Check for Not trait implementation

Author: xordi

clippy_lints/src/bool_assert_comparison.rs

@@ -1,9 +1,11 @@
-use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::{ast_utils, is_direct_expn_of};
-use rustc_ast::ast::{Expr, ExprKind, Lit, LitKind};
+use clippy_utils::{diagnostics::span_lint_and_sugg, higher, is_direct_expn_of, ty::implements_trait};
+use rustc_ast::ast::LitKind;
 use rustc_errors::Applicability;
-use rustc_lint::{EarlyContext, EarlyLintPass};
+use rustc_hir::*;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::symbol::Ident;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -28,45 +30,77 @@ declare_clippy_lint! {
 
 declare_lint_pass!(BoolAssertComparison => [BOOL_ASSERT_COMPARISON]);
 
-fn is_bool_lit(e: &Expr) -> bool {
+fn is_bool_lit(e: &Expr<'_>) -> bool {
     matches!(
         e.kind,
         ExprKind::Lit(Lit {
-            kind: LitKind::Bool(_),
+            node: LitKind::Bool(_),
             ..
         })
     ) && !e.span.from_expansion()
 }
 
-impl EarlyLintPass for BoolAssertComparison {
-    fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
+fn impl_not_trait_with_bool_out(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> bool {
+    let ty = cx.typeck_results().expr_ty(e);
+
+    cx.tcx
+        .lang_items()
+        .not_trait()
+        .filter(|id| implements_trait(cx, ty, *id, &[]))
+        .and_then(|id| {
+            cx.tcx.associated_items(id).find_by_name_and_kind(
+                cx.tcx,
+                Ident::from_str("Output"),
+                ty::AssocKind::Type,
+                id,
+            )
+        })
+        .map_or(false, |item| {
+            let proj = cx.tcx.mk_projection(item.def_id, cx.tcx.mk_substs_trait(ty, &[]));
+            let nty = cx.tcx.normalize_erasing_regions(cx.param_env, proj);
+
+            nty.is_bool()
+        })
+}
+
+impl<'tcx> LateLintPass<'tcx> for BoolAssertComparison {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
         let macros = ["assert_eq", "debug_assert_eq"];
         let inverted_macros = ["assert_ne", "debug_assert_ne"];
 
         for mac in macros.iter().chain(inverted_macros.iter()) {
-            if let Some(span) = is_direct_expn_of(e.span, mac) {
-                if let Some([a, b]) = ast_utils::extract_assert_macro_args(e) {
-                    let nb_bool_args = is_bool_lit(a) as usize + is_bool_lit(b) as usize;
+            if let Some(span) = is_direct_expn_of(expr.span, mac) {
+                if let Some(args) = higher::extract_assert_macro_args(expr) {
+                    if let [a, b, ..] = args[..] {
+                        let nb_bool_args = is_bool_lit(a) as usize + is_bool_lit(b) as usize;
+
+                        if nb_bool_args != 1 {
+                            // If there are two boolean arguments, we definitely don't understand
+                            // what's going on, so better leave things as is...
+                            //
+                            // Or there is simply no boolean and then we can leave things as is!
+                            return;
+                        }
 
-                    if nb_bool_args != 1 {
-                        // If there are two boolean arguments, we definitely don't understand
-                        // what's going on, so better leave things as is...
-                        //
-                        // Or there is simply no boolean and then we can leave things as is!
+                        if !impl_not_trait_with_bool_out(cx, a) || !impl_not_trait_with_bool_out(cx, b) {
+                            // At this point the expression which is not a boolean
+                            // literal does not implement Not trait with a bool output,
+                            // so we cannot suggest to rewrite our code
+                            return;
+                        }
+
+                        let non_eq_mac = &mac[..mac.len() - 3];
+                        span_lint_and_sugg(
+                            cx,
+                            BOOL_ASSERT_COMPARISON,
+                            span,
+                            &format!("used `{}!` with a literal bool", mac),
+                            "replace it with",
+                            format!("{}!(..)", non_eq_mac),
+                            Applicability::MaybeIncorrect,
+                        );
                         return;
                     }
-
-                    let non_eq_mac = &mac[..mac.len() - 3];
-                    span_lint_and_sugg(
-                        cx,
-                        BOOL_ASSERT_COMPARISON,
-                        span,
-                        &format!("used `{}!` with a literal bool", mac),
-                        "replace it with",
-                        format!("{}!(..)", non_eq_mac),
-                        Applicability::MaybeIncorrect,
-                    );
-                    return;
                 }
             }
         }

clippy_lints/src/lib.rs

@@ -2115,7 +2115,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| box from_str_radix_10::FromStrRadix10);
     store.register_late_pass(|| box manual_map::ManualMap);
     store.register_late_pass(move || box if_then_some_else_none::IfThenSomeElseNone::new(msrv));
-    store.register_early_pass(|| box bool_assert_comparison::BoolAssertComparison);
+    store.register_late_pass(|| box bool_assert_comparison::BoolAssertComparison);
     store.register_early_pass(move || box module_style::ModStyle);
     store.register_late_pass(|| box unused_async::UnusedAsync);
     let disallowed_types = conf.disallowed_types.iter().cloned().collect::<FxHashSet<_>>();