
 fn main() {
     let a = 5;
     let _iter = TrieMapIterator{node: &a};
-    _iter.node = & //~ ERROR cannot assign to immutable field
+    _iter.node = & //[ast]~ ERROR cannot assign to immutable field
+                   //[mir]~^ ERROR cannot assign to immutable field `_iter.node` (Ast)
+                   // FIXME Error for MIR
     panic!()
 }