diff --git a/clippy_lints/src/loops/unused_enumerate_index.rs b/clippy_lints/src/loops/unused_enumerate_index.rs index dd7fae79d9ba..31f0f1cfeba3 100644 --- a/clippy_lints/src/loops/unused_enumerate_index.rs +++ b/clippy_lints/src/loops/unused_enumerate_index.rs @@ -1,62 +1,41 @@ use super::UNUSED_ENUMERATE_INDEX; use clippy_utils::diagnostics::{multispan_sugg, span_lint_and_then}; use clippy_utils::source::snippet; -use clippy_utils::{pat_is_wild, sugg}; +use clippy_utils::{match_def_path, pat_is_wild, sugg}; use rustc_hir::def::DefKind; use rustc_hir::{Expr, ExprKind, Pat, PatKind}; use rustc_lint::LateContext; use rustc_middle::ty; /// Checks for the `UNUSED_ENUMERATE_INDEX` lint. -pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, arg: &'tcx Expr<'_>, body: &'tcx Expr<'_>) { - let PatKind::Tuple([index, elem], _) = pat.kind else { - return; - }; - - let ExprKind::MethodCall(_method, self_arg, [], _) = arg.kind else { - return; - }; - - let ty = cx.typeck_results().expr_ty(arg); - - if !pat_is_wild(cx, &index.kind, body) { - return; +/// +/// The lint is also partially implemented in `clippy_lints/src/methods/unused_enumerate_index.rs`. +pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, pat: &Pat<'tcx>, arg: &Expr<'_>, body: &'tcx Expr<'tcx>) { + if let PatKind::Tuple([index, elem], _) = pat.kind + && let ExprKind::MethodCall(_method, self_arg, [], _) = arg.kind + && let ty = cx.typeck_results().expr_ty(arg) + && pat_is_wild(cx, &index.kind, body) + && let ty::Adt(base, _) = *ty.kind() + && match_def_path(cx, base.did(), &clippy_utils::paths::CORE_ITER_ENUMERATE_STRUCT) + && let Some((DefKind::AssocFn, call_id)) = cx.typeck_results().type_dependent_def(arg.hir_id) + && match_def_path(cx, call_id, &clippy_utils::paths::CORE_ITER_ENUMERATE_METHOD) + { + span_lint_and_then( + cx, + UNUSED_ENUMERATE_INDEX, + arg.span, + "you seem to use `.enumerate()` and immediately discard the index", + |diag| { + let base_iter = sugg::Sugg::hir(cx, self_arg, "base iter"); + multispan_sugg( + diag, + "remove the `.enumerate()` call", + vec![ + (pat.span, snippet(cx, elem.span, "..").into_owned()), + (arg.span, base_iter.to_string()), + ], + ); + }, + ); } - - let name = match *ty.kind() { - ty::Adt(base, _substs) => cx.tcx.def_path_str(base.did()), - _ => return, - }; - - if name != "std::iter::Enumerate" && name != "core::iter::Enumerate" { - return; - } - - let Some((DefKind::AssocFn, call_id)) = cx.typeck_results().type_dependent_def(arg.hir_id) else { - return; - }; - - let call_name = cx.tcx.def_path_str(call_id); - - if call_name != "std::iter::Iterator::enumerate" && call_name != "core::iter::Iterator::enumerate" { - return; - } - - span_lint_and_then( - cx, - UNUSED_ENUMERATE_INDEX, - arg.span, - "you seem to use `.enumerate()` and immediately discard the index", - |diag| { - let base_iter = sugg::Sugg::hir(cx, self_arg, "base iter"); - multispan_sugg( - diag, - "remove the `.enumerate()` call", - vec![ - (pat.span, snippet(cx, elem.span, "..").into_owned()), - (arg.span, base_iter.to_string()), - ], - ); - }, - ); } diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs index e0029e0146e3..0ba706150818 100644 --- a/clippy_lints/src/methods/mod.rs +++ b/clippy_lints/src/methods/mod.rs @@ -119,6 +119,7 @@ mod unnecessary_literal_unwrap; mod unnecessary_result_map_or_else; mod unnecessary_sort_by; mod