Improve 'mut ' diagnostic.

4 files changed, 43 insertions, 14 deletions

diff --git a/src/test/ui/parser/issue-32501.rs b/src/test/ui/parser/issue-32501.rs
index 695baf81872..500242030c6 100644
--- a/src/test/ui/parser/issue-32501.rs
+++ b/src/test/ui/parser/issue-32501.rs
@@ -5,5 +5,5 @@ fn main() {
     let mut b = 0;
     let mut _b = 0;
     let mut _ = 0;
-    //~^ ERROR `mut` must be attached to each individual binding
+    //~^ ERROR `mut` must be followed by a named binding
 }
diff --git a/src/test/ui/parser/issue-32501.stderr b/src/test/ui/parser/issue-32501.stderr
index f5d3300cf9c..d53302449a8 100644
--- a/src/test/ui/parser/issue-32501.stderr
+++ b/src/test/ui/parser/issue-32501.stderr
@@ -1,8 +1,10 @@
-error: `mut` must be attached to each individual binding
+error: `mut` must be followed by a named binding
   --> $DIR/issue-32501.rs:7:9
    |
 LL |     let mut _ = 0;
-   |         ^^^^^ help: add `mut` to each binding: `_`
+   |         ^^^^^ help: remove the `mut` prefix: `_`
+   |
+   = note: `mut` may be followed by `variable` and `variable @ pattern`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/parser/mut-patterns.rs b/src/test/ui/parser/mut-patterns.rs
index 0c78ca726e0..d46186a0fea 100644
--- a/src/test/ui/parser/mut-patterns.rs
+++ b/src/test/ui/parser/mut-patterns.rs
@@ -6,6 +6,9 @@
 #![allow(warnings)]
 
 pub fn main() {
+    let mut _ = 0; //~ ERROR `mut` must be followed by a named binding
+    let mut (_, _) = (0, 0); //~ ERROR `mut` must be followed by a named binding
+
     let mut mut x = 0;
     //~^ ERROR `mut` on a binding may not be repeated
     //~| remove the additional `mut`s
diff --git a/src/test/ui/parser/mut-patterns.stderr b/src/test/ui/parser/mut-patterns.stderr
index a1293129e2e..18ffaa52558 100644
--- a/src/test/ui/parser/mut-patterns.stderr
+++ b/src/test/ui/parser/mut-patterns.stderr
@@ -1,29 +1,49 @@
+error: `mut` must be followed by a named binding
+  --> $DIR/mut-patterns.rs:9:9
+   |
+LL |     let mut _ = 0;
+   |         ^^^^^ help: remove the `mut` prefix: `_`
+   |
+   = note: `mut` may be followed by `variable` and `variable @ pattern`
+
+error: `mut` must be followed by a named binding
+  --> $DIR/mut-patterns.rs:10:9
+   |
+LL |     let mut (_, _) = (0, 0);
+   |         ^^^^^^^^^^ help: remove the `mut` prefix: `(_, _)`
+   |
+   = note: `mut` may be followed by `variable` and `variable @ pattern`
+
 error: `mut` on a binding may not be repeated
-  --> $DIR/mut-patterns.rs:9:13
+  --> $DIR/mut-patterns.rs:12:13
    |
 LL |     let mut mut x = 0;
    |             ^^^ help: remove the additional `mut`s
 
 error: `mut` must be attached to each individual binding
-  --> $DIR/mut-patterns.rs:14:9
+  --> $DIR/mut-patterns.rs:17:9
    |
 LL |     let mut Foo { x: x } = Foo { x: 3 };
    |         ^^^^^^^^^^^^^^^^ help: add `mut` to each binding: `Foo { x: mut x }`
+   |
+   = note: `mut` may be followed by `variable` and `variable @ pattern`
 
 error: `mut` must be attached to each individual binding
-  --> $DIR/mut-patterns.rs:18:9
+  --> $DIR/mut-patterns.rs:21:9
    |
 LL |     let mut Foo { x } = Foo { x: 3 };
    |         ^^^^^^^^^^^^^ help: add `mut` to each binding: `Foo { mut x }`
+   |
+   = note: `mut` may be followed by `variable` and `variable @ pattern`
 
 error: `mut` on a binding may not be repeated
-  --> $DIR/mut-patterns.rs:23:13
+  --> $DIR/mut-patterns.rs:26:13
    |
 LL |     let mut mut yield(become, await) = r#yield(0, 0);
    |             ^^^ help: remove the additional `mut`s
 
 error: expected identifier, found reserved keyword `yield`
-  --> $DIR/mut-patterns.rs:23:17
+  --> $DIR/mut-patterns.rs:26:17
    |
 LL |     let mut mut yield(become, await) = r#yield(0, 0);
    |                 ^^^^^ expected identifier, found reserved keyword
@@ -33,7 +53,7 @@ LL |     let mut mut r#yield(become, await) = r#yield(0, 0);
    |                 ^^^^^^^
 
 error: expected identifier, found reserved keyword `become`
-  --> $DIR/mut-patterns.rs:23:23
+  --> $DIR/mut-patterns.rs:26:23
    |
 LL |     let mut mut yield(become, await) = r#yield(0, 0);
    |                       ^^^^^^ expected identifier, found reserved keyword
@@ -43,7 +63,7 @@ LL |     let mut mut yield(r#become, await) = r#yield(0, 0);
    |                       ^^^^^^^^
 
 error: expected identifier, found reserved keyword `await`
-  --> $DIR/mut-patterns.rs:23:31
+  --> $DIR/mut-patterns.rs:26:31
    |
 LL |     let mut mut yield(become, await) = r#yield(0, 0);
    |                               ^^^^^ expected identifier, found reserved keyword
@@ -53,19 +73,23 @@ LL |     let mut mut yield(become, r#await) = r#yield(0, 0);
    |                               ^^^^^^^
 
 error: `mut` must be attached to each individual binding
-  --> $DIR/mut-patterns.rs:23:9
+  --> $DIR/mut-patterns.rs:26:9
    |
 LL |     let mut mut yield(become, await) = r#yield(0, 0);
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `mut` to each binding: `r#yield(mut r#become, mut r#await)`
+   |
+   = note: `mut` may be followed by `variable` and `variable @ pattern`
 
 error: `mut` must be attached to each individual binding
-  --> $DIR/mut-patterns.rs:32:9
+  --> $DIR/mut-patterns.rs:35:9
    |
 LL |     let mut W(mut a, W(b, W(ref c, W(d, B { box f }))))
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: add `mut` to each binding: `W(mut a, W(mut b, W(ref c, W(mut d, B { box mut f }))))`
+   |
+   = note: `mut` may be followed by `variable` and `variable @ pattern`
 
 error: expected identifier, found `x`
-  --> $DIR/mut-patterns.rs:39:21
+  --> $DIR/mut-patterns.rs:42:21
    |
 LL |             let mut $p = 0;
    |                     ^^ expected identifier
@@ -73,5 +97,5 @@ LL |             let mut $p = 0;
 LL |     foo!(x);
    |     -------- in this macro invocation
 
-error: aborting due to 10 previous errors
+error: aborting due to 12 previous errors