NLL: Updates to diagnostic output in `test/ui`.

31 files changed, 163 insertions, 103 deletions

diff --git a/src/test/ui/augmented-assignments.nll.stderr b/src/test/ui/augmented-assignments.nll.stderr
index deb2e7ed4a3..592f666eff8 100644
--- a/src/test/ui/augmented-assignments.nll.stderr
+++ b/src/test/ui/augmented-assignments.nll.stderr
@@ -17,6 +17,9 @@ LL | |     x;  //~ value moved here
 error[E0596]: cannot borrow immutable item `y` as mutable
   --> $DIR/augmented-assignments.rs:30:5
    |
+LL |     let y = Int(2);
+   |         - help: consider changing this to be mutable: `mut y`
+LL |     //~^ consider changing this to `mut y`
 LL |     y   //~ error: cannot borrow immutable local variable `y` as mutable
    |     ^ cannot borrow as mutable
 
diff --git a/src/test/ui/borrowck/issue-45983.nll.stderr b/src/test/ui/borrowck/issue-45983.nll.stderr
index 1aec71fee34..a008a408d97 100644
--- a/src/test/ui/borrowck/issue-45983.nll.stderr
+++ b/src/test/ui/borrowck/issue-45983.nll.stderr
@@ -14,13 +14,13 @@ error[E0594]: cannot assign to immutable item `x`
   --> $DIR/issue-45983.rs:17:18
    |
 LL |     give_any(|y| x = Some(y));
-   |                  ^^^^^^^^^^^ cannot mutate
-   |
-   = note: the value which is causing this path not to be mutable is...: `x`
+   |                  ^^^^^^^^^^^ cannot assign
 
 error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/issue-45983.rs:17:14
    |
+LL |     let x = None;
+   |         - help: consider changing this to be mutable: `mut x`
 LL |     give_any(|y| x = Some(y));
    |              ^^^^^^^^^^^^^^^ cannot borrow as mutable
 
diff --git a/src/test/ui/borrowck/mut-borrow-of-mut-ref.nll.stderr b/src/test/ui/borrowck/mut-borrow-of-mut-ref.nll.stderr
index f8b84bce04e..0674c823016 100644
--- a/src/test/ui/borrowck/mut-borrow-of-mut-ref.nll.stderr
+++ b/src/test/ui/borrowck/mut-borrow-of-mut-ref.nll.stderr
@@ -1,6 +1,8 @@
 error[E0596]: cannot borrow immutable item `b` as mutable
   --> $DIR/mut-borrow-of-mut-ref.rs:18:7
    |
+LL | fn f(b: &mut i32) {
+   |      - help: consider changing this to be mutable: `mut b`
 LL |     g(&mut b) //~ ERROR cannot borrow
    |       ^^^^^^ cannot borrow as mutable
 
diff --git a/src/test/ui/codemap_tests/huge_multispan_highlight.nll.stderr b/src/test/ui/codemap_tests/huge_multispan_highlight.nll.stderr
index 4526616e488..da0b201f5d4 100644
--- a/src/test/ui/codemap_tests/huge_multispan_highlight.nll.stderr
+++ b/src/test/ui/codemap_tests/huge_multispan_highlight.nll.stderr
@@ -1,6 +1,9 @@
 error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/huge_multispan_highlight.rs:100:13
    |
+LL |     let x = "foo";
+   |         - help: consider changing this to be mutable: `mut x`
+...
 LL |     let y = &mut x; //~ ERROR cannot borrow
    |             ^^^^^^ cannot borrow as mutable
 
diff --git a/src/test/ui/did_you_mean/issue-31424.nll.stderr b/src/test/ui/did_you_mean/issue-31424.nll.stderr
index 6b63f64c699..21c5e3608c0 100644
--- a/src/test/ui/did_you_mean/issue-31424.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-31424.nll.stderr
@@ -7,6 +7,8 @@ LL |         (&mut self).bar(); //~ ERROR cannot borrow
 error[E0596]: cannot borrow immutable item `self` as mutable
   --> $DIR/issue-31424.rs:23:9
    |
+LL |     fn bar(self: &mut Self) {
+   |            ---- help: consider changing this to be mutable: `mut self`
 LL |         (&mut self).bar(); //~ ERROR cannot borrow
    |         ^^^^^^^^^^^ cannot borrow as mutable
 