unnecessary_to_owned; +mod unused_enumerate_index; mod unwrap_expect_used; mod useless_asref; mod utils; @@ -4429,6 +4430,7 @@ impl Methods { zst_offset::check(cx, expr, recv); }, ("all", [arg]) => { + unused_enumerate_index::check(cx, expr, recv, arg); if let Some(("cloned", recv2, [], _, _)) = method_call(recv) { iter_overeager_cloned::check( cx, @@ -4447,23 +4449,26 @@ impl Methods { unnecessary_lazy_eval::check(cx, expr, recv, arg, "and"); } }, - ("any", [arg]) => match method_call(recv) { - Some(("cloned", recv2, [], _, _)) => iter_overeager_cloned::check( - cx, - expr, - recv, - recv2, - iter_overeager_cloned::Op::NeedlessMove(arg), - false, - ), - Some(("chars", recv, _, _, _)) - if let ExprKind::Closure(arg) = arg.kind - && let body = cx.tcx.hir().body(arg.body) - && let [param] = body.params => - { - string_lit_chars_any::check(cx, expr, recv, param, peel_blocks(body.value), &self.msrv); - }, - _ => {}, + ("any", [arg]) => { + unused_enumerate_index::check(cx, expr, recv, arg); + match method_call(recv) { + Some(("cloned", recv2, [], _, _)) => iter_overeager_cloned::check( + cx, + expr, + recv, + recv2, + iter_overeager_cloned::Op::NeedlessMove(arg), + false, + ), + Some(("chars", recv, _, _, _)) + if let ExprKind::Closure(arg) = arg.kind + && let body = cx.tcx.hir().body(arg.body) + && let [param] = body.params => + { + string_lit_chars_any::check(cx, expr, recv, param, peel_blocks(body.value), &self.msrv); + }, + _ => {}, + } }, ("arg", [arg]) => { suspicious_command_arg_space::check(cx, recv, arg, span); @@ -4596,14 +4601,17 @@ impl Methods { } }, ("filter_map", [arg]) => { + unused_enumerate_index::check(cx, expr, recv, arg); unnecessary_filter_map::check(cx, expr, arg, name); filter_map_bool_then::check(cx, expr, arg, call_span); filter_map_identity::check(cx, expr, arg, span); }, ("find_map", [arg]) => { + unused_enumerate_index::check(cx, expr, recv, arg); unnecessary_filter_map::check(cx, expr, arg, name); }, ("flat_map", [arg]) => { + unused_enumerate_index::check(cx, expr, recv, arg); flat_map_identity::check(cx, expr, arg, span); flat_map_option::check(cx, expr, arg, span); }, @@ -4625,17 +4633,20 @@ impl Methods { manual_try_fold::check(cx, expr, init, acc, call_span, &self.msrv); unnecessary_fold::check(cx, expr, init, acc, span); }, - ("for_each", [arg]) => match method_call(recv) { - Some(("inspect", _, [_], span2, _)) => inspect_for_each::check(cx, expr, span2), - Some(("cloned", recv2, [], _, _)) => iter_overeager_cloned::check( - cx, - expr, - recv, - recv2, - iter_overeager_cloned::Op::NeedlessMove(arg), - false, - ), - _ => {}, + ("for_each", [arg]) => { + unused_enumerate_index::check(cx, expr, recv, arg); + match method_call(recv) { + Some(("inspect", _, [_], span2, _)) => inspect_for_each::check(cx, expr, span2), + Some(("cloned", recv2, [], _, _)) => iter_overeager_cloned::check( + cx, + expr, + recv, + recv2, + iter_overeager_cloned::Op::NeedlessMove(arg), + false, + ), + _ => {}, + } }, ("get", [arg]) => { get_first::check(cx, expr, recv, arg); @@ -4682,6 +4693,7 @@ impl Methods { }, (name @ ("map" | "map_err"), [m_arg]) => { if name == "map" { + unused_enumerate_index::check(cx, expr, recv, m_arg); map_clone::check(cx, expr, recv, m_arg, &self.msrv); match method_call(recv) { Some((map_name @ ("iter" | "into_iter"), recv2, _, _, _)) => { diff --git a/clippy_lints/src/methods/unused_enumerate_index.rs