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Diffstat (limited to 'src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs')
| -rw-r--r-- | src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs | 228 |
1 files changed, 228 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs b/src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs new file mode 100644 index 000000000..ed5a75b0f --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs @@ -0,0 +1,228 @@ +use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::is_trait_method; +use clippy_utils::sugg::Sugg; +use clippy_utils::ty::implements_trait; +use if_chain::if_chain; +use rustc_errors::Applicability; +use rustc_hir::{Closure, Expr, ExprKind, Mutability, Param, Pat, PatKind, Path, PathSegment, QPath}; +use rustc_lint::LateContext; +use rustc_middle::ty::{self, subst::GenericArgKind}; +use rustc_span::sym; +use rustc_span::symbol::Ident; +use std::iter; + +use super::UNNECESSARY_SORT_BY; + +enum LintTrigger { + Sort(SortDetection), + SortByKey(SortByKeyDetection), +} + +struct SortDetection { + vec_name: String, +} + +struct SortByKeyDetection { + vec_name: String, + closure_arg: String, + closure_body: String, + reverse: bool, +} + +/// Detect if the two expressions are mirrored (identical, except one +/// contains a and the other replaces it with b) +fn mirrored_exprs(a_expr: &Expr<'_>, a_ident: &Ident, b_expr: &Expr<'_>, b_ident: &Ident) -> bool { + match (&a_expr.kind, &b_expr.kind) { + // Two boxes with mirrored contents + (ExprKind::Box(left_expr), ExprKind::Box(right_expr)) => { + mirrored_exprs(left_expr, a_ident, right_expr, b_ident) + }, + // Two arrays with mirrored contents + (ExprKind::Array(left_exprs), ExprKind::Array(right_exprs)) => { + iter::zip(*left_exprs, *right_exprs).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident)) + }, + // The two exprs are function calls. + // Check to see that the function itself and its arguments are mirrored + (ExprKind::Call(left_expr, left_args), ExprKind::Call(right_expr, right_args)) => { + mirrored_exprs(left_expr, a_ident, right_expr, b_ident) + && iter::zip(*left_args, *right_args).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident)) + }, + // The two exprs are method calls. + // Check to see that the function is the same and the arguments are mirrored + // This is enough because the receiver of the method is listed in the arguments + ( + ExprKind::MethodCall(left_segment, left_receiver, left_args, _), + ExprKind::MethodCall(right_segment, right_receiver, right_args, _), + ) => { + left_segment.ident == right_segment.ident + && iter::zip(*left_args, *right_args).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident)) + && mirrored_exprs(left_receiver, a_ident, right_receiver, b_ident) + }, + // Two tuples with mirrored contents + (ExprKind::Tup(left_exprs), ExprKind::Tup(right_exprs)) => { + iter::zip(*left_exprs, *right_exprs).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident)) + }, + // Two binary ops, which are the same operation and which have mirrored arguments + (ExprKind::Binary(left_op, left_left, left_right), ExprKind::Binary(right_op, right_left, right_right)) => { + left_op.node == right_op.node + && mirrored_exprs(left_left, a_ident, right_left, b_ident) + && mirrored_exprs(left_right, a_ident, right_right, b_ident) + }, + // Two unary ops, which are the same operation and which have the same argument + (ExprKind::Unary(left_op, left_expr), ExprKind::Unary(right_op, right_expr)) => { + left_op == right_op && mirrored_exprs(left_expr, a_ident, right_expr, b_ident) + }, + // The two exprs are literals of some kind + (ExprKind::Lit(left_lit), ExprKind::Lit(right_lit)) => left_lit.node == right_lit.node, + (ExprKind::Cast(left, _), ExprKind::Cast(right, _)) => mirrored_exprs(left, a_ident, right, b_ident), + (ExprKind::DropTemps(left_block), ExprKind::DropTemps(right_block)) => { + mirrored_exprs(left_block, a_ident, right_block, b_ident) + }, + (ExprKind::Field(left_expr, left_ident), ExprKind::Field(right_expr, right_ident)) => { + left_ident.name == right_ident.name && mirrored_exprs(left_expr, a_ident, right_expr, right_ident) + }, + // Two paths: either