diff --git a/src/test/ui/did_you_mean/issue-34126.nll.stderr b/src/test/ui/did_you_mean/issue-34126.nll.stderr
index 81f858f6bfc..8dedb6ec4db 100644
--- a/src/test/ui/did_you_mean/issue-34126.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-34126.nll.stderr
@@ -2,7 +2,10 @@ error[E0596]: cannot borrow immutable item `self` as mutable
   --> $DIR/issue-34126.rs:16:18
    |
 LL |         self.run(&mut self); //~ ERROR cannot borrow
-   |                  ^^^^^^^^^ cannot borrow as mutable
+   |                  ^^^^^^^^^
+   |                  |
+   |                  cannot borrow as mutable
+   |                  try removing `&mut` here
 
 error[E0502]: cannot borrow `self` as mutable because it is also borrowed as immutable
   --> $DIR/issue-34126.rs:16:18
diff --git a/src/test/ui/did_you_mean/issue-34337.nll.stderr b/src/test/ui/did_you_mean/issue-34337.nll.stderr
index 258e1bb1ad7..d2271e8e7de 100644
--- a/src/test/ui/did_you_mean/issue-34337.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-34337.nll.stderr
@@ -2,7 +2,10 @@ error[E0596]: cannot borrow immutable item `key` as mutable
   --> $DIR/issue-34337.rs:16:9
    |
 LL |     get(&mut key); //~ ERROR cannot borrow
-   |         ^^^^^^^^ cannot borrow as mutable
+   |         ^^^^^^^^
+   |         |
+   |         cannot borrow as mutable
+   |         try removing `&mut` here
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/did_you_mean/issue-35937.nll.stderr b/src/test/ui/did_you_mean/issue-35937.nll.stderr
index 40b640b63cf..f070921558f 100644
--- a/src/test/ui/did_you_mean/issue-35937.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-35937.nll.stderr
@@ -1,10 +1,10 @@
 error[E0596]: cannot borrow immutable item `f.v` as mutable
   --> $DIR/issue-35937.rs:17:5
    |
+LL |     let f = Foo { v: Vec::new() };
+   |         - help: consider changing this to be mutable: `mut f`
 LL |     f.v.push("cat".to_string()); //~ ERROR cannot borrow
    |     ^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `f`
 
 error[E0384]: cannot assign twice to immutable variable `s.x`
   --> $DIR/issue-35937.rs:26:5
diff --git a/src/test/ui/did_you_mean/issue-37139.nll.stderr b/src/test/ui/did_you_mean/issue-37139.nll.stderr
index 29c7192a98b..e51a1baad25 100644
--- a/src/test/ui/did_you_mean/issue-37139.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-37139.nll.stderr
@@ -2,7 +2,10 @@ error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/issue-37139.rs:22:18
    |
 LL |             test(&mut x); //~ ERROR cannot borrow immutable
-   |                  ^^^^^^ cannot borrow as mutable
+   |                  ^^^^^^
+   |                  |
+   |                  cannot borrow as mutable
+   |                  try removing `&mut` here
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/did_you_mean/issue-38147-1.nll.stderr b/src/test/ui/did_you_mean/issue-38147-1.nll.stderr
index 8e442677951..76b8c8ebf60 100644
--- a/src/test/ui/did_you_mean/issue-38147-1.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-38147-1.nll.stderr
@@ -1,10 +1,10 @@
 error[E0596]: cannot borrow immutable item `*self.s` as mutable
   --> $DIR/issue-38147-1.rs:27:9
    |
+LL |     fn f(&self) {
+   |          ----- help: consider changing this to be a mutable reference: `&mut Foo<'_>`
 LL |         self.s.push('x'); //~ ERROR cannot borrow data mutably
-   |         ^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*self`
+   |         ^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/did_you_mean/issue-38147-4.nll.stderr b/src/test/ui/did_you_mean/issue-38147-4.nll.stderr
index 6808222cc32..c875957623b 100644
--- a/src/test/ui/did_you_mean/issue-38147-4.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-38147-4.nll.stderr
@@ -1,10 +1,10 @@
 error[E0596]: cannot borrow immutable item `*f.s` as mutable
   --> $DIR/issue-38147-4.rs:16:5
    |
+LL | fn f(x: usize, f: &Foo) {
+   |                   ---- help: consider changing this to be a mutable reference: `&mut Foo<'_>`
 LL |     f.s.push('x'); //~ ERROR cannot borrow data mutably
-   |     ^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*f`
+   |     ^^^ `f` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/did_you_mean/issue-39544.nll.stderr b/src/test/ui/did_you_mean/issue-39544.nll.stderr
index f5f5b675e77..02c1debca69 100644
--- a/src/test/ui/did_you_mean/issue-39544.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-39544.nll.stderr
@@ -1,96 +1,100 @@
 error[E0596]: cannot borrow immutable item `z.x` as mutable
   --> $DIR/issue-39544.rs:21:13
    |
+LL |     let z = Z { x: X::Y };
+   |         - help: consider changing this to be mutable: `mut z`
 LL |     let _ = &mut z.x; //~ ERROR cannot borrow
    |             ^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `z`
 
