fix: unnested_or_patterns suggests wrongly in let (#14401)

Closes #9952

changelog: [`unnested_or_patterns`] fix wrong suggestion in `let`

Author: y21

clippy_lints/src/unnested_or_patterns.rs

@@ -120,18 +120,25 @@ fn lint_unnested_or_patterns(cx: &EarlyContext<'_>, pat: &Pat) {
 
 /// Remove all `(p)` patterns in `pat`.
 fn remove_all_parens(pat: &mut P<Pat>) {
-    struct Visitor;
+    #[derive(Default)]
+    struct Visitor {
+        /// If is not in the outer most pattern. This is needed to avoid removing the outermost
+        /// parens because top-level or-patterns are not allowed in let statements.
+        is_inner: bool,
+    }
+
     impl MutVisitor for Visitor {
         fn visit_pat(&mut self, pat: &mut P<Pat>) {
+            let is_inner = mem::replace(&mut self.is_inner, true);
             walk_pat(self, pat);
             let inner = match &mut pat.kind {
-                Paren(i) => mem::replace(&mut i.kind, Wild),
+                Paren(i) if is_inner => mem::replace(&mut i.kind, Wild),
                 _ => return,
             };
             pat.kind = inner;
         }
     }
-    Visitor.visit_pat(pat);
+    Visitor::default().visit_pat(pat);
 }
 
 /// Insert parens where necessary according to Rust's precedence rules for patterns.

tests/ui/unnested_or_patterns.fixed

@@ -64,3 +64,16 @@ fn msrv_1_53() {
     if let [1 | 53] = [0] {}
     //~^ unnested_or_patterns
 }
+
+mod issue9952 {
+    fn or_in_local() {
+        let (0 | 1 | _) = 0;
+        //~^ unnested_or_patterns
+
+        if let (0 | 1 | _) = 0 {}
+        //~^ unnested_or_patterns
+    }
+
+    fn or_in_param((x | x | x): i32) {}
+    //~^ unnested_or_patterns
+}

tests/ui/unnested_or_patterns.rs

@@ -64,3 +64,16 @@ fn msrv_1_53() {
     if let [1] | [53] = [0] {}
     //~^ unnested_or_patterns
 }
+
+mod issue9952 {
+    fn or_in_local() {
+        let (0 | (1 | _)) = 0;
+        //~^ unnested_or_patterns
+
+        if let (0 | (1 | _)) = 0 {}
+        //~^ unnested_or_patterns
+    }
+
+    fn or_in_param((x | (x | x)): i32) {}
+    //~^ unnested_or_patterns
+}

tests/ui/unnested_or_patterns.stderr

@@ -204,5 +204,41 @@ LL -     if let [1] | [53] = [0] {}
 LL +     if let [1 | 53] = [0] {}
    |
 
-error: aborting due to 17 previous errors
+error: unnested or-patterns
+  --> tests/ui/unnested_or_patterns.rs:70:13
+   |
+LL |         let (0 | (1 | _)) = 0;
+   |             ^^^^^^^^^^^^^
+   |
+help: nest the patterns
+   |
+LL -         let (0 | (1 | _)) = 0;
+LL +         let (0 | 1 | _) = 0;
+   |
+
+error: unnested or-patterns
+  --> tests/ui/unnested_or_patterns.rs:73:16
+   |
+LL |         if let (0 | (1 | _)) = 0 {}
+   |                ^^^^^^^^^^^^^
+   |
+help: nest the patterns
+   |
+LL -         if let (0 | (1 | _)) = 0 {}
+LL +         if let (0 | 1 | _) = 0 {}
+   |
+
+error: unnested or-patterns
+  --> tests/ui/unnested_or_patterns.rs:77:20
+   |
+LL |     fn or_in_param((x | (x | x)): i32) {}
+   |                    ^^^^^^^^^^^^^
+   |
+help: nest the patterns
+   |
+LL -     fn or_in_param((x | (x | x)): i32) {}
+LL +     fn or_in_param((x | x | x): i32) {}
+   |
+
+error: aborting due to 20 previous errors