Extend `NONMINIMAL_BOOL` lint

3 files changed, 59 insertions, 1 deletions

diff --git a/clippy_lints/src/booleans.rs b/clippy_lints/src/booleans.rs
index 2d1c250ace9..3c17f65f0d3 100644
--- a/clippy_lints/src/booleans.rs
+++ b/clippy_lints/src/booleans.rs
@@ -85,6 +85,32 @@ impl<'tcx> LateLintPass<'tcx> for NonminimalBool {
     ) {
         NonminimalBoolVisitor { cx }.visit_body(body);
     }
+
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
+        if let ExprKind::Unary(UnOp::Not, sub) = expr.kind
+            && !expr.span.from_expansion()
+            && let ExprKind::Binary(op, left, right) = sub.kind
+        {
+            let new_op = match op.node {
+                BinOpKind::Eq => "!=",
+                BinOpKind::Ne => "==",
+                _ => return,
+            };
+            let Some(left) = snippet_opt(cx, left.span) else { return };
+            let Some(right) = snippet_opt(cx, right.span) else {
+                return;
+            };
+            span_lint_and_sugg(
+                cx,
+                NONMINIMAL_BOOL,
+                expr.span,
+                "this boolean expression can be simplified",
+                "try",
+                format!("{left} {new_op} {right}"),
+                Applicability::MachineApplicable,
+            );
+        }
+    }
 }
 struct NonminimalBoolVisitor<'a, 'tcx> {
     cx: &'a LateContext<'tcx>,
diff --git a/tests/ui/nonminimal_bool.rs b/tests/ui/nonminimal_bool.rs
index f7c3df7066f..ee092b9aca6 100644
--- a/tests/ui/nonminimal_bool.rs
+++ b/tests/ui/nonminimal_bool.rs
@@ -156,3 +156,11 @@ fn issue11932() {
         x % 3 == 0
     };
 }
+
+fn issue_5794() {
+    let a = 0;
+    if !(12 == a) {} //~ ERROR: this boolean expression can be simplified
+    if !(a == 12) {} //~ ERROR: this boolean expression can be simplified
+    if !(12 != a) {} //~ ERROR: this boolean expression can be simplified
+    if !(a != 12) {} //~ ERROR: this boolean expression can be simplified
+}
diff --git a/tests/ui/nonminimal_bool.stderr b/tests/ui/nonminimal_bool.stderr
index fd1568d94e3..856b5cd0869 100644
--- a/tests/ui/nonminimal_bool.stderr
+++ b/tests/ui/nonminimal_bool.stderr
@@ -114,5 +114,29 @@ error: this boolean expression can be simplified
 LL |     if matches!(true, true) && true {
    |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `matches!(true, true)`
 
-error: aborting due to 13 previous errors
+error: this boolean expression can be simplified
+  --> $DIR/nonminimal_bool.rs:162:8
+   |
+LL |     if !(12 == a) {}
+   |        ^^^^^^^^^^ help: try: `12 != a`
+
+error: this boolean expression can be simplified
+  --> $DIR/nonminimal_bool.rs:163:8
+   |
+LL |     if !(a == 12) {}
+   |        ^^^^^^^^^^ help: try: `a != 12`
+
+error: this boolean expression can be simplified
+  --> $DIR/nonminimal_bool.rs:164:8
+   |
+LL |     if !(12 != a) {}
+   |        ^^^^^^^^^^ help: try: `12 == a`
+
+error: this boolean expression can be simplified
+  --> $DIR/nonminimal_bool.rs:165:8
+   |
+LL |     if !(a != 12) {}
+   |        ^^^^^^^^^^ help: try: `a == 12`
+
+error: aborting due to 17 previous errors