diff --git a/clippy_lints/src/loops.rs b/clippy_lints/src/loops.rs index 7e3876ff49b4..e9ce804320fc 100644 --- a/clippy_lints/src/loops.rs +++ b/clippy_lints/src/loops.rs @@ -1,14 +1,14 @@ use crate::consts::constant; use crate::reexport::Name; use crate::utils::paths; +use crate::utils::sugg::Sugg; use crate::utils::usage::{is_unused, mutated_variables}; use crate::utils::{ get_enclosing_block, get_parent_expr, get_trait_def_id, has_iter_method, higher, implements_trait, - is_integer_const, is_no_std_crate, is_refutable, last_path_segment, match_trait_method, match_type, match_var, - multispan_sugg, snippet, snippet_opt, snippet_with_applicability, span_lint, span_lint_and_help, - span_lint_and_sugg, span_lint_and_then, SpanlessEq, + is_integer_const, is_no_std_crate, is_refutable, is_type_diagnostic_item, last_path_segment, match_trait_method, + match_type, match_var, multispan_sugg, qpath_res, snippet, snippet_opt, snippet_with_applicability, span_lint, + span_lint_and_help, span_lint_and_sugg, span_lint_and_then, sugg, SpanlessEq, }; -use crate::utils::{is_type_diagnostic_item, qpath_res, sugg}; use if_chain::if_chain; use rustc_ast::ast; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; @@ -17,7 +17,7 @@ use rustc_hir::def::{DefKind, Res}; use rustc_hir::intravisit::{walk_block, walk_expr, walk_pat, walk_stmt, NestedVisitorMap, Visitor}; use rustc_hir::{ def_id, BinOpKind, BindingAnnotation, Block, BorrowKind, Expr, ExprKind, GenericArg, HirId, InlineAsmOperand, - LoopSource, MatchSource, Mutability, Node, Pat, PatKind, QPath, Stmt, StmtKind, + Local, LoopSource, MatchSource, Mutability, Node, Pat, PatKind, QPath, Stmt, StmtKind, }; use rustc_infer::infer::TyCtxtInferExt; use rustc_lint::{LateContext, LateLintPass, LintContext}; @@ -27,7 +27,7 @@ use rustc_middle::middle::region; use rustc_middle::ty::{self, Ty, TyS}; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::source_map::Span; -use rustc_span::symbol::Symbol; +use rustc_span::symbol::{sym, Ident, Symbol}; use rustc_typeck::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId}; use std::iter::{once, Iterator}; use std::mem; @@ -2358,6 +2358,10 @@ impl<'a, 'tcx> Visitor<'tcx> for VarCollectorVisitor<'a, 'tcx> { const NEEDLESS_COLLECT_MSG: &str = "avoid using `collect()` when not needed"; fn check_needless_collect<'tcx>(expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) { + check_needless_collect_direct_usage(expr, cx); + check_needless_collect_indirect_usage(expr, cx); +} +fn check_needless_collect_direct_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) { if_chain! { if let ExprKind::MethodCall(ref method, _, ref args, _) = expr.kind; if let ExprKind::MethodCall(ref chain_method, _, _, _) = args[0].kind; @@ -2425,6 +2429,157 @@ fn check_needless_collect<'tcx>(expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) { } } +fn check_needless_collect_indirect_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateContext<'tcx>) { + if let ExprKind::Block(ref block, _) = expr.kind { + for ref stmt in block.stmts { + if_chain! { + if let StmtKind::Local( + Local { pat: Pat { kind: PatKind::Binding(_, _, ident, .. ), .. }, + init: Some(ref init_expr), .. } + ) = stmt.kind; + if let ExprKind::MethodCall(ref method_name, _, &[ref iter_source], ..) = init_expr.kind; + if method_name.ident.name == sym!(collect) && match_trait_method(cx, &init_expr, &paths::ITERATOR); + if let Some(ref generic_args) = method_name.args; + if let Some(GenericArg::Type(ref ty)) = generic_args.args.get(0); + if let ty = cx.typeck_results().node_type(ty.hir_id); + if is_type_diagnostic_item(cx, ty, sym::vec_type) || + is_type_diagnostic_item(cx, ty, sym!(vecdeque_type)) || + match_type(cx, ty, &paths::LINKED_LIST); + if let Some(iter_calls) = detect_iter_and_into_iters(block, *ident); + if iter_calls.len() == 1; + then { + // Suggest replacing iter_call with iter_replacement, and removing stmt + let iter_call = &iter_calls[0]; + span_lint_and_then( + cx, + NEEDLESS_COLLECT, + stmt.span.until(iter_call.span), + NEEDLESS_COLLECT_MSG, + |diag| { + let iter_replacement = format!("{}{}", Sugg::hir(cx, iter_source, ".."), iter_call.get_iter_method(cx)); + diag.multipart_suggestion( + iter_call.get_suggestion_text(), + vec![ + (stmt.span, String::new()), + (iter_call.span, iter_replacement) + ], + Applicability::MachineApplicable,// MaybeIncorrect, + ).emit(); + }, + ); + } + } + } + } +} + +struct IterFunction { + func: IterFunctionKind, + span: Span, +} +impl IterFunction { + fn get_iter_method(&self, cx: &LateContext<'_>) -> String { + match &self.func { + IterFunctionKind::IntoIter => String::new(), + IterFunctionKind::Len => String::from(".count()"), + IterFunctionKind::IsEmpty => String::from(".next().is_none()"), + IterFunctionKind::Contains(span) => format!