b/clippy_lints/src/methods/unused_enumerate_index.rs new file mode 100644 index 000000000000..e5cc898612e9 --- /dev/null +++ b/clippy_lints/src/methods/unused_enumerate_index.rs @@ -0,0 +1,135 @@ +use clippy_utils::diagnostics::{multispan_sugg_with_applicability, span_lint_hir_and_then}; +use clippy_utils::paths::{CORE_ITER_ENUMERATE_METHOD, CORE_ITER_ENUMERATE_STRUCT}; +use clippy_utils::source::{snippet, snippet_opt}; +use clippy_utils::{expr_or_init, is_trait_method, match_def_path, pat_is_wild}; +use rustc_errors::Applicability; +use rustc_hir::{Expr, ExprKind, FnDecl, PatKind, TyKind}; +use rustc_lint::LateContext; +use rustc_middle::ty::AdtDef; +use rustc_span::{sym, Span}; + +use crate::loops::UNUSED_ENUMERATE_INDEX; + +/// Check for the `UNUSED_ENUMERATE_INDEX` lint outside of loops. +/// +/// The lint is declared in `clippy_lints/src/loops/mod.rs`. There, the following pattern is +/// checked: +/// ```ignore +/// for (_, x) in some_iter.enumerate() { +/// // Index is ignored +/// } +/// ``` +/// +/// This `check` function checks for chained method calls constructs where we can detect that the +/// index is unused. Currently, this checks only for the following patterns: +/// ```ignore +/// some_iter.enumerate().map_function(|(_, x)| ..) +/// let x = some_iter.enumerate(); +/// x.map_function(|(_, x)| ..) +/// ``` +/// where `map_function` is one of `all`, `any`, `filter_map`, `find_map`, `flat_map`, `for_each` or +/// `map`. +/// +/// # Preconditions +/// This function must be called not on the `enumerate` call expression itself, but on any of the +/// map functions listed above. It will ensure that `recv` is a `std::iter::Enumerate` instance and +/// that the method call is one of the `std::iter::Iterator` trait. +/// +/// * `call_expr`: The map function call expression +/// * `recv`: The receiver of the call +/// * `closure_arg`: The argument to the map function call containing the closure/function to apply +pub(super) fn check(cx: &LateContext<'_>, call_expr: &Expr<'_>, recv: &Expr<'_>, closure_arg: &Expr<'_>) { + let recv_ty = cx.typeck_results().expr_ty(recv); + if let Some(recv_ty_defid) = recv_ty.ty_adt_def().map(AdtDef::did) + // If we call a method on a `std::iter::Enumerate` instance + && match_def_path(cx, recv_ty_defid, &CORE_ITER_ENUMERATE_STRUCT) + // If we are calling a method of the `Iterator` trait + && is_trait_method(cx, call_expr, sym::Iterator) + // And the map argument is a closure + && let ExprKind::Closure(closure) = closure_arg.kind + && let closure_body = cx.tcx.hir().body(closure.body) + // And that closure has one argument ... + && let [closure_param] = closure_body.params + // .. which is a tuple of 2 elements + && let PatKind::Tuple([index, elem], ..) = closure_param.pat.kind + // And that the first element (the index) is either `_` or unused in the body + && pat_is_wild(cx, &index.kind, closure_body) + // Try to find the initializer for `recv`. This is needed in case `recv` is a local_binding. In the + // first example below, `expr_or_init` would return `recv`. + // ``` + // iter.enumerate().map(|(_, x)| x) + // ^^^^^^^^^^^^^^^^ `recv`, a call to `std::iter::Iterator::enumerate` + // + // let binding = iter.enumerate(); + // ^^^^^^^^^^^^^^^^ `recv_init_expr` + // binding.map(|(_, x)| x) + // ^^^^^^^ `recv`, not a call to `std::iter::Iterator::enumerate` + // ``` + && let