 error[E0596]: cannot borrow immutable item `self.x` as mutable
   --> $DIR/issue-39544.rs:26:17
    |
+LL |     fn foo<'z>(&'z self) {
+   |                -------- help: consider changing this to be a mutable reference: `&mut Z`
 LL |         let _ = &mut self.x; //~ ERROR cannot borrow
-   |                 ^^^^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*self`
+   |                 ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `self.x` as mutable
   --> $DIR/issue-39544.rs:30:17
    |
+LL |     fn foo1(&self, other: &Z) {
+   |             ----- help: consider changing this to be a mutable reference: `&mut Z`
 LL |         let _ = &mut self.x; //~ ERROR cannot borrow
-   |                 ^^^^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*self`
+   |                 ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `other.x` as mutable
   --> $DIR/issue-39544.rs:31:17
    |
+LL |     fn foo1(&self, other: &Z) {
+   |                           -- help: consider changing this to be a mutable reference: `&mut Z`
+LL |         let _ = &mut self.x; //~ ERROR cannot borrow
 LL |         let _ = &mut other.x; //~ ERROR cannot borrow
-   |                 ^^^^^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*other`
+   |                 ^^^^^^^^^^^^ `other` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `self.x` as mutable
   --> $DIR/issue-39544.rs:35:17
    |
+LL |     fn foo2<'a>(&'a self, other: &Z) {
+   |                 -------- help: consider changing this to be a mutable reference: `&mut Z`
 LL |         let _ = &mut self.x; //~ ERROR cannot borrow
-   |                 ^^^^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*self`
+   |                 ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `other.x` as mutable
   --> $DIR/issue-39544.rs:36:17
    |
+LL |     fn foo2<'a>(&'a self, other: &Z) {
+   |                                  -- help: consider changing this to be a mutable reference: `&mut Z`
+LL |         let _ = &mut self.x; //~ ERROR cannot borrow
 LL |         let _ = &mut other.x; //~ ERROR cannot borrow
-   |                 ^^^^^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*other`
+   |                 ^^^^^^^^^^^^ `other` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `self.x` as mutable
   --> $DIR/issue-39544.rs:40:17
    |
+LL |     fn foo3<'a>(self: &'a Self, other: &Z) {
+   |                       -------- help: consider changing this to be a mutable reference: `&mut Z`
 LL |         let _ = &mut self.x; //~ ERROR cannot borrow
-   |                 ^^^^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*self`
+   |                 ^^^^^^^^^^^ `self` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `other.x` as mutable
   --> $DIR/issue-39544.rs:41:17
    |
+LL |     fn foo3<'a>(self: &'a Self, other: &Z) {
+   |                                        -- help: consider changing this to be a mutable reference: `&mut Z`
+LL |         let _ = &mut self.x; //~ ERROR cannot borrow
 LL |         let _ = &mut other.x; //~ ERROR cannot borrow
-   |                 ^^^^^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*other`
+   |                 ^^^^^^^^^^^^ `other` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `other.x` as mutable
   --> $DIR/issue-39544.rs:45:17
    |
+LL |     fn foo4(other: &Z) {
+   |                    -- help: consider changing this to be a mutable reference: `&mut Z`
 LL |         let _ = &mut other.x; //~ ERROR cannot borrow
-   |                 ^^^^^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*other`
+   |                 ^^^^^^^^^^^^ `other` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `z.x` as mutable
   --> $DIR/issue-39544.rs:51:13
    |
+LL | pub fn with_arg(z: Z, w: &Z) {
+   |                 - help: consider changing this to be mutable: `mut z`
 LL |     let _ = &mut z.x; //~ ERROR cannot borrow
    |             ^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `z`
 
 error[E0596]: cannot borrow immutable item `w.x` as mutable
   --> $DIR/issue-39544.rs:52:13
    |
+LL | pub fn with_arg(z: Z, w: &Z) {
+   |                          -- help: consider changing this to be a mutable reference: `&mut Z`
+LL |     let _ = &mut z.x; //~ ERROR cannot borrow
 LL |     let _ = &mut w.x; //~ ERROR cannot borrow
-   |             ^^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*w`
+   |             ^^^^^^^^ `w` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
-error[E0594]: cannot assign to immutable item `*x.0`
+error[E0594]: cannot assign to `*x.0` which is behind a `&` reference
   --> $DIR/issue-39544.rs:58:5
    |
 LL |     *x.0 = 1;
-   |     ^^^^^^^^ cannot mutate
+   |     ^^^^^^^^ cannot assign
 
