Add lint unnecessary_option_map_or_else

CHANGELOG.md

@@ -6292,6 +6292,7 @@ Released 2018-09-13
 [`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
+[`unnecessary_option_map_or_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_option_map_or_else
 [`unnecessary_owned_empty_strings`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_owned_empty_strings
 [`unnecessary_result_map_or_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_result_map_or_else
 [`unnecessary_safety_comment`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_safety_comment

clippy_lints/src/declared_lints.rs

@@ -477,6 +477,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::methods::UNNECESSARY_LITERAL_UNWRAP_INFO,
     crate::methods::UNNECESSARY_MAP_OR_INFO,
     crate::methods::UNNECESSARY_MIN_OR_MAX_INFO,
+    crate::methods::UNNECESSARY_OPTION_MAP_OR_ELSE_INFO,
     crate::methods::UNNECESSARY_RESULT_MAP_OR_ELSE_INFO,
     crate::methods::UNNECESSARY_SORT_BY_INFO,
     crate::methods::UNNECESSARY_TO_OWNED_INFO,

clippy_lints/src/methods/mod.rs

@@ -130,6 +130,7 @@ mod unnecessary_lazy_eval;
 mod unnecessary_literal_unwrap;
 mod unnecessary_map_or;
 mod unnecessary_min_or_max;
+mod unnecessary_option_map_or_else;
 mod unnecessary_result_map_or_else;
 mod unnecessary_sort_by;
 mod unnecessary_to_owned;
@@ -4529,6 +4530,31 @@ declare_clippy_lint! {
     "detect swap with a temporary value"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for usage of `.map_or_else()` "map closure" for `Option` type.
+    ///
+    /// ### Why is this bad?
+    /// This can be written more concisely by using `unwrap_or_else()`.
+    ///
+    /// ### Example
+    /// ```no_run
+    /// let k = 10;
+    /// let x: Option<u32> = Some(4);
+    /// let y = x.map_or_else(|| 2 * k, |n| n);
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// let k = 10;
+    /// let x: Option<u32> = Some(4);
+    /// let y = x.unwrap_or_else(|| 2 * k);
+    /// ```
+    #[clippy::version = "1.88.0"]
+    pub UNNECESSARY_OPTION_MAP_OR_ELSE,
+    suspicious,
+    "making no use of the \"map closure\" when calling `.map_or_else(|| 2 * k, |n| n)`"
+}
+
 #[expect(clippy::struct_excessive_bools)]
 pub struct Methods {
     avoid_breaking_exported_api: bool,
@@ -4707,6 +4733,7 @@ impl_lint_pass!(Methods => [
     MANUAL_CONTAINS,
     IO_OTHER_ERROR,
     SWAP_WITH_TEMPORARY,
+    UNNECESSARY_OPTION_MAP_OR_ELSE,
 ]);
 
 /// Extracts a method call name, args, and `Span` of the method name.
@@ -5262,6 +5289,7 @@ impl Methods {
                 },
                 ("map_or_else", [def, map]) => {
                     result_map_or_else_none::check(cx, expr, recv, def, map);
+                    unnecessary_option_map_or_else::check(cx, expr, recv, def, map);
                     unnecessary_result_map_or_else::check(cx, expr, recv, def, map);
                 },
                 ("next", []) => {

clippy_lints/src/methods/unnecessary_option_map_or_else.rs

@@ -0,0 +1,73 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::peel_blocks;
+use clippy_utils::source::snippet;
+use clippy_utils::ty::is_type_diagnostic_item;
+use rustc_errors::Applicability;
+use rustc_hir::{Closure, Expr, ExprKind, HirId, QPath};
+use rustc_lint::LateContext;
+use rustc_span::symbol::sym;
+
+use super::UNNECESSARY_OPTION_MAP_OR_ELSE;
+use super::utils::get_last_chain_binding_hir_id;
+
+fn emit_lint(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, def_arg: &Expr<'_>) {
+    let msg = "unused \"map closure\" when calling `Option::map_or_else` value";
+    let self_snippet = snippet(cx, recv.span, "..");
+    let err_snippet = snippet(cx, def_arg.span, "..");
+    span_lint_and_sugg(
+        cx,
+        UNNECESSARY_OPTION_MAP_OR_ELSE,
+        expr.span,
+        msg,
+        "consider using `unwrap_or_else`",
+        format!("{self_snippet}.unwrap_or_else({err_snippet})"),
+        Applicability::MachineApplicable,
+    );
+}
+
+fn handle_qpath(
+    cx: &LateContext<'_>,
+    expr: &Expr<'_>,
+    recv: &Expr<'_>,
+    def_arg: &Expr<'_>,
+    expected_hir_id: HirId,
+    qpath: QPath<'_>,
+) {
+    if let QPath::Resolved(_, path) = qpath
+        && let rustc_hir::def::Res::Local(hir_id) = path.res
+        && expected_hir_id == hir_id
+    {
+        emit_lint(cx, expr, recv, def_arg);
+    }
+}
+
+/// lint use of `_.map_or_else(|err| err, |n| n)` for `Option`s.
+pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, def_arg: &Expr<'_>, map_arg: &Expr<'_>) {
+    // lint if the caller of `map_or_else()` is an `Option`
+    if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Option)
+        && let ExprKind::Closure(&Closure { body, .. }) = map_arg.kind
+        && let body = cx.tcx.hir_body(body)
+        && let Some(first_param) = body.params.first()
+    {
+        let body_expr = peel_blocks(body.value);
+
+        match body_expr.kind {
+            ExprKind::Path(qpath) => {
+                handle_qpath(cx, expr, recv, def_arg, first_param.pat.hir_id, qpath);
+            },
+            // If this is a block (that wasn't peeled off), then it means there are statements.
+            ExprKind::Block(block, _) => {
+                if let Some(block_expr) = block.expr
+                        // First we ensure that this is a "binding chain" (each statement is a binding
+                        // of the previous one) and that it is a binding of the closure argument.
+                        && let Some(last_chain_binding_id) =
+                            get_last_chain_binding_hir_id(first_param.pat.hir_id, block.stmts)
+                        && let ExprKind::Path(qpath) = block_expr.kind
+                {
+                    handle_qpath(cx, expr, recv, def_arg, last_chain_binding_id, qpath);
+                }
+            },
+            _ => {},
+        }
+    }
+}

