Fix match_ref_pats FP on match scrutinee of never type (#15474)

Closes rust-lang/rust-clippy#15378

changelog: [`match_ref_pats`] fix FP on match scrutinee of never type

clippy_lints/src/matches/match_ref_pats.rs

@@ -17,6 +17,11 @@ where
         return;
     }
 
+    // `!` cannot be deref-ed
+    if cx.typeck_results().expr_ty(scrutinee).is_never() {
+        return;
+    }
+
     let (first_sugg, msg, title);
     let ctxt = expr.span.ctxt();
     let mut app = Applicability::Unspecified;

tests/ui/match_ref_pats.fixed

@@ -1,6 +1,12 @@
 #![warn(clippy::match_ref_pats)]
 #![allow(dead_code, unused_variables)]
-#![allow(clippy::enum_variant_names, clippy::equatable_if_let, clippy::uninlined_format_args)]
+#![allow(
+    clippy::enum_variant_names,
+    clippy::equatable_if_let,
+    clippy::uninlined_format_args,
+    clippy::empty_loop,
+    clippy::diverging_sub_expression
+)]
 
 fn ref_pats() {
     {
@@ -120,4 +126,32 @@ mod issue_7740 {
     }
 }
 
+mod issue15378 {
+    fn never_in_match() {
+        match unimplemented!() {
+            &_ => {},
+            &&&42 => {
+                todo!()
+            },
+            _ => {},
+        }
+
+        match panic!() {
+            &_ => {},
+            &&&42 => {
+                todo!()
+            },
+            _ => {},
+        }
+
+        match loop {} {
+            &_ => {},
+            &&&42 => {
+                todo!()
+            },
+            _ => {},
+        }
+    }
+}
+
 fn main() {}

tests/ui/match_ref_pats.rs

@@ -1,6 +1,12 @@
 #![warn(clippy::match_ref_pats)]
 #![allow(dead_code, unused_variables)]
-#![allow(clippy::enum_variant_names, clippy::equatable_if_let, clippy::uninlined_format_args)]
+#![allow(
+    clippy::enum_variant_names,
+    clippy::equatable_if_let,
+    clippy::uninlined_format_args,
+    clippy::empty_loop,
+    clippy::diverging_sub_expression
+)]
 
 fn ref_pats() {
     {
@@ -120,4 +126,32 @@ mod issue_7740 {
     }
 }
 
+mod issue15378 {
+    fn never_in_match() {
+        match unimplemented!() {
+            &_ => {},
+            &&&42 => {
+                todo!()
+            },
+            _ => {},
+        }
+
+        match panic!() {
+            &_ => {},
+            &&&42 => {
+                todo!()
+            },
+            _ => {},
+        }
+
+        match loop {} {
+            &_ => {},
+            &&&42 => {
+                todo!()
+            },
+            _ => {},
+        }
+    }
+}
+
 fn main() {}

tests/ui/match_ref_pats.stderr

@@ -1,5 +1,5 @@
 error: you don't need to add `&` to all patterns
-  --> tests/ui/match_ref_pats.rs:8:9
+  --> tests/ui/match_ref_pats.rs:14:9
    |
 LL | /         match v {
 LL | |
@@ -19,7 +19,7 @@ LL ~             None => println!("none"),
    |
 
 error: you don't need to add `&` to both the expression and the patterns
-  --> tests/ui/match_ref_pats.rs:26:5
+  --> tests/ui/match_ref_pats.rs:32:5
    |
 LL | /     match &w {
 LL | |
@@ -37,7 +37,7 @@ LL ~         None => println!("none"),
    |
 
 error: redundant pattern matching, consider using `is_none()`
-  --> tests/ui/match_ref_pats.rs:39:12
+  --> tests/ui/match_ref_pats.rs:45:12
    |
 LL |     if let &None = a {
    |     -------^^^^^---- help: try: `if a.is_none()`
@@ -46,13 +46,13 @@ LL |     if let &None = a {
    = help: to override `-D warnings` add `#[allow(clippy::redundant_pattern_matching)]`
 
 error: redundant pattern matching, consider using `is_none()`
-  --> tests/ui/match_ref_pats.rs:45:12
+  --> tests/ui/match_ref_pats.rs:51:12
    |
 LL |     if let &None = &b {
    |     -------^^^^^----- help: try: `if b.is_none()`
 
 error: you don't need to add `&` to all patterns
-  --> tests/ui/match_ref_pats.rs:106:9
+  --> tests/ui/match_ref_pats.rs:112:9
    |
 LL | /         match foobar_variant!(0) {
 LL | |