 error: aborting due to 12 previous errors
 
diff --git a/src/test/ui/did_you_mean/issue-40823.nll.stderr b/src/test/ui/did_you_mean/issue-40823.nll.stderr
index 489e1c39c46..1fd75de8128 100644
--- a/src/test/ui/did_you_mean/issue-40823.nll.stderr
+++ b/src/test/ui/did_you_mean/issue-40823.nll.stderr
@@ -1,8 +1,10 @@
 error[E0596]: cannot borrow immutable item `*buf` as mutable
   --> $DIR/issue-40823.rs:13:5
    |
+LL |     let mut buf = &[1, 2, 3, 4];
+   |                   ------------- help: consider changing this to be a mutable reference: `&mut [1, 2, 3, 4]`
 LL |     buf.iter_mut(); //~ ERROR cannot borrow immutable borrowed content
-   |     ^^^ cannot borrow as mutable
+   |     ^^^ `buf` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/error-codes/E0389.nll.stderr b/src/test/ui/error-codes/E0389.nll.stderr
index 0525e16239d..66e46dfe29d 100644
--- a/src/test/ui/error-codes/E0389.nll.stderr
+++ b/src/test/ui/error-codes/E0389.nll.stderr
@@ -1,4 +1,4 @@
-error[E0594]: cannot assign to data in a `&` reference
+error[E0594]: cannot assign to `fancy_ref.num` which is behind a `&` reference
   --> $DIR/E0389.rs:18:5
    |
 LL |     let fancy_ref = &(&mut fancy);
diff --git a/src/test/ui/issue-36400.nll.stderr b/src/test/ui/issue-36400.nll.stderr
index 80459937479..be10b1d517b 100644
--- a/src/test/ui/issue-36400.nll.stderr
+++ b/src/test/ui/issue-36400.nll.stderr
@@ -1,10 +1,10 @@
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/issue-36400.rs:15:7
    |
+LL |     let x = Box::new(3);
+   |         - help: consider changing this to be mutable: `mut x`
 LL |     f(&mut *x); //~ ERROR cannot borrow immutable
    |       ^^^^^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `x`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.nll.stderr b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.nll.stderr
index f58f33c9a9a..01e26980323 100644
--- a/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.nll.stderr
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-fn-items.nll.stderr
@@ -15,6 +15,8 @@ LL |   y.push(z); //~ ERROR lifetime mismatch
 error[E0596]: cannot borrow immutable item `y` as mutable
   --> $DIR/ex3-both-anon-regions-using-fn-items.rs:11:3
    |
+LL | fn foo(x:fn(&u8, &u8), y: Vec<&u8>, z: &u8) {
+   |                        - help: consider changing this to be mutable: `mut y`
 LL |   y.push(z); //~ ERROR lifetime mismatch
    |   ^ cannot borrow as mutable
 
diff --git a/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.nll.stderr b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.nll.stderr
index 4bfb4ac2833..a61d49fc953 100644
--- a/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.nll.stderr
+++ b/src/test/ui/lifetime-errors/ex3-both-anon-regions-using-trait-objects.nll.stderr
@@ -15,6 +15,8 @@ LL |   y.push(z); //~ ERROR lifetime mismatch
 error[E0596]: cannot borrow immutable item `y` as mutable
   --> $DIR/ex3-both-anon-regions-using-trait-objects.rs:11:3
    |
+LL | fn foo(x:Box<Fn(&u8, &u8)> , y: Vec<&u8>, z: &u8) {
+   |                              - help: consider changing this to be mutable: `mut y`
 LL |   y.push(z); //~ ERROR lifetime mismatch
    |   ^ cannot borrow as mutable
 