tests/ui/option_if_let_else.fixed

@@ -6,7 +6,8 @@
     clippy::redundant_locals,
     clippy::manual_midpoint,
     clippy::manual_unwrap_or_default,
-    clippy::manual_unwrap_or
+    clippy::manual_unwrap_or,
+    clippy::unnecessary_option_map_or_else
 )]
 
 fn bad1(string: Option<&str>) -> (bool, &str) {

tests/ui/option_if_let_else.rs

@@ -6,7 +6,8 @@
     clippy::redundant_locals,
     clippy::manual_midpoint,
     clippy::manual_unwrap_or_default,
-    clippy::manual_unwrap_or
+    clippy::manual_unwrap_or,
+    clippy::unnecessary_option_map_or_else
 )]
 
 fn bad1(string: Option<&str>) -> (bool, &str) {

tests/ui/option_if_let_else.stderr

@@ -1,5 +1,5 @@
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:13:5
+  --> tests/ui/option_if_let_else.rs:14:5
    |
 LL | /     if let Some(x) = string {
 LL | |
@@ -13,19 +13,19 @@ LL | |     }
    = help: to override `-D warnings` add `#[allow(clippy::option_if_let_else)]`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:32:13
+  --> tests/ui/option_if_let_else.rs:33:13
    |
 LL |     let _ = if let Some(s) = *string { s.len() } else { 0 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `string.map_or(0, |s| s.len())`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:34:13
+  --> tests/ui/option_if_let_else.rs:35:13
    |
 LL |     let _ = if let Some(s) = &num { s } else { &0 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.as_ref().map_or(&0, |s| s)`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:36:13
+  --> tests/ui/option_if_let_else.rs:37:13
    |
 LL |       let _ = if let Some(s) = &mut num {
    |  _____________^
@@ -47,13 +47,13 @@ LL ~     });
    |
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:43:13
+  --> tests/ui/option_if_let_else.rs:44:13
    |
 LL |     let _ = if let Some(ref s) = num { s } else { &0 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `num.as_ref().map_or(&0, |s| s)`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:45:13
+  --> tests/ui/option_if_let_else.rs:46:13
    |
 LL |       let _ = if let Some(mut s) = num {
    |  _____________^
@@ -75,7 +75,7 @@ LL ~     });
    |
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:52:13
+  --> tests/ui/option_if_let_else.rs:53:13
    |
 LL |       let _ = if let Some(ref mut s) = num {
    |  _____________^
@@ -97,7 +97,7 @@ LL ~     });
    |
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:62:5
+  --> tests/ui/option_if_let_else.rs:63:5
    |
 LL | /     if let Some(x) = arg {
 LL | |
@@ -118,7 +118,7 @@ LL +     })
    |
 
 error: use Option::map_or_else instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:76:13
+  --> tests/ui/option_if_let_else.rs:77:13
    |
 LL |       let _ = if let Some(x) = arg {
    |  _____________^
@@ -131,7 +131,7 @@ LL | |     };
    | |_____^ help: try: `arg.map_or_else(side_effect, |x| x)`
 
 error: use Option::map_or_else instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:86:13
+  --> tests/ui/option_if_let_else.rs:87:13
    |
 LL |       let _ = if let Some(x) = arg {
    |  _____________^
@@ -154,7 +154,7 @@ LL ~     }, |x| x * x * x * x);
    |
 