recv_init_expr = expr_or_init(cx, recv) + // Make sure the initializer is a method call. It may be that the `Enumerate` comes from something + // that we cannot control. + // This would for instance happen with: + // ``` + // external_lib::some_function_returning_enumerate().map(|(_, x)| x) + // ``` + && let ExprKind::MethodCall(_, enumerate_recv, _, enumerate_span) = recv_init_expr.kind + && let Some(enumerate_defid) = cx.typeck_results().type_dependent_def_id(recv_init_expr.hir_id) + // Make sure the method call is `std::iter::Iterator::enumerate`. + && match_def_path(cx, enumerate_defid, &CORE_ITER_ENUMERATE_METHOD) + { + // Check if the tuple type was explicit. It may be the type system _needs_ the type of the element + // that would be explicited in the closure. + let new_closure_param = match find_elem_explicit_type_span(closure.fn_decl) { + // We have an explicit type. Get its snippet, that of the binding name, and do `binding: ty`. + // Fallback to `..` if we fail getting either snippet. + Some(ty_span) => snippet_opt(cx, elem.span) + .and_then(|binding_name| snippet_opt(cx, ty_span).map(|ty_name| format!("{binding_name}: {ty_name}"))) + .unwrap_or_else(|| "..".to_string()), + // Otherwise, we have no explicit type. We can replace with the binding name of the element. + None => snippet(cx, elem.span, "..").into_owned(), + }; + + // Suggest removing the tuple from the closure and the preceding call to `enumerate`, whose span we + // can get from the `MethodCall`. + span_lint_hir_and_then( + cx, + UNUSED_ENUMERATE_INDEX, + recv_init_expr.hir_id, + enumerate_span, + "you seem to use `.enumerate()` and immediately discard the index", + |diag| { + multispan_sugg_with_applicability( + diag, + "remove the `.enumerate()` call", + Applicability::MachineApplicable, + vec![ + (closure_param.span, new_closure_param), + ( + enumerate_span.with_lo(enumerate_recv.span.source_callsite().hi()), + String::new(), + ), + ], + ); + }, + ); + } +} + +/// Find the span of the explicit type of the element. +/// +/// # Returns +/// If the tuple argument: +/// * Has no explicit type, returns `None` +/// * Has an explicit tuple type with an implicit element type (`(usize, _)`), returns `None` +/// * Has an explicit tuple type with an explicit element type (`(_, i32)`), returns the span for +/// the element type. +fn find_elem_explicit_type_span(fn_decl: &FnDecl<'_>) -> Option { + if let [tuple_ty] = fn_decl.inputs + && let TyKind::Tup([_idx_ty, elem_ty]) = tuple_ty.kind + && !matches!(elem_ty.kind, TyKind::Err(..) | TyKind::Infer) + { + Some(elem_ty.span) + } else { + None + } +} diff --git a/clippy_utils/src/paths.rs b/clippy_utils/src/paths.rs index 987f28192a85..456b8019e95c 100644 --- a/clippy_utils/src/paths.rs +++ b/clippy_utils/src/paths.rs @@ -19,6 +19,8 @@ pub const BTREESET_ITER: [&str; 6] = ["alloc", "collections", "btree", "set", "B pub const CLONE_TRAIT_METHOD: [&str; 4] = ["core", "clone", "Clone", "clone"]; pub const CORE_ITER_CLONED: [&str; 6] = ["core", "iter", "traits", "iterator", "Iterator", "cloned"]; pub const CORE_ITER_COPIED: [&str; 6] = ["core", "iter", "traits", "iterator", "Iterator", "copied"]; +pub const CORE_ITER_ENUMERATE_METHOD: [&str; 6] = ["core", "iter", "traits", "iterator", "Iterator", "enumerate"]; +pub const CORE_ITER_ENUMERATE_STRUCT: [&str; 5] = ["core", "iter", "adapters", "enumerate", "Enumerate"]; pub