diff --git a/src/test/ui/macros/span-covering-argument-1.nll.stderr b/src/test/ui/macros/span-covering-argument-1.nll.stderr
index a12baab4159..213eddee720 100644
--- a/src/test/ui/macros/span-covering-argument-1.nll.stderr
+++ b/src/test/ui/macros/span-covering-argument-1.nll.stderr
@@ -1,6 +1,8 @@
 error[E0596]: cannot borrow immutable item `foo` as mutable
   --> $DIR/span-covering-argument-1.rs:15:14
    |
+LL |             let $s = 0;
+   |                 -- help: consider changing this to be mutable: `mut foo`
 LL |             *&mut $s = 0;
    |              ^^^^^^^ cannot borrow as mutable
 ...
diff --git a/src/test/ui/nll/issue-47388.stderr b/src/test/ui/nll/issue-47388.stderr
index f3952c49a2a..96e9f155414 100644
--- a/src/test/ui/nll/issue-47388.stderr
+++ b/src/test/ui/nll/issue-47388.stderr
@@ -1,4 +1,4 @@
-error[E0594]: cannot assign to data in a `&` reference
+error[E0594]: cannot assign to `fancy_ref.num` which is behind a `&` reference
   --> $DIR/issue-47388.rs:18:5
    |
 LL |     let fancy_ref = &(&mut fancy);
diff --git a/src/test/ui/rfc-2005-default-binding-mode/enum.nll.stderr b/src/test/ui/rfc-2005-default-binding-mode/enum.nll.stderr
index b97bdeea409..8aa7e8a417c 100644
--- a/src/test/ui/rfc-2005-default-binding-mode/enum.nll.stderr
+++ b/src/test/ui/rfc-2005-default-binding-mode/enum.nll.stderr
@@ -1,26 +1,20 @@
-error[E0594]: cannot assign to data in a `&` reference
+error[E0594]: cannot assign to `*x` which is behind a `&` reference
   --> $DIR/enum.rs:19:5
    |
-LL |     let Wrap(x) = &Wrap(3);
-   |              - help: consider changing this to be a mutable reference: `&mut`
 LL |     *x += 1; //~ ERROR cannot assign to immutable
-   |     ^^^^^^^
+   |     ^^^^^^^ cannot assign
 
-error[E0594]: cannot assign to data in a `&` reference
+error[E0594]: cannot assign to `*x` which is behind a `&` reference
   --> $DIR/enum.rs:23:9
    |
-LL |     if let Some(x) = &Some(3) {
-   |                 - help: consider changing this to be a mutable reference: `&mut`
 LL |         *x += 1; //~ ERROR cannot assign to immutable
-   |         ^^^^^^^
+   |         ^^^^^^^ cannot assign
 
-error[E0594]: cannot assign to data in a `&` reference
+error[E0594]: cannot assign to `*x` which is behind a `&` reference
   --> $DIR/enum.rs:29:9
    |
-LL |     while let Some(x) = &Some(3) {
-   |                    - help: consider changing this to be a mutable reference: `&mut`
 LL |         *x += 1; //~ ERROR cannot assign to immutable
-   |         ^^^^^^^
+   |         ^^^^^^^ cannot assign
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/rfc-2005-default-binding-mode/explicit-mut.nll.stderr b/src/test/ui/rfc-2005-default-binding-mode/explicit-mut.nll.stderr
index 3ee4dc07bb8..4e00dec7616 100644
--- a/src/test/ui/rfc-2005-default-binding-mode/explicit-mut.nll.stderr
+++ b/src/test/ui/rfc-2005-default-binding-mode/explicit-mut.nll.stderr
@@ -1,26 +1,20 @@
-error[E0594]: cannot assign to data in a `&` reference
+error[E0594]: cannot assign to `*n` which is behind a `&` reference
   --> $DIR/explicit-mut.rs:17:13
    |
-LL |         Some(n) => {
-   |              - help: consider changing this to be a mutable reference: `&mut`
 LL |             *n += 1; //~ ERROR cannot assign to immutable
-   |             ^^^^^^^
+   |             ^^^^^^^ cannot assign
 
-error[E0594]: cannot assign to data in a `&` reference
+error[E0594]: cannot assign to `*n` which is behind a `&` reference
   --> $DIR/explicit-mut.rs:25:13
    |
-LL |         Some(n) => {
-   |              - help: consider changing this to be a mutable reference: `&mut`
 LL |             *n += 1; //~ ERROR cannot assign to immutable
-   |             ^^^^^^^
+   |             ^^^^^^^ cannot assign
 
-error[E0594]: cannot assign to data in a `&` reference
+error[E0594]: cannot assign to `*n` which is behind a `&` reference
   --> $DIR/explicit-mut.rs:33:13
    |
-LL |         Some(n) => {
-   |              - help: consider changing this to be a mutable reference: `&mut`
 LL |             *n += 1; //~ ERROR cannot assign to immutable
-   |             ^^^^^^^
+   |             ^^^^^^^ cannot assign
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/span/borrowck-borrow-overloaded-auto-deref-mut.nll.stderr b/src/test/ui/span/borrowck-borrow-overloaded-auto-deref-mut.nll.stderr
index 172828b9a40..3282fbba6c5 100644
--- a/src/test/ui/span/borrowck-borrow-overloaded-auto-deref-mut.nll.stderr
+++ b/src/test/ui/span/borrowck-borrow-overloaded-auto-deref-mut.nll.stderr
@@ -1,50 +1,66 @@
 error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/borrowck-borrow-overloaded-auto-deref-mut.rs:63:24
    |
+LL | fn deref_mut_field1(x: Own<Point>) {
+   |                     - help: consider changing this to be mutable: `mut x`
 LL |     let __isize = &mut x.y; //~ ERROR cannot borrow
    |                        ^ cannot borrow as mutable
 
