Fixes in various places

Author: Nadrieril

clippy_utils/src/lib.rs

@@ -2931,6 +2931,7 @@ pub fn expr_use_ctxt<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'tcx>) -> ExprU
             moved_before_use,
             same_ctxt,
         },
+        #[allow(unreachable_patterns)]
         Some(ControlFlow::Break(_)) => unreachable!("type of node is ControlFlow<!>"),
         None => ExprUseCtxt {
             node: Node::Crate(cx.tcx.hir().root_module()),

tests/ui/single_match_else.fixed

@@ -89,7 +89,7 @@ fn main() {
 
     // lint here
     use std::convert::Infallible;
-    if let Ok(a) = Result::<i32, Infallible>::Ok(1) { println!("${:?}", a) } else {
+    if let Ok(a) = Result::<i32, &Infallible>::Ok(1) { println!("${:?}", a) } else {
         println!("else block");
         return;
     }

tests/ui/single_match_else.rs

@@ -98,7 +98,7 @@ fn main() {
 
     // lint here
     use std::convert::Infallible;
-    match Result::<i32, Infallible>::Ok(1) {
+    match Result::<i32, &Infallible>::Ok(1) {
         Ok(a) => println!("${:?}", a),
         Err(_) => {
             println!("else block");

tests/ui/single_match_else.stderr

@@ -64,7 +64,7 @@ LL +     }
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
   --> tests/ui/single_match_else.rs:101:5
    |
-LL | /     match Result::<i32, Infallible>::Ok(1) {
+LL | /     match Result::<i32, &Infallible>::Ok(1) {
 LL | |         Ok(a) => println!("${:?}", a),
 LL | |         Err(_) => {
 LL | |             println!("else block");
@@ -75,7 +75,7 @@ LL | |     }
    |
 help: try
    |
-LL ~     if let Ok(a) = Result::<i32, Infallible>::Ok(1) { println!("${:?}", a) } else {
+LL ~     if let Ok(a) = Result::<i32, &Infallible>::Ok(1) { println!("${:?}", a) } else {
 LL +         println!("else block");
 LL +         return;
 LL +     }