add additional cases for map_or lint

Author: Jacherr

clippy_lints/src/methods/unnecessary_pattern_matching.rs

@@ -1,4 +1,5 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::eager_or_lazy::switch_to_eager_eval;
 use clippy_utils::path_to_local_id;
 use clippy_utils::source::snippet;
 use clippy_utils::ty::is_type_diagnostic_item;
@@ -19,35 +20,47 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, def:
         || is_type_diagnostic_item(cx, recv_ty, sym::Result))
     // check we are dealing with boolean map_or
     && let Bool(def_bool) = def_kind.node
-    && def_bool == false
     && let ExprKind::Closure(map_closure) = map.kind
     && let closure_body = cx.tcx.hir().body(map_closure.body)
     && let closure_body_value = closure_body.value.peel_blocks()
-    // check we are dealing with equality statement in the closure
+    // switching from closure to direct comparison changes the comparison
+    // from lazy (when map_or evaluates to first param) to eager, so we force eager here
+    // this stops the lint running whenever the closure has a potentially expensive
+    // computation inside of it
+    && switch_to_eager_eval(cx, closure_body_value)
     && let ExprKind::Binary(op, l, r) = closure_body_value.kind
     && let Some(param) = closure_body.params.first()
     && let PatKind::Binding(_, hir_id, _, _) = param.pat.kind
-    && BinOpKind::Eq == op.node
-    && (path_to_local_id(l, hir_id) || path_to_local_id(r, hir_id))
+    // checking that map_or is either:
+    // .map_or(false, |x| x == y) OR .map_or(true, |x| x != y)
+    && ((BinOpKind::Eq == op.node && !def_bool) || (BinOpKind::Ne == op.node && def_bool))
+    // check that either the left or right side of the comparison
+    // is the binding param to the closure
+    // xor, because if its both then thats a strange edge case and
+    // we can just ignore it, since by default clippy will error on this
+    && (path_to_local_id(l, hir_id) ^ path_to_local_id(r, hir_id))
     {
         let wrap = if is_type_diagnostic_item(cx, recv_ty, sym::Option) {
             "Some"
         } else {
             "Result"
         };
 
+        let comparator = if BinOpKind::Eq == op.node { "==" } else { "!=" };
+
         // we already checked either l or r is the local id earlier
         let non_binding_location = if path_to_local_id(l, hir_id) { r } else { l };
 
         span_lint_and_sugg(
             cx,
             UNNECESSARY_PATTERN_MATCHING,
             expr.span,
-            "`map_or` here is redundant, use typical equality instead",
+            "`map_or` here is redundant, use standard comparison instead",
             "try",
             format!(
-                "{} == {}({})",
+                "{} {} {}({})",
                 snippet(cx, recv.span, ".."),
+                comparator,
                 wrap,
                 snippet(cx, non_binding_location.span.source_callsite(), "..")
             ),