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-borrow-overloaded-auto-deref-mut.rs:75:10
    |
+LL | fn deref_extend_mut_field1(x: &Own<Point>) -> &mut isize {
+   |                               ----------- help: consider changing this to be a mutable reference: `&mut Own<Point>`
 LL |     &mut x.y //~ ERROR cannot borrow
-   |          ^ cannot borrow as mutable
+   |          ^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/borrowck-borrow-overloaded-auto-deref-mut.rs:98:5
    |
+LL | fn assign_field1<'a>(x: Own<Point>) {
+   |                      - help: consider changing this to be mutable: `mut x`
 LL |     x.y = 3; //~ ERROR cannot borrow
    |     ^ cannot borrow as mutable
 
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-borrow-overloaded-auto-deref-mut.rs:102:5
    |
+LL | fn assign_field2<'a>(x: &'a Own<Point>) {
+   |                         -------------- help: consider changing this to be a mutable reference: `&mut Own<Point>`
 LL |     x.y = 3; //~ ERROR cannot borrow
-   |     ^ cannot borrow as mutable
+   |     ^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/borrowck-borrow-overloaded-auto-deref-mut.rs:119:5
    |
+LL | fn deref_mut_method1(x: Own<Point>) {
+   |                      - help: consider changing this to be mutable: `mut x`
 LL |     x.set(0, 0); //~ ERROR cannot borrow
    |     ^ cannot borrow as mutable
 
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-borrow-overloaded-auto-deref-mut.rs:131:5
    |
+LL | fn deref_extend_mut_method1(x: &Own<Point>) -> &mut isize {
+   |                                ----------- help: consider changing this to be a mutable reference: `&mut Own<Point>`
 LL |     x.y_mut() //~ ERROR cannot borrow
-   |     ^ cannot borrow as mutable
+   |     ^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/borrowck-borrow-overloaded-auto-deref-mut.rs:139:6
    |
+LL | fn assign_method1<'a>(x: Own<Point>) {
+   |                       - help: consider changing this to be mutable: `mut x`
 LL |     *x.y_mut() = 3; //~ ERROR cannot borrow
    |      ^ cannot borrow as mutable
 
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-borrow-overloaded-auto-deref-mut.rs:143:6
    |
+LL | fn assign_method2<'a>(x: &'a Own<Point>) {
+   |                          -------------- help: consider changing this to be a mutable reference: `&mut Own<Point>`
 LL |     *x.y_mut() = 3; //~ ERROR cannot borrow
-   |      ^ cannot borrow as mutable
+   |      ^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to 8 previous errors
 
diff --git a/src/test/ui/span/borrowck-borrow-overloaded-deref-mut.nll.stderr b/src/test/ui/span/borrowck-borrow-overloaded-deref-mut.nll.stderr
index 24abe85de76..0b1bfd8cee6 100644
--- a/src/test/ui/span/borrowck-borrow-overloaded-deref-mut.nll.stderr
+++ b/src/test/ui/span/borrowck-borrow-overloaded-deref-mut.nll.stderr
@@ -1,26 +1,34 @@
 error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/borrowck-borrow-overloaded-deref-mut.rs:39:25
    |
+LL | fn deref_mut1(x: Own<isize>) {
+   |               - help: consider changing this to be mutable: `mut x`
 LL |     let __isize = &mut *x; //~ ERROR cannot borrow
    |                         ^ cannot borrow as mutable
 
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-borrow-overloaded-deref-mut.rs:51:11
    |
+LL | fn deref_extend_mut1<'a>(x: &'a Own<isize>) -> &'a mut isize {
+   |                             -------------- help: consider changing this to be a mutable reference: `&mut Own<isize>`
 LL |     &mut **x //~ ERROR cannot borrow
-   |           ^^ cannot borrow as mutable
+   |           ^^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `x` as mutable
   --> $DIR/borrowck-borrow-overloaded-deref-mut.rs:59:6
    |
+LL | fn assign1<'a>(x: Own<isize>) {
+   |                - help: consider changing this to be mutable: `mut x`
 LL |     *x = 3; //~ ERROR cannot borrow
    |      ^ cannot borrow as mutable
 
