| use crate::consts::constant; |
| use crate::reexport::Name; |
| use crate::utils::paths; |
| 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, |
| }; |
| 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}; |
| use rustc_errors::Applicability; |
| 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, |
| }; |
| use rustc_infer::infer::TyCtxtInferExt; |
| use rustc_lint::{LateContext, LateLintPass, LintContext}; |
| use rustc_middle::hir::map::Map; |
| use rustc_middle::lint::in_external_macro; |
| 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_typeck::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId}; |
| use std::iter::{once, Iterator}; |
| use std::mem; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for for-loops that manually copy items between |
| /// slices that could be optimized by having a memcpy. |
| /// |
| /// **Why is this bad?** It is not as fast as a memcpy. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let src = vec![1]; |
| /// # let mut dst = vec![0; 65]; |
| /// for i in 0..src.len() { |
| /// dst[i + 64] = src[i]; |
| /// } |
| /// ``` |
| /// Could be written as: |
| /// ```rust |
| /// # let src = vec![1]; |
| /// # let mut dst = vec![0; 65]; |
| /// dst[64..(src.len() + 64)].clone_from_slice(&src[..]); |
| /// ``` |
| pub MANUAL_MEMCPY