(".any(|x| x == {})", snippet(cx, *span, "..")), + } + } + fn get_suggestion_text(&self) -> &'static str { + match &self.func { + IterFunctionKind::IntoIter => { + "Use the original Iterator instead of collecting it and then producing a new one" + }, + IterFunctionKind::Len => { + "Take the original Iterator's count instead of collecting it and finding the length" + }, + IterFunctionKind::IsEmpty => { + "Check if the original Iterator has anything instead of collecting it and seeing if it's empty" + }, + IterFunctionKind::Contains(_) => { + "Check if the original Iterator contains an element instead of collecting then checking" + }, + } + } +} +enum IterFunctionKind { + IntoIter, + Len, + IsEmpty, + Contains(Span), +} + +struct IterFunctionVisitor { + uses: Vec, + seen_other: bool, + target: Ident, +} +impl<'tcx> Visitor<'tcx> for IterFunctionVisitor { + fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) { + // Check function calls on our collection + if_chain! { + if let ExprKind::MethodCall(method_name, _, ref args, _) = &expr.kind; + if let Some(Expr { kind: ExprKind::Path(QPath::Resolved(_, ref path)), .. }) = args.get(0); + if let &[name] = &path.segments; + if name.ident == self.target; + then { + let len = sym!(len); + let is_empty = sym!(is_empty); + let contains = sym!(contains); + match method_name.ident.name { + sym::into_iter => self.uses.push( + IterFunction { func: IterFunctionKind::IntoIter, span: expr.span } + ), + name if name == len => self.uses.push( + IterFunction { func: IterFunctionKind::Len, span: expr.span } + ), + name if name == is_empty => self.uses.push( + IterFunction { func: IterFunctionKind::IsEmpty, span: expr.span } + ), + name if name == contains => self.uses.push( + IterFunction { func: IterFunctionKind::Contains(args[1].span), span: expr.span } + ), + _ => self.seen_other = true, + } + return + } + } + // Check if the collection is used for anything else + if_chain! { + if let Expr { kind: ExprKind::Path(QPath::Resolved(_, ref path)), .. } = expr; + if let &[name] = &path.segments; + if name.ident == self.target; + then { + self.seen_other = true; + } else { + walk_expr(self, expr); + } + } + } + + type Map = Map<'tcx>; + fn nested_visit_map(&mut self) -> NestedVisitorMap { + NestedVisitorMap::None + } +} + +/// Detect the occurences of calls to `iter` or `into_iter` for the +/// given identifier +fn detect_iter_and_into_iters<'tcx>(block: &'tcx Block<'tcx>, identifier: Ident) -> Option> { + let mut visitor = IterFunctionVisitor { + uses: Vec::new(), + target: identifier, + seen_other: false, + }; + visitor.visit_block(block); + if visitor.seen_other { + None + } else { + Some(visitor.uses) + } +} + fn shorten_span(expr: &Expr<'_>, target_fn_name: Symbol) -> Span { let mut current_expr = expr; while let ExprKind::MethodCall(ref path, ref span, ref args, _) = current_expr.kind { diff --git a/tests/ui/needless_collect_indirect.rs b/tests/ui/needless_collect_indirect.rs new file mode 100644 index 000000000000..4cf03e820352 --- /dev/null +++ b/tests/ui/needless_collect_indirect.rs @@ -0,0 +1,19 @@ +use std::collections::{HashMap, VecDeque}; + +fn main() { + let sample = [1; 5]; + let indirect_iter = sample.iter().collect::>(); + indirect_iter.into_iter().map(|x| (x, x + 1)).collect::>(); + let indirect_len = sample.iter().collect::>(); + indirect_len.len(); + let indirect_empty = sample.iter().collect::>(); + indirect_empty.is_empty(); + let indirect_contains = sample.iter().collect::>(); + indirect_contains.contains(&&5); + let indirect_negative = sample.iter().collect::>(); + indirect_negative.len(); + indirect_negative + .into_iter() + .map(|x| (*x, *x + 1)) + .collect::>(); +} diff --git a/tests/ui/needless_collect_indirect.stderr b/tests/ui/needless_collect_indirect.stderr new file mode 100644 index 000000000000..0c1e61d74966 --- /dev/null +++ b/tests/ui/needless_collect_indirect.stderr @@ -0,0 +1,55 @@ +error: avoid using `collect()` when not needed + --> $DIR/needless_collect_indirect.rs:5:5 + | +LL | / let indirect_iter = sample.iter().collect::>(); +LL | | indirect_iter.into_iter().map(|x| (x, x + 1)).collect::>(); + | |____^ + | + = note: `-D clippy::needless-collect` implied by `-D warnings` +help: Use the original Iterator instead of collecting it and then producing a new one + | +LL | +LL | sample.iter().map(|x| (x, x + 1)).collect::>(); + | + +error: avoid using `collect()` when not needed + --> $DIR/needless_collect_indirect.rs:7:5 + | +LL | / let indirect_len = sample.iter().collect::>(); +LL | | indirect_len.len(); + | |____^ + | +help: Take the original Iterator's count instead of collecting it and finding the length + | +LL | +LL | sample.iter().count(); + | + +error: avoid using `collect()` when not needed + --> $DIR/needless_collect_indirect.rs:9:5 + | +LL | / let indirect_empty = sample.iter().collect::>(); +LL | | indirect_empty.is_empty(); + | |____^ + | +help: Check if the original Iterator has anything instead of collecting it and seeing if it's empty + | +LL | +LL | sample.iter().next().is_none(); + | + +error: avoid using `collect()` when not needed + --> $DIR/needless_collect_indirect.rs:11:5 + | +LL | / let indirect_contains = sample.iter().collect::>(); +LL | | indirect_contains.contains(&&5); + | |____^ + | +help: Check if the original Iterator contains an element instead of collecting then checking + | +LL | +LL | sample.iter().any(|x| x == &&5); + | + +error: aborting due to 4 previous errors +