New lint: unnecessary_map_or (#11796)

Closes rust-lang/rust-clippy#10118

This lint checks `map_or` method calls to check if they can be
consolidated down to something simpler and/or more readable.

For example, the code
```rs
let x = Some(5);
x.map_or(false, |n| n == 5)
```

can be rewritten as
```rs
let x = Some(5);
x == Some(5)
```

In addition, when the closure is more complex, the code can be altered
from, say,
```rs
let x = Ok::<Vec<i32>, i32>(vec![5]);
x.map_or(false, |n| n == [5])
```
into
```rs
let x = Ok::<Vec<i32>, i32>(vec![5]);
x.is_some_and(|n| n == [5])
```

This lint also considers cases where the `map_or` can be chained with
other method calls, and accommodates accordingly by adding extra
parentheses as needed to the suggestion.

changelog: add new lint `unnecessary_map_or`

Author: Centri3

CHANGELOG.md

@@ -6071,6 +6071,7 @@ Released 2018-09-13
 [`unnecessary_literal_bound`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_literal_bound
 [`unnecessary_literal_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_literal_unwrap
 [`unnecessary_map_on_constructor`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_map_on_constructor
+[`unnecessary_map_or`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_map_or
 [`unnecessary_min_or_max`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_min_or_max
 [`unnecessary_mut_passed`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_mut_passed
 [`unnecessary_operation`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_operation

clippy_dev/src/setup/vscode.rs

@@ -84,7 +84,7 @@ fn delete_vs_task_file(path: &Path) -> bool {
 /// It may fail silently.
 fn try_delete_vs_directory_if_empty() {
     let path = Path::new(VSCODE_DIR);
-    if path.read_dir().map_or(false, |mut iter| iter.next().is_none()) {
+    if path.read_dir().is_ok_and(|mut iter| iter.next().is_none()) {
         // The directory is empty. We just try to delete it but allow a silence
         // fail as an empty `.vscode` directory is still valid
         let _silence_result = fs::remove_dir(path);

clippy_lints/src/attrs/useless_attribute.rs

@@ -16,7 +16,7 @@ pub(super) fn check(cx: &EarlyContext<'_>, item: &Item, attrs: &[Attribute]) {
             return;
         }
         if let Some(lint_list) = &attr.meta_item_list() {
-            if attr.ident().map_or(false, |ident| is_lint_level(ident.name, attr.id)) {
+            if attr.ident().is_some_and(|ident| is_lint_level(ident.name, attr.id)) {
                 for lint in lint_list {
                     match item.kind {
                         ItemKind::Use(..) => {

clippy_lints/src/attrs/utils.rs

@@ -50,7 +50,7 @@ fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_
         block
             .expr
             .as_ref()
-            .map_or(false, |e| is_relevant_expr(cx, typeck_results, e)),
+            .is_some_and(|e| is_relevant_expr(cx, typeck_results, e)),
         |stmt| match &stmt.kind {
             StmtKind::Let(_) => true,
             StmtKind::Expr(expr) | StmtKind::Semi(expr) => is_relevant_expr(cx, typeck_results, expr),
@@ -60,7 +60,7 @@ fn is_relevant_block(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_
 }
 
 fn is_relevant_expr(cx: &LateContext<'_>, typeck_results: &ty::TypeckResults<'_>, expr: &Expr<'_>) -> bool {
-    if macro_backtrace(expr.span).last().map_or(false, |macro_call| {
+    if macro_backtrace(expr.span).last().is_some_and(|macro_call| {
         is_panic(cx, macro_call.def_id) || cx.tcx.item_name(macro_call.def_id) == sym::unreachable
     }) {
         return false;

clippy_lints/src/bool_assert_comparison.rs

@@ -60,8 +60,8 @@ fn is_impl_not_trait_with_bool_out<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -
                 trait_id,
             )
         })
-        .map_or(false, |assoc_item| {
-            let proj = Ty::new_projection_from_args(cx.tcx, assoc_item.def_id, cx.tcx.mk_args_trait(ty, []));
+        .is_some_and(|assoc_item| {
+            let proj = Ty::new_projection(cx.tcx, assoc_item.def_id, cx.tcx.mk_args_trait(ty, []));
             let nty = cx.tcx.normalize_erasing_regions(cx.param_env, proj);
 
             nty.is_bool()

clippy_lints/src/booleans.rs

@@ -667,5 +667,5 @@ fn implements_ord(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     let ty = cx.typeck_results().expr_ty(expr);
     cx.tcx
         .get_diagnostic_item(sym::Ord)
-        .map_or(false, |id| implements_trait(cx, ty, id, &[]))
+        .is_some_and(|id| implements_trait(cx, ty, id, &[]))
 }

