Adapt clippy test.

Author: cjgillot

src/tools/clippy/tests/ui/infallible_destructuring_match.fixed

@@ -1,5 +1,5 @@
 //@run-rustfix
-#![feature(exhaustive_patterns, never_type)]
+#![feature(never_type)]
 #![allow(dead_code, unreachable_code, unused_variables)]
 #![allow(clippy::let_and_return)]
 

src/tools/clippy/tests/ui/infallible_destructuring_match.rs

@@ -1,5 +1,5 @@
 //@run-rustfix
-#![feature(exhaustive_patterns, never_type)]
+#![feature(never_type)]
 #![allow(dead_code, unreachable_code, unused_variables)]
 #![allow(clippy::let_and_return)]
 

src/tools/clippy/tests/ui/single_match_else.fixed

@@ -2,6 +2,7 @@
 //@aux-build: proc_macros.rs
 #![warn(clippy::single_match_else)]
 #![allow(unused, clippy::needless_return, clippy::no_effect, clippy::uninlined_format_args)]
+#![allow(irrefutable_let_patterns)] // The fixed code may introduce some cases.
 extern crate proc_macros;
 use proc_macros::with_span;
 

src/tools/clippy/tests/ui/single_match_else.rs

@@ -2,6 +2,7 @@
 //@aux-build: proc_macros.rs
 #![warn(clippy::single_match_else)]
 #![allow(unused, clippy::needless_return, clippy::no_effect, clippy::uninlined_format_args)]
+#![allow(irrefutable_let_patterns)] // The fixed code may introduce some cases.
 extern crate proc_macros;
 use proc_macros::with_span;
 

src/tools/clippy/tests/ui/single_match_else.stderr

@@ -1,5 +1,5 @@
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:17:13
+  --> $DIR/single_match_else.rs:18:13
    |
 LL |       let _ = match ExprNode::Butterflies {
    |  _____________^
@@ -21,7 +21,7 @@ LL ~     };
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:82:5
+  --> $DIR/single_match_else.rs:83:5
    |
 LL | /     match Some(1) {
 LL | |         Some(a) => println!("${:?}", a),
@@ -41,7 +41,7 @@ LL +     }
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:91:5
+  --> $DIR/single_match_else.rs:92:5
    |
 LL | /     match Some(1) {
 LL | |         Some(a) => println!("${:?}", a),
@@ -61,7 +61,7 @@ LL +     }
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:101:5
+  --> $DIR/single_match_else.rs:102:5
    |
 LL | /     match Result::<i32, Infallible>::Ok(1) {
 LL | |         Ok(a) => println!("${:?}", a),
@@ -81,7 +81,7 @@ LL +     }
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:110:5
+  --> $DIR/single_match_else.rs:111:5
    |
 LL | /     match Cow::from("moo") {
 LL | |         Cow::Owned(a) => println!("${:?}", a),
@@ -101,7 +101,7 @@ LL +     }
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:120:5
+  --> $DIR/single_match_else.rs:121:5
    |
 LL | /     match bar {
 LL | |         Some(v) => unsafe {
@@ -124,7 +124,7 @@ LL +     }
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:131:5
+  --> $DIR/single_match_else.rs:132:5
    |
 LL | /     match bar {
 LL | |         Some(v) => {
@@ -148,7 +148,7 @@ LL +     } }
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:143:5
+  --> $DIR/single_match_else.rs:144:5
    |
 LL | /     match bar {
 LL | |         Some(v) => unsafe {
@@ -172,7 +172,7 @@ LL +     } }
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> $DIR/single_match_else.rs:155:5
+  --> $DIR/single_match_else.rs:156:5
    |
 LL | /     match bar {
 LL | |         #[rustfmt::skip]