diff --git a/CHANGELOG.md b/CHANGELOG.md index 0897bdb69..471163499 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -5679,6 +5679,7 @@ Released 2018-09-13 [`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_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 [`unnecessary_safety_doc`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_safety_doc [`unnecessary_self_imports`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_self_imports diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs index 7d6f3f345..23d098315 100644 --- a/clippy_lints/src/declared_lints.rs +++ b/clippy_lints/src/declared_lints.rs @@ -453,6 +453,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[ crate::methods::UNNECESSARY_JOIN_INFO, crate::methods::UNNECESSARY_LAZY_EVALUATIONS_INFO, crate::methods::UNNECESSARY_LITERAL_UNWRAP_INFO, + crate::methods::UNNECESSARY_RESULT_MAP_OR_ELSE_INFO, crate::methods::UNNECESSARY_SORT_BY_INFO, crate::methods::UNNECESSARY_TO_OWNED_INFO, crate::methods::UNWRAP_OR_DEFAULT_INFO, diff --git a/clippy_lints/src/methods/map_unwrap_or.rs b/clippy_lints/src/methods/map_unwrap_or.rs index 52ea584a2..3226fa9cd 100644 --- a/clippy_lints/src/methods/map_unwrap_or.rs +++ b/clippy_lints/src/methods/map_unwrap_or.rs @@ -21,7 +21,7 @@ pub(super) fn check<'tcx>( unwrap_arg: &'tcx hir::Expr<'_>, msrv: &Msrv, ) -> bool { - // lint if the caller of `map()` is an `Option` + // lint if the caller of `map()` is an `Option` or a `Result`. let is_option = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Option); let is_result = is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result); diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs index 03bcf1089..bac72fd25 100644 --- a/clippy_lints/src/methods/mod.rs +++ b/clippy_lints/src/methods/mod.rs @@ -113,6 +113,7 @@ mod unnecessary_iter_cloned; mod unnecessary_join; mod unnecessary_lazy_eval; mod unnecessary_literal_unwrap; +mod unnecessary_result_map_or_else; mod unnecessary_sort_by; mod unnecessary_to_owned; mod unwrap_expect_used; @@ -3951,6 +3952,31 @@ declare_clippy_lint! { "cloning an `Option` via `as_ref().cloned()`" } +declare_clippy_lint! { + /// ### What it does + /// Checks for usage of `.map_or_else()` "map closure" for `Result` type. + /// + /// ### Why is this bad? + /// This can be written more concisely by using `unwrap_or_else()`. + /// + /// ### Example + /// ```no_run + /// # fn handle_error(_: ()) -> u32 { 0 } + /// let x: Result = Ok(0); + /// let y = x.map_or_else(|err| handle_error(err), |n| n); + /// ``` + /// Use instead: + /// ```no_run + /// # fn handle_error(_: ()) -> u32 { 0 } + /// let x: Result = Ok(0); + /// let y = x.unwrap_or_else(|err| handle_error(err)); + /// ``` + #[clippy::version = "1.77.0"] + pub UNNECESSARY_RESULT_MAP_OR_ELSE, + suspicious, + "making no use of the \"map closure\" when calling `.map_or_else(|err| handle_error(err), |n| n)`" +} + pub struct Methods { avoid_breaking_exported_api: bool, msrv: Msrv, @@ -4109,6 +4135,7 @@ impl_lint_pass!(Methods => [ MANUAL_IS_VARIANT_AND, STR_SPLIT_AT_NEWLINE, OPTION_AS_REF_CLONED, + UNNECESSARY_RESULT_MAP_OR_ELSE, ]); /// Extracts a method call name, args, and `Span` of the method name. @@ -4592,6 +4619,7 @@ impl Methods { }, ("map_or_else", [def, map]) => { result_map_or_else_none::check(cx, expr, recv, def, map); + unnecessary_result_map_or_else::check(cx, expr, recv, def, map); }, ("next", []) => { if let Some((name2, recv2, args2, _, _)) = method_call(recv) { diff --git a/clippy_lints/src/methods/unnecessary_result_map_or_else.rs b/clippy_lints/src/methods/unnecessary_result_map_or_else.rs new file mode 100644 index 000000000..7b0cf48ac --- /dev/null +++ b/clippy_lints/src/methods/unnecessary_result_map_or_else.rs @@ -0,0 +1,95 @@ +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 as hir; +use rustc_hir::{Closure, Expr, ExprKind, HirId, QPath, Stmt, StmtKind}; +use rustc_lint::LateContext; +use rustc_span::symbol::sym; + +use super::UNNECESSARY_RESULT_MAP_OR_ELSE; + +fn emit_lint(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, def_arg: &Expr<'_>) { + let msg = "unused \"map closure\" when calling `Result::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_RESULT_MAP_OR_ELSE, + expr.span, + msg, + "consider using `unwrap_or_else`", + format!