 error: use Option::map_or_else instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:120:13
+  --> tests/ui/option_if_let_else.rs:121:13
    |
 LL | /             if let Some(idx) = s.find('.') {
 LL | |
@@ -165,7 +165,7 @@ LL | |             }
    | |_____________^ help: try: `s.find('.').map_or_else(|| vec![s.to_string()], |idx| vec![s[..idx].to_string(), s[idx..].to_string()])`
 
 error: use Option::map_or_else instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:132:5
+  --> tests/ui/option_if_let_else.rs:133:5
    |
 LL | /     if let Ok(binding) = variable {
 LL | |
@@ -189,13 +189,13 @@ LL +     })
    |
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:157:13
+  --> tests/ui/option_if_let_else.rs:158:13
    |
 LL |     let _ = if let Some(x) = optional { x + 2 } else { 5 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `optional.map_or(5, |x| x + 2)`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:168:13
+  --> tests/ui/option_if_let_else.rs:169:13
    |
 LL |       let _ = if let Some(x) = Some(0) {
    |  _____________^
@@ -217,13 +217,13 @@ LL ~         });
    |
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:197:13
+  --> tests/ui/option_if_let_else.rs:198:13
    |
 LL |     let _ = if let Some(x) = Some(0) { s.len() + x } else { s.len() };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `Some(0).map_or(s.len(), |x| s.len() + x)`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:202:13
+  --> tests/ui/option_if_let_else.rs:203:13
    |
 LL |       let _ = if let Some(x) = Some(0) {
    |  _____________^
@@ -245,7 +245,7 @@ LL ~     });
    |
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:242:13
+  --> tests/ui/option_if_let_else.rs:243:13
    |
 LL |       let _ = match s {
    |  _____________^
@@ -256,7 +256,7 @@ LL | |     };
    | |_____^ help: try: `s.map_or(1, |string| string.len())`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:247:13
+  --> tests/ui/option_if_let_else.rs:248:13
    |
 LL |       let _ = match Some(10) {
    |  _____________^
@@ -267,7 +267,7 @@ LL | |     };
    | |_____^ help: try: `Some(10).map_or(5, |a| a + 1)`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:254:13
+  --> tests/ui/option_if_let_else.rs:255:13
    |
 LL |       let _ = match res {
    |  _____________^
@@ -278,7 +278,7 @@ LL | |     };
    | |_____^ help: try: `res.map_or(1, |a| a + 1)`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:259:13
+  --> tests/ui/option_if_let_else.rs:260:13
    |
 LL |       let _ = match res {
    |  _____________^
@@ -289,13 +289,13 @@ LL | |     };
    | |_____^ help: try: `res.map_or(1, |a| a + 1)`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:264:13
+  --> tests/ui/option_if_let_else.rs:265:13
    |
 LL |     let _ = if let Ok(a) = res { a + 1 } else { 5 };
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `res.map_or(5, |a| a + 1)`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:282:17
+  --> tests/ui/option_if_let_else.rs:283:17
    |
 LL |           let _ = match initial {
    |  _________________^
@@ -306,7 +306,7 @@ LL | |         };
    | |_________^ help: try: `initial.as_ref().map_or(42, |value| do_something(value))`
 
 error: use Option::map_or instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:290:17
+  --> tests/ui/option_if_let_else.rs:291:17
    |
 LL |           let _ = match initial {
    |  _________________^
@@ -317,7 +317,7 @@ LL | |         };
    | |_________^ help: try: `initial.as_mut().map_or(42, |value| do_something2(value))`
 
 error: use Option::map_or_else instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:314:24
+  --> tests/ui/option_if_let_else.rs:315:24
    |
 LL |       let mut _hashmap = if let Some(hm) = &opt {
    |  ________________________^
@@ -329,7 +329,7 @@ LL | |     };
    | |_____^ help: try: `opt.as_ref().map_or_else(HashMap::new, |hm| hm.clone())`
 
 error: use Option::map_or_else instead of an if let/else
-  --> tests/ui/option_if_let_else.rs:321:19
+  --> tests/ui/option_if_let_else.rs:322:19
    |
 LL |     let mut _hm = if let Some(hm) = &opt { hm.clone() } else { new_map!() };
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `opt.as_ref().map_or_else(|| new_map!(), |hm| hm.clone())`

tests/ui/or_fun_call.fixed

@@ -5,6 +5,7 @@
     clippy::uninlined_format_args,
     clippy::unnecessary_wraps,
     clippy::unnecessary_literal_unwrap,
+    clippy::unnecessary_option_map_or_else,
     clippy::useless_vec
 )]
 

tests/ui/or_fun_call.rs

@@ -5,6 +5,7 @@
     clippy::uninlined_format_args,
     clippy::unnecessary_wraps,
     clippy::unnecessary_literal_unwrap,
+    clippy::unnecessary_option_map_or_else,
     clippy::useless_vec
 )]