const CORE_ITER_FILTER: [&str; 6] = ["core", "iter", "traits", "iterator", "Iterator", "filter"]; pub const CORE_RESULT_OK_METHOD: [&str; 4] = ["core", "result", "Result", "ok"]; pub const CSTRING_AS_C_STR: [&str; 5] = ["alloc", "ffi", "c_str", "CString", "as_c_str"]; diff --git a/tests/ui/unused_enumerate_index.fixed b/tests/ui/unused_enumerate_index.fixed index d079807ab587..cffd02b0acc8 100644 --- a/tests/ui/unused_enumerate_index.fixed +++ b/tests/ui/unused_enumerate_index.fixed @@ -1,8 +1,12 @@ -#![allow(unused)] +#![allow(unused, clippy::map_identity)] #![warn(clippy::unused_enumerate_index)] use std::iter::Enumerate; +fn get_enumerate() -> Enumerate> { + vec![1].into_iter().enumerate() +} + fn main() { let v = [1, 2, 3]; for x in v.iter() { @@ -55,4 +59,48 @@ fn main() { for x in dummy { println!("{x}"); } + + let _ = vec![1, 2, 3].into_iter().map(|x| println!("{x}")); + + let p = vec![1, 2, 3].into_iter(); + p.map(|x| println!("{x}")); + + // This shouldn't trigger the lint. `get_enumerate` may come from an external library on which we + // have no control. + let p = get_enumerate(); + p.map(|(_, x)| println!("{x}")); + + // This shouldn't trigger the lint. The `enumerate` call is in a different context. + macro_rules! mac { + () => { + [1].iter().enumerate() + }; + } + _ = mac!().map(|(_, v)| v); + + macro_rules! mac2 { + () => { + [1].iter() + }; + } + _ = mac2!().map(|_v| {}); + + // This shouldn't trigger the lint because of the `allow`. + #[allow(clippy::unused_enumerate_index)] + let v = [1].iter().enumerate(); + v.map(|(_, _x)| {}); + + // This should keep the explicit type of `x`. + let v = [1, 2, 3].iter().copied(); + let x = v.map(|x: i32| x).sum::(); + assert_eq!(x, 6); + + // This should keep the explicit type of `x`. + let v = [1, 2, 3].iter().copied(); + let x = v.map(|x: i32| x).sum::(); + assert_eq!(x, 6); + + let v = [1, 2, 3].iter().copied(); + let x = v.map(|x| x).sum::(); + assert_eq!(x, 6); } diff --git a/tests/ui/unused_enumerate_index.rs b/tests/ui/unused_enumerate_index.rs index 2d524da76327..f2b5f8b91247 100644 --- a/tests/ui/unused_enumerate_index.rs +++ b/tests/ui/unused_enumerate_index.rs @@ -1,8 +1,12 @@ -#![allow(unused)] +#![allow(unused, clippy::map_identity)] #![warn(clippy::unused_enumerate_index)] use std::iter::Enumerate; +fn get_enumerate() -> Enumerate> { + vec![1].into_iter().enumerate() +} + fn main() { let v = [1, 2, 3]; for (_, x) in v.iter().enumerate() { @@ -55,4 +59,48 @@ fn main() { for (_, x) in dummy.enumerate() { println!("{x}"); } + + let _ = vec![1, 2, 3].into_iter().enumerate().map(|(_, x)| println!("{x}")); + + let p = vec![1, 2, 3].into_iter().enumerate(); + p.map(|(_, x)| println!("{x}")); + + // This shouldn't trigger the lint. `get_enumerate` may come from an external library on which we + // have no control. + let p = get_enumerate(); + p.map(|(_, x)| println!("{x}")); + + // This shouldn't trigger the lint. The `enumerate` call is in a different context. + macro_rules! mac { + () => { + [1].iter().enumerate() + }; + } + _ = mac!().map(|(_, v)| v); + + macro_rules! mac2 { + () => { + [1].iter() + }; + } + _ = mac2!().enumerate().map(|(_, _v)| {}); + + // This shouldn't trigger the lint because of the `allow`. + #[allow(clippy::unused_enumerate_index)] + let v = [1].iter().enumerate(); + v.map(|(_, _x)| {}); + + // This should keep the explicit type of `x`. + let v = [1, 2, 3].iter().copied().enumerate(); + let x = v.map(|(_, x): (usize, i32)| x).sum::(); + assert_eq!