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-borrow-overloaded-deref-mut.rs:63:6
    |
+LL | fn assign2<'a>(x: &'a Own<isize>) {
+   |                   -------------- help: consider changing this to be a mutable reference: `&mut Own<isize>`
 LL |     **x = 3; //~ ERROR cannot borrow
-   |      ^^ cannot borrow as mutable
+   |      ^^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/span/borrowck-call-is-borrow-issue-12224.nll.stderr b/src/test/ui/span/borrowck-call-is-borrow-issue-12224.nll.stderr
index 26e9ea4dc0b..c4bdef21de4 100644
--- a/src/test/ui/span/borrowck-call-is-borrow-issue-12224.nll.stderr
+++ b/src/test/ui/span/borrowck-call-is-borrow-issue-12224.nll.stderr
@@ -15,16 +15,18 @@ LL | |     }));
 error[E0596]: cannot borrow immutable item `*f` as mutable
   --> $DIR/borrowck-call-is-borrow-issue-12224.rs:35:5
    |
+LL | fn test2<F>(f: &F) where F: FnMut() {
+   |                -- help: consider changing this to be a mutable reference: `&mut F`
 LL |     (*f)();
-   |     ^^^^ cannot borrow as mutable
+   |     ^^^^ `f` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `*f.f` as mutable
   --> $DIR/borrowck-call-is-borrow-issue-12224.rs:44:5
    |
+LL | fn test4(f: &Test) {
+   |             ----- help: consider changing this to be a mutable reference: `&mut Test<'_>`
 LL |     f.f.call_mut(())
-   |     ^^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*f`
+   |     ^^^ `f` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0507]: cannot move out of borrowed content
   --> $DIR/borrowck-call-is-borrow-issue-12224.rs:66:13
diff --git a/src/test/ui/span/borrowck-call-method-from-mut-aliasable.nll.stderr b/src/test/ui/span/borrowck-call-method-from-mut-aliasable.nll.stderr
index 43934bf4aee..0bc614589e3 100644
--- a/src/test/ui/span/borrowck-call-method-from-mut-aliasable.nll.stderr
+++ b/src/test/ui/span/borrowck-call-method-from-mut-aliasable.nll.stderr
@@ -1,8 +1,11 @@
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-call-method-from-mut-aliasable.rs:27:5
    |
+LL | fn b(x: &Foo) {
+   |         ---- help: consider changing this to be a mutable reference: `&mut Foo`
+LL |     x.f();
 LL |     x.h(); //~ ERROR cannot borrow
-   |     ^ cannot borrow as mutable
+   |     ^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/span/borrowck-fn-in-const-b.nll.stderr b/src/test/ui/span/borrowck-fn-in-const-b.nll.stderr
index d3c6fd66599..1cb2c92833c 100644
--- a/src/test/ui/span/borrowck-fn-in-const-b.nll.stderr
+++ b/src/test/ui/span/borrowck-fn-in-const-b.nll.stderr
@@ -1,8 +1,10 @@
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-fn-in-const-b.rs:17:9
    |
+LL |     fn broken(x: &Vec<String>) {
+   |                  ------------ help: consider changing this to be a mutable reference: `&mut std::vec::Vec<std::string::String>`
 LL |         x.push(format!("this is broken"));
-   |         ^ cannot borrow as mutable
+   |         ^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/span/borrowck-object-mutability.nll.stderr b/src/test/ui/span/borrowck-object-mutability.nll.stderr
index 9b5e084bd37..cf615eed556 100644
--- a/src/test/ui/span/borrowck-object-mutability.nll.stderr
+++ b/src/test/ui/span/borrowck-object-mutability.nll.stderr
@@ -1,16 +1,20 @@
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-object-mutability.rs:19:5
    |
+LL | fn borrowed_receiver(x: &Foo) {
+   |                         ---- help: consider changing this to be a mutable reference: `&mut Foo`
+LL |     x.borrowed();
 LL |     x.borrowed_mut(); //~ ERROR cannot borrow
-   |     ^ cannot borrow as mutable
+   |     ^ `x` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `*x` as mutable
   --> $DIR/borrowck-object-mutability.rs:29:5
    |
+LL | fn owned_receiver(x: Box<Foo>) {
+   |                   - help: consider changing this to be mutable: `mut x`
+LL |     x.borrowed();
 LL |     x.borrowed_mut(); //~ ERROR cannot borrow
    |     ^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `x`
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/span/mut-arg-hint.nll.stderr b/src/test/ui/span/mut-arg-hint.nll.stderr
index 8e1cb9720e2..cd19059fdae 100644
--- a/src/test/ui/span/mut-arg-hint.nll.stderr
+++ b/src/test/ui/span/mut-arg-hint.nll.stderr
@@ -1,20 +1,26 @@
 error[E0596]: cannot borrow immutable item `*a` as mutable
   --> $DIR/mut-arg-hint.rs:13:9
    |
+LL |     fn foo(mut a: &String) {
+   |                   ------- help: consider changing this to be a mutable reference: `&mut std::string::String`
 LL |         a.push_str("bar"); //~ ERROR cannot borrow immutable borrowed content
-   |         ^ cannot borrow as mutable
+   |         ^ `a` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `*a` as mutable
   --> $DIR/mut-arg-hint.rs:18:5
    |
+LL | pub fn foo<'a>(mut a: &'a String) {
+   |                       ---------- help: consider changing this to be a mutable reference: `&mut std::string::String`
 LL |     a.push_str("foo"); //~ ERROR cannot borrow immutable borrowed content
-   |     ^ cannot borrow as mutable
+   |     ^ `a` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `*a` as mutable
   --> $DIR/mut-arg-hint.rs:25:9
    |
+LL |     pub fn foo(mut a: &String) {
+   |                       ------- help: consider changing this to be a mutable reference: `&mut std::string::String`
 LL |         a.push_str("foo"); //~ ERROR cannot borrow immutable borrowed content
-   |         ^ cannot borrow as mutable
+   |         ^ `a` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to 3 previous errors
 