one is a and the other is b, or they're identical to each other + ( + ExprKind::Path(QPath::Resolved( + _, + Path { + segments: left_segments, + .. + }, + )), + ExprKind::Path(QPath::Resolved( + _, + Path { + segments: right_segments, + .. + }, + )), + ) => { + (iter::zip(*left_segments, *right_segments).all(|(left, right)| left.ident == right.ident) + && left_segments + .iter() + .all(|seg| &seg.ident != a_ident && &seg.ident != b_ident)) + || (left_segments.len() == 1 + && &left_segments[0].ident == a_ident + && right_segments.len() == 1 + && &right_segments[0].ident == b_ident) + }, + // Matching expressions, but one or both is borrowed + ( + ExprKind::AddrOf(left_kind, Mutability::Not, left_expr), + ExprKind::AddrOf(right_kind, Mutability::Not, right_expr), + ) => left_kind == right_kind && mirrored_exprs(left_expr, a_ident, right_expr, b_ident), + (_, ExprKind::AddrOf(_, Mutability::Not, right_expr)) => mirrored_exprs(a_expr, a_ident, right_expr, b_ident), + (ExprKind::AddrOf(_, Mutability::Not, left_expr), _) => mirrored_exprs(left_expr, a_ident, b_expr, b_ident), + _ => false, + } +} + +fn detect_lint(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, arg: &Expr<'_>) -> Option<LintTrigger> { + if_chain! { + if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id); + if let Some(impl_id) = cx.tcx.impl_of_method(method_id); + if cx.tcx.type_of(impl_id).is_slice(); + if let ExprKind::Closure(&Closure { body, .. }) = arg.kind; + if let closure_body = cx.tcx.hir().body(body); + if let &[ + Param { pat: Pat { kind: PatKind::Binding(_, _, left_ident, _), .. }, ..}, + Param { pat: Pat { kind: PatKind::Binding(_, _, right_ident, _), .. }, .. } + ] = &closure_body.params; + if let ExprKind::MethodCall(method_path, left_expr, [right_expr], _) = closure_body.value.kind; + if method_path.ident.name == sym::cmp; + if is_trait_method(cx, closure_body.value, sym::Ord); + then { + let (closure_body, closure_arg, reverse) = if mirrored_exprs( + left_expr, + left_ident, + right_expr, + right_ident + ) { + (Sugg::hir(cx, left_expr, "..").to_string(), left_ident.name.to_string(), false) + } else if mirrored_exprs(left_expr, right_ident, right_expr, left_ident) { + (Sugg::hir(cx, left_expr, "..").to_string(), right_ident.name.to_string(), true) + } else { + return None; + }; + let vec_name = Sugg::hir(cx, recv, "..").to_string(); + + if_chain! { + if let ExprKind::Path(QPath::Resolved(_, Path { + segments: [PathSegment { ident: left_name, .. }], .. + })) = &left_expr.kind; + if left_name == left_ident; + if cx.tcx.get_diagnostic_item(sym::Ord).map_or(false, |id| { + implements_trait(cx, cx.typeck_results().expr_ty(left_expr), id, &[]) + }); + then { + return Some(LintTrigger::Sort(SortDetection { vec_name })); + } + } + + if !expr_borrows(cx, left_expr) { + return Some(LintTrigger::SortByKey(SortByKeyDetection { + vec_name, + closure_arg, + closure_body, + reverse, + })); + } + } + } + + None +} + +fn expr_borrows(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { + let ty = cx.typeck_results().expr_ty(expr); + matches!(ty.kind(), ty::Ref(..)) || ty.walk().any(|arg| matches!(arg.unpack(), GenericArgKind::Lifetime(_))) +} + +pub(super) fn check<'tcx>( + cx: &LateContext<'tcx>, + expr: &'tcx Expr<'_>, + recv: &'tcx Expr<'_>, + arg: &'tcx Expr<'_>, + is_unstable: bool, +) { + match detect_lint(cx, expr, recv, arg) { + Some(LintTrigger::SortByKey(trigger)) => span_lint_and_sugg( + cx, + UNNECESSARY_SORT_BY, + expr.span, + "use Vec::sort_by_key here instead", + "try", + format!( + "{}.sort{}_by_key(|{}| {})", + trigger.vec_name, + if is_unstable { "_unstable" } else { "" }, + trigger.closure_arg, + if trigger.reverse { + format!("std::cmp::Reverse({})", trigger.closure_body) + } else { + trigger.closure_body.to_string() + }, + ), + if trigger.reverse { + Applicability::MaybeIncorrect + } else { + Applicability::MachineApplicable + }, + ), + Some(LintTrigger::Sort(trigger)) => span_lint_and_sugg( + cx, + UNNECESSARY_SORT_BY, + expr.span, + "use Vec::sort here instead", + "try", + format!( + "{}.sort{}()", + trigger.vec_name, + if is_unstable { "_unstable" } else { "" }, + ), + Applicability::MachineApplicable, + ), + None => {}, + } +} |