(x, 6); + + // This should keep the explicit type of `x`. + let v = [1, 2, 3].iter().copied().enumerate(); + let x = v.map(|(_, x): (_, i32)| x).sum::(); + assert_eq!(x, 6); + + let v = [1, 2, 3].iter().copied().enumerate(); + let x = v.map(|(_, x)| x).sum::(); + assert_eq!(x, 6); } diff --git a/tests/ui/unused_enumerate_index.stderr b/tests/ui/unused_enumerate_index.stderr index 7bd7d29117e2..6ec07dcbff0a 100644 --- a/tests/ui/unused_enumerate_index.stderr +++ b/tests/ui/unused_enumerate_index.stderr @@ -1,5 +1,5 @@ error: you seem to use `.enumerate()` and immediately discard the index - --> tests/ui/unused_enumerate_index.rs:8:19 + --> tests/ui/unused_enumerate_index.rs:12:19 | LL | for (_, x) in v.iter().enumerate() { | ^^^^^^^^^^^^^^^^^^^^ @@ -12,7 +12,7 @@ LL | for x in v.iter() { | ~ ~~~~~~~~ error: you seem to use `.enumerate()` and immediately discard the index - --> tests/ui/unused_enumerate_index.rs:55:19 + --> tests/ui/unused_enumerate_index.rs:59:19 | LL | for (_, x) in dummy.enumerate() { | ^^^^^^^^^^^^^^^^^ @@ -22,5 +22,77 @@ help: remove the `.enumerate()` call LL | for x in dummy { | ~ ~~~~~ -error: aborting due to 2 previous errors +error: you seem to use `.enumerate()` and immediately discard the index + --> tests/ui/unused_enumerate_index.rs:63:39 + | +LL | let _ = vec![1, 2, 3].into_iter().enumerate().map(|(_, x)| println!("{x}")); + | ^^^^^^^^^^^ + | +help: remove the `.enumerate()` call + | +LL - let _ = vec![1, 2, 3].into_iter().enumerate().map(|(_, x)| println!("{x}")); +LL + let _ = vec![1, 2, 3].into_iter().map(|x| println!("{x}")); + | + +error: you seem to use `.enumerate()` and immediately discard the index + --> tests/ui/unused_enumerate_index.rs:65:39 + | +LL | let p = vec![1, 2, 3].into_iter().enumerate(); + | ^^^^^^^^^^^ + | +help: remove the `.enumerate()` call + | +LL ~ let p = vec![1, 2, 3].into_iter(); +LL ~ p.map(|x| println!("{x}")); + | + +error: you seem to use `.enumerate()` and immediately discard the index + --> tests/ui/unused_enumerate_index.rs:86:17 + | +LL | _ = mac2!().enumerate().map(|(_, _v)| {}); + | ^^^^^^^^^^^ + | +help: remove the `.enumerate()` call + | +LL - _ = mac2!().enumerate().map(|(_, _v)| {}); +LL + _ = mac2!().map(|_v| {}); + | + +error: you seem to use `.enumerate()` and immediately discard the index + --> tests/ui/unused_enumerate_index.rs:94:39 + | +LL | let v = [1, 2, 3].iter().copied().enumerate(); + | ^^^^^^^^^^^ + | +help: remove the `.enumerate()` call + | +LL ~ let v = [1, 2, 3].iter().copied(); +LL ~ let x = v.map(|x: i32| x).sum::(); + | + +error: you seem to use `.enumerate()` and immediately discard the index + --> tests/ui/unused_enumerate_index.rs:99:39 + | +LL | let v = [1, 2, 3].iter().copied().enumerate(); + | ^^^^^^^^^^^ + | +help: remove the `.enumerate()` call + | +LL ~ let v = [1, 2, 3].iter().copied(); +LL ~ let x = v.map(|x: i32| x).sum::(); + | + +error: you seem to use `.enumerate()` and immediately discard the index + --> tests/ui/unused_enumerate_index.rs:103:39 + | +LL | let v = [1, 2, 3].iter().copied().enumerate(); + | ^^^^^^^^^^^ + | +help: remove the `.enumerate()` call + | +LL ~ let v = [1, 2, 3].iter().copied(); +LL ~ let x = v.map(|x| x).sum::(); + | + +error: aborting due to 8 previous errors