diff --git a/src/test/ui/suggestions/closure-immutable-outer-variable.nll.stderr b/src/test/ui/suggestions/closure-immutable-outer-variable.nll.stderr
index bc655114c2b..335ccefe8a0 100644
--- a/src/test/ui/suggestions/closure-immutable-outer-variable.nll.stderr
+++ b/src/test/ui/suggestions/closure-immutable-outer-variable.nll.stderr
@@ -2,7 +2,7 @@ error[E0594]: cannot assign to immutable item `y`
   --> $DIR/closure-immutable-outer-variable.rs:21:26
    |
 LL |     foo(Box::new(move || y = false) as Box<_>); //~ ERROR cannot assign to captured outer variable
-   |                          ^^^^^^^^^ cannot mutate
+   |                          ^^^^^^^^^ cannot assign
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/suggestions/fn-closure-mutable-capture.nll.stderr b/src/test/ui/suggestions/fn-closure-mutable-capture.nll.stderr
index ed691843f9b..7ef21d3720d 100644
--- a/src/test/ui/suggestions/fn-closure-mutable-capture.nll.stderr
+++ b/src/test/ui/suggestions/fn-closure-mutable-capture.nll.stderr
@@ -1,8 +1,8 @@
-error[E0594]: cannot assign to immutable item `x`
+error[E0594]: cannot assign to `x` which is behind a `&` reference
   --> $DIR/fn-closure-mutable-capture.rs:15:17
    |
 LL |     bar(move || x = 1);
-   |                 ^^^^^ cannot mutate
+   |                 ^^^^^ cannot assign
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/trivial-bounds-inconsistent-copy-reborrow.nll.stderr b/src/test/ui/trivial-bounds-inconsistent-copy-reborrow.nll.stderr
index 66547863db2..1a36b0c4839 100644
--- a/src/test/ui/trivial-bounds-inconsistent-copy-reborrow.nll.stderr
+++ b/src/test/ui/trivial-bounds-inconsistent-copy-reborrow.nll.stderr
@@ -1,18 +1,18 @@
 error[E0596]: cannot borrow immutable item `**t` as mutable
   --> $DIR/trivial-bounds-inconsistent-copy-reborrow.rs:16:5
    |
+LL | fn reborrow_mut<'a>(t: &'a &'a mut i32) -> &'a mut i32 where &'a mut i32: Copy {
+   |                        --------------- help: consider changing this to be a mutable reference: `&mut &mut i32`
 LL |     *t //~ ERROR
-   |     ^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*t`
+   |     ^^ `t` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error[E0596]: cannot borrow immutable item `**t` as mutable
   --> $DIR/trivial-bounds-inconsistent-copy-reborrow.rs:20:6
    |
+LL | fn copy_reborrow_mut<'a>(t: &'a &'a mut i32) -> &'a mut i32 where &'a mut i32: Copy {
+   |                             --------------- help: consider changing this to be a mutable reference: `&mut &mut i32`
 LL |     {*t} //~ ERROR
-   |      ^^ cannot borrow as mutable
-   |
-   = note: the value which is causing this path not to be mutable is...: `*t`
+   |      ^^ `t` is a `&` reference, so the data it refers to cannot be borrowed as mutable
 
 error: aborting due to 2 previous errors