clippy_lints/src/box_default.rs

@@ -45,7 +45,7 @@ impl LateLintPass<'_> for BoxDefault {
             // And that method is `new`
             && seg.ident.name == sym::new
             // And the call is that of a `Box` method
-            && path_def_id(cx, ty).map_or(false, |id| Some(id) == cx.tcx.lang_items().owned_box())
+            && path_def_id(cx, ty).is_some_and(|id| Some(id) == cx.tcx.lang_items().owned_box())
             // And the single argument to the call is another function call
             // This is the `T::default()` (or default equivalent) of `Box::new(T::default())`
             && let ExprKind::Call(arg_path, _) = arg.kind
@@ -83,9 +83,9 @@ fn is_plain_default(cx: &LateContext<'_>, arg_path: &Expr<'_>) -> bool {
 }
 
 fn is_local_vec_expn(cx: &LateContext<'_>, expr: &Expr<'_>, ref_expr: &Expr<'_>) -> bool {
-    macro_backtrace(expr.span).next().map_or(false, |call| {
-        cx.tcx.is_diagnostic_item(sym::vec_macro, call.def_id) && call.span.eq_ctxt(ref_expr.span)
-    })
+    macro_backtrace(expr.span)
+        .next()
+        .is_some_and(|call| cx.tcx.is_diagnostic_item(sym::vec_macro, call.def_id) && call.span.eq_ctxt(ref_expr.span))
 }
 
 #[derive(Default)]

clippy_lints/src/casts/unnecessary_cast.rs

@@ -159,8 +159,7 @@ pub(super) fn check<'tcx>(
         // The same is true if the expression encompassing the cast expression is a unary
         // expression or an addressof expression.
         let needs_block = matches!(cast_expr.kind, ExprKind::Unary(..) | ExprKind::AddrOf(..))
-            || get_parent_expr(cx, expr)
-                .map_or(false, |e| matches!(e.kind, ExprKind::Unary(..) | ExprKind::AddrOf(..)));
+            || get_parent_expr(cx, expr).is_some_and(|e| matches!(e.kind, ExprKind::Unary(..) | ExprKind::AddrOf(..)));
 
         span_lint_and_sugg(
             cx,

clippy_lints/src/comparison_chain.rs

@@ -110,7 +110,7 @@ impl<'tcx> LateLintPass<'tcx> for ComparisonChain {
                 let is_ord = cx
                     .tcx
                     .get_diagnostic_item(sym::Ord)
-                    .map_or(false, |id| implements_trait(cx, ty, id, &[]));
+                    .is_some_and(|id| implements_trait(cx, ty, id, &[]));
 
                 if !is_ord {
                     return;

clippy_lints/src/copies.rs

@@ -345,7 +345,7 @@ fn eq_binding_names(s: &Stmt<'_>, names: &[(HirId, Symbol)]) -> bool {
         let mut i = 0usize;
         let mut res = true;
         l.pat.each_binding_or_first(&mut |_, _, _, name| {
-            if names.get(i).map_or(false, |&(_, n)| n == name.name) {
+            if names.get(i).is_some_and(|&(_, n)| n == name.name) {
                 i += 1;
             } else {
                 res = false;
@@ -389,12 +389,10 @@ fn eq_stmts(
         let new_bindings = &moved_bindings[old_count..];
         blocks
             .iter()
-            .all(|b| get_stmt(b).map_or(false, |s| eq_binding_names(s, new_bindings)))
+            .all(|b| get_stmt(b).is_some_and(|s| eq_binding_names(s, new_bindings)))
     } else {
         true
-    }) && blocks
-        .iter()
-        .all(|b| get_stmt(b).map_or(false, |s| eq.eq_stmt(s, stmt)))
+    }) && blocks.iter().all(|b| get_stmt(b).is_some_and(|s| eq.eq_stmt(s, stmt)))
 }
 
 #[expect(clippy::too_many_lines)]
@@ -451,9 +449,7 @@ fn scan_block_for_eq<'tcx>(
     //     x + 50
     let expr_hash_eq = if let Some(e) = block.expr {
         let hash = hash_expr(cx, e);
-        blocks
-            .iter()
-            .all(|b| b.expr.map_or(false, |e| hash_expr(cx, e) == hash))
+        blocks.iter().all(|b| b.expr.is_some_and(|e| hash_expr(cx, e) == hash))
     } else {
         blocks.iter().all(|b| b.expr.is_none())
     };
@@ -514,7 +510,7 @@ fn scan_block_for_eq<'tcx>(
         });
     if let Some(e) = block.expr {
         for block in blocks {
-            if block.expr.map_or(false, |expr| !eq.eq_expr(expr, e)) {
+            if block.expr.is_some_and(|expr| !eq.eq_expr(expr, e)) {
                 moved_locals.truncate(moved_locals_at_start);
                 return BlockEq {
                     start_end_eq,
@@ -533,7 +529,7 @@ fn scan_block_for_eq<'tcx>(
 }
 
 fn check_for_warn_of_moved_symbol(cx: &LateContext<'_>, symbols: &[(HirId, Symbol)], if_expr: &Expr<'_>) -> bool {
-    get_enclosing_block(cx, if_expr.hir_id).map_or(false, |block| {
+    get_enclosing_block(cx, if_expr.hir_id).is_some_and(|block| {
         let ignore_span = block.span.shrink_to_lo().to(if_expr.span);
 
         symbols