Update the existing compile-fail tests to reflect diagnostic changes in NLL.

Author: pnkfelix

src/test/compile-fail/assign-imm-local-twice.rs

@@ -13,6 +13,7 @@
 
 fn test() {
     let v: isize;
+    //[mir]~^ NOTE consider changing this to `mut v`
     v = 1; //[ast]~ NOTE first assignment
            //[mir]~^ NOTE first assignment
     println!("v={}", v);

src/test/compile-fail/issue-45199.rs

@@ -13,6 +13,7 @@
 
 fn test_drop_replace() {
     let b: Box<isize>;
+    //[mir]~^ NOTE consider changing this to `mut b`
     b = Box::new(1);    //[ast]~ NOTE first assignment
                         //[mir]~^ NOTE first assignment
     b = Box::new(2);    //[ast]~ ERROR cannot assign twice to immutable variable
@@ -24,14 +25,15 @@ fn test_drop_replace() {
 fn test_call() {
     let b = Box::new(1);    //[ast]~ NOTE first assignment
                             //[mir]~^ NOTE first assignment
+                            //[mir]~| NOTE consider changing this to `mut b`
     b = Box::new(2);        //[ast]~ ERROR cannot assign twice to immutable variable
                             //[mir]~^ ERROR cannot assign twice to immutable variable `b`
                             //[ast]~| NOTE cannot assign twice to immutable
                             //[mir]~| NOTE cannot assign twice to immutable
 }
 
 fn test_args(b: Box<i32>) {  //[ast]~ NOTE first assignment
-                                //[mir]~^ NOTE argument not declared as `mut`
+                                //[mir]~^ NOTE consider changing this to `mut b`
     b = Box::new(2);            //[ast]~ ERROR cannot assign twice to immutable variable
                                 //[mir]~^ ERROR cannot assign to immutable argument `b`
                                 //[ast]~| NOTE cannot assign twice to immutable

src/test/compile-fail/liveness-assign-imm-local-in-loop.rs

@@ -13,6 +13,7 @@
 
 fn test() {
     let v: isize;
+    //[mir]~^ NOTE consider changing this to `mut v`
     loop {
         v = 1; //[ast]~ ERROR cannot assign twice to immutable variable
                //[mir]~^ ERROR cannot assign twice to immutable variable `v`

src/test/compile-fail/liveness-assign-imm-local-in-op-eq.rs

@@ -13,6 +13,7 @@
 
 fn test() {
     let v: isize;
+    //[mir]~^ NOTE consider changing this to `mut v`
     v = 2;  //[ast]~ NOTE first assignment
             //[mir]~^ NOTE first assignment
     v += 1; //[ast]~ ERROR cannot assign twice to immutable variable

src/test/compile-fail/liveness-assign-imm-local-with-drop.rs

@@ -14,6 +14,7 @@
 fn test() {
     let b = Box::new(1); //[ast]~ NOTE first assignment
                          //[mir]~^ NOTE first assignment
+                         //[mir]~| NOTE consider changing this to `mut b`
     drop(b);
     b = Box::new(2); //[ast]~ ERROR cannot assign twice to immutable variable
                      //[mir]~^ ERROR cannot assign twice to immutable variable `b`

src/test/compile-fail/liveness-assign-imm-local-with-init.rs

@@ -14,6 +14,7 @@
 fn test() {
     let v: isize = 1; //[ast]~ NOTE first assignment
                       //[mir]~^ NOTE first assignment
+                      //[mir]~| NOTE consider changing this to `mut v`
     v.clone();
     v = 2; //[ast]~ ERROR cannot assign twice to immutable variable
            //[mir]~^ ERROR cannot assign twice to immutable variable `v`