Rollup merge of #145827 - estebank:issue-51976, r=jackh726

On unused binding or binding not present in all patterns, suggest potential typo of unit struct/variant or const

When encountering an or-pattern with a binding not available in all patterns, look for consts and unit struct/variants that have similar names as the binding to detect typos.

```
error[E0408]: variable `Ban` is not bound in all patterns
  --> $DIR/binding-typo.rs:22:9
   |
LL |         (Foo, _) | (Ban, Foo) => {}
   |         ^^^^^^^^    --- variable not in all patterns
   |         |
   |         pattern doesn't bind `Ban`
   |
help: you might have meant to use the similarly named unit variant `Bar`
   |
LL -         (Foo, _) | (Ban, Foo) => {}
LL +         (Foo, _) | (Bar, Foo) => {}
   |
```

For items that are not in the immedate scope, suggest the full path for them:

```
error[E0408]: variable `Non` is not bound in all patterns
  --> $DIR/binding-typo-2.rs:51:16
   |
LL |         (Non | Some(_))=> {}
   |          ---   ^^^^^^^ pattern doesn't bind `Non`
   |          |
   |          variable not in all patterns
   |
help: you might have meant to use the similarly named unit variant `None`
   |
LL -         (Non | Some(_))=> {}
LL +         (core::option::Option::None | Some(_))=> {}
   |
```

When encountering a typo in a pattern that gets interpreted as an unused binding, look for unit struct/variant of the same type as the binding:

```
error: unused variable: `Non`
  --> $DIR/binding-typo-2.rs:36:9
   |
LL |         Non => {}
   |         ^^^
   |
help: if this is intentional, prefix it with an underscore
   |
LL |         _Non => {}
   |         +
help: you might have meant to pattern match on the similarly named variant `None`
   |
LL -         Non => {}
LL +         std::prelude::v1::None => {}
   |
```

 Suggest constant on unused binding in a pattern

```
error: unused variable: `Batery`
  --> $DIR/binding-typo-2.rs:110:9
   |
LL |         Batery => {}
   |         ^^^^^^
   |
help: if this is intentional, prefix it with an underscore
   |
LL |         _Batery => {}
   |         +
help: you might have meant to pattern match on the similarly named constant `Battery`
   |
LL |         Battery => {}
   |            +
```

Fix rust-lang/rust#51976.

2 files changed, 12 insertions, 12 deletions

diff --git a/tests/ui/resolve/resolve-inconsistent-names.rs b/tests/ui/resolve/resolve-inconsistent-names.rs
index 9a40b20346c..96504720e83 100644
--- a/tests/ui/resolve/resolve-inconsistent-names.rs
+++ b/tests/ui/resolve/resolve-inconsistent-names.rs
@@ -10,8 +10,8 @@ pub mod m {
 fn main() {
     let y = 1;
     match y {
-       a | b => {} //~  ERROR variable `a` is not bound in all patterns
-                   //~| ERROR variable `b` is not bound in all patterns
+        a | b => {} //~  ERROR variable `a` is not bound in all patterns
+        //~| ERROR variable `b` is not bound in all patterns
     }
 
     let x = (E::A, E::B);
diff --git a/tests/ui/resolve/resolve-inconsistent-names.stderr b/tests/ui/resolve/resolve-inconsistent-names.stderr
index 5fac622eef2..d2333150961 100644
--- a/tests/ui/resolve/resolve-inconsistent-names.stderr
+++ b/tests/ui/resolve/resolve-inconsistent-names.stderr
@@ -1,18 +1,18 @@
 error[E0408]: variable `b` is not bound in all patterns
-  --> $DIR/resolve-inconsistent-names.rs:13:8
+  --> $DIR/resolve-inconsistent-names.rs:13:9
    |
-LL |        a | b => {}
-   |        ^   - variable not in all patterns
-   |        |
-   |        pattern doesn't bind `b`
+LL |         a | b => {}
+   |         ^   - variable not in all patterns
+   |         |
+   |         pattern doesn't bind `b`
 
 error[E0408]: variable `a` is not bound in all patterns
-  --> $DIR/resolve-inconsistent-names.rs:13:12
+  --> $DIR/resolve-inconsistent-names.rs:13:13
    |
-LL |        a | b => {}
-   |        -   ^ pattern doesn't bind `a`
-   |        |
-   |        variable not in all patterns
+LL |         a | b => {}
+   |         -   ^ pattern doesn't bind `a`
+   |         |
+   |         variable not in all patterns
 
 error[E0408]: variable `c` is not bound in all patterns
   --> $DIR/resolve-inconsistent-names.rs:19:9