fix: cmp_null wrongly unmangled macros

clippy_lints/src/ptr/cmp_null.rs

@@ -14,13 +14,14 @@ pub(super) fn check<'tcx>(
     l: &Expr<'_>,
     r: &Expr<'_>,
 ) -> bool {
+    let mut applicability = Applicability::MachineApplicable;
     let non_null_path_snippet = match (
         is_lint_allowed(cx, CMP_NULL, expr.hir_id),
         is_null_path(cx, l),
         is_null_path(cx, r),
     ) {
-        (false, true, false) if let Some(sugg) = Sugg::hir_opt(cx, r) => sugg.maybe_paren(),
-        (false, false, true) if let Some(sugg) = Sugg::hir_opt(cx, l) => sugg.maybe_paren(),
+        (false, true, false) => Sugg::hir_with_context(cx, r, expr.span.ctxt(), "..", &mut applicability).maybe_paren(),
+        (false, false, true) => Sugg::hir_with_context(cx, l, expr.span.ctxt(), "..", &mut applicability).maybe_paren(),
         _ => return false,
     };
     let invert = if op == BinOpKind::Eq { "" } else { "!" };
@@ -32,7 +33,7 @@ pub(super) fn check<'tcx>(
         "comparing with null is better expressed by the `.is_null()` method",
         "try",
         format!("{invert}{non_null_path_snippet}.is_null()",),
-        Applicability::MachineApplicable,
+        applicability,
     );
     true
 }

tests/ui/cmp_null.fixed

@@ -38,3 +38,23 @@ fn issue15010() {
     debug_assert!(!f.is_null());
     //~^ cmp_null
 }
+
+fn issue16281() {
+    use std::ptr;
+
+    struct Container {
+        value: *const i32,
+    }
+    let x = Container { value: ptr::null() };
+
+    macro_rules! dot_value {
+        ($obj:expr) => {
+            $obj.value
+        };
+    }
+
+    if dot_value!(x).is_null() {
+        //~^ cmp_null
+        todo!()
+    }
+}

tests/ui/cmp_null.rs

@@ -38,3 +38,23 @@ fn issue15010() {
     debug_assert!(f != std::ptr::null_mut());
     //~^ cmp_null
 }
+
+fn issue16281() {
+    use std::ptr;
+
+    struct Container {
+        value: *const i32,
+    }
+    let x = Container { value: ptr::null() };
+
+    macro_rules! dot_value {
+        ($obj:expr) => {
+            $obj.value
+        };
+    }
+
+    if dot_value!(x) == ptr::null() {
+        //~^ cmp_null
+        todo!()
+    }
+}

tests/ui/cmp_null.stderr

@@ -37,5 +37,11 @@ error: comparing with null is better expressed by the `.is_null()` method
 LL |     debug_assert!(f != std::ptr::null_mut());
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `!f.is_null()`
 
-error: aborting due to 6 previous errors
+error: comparing with null is better expressed by the `.is_null()` method
+  --> tests/ui/cmp_null.rs:56:8
+   |
+LL |     if dot_value!(x) == ptr::null() {
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `dot_value!(x).is_null()`
+
+error: aborting due to 7 previous errors