("{self_snippet}.unwrap_or_else({err_snippet})"), + Applicability::MachineApplicable, + ); +} + +fn get_last_chain_binding_hir_id(mut hir_id: HirId, statements: &[Stmt<'_>]) -> Option { + for stmt in statements { + if let StmtKind::Local(local) = stmt.kind + && let Some(init) = local.init + && let ExprKind::Path(QPath::Resolved(_, path)) = init.kind + && let hir::def::Res::Local(local_hir_id) = path.res + && local_hir_id == hir_id + { + hir_id = local.pat.hir_id; + } else { + return None; + } + } + Some(hir_id) +} + +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 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 `Result`s. +pub(super) fn check<'tcx>( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + recv: &'tcx Expr<'_>, + def_arg: &'tcx Expr<'_>, + map_arg: &'tcx Expr<'_>, +) { + // lint if the caller of `map_or_else()` is a `Result` + if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Result) + && 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); + } + }, + _ => {}, + } + } +} diff --git a/tests/ui/unnecessary_result_map_or_else.fixed b/tests/ui/unnecessary_result_map_or_else.fixed new file mode 100644 index 000000000..224e0b52d --- /dev/null +++ b/tests/ui/unnecessary_result_map_or_else.fixed @@ -0,0 +1,61 @@ +#![warn(clippy::unnecessary_result_map_or_else)] +#![allow(clippy::unnecessary_literal_unwrap, clippy::let_and_return, clippy::let_unit_value)] + +fn main() { + let x: Result<(), ()> = Ok(()); + x.unwrap_or_else(|err| err); //~ ERROR: unused "map closure" when calling + + // Type ascribtion. + let x: Result<(), ()> = Ok(()); + x.unwrap_or_else(|err: ()| err); //~ ERROR: unused "map closure" when calling + + // Auto-deref. + let y = String::new(); + let x: Result<&String, &String> = Ok(&y); + let y: &str = x.unwrap_or_else(|err| err); //~ ERROR: unused "map closure" when calling + + // Temporary variable. + let x: Result<(), ()> = Ok(()); + x.unwrap_or_else(|err| err); + + // Should not warn. + let x: Result = Ok(0); + x.map_or_else(|err| err, |n| n + 1); + + // Should not warn. + let y = (); + let x: Result<(), ()> = Ok(()); + x.map_or_else(|err| err, |_| y); + + // Should not warn. + let y = (); + let x: Result<(), ()> = Ok(()); + x.map_or_else( + |err| err, + |_| { + let tmp = y; + tmp + }, + ); + + // Should not warn. + let x: Result = Ok(1); + x.map_or_else( + |err| err, + |n| { + let tmp = n + 1; + tmp + }, + ); + + // Should not warn. + let y = 0; + let x: Result = Ok(1); + x.map_or_else( + |err| err, + |n| { + let tmp = n; + y + }, + ); +} diff --git a/tests/ui/unnecessary_result_map_or_else.rs b/tests/ui/unnecessary_result_map_or_else.rs new file mode 100644 index 000000000..4fe950a4c --- /dev/null +++ b/tests/ui/unnecessary_result_map_or_else.rs @@ -0,0 +1,69 @@ +#![warn(clippy::unnecessary_result_map_or_else)] +#![allow(clippy::unnecessary_literal_unwrap, clippy::let_and_return, clippy::let_unit_value)] + +fn main() { + let x: Result<(), ()> = Ok(()); + x.map_or_else(|err| err, |n| n); //~ ERROR: unused "map closure" when calling + + // Type ascribtion. + let x: Result<(), ()> = Ok(()); + x.map_or_else(|err: ()| err, |n: ()| n); //~ ERROR: unused "map closure" when calling + + // Auto-deref. + let y = String::new(); + let x: Result<&String, &String> = Ok(&y); + let y: &str = x.map_or_else(|err| err, |n| n); //~ ERROR: unused "map closure" when calling + + // Temporary variable. + let x: Result<(), ()> = Ok(()); + x.map_or_else( + //~^ ERROR: unused "map closure" when calling + |err| err, + |n| { + let tmp = n; + let tmp2 = tmp; + tmp2 + }, + ); + + // Should not warn. + let x: Result = Ok(0); + x.map_or_else(|err| err, |n| n + 1); + + // Should not warn. + let y = (); + let x: Result<(), ()> = Ok(()); + x.map_or_else(|err| err, |_| y); + + // Should not warn. + let y = (); + let x: Result<(), ()> = Ok(()); + x.map_or_else( + |err| err, + |_| { + let tmp = y; + tmp + }, + ); + + // Should not warn. + let x: Result = Ok(1); + x.map_or_else( + |err| err, + |n| { + let tmp = n + 1; + tmp + }, + ); + + // Should not warn. + let y = 0; + let x: Result = Ok(1); + x.map_or_else( + |err| err, + |n| { + let tmp = n; + y + }, + ); +} diff --git a/tests/ui/unnecessary_result_map_or_else.stderr b/tests/ui/unnecessary_result_map_or_else.stderr new file mode 100644 index 000000000..0f83be5d5 --- /dev/null +++ b/tests/ui/unnecessary_result_map_or_else.stderr @@ -0,0 +1,35 @@ +error: unused "map closure" when calling `Result::map_or_else` value + --> $DIR/unnecessary_result_map_or_else.rs:6:5 + | +LL | x.map_or_else(|err| err, |n| n); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `unwrap_or_else`: `x.unwrap_or_else(|err| err)` + | + = note: `-D clippy::unnecessary-result-map-or-else` implied by `-D warnings` + = help: to override `-D warnings` add `#[allow(clippy::unnecessary_result_map_or_else)]` + +error: unused "map closure" when calling `Result::map_or_else` value + --> $DIR/unnecessary_result_map_or_else.rs:10:5 + | +LL | x.map_or_else(|err: ()| err, |n: ()| n); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `unwrap_or_else`: `x.unwrap_or_else(|err: ()| err)` + +error: unused "map closure" when calling `Result::map_or_else` value + --> $DIR/unnecessary_result_map_or_else.rs:15:19 + | +LL | let y: &str = x.map_or_else(|err| err, |n| n); + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `unwrap_or_else`: `x.unwrap_or_else(|err| err)` + +error: unused "map closure" when calling `Result::map_or_else` value + --> $DIR/unnecessary_result_map_or_else.rs:19:5 + | +LL | / x.map_or_else( +LL | | +LL | | |err| err, +LL | | |n| { +... | +LL | | }, +LL | | ); + | |_____^ help: consider using `unwrap_or_else`: `x.unwrap_or_else(|err| err)` + +error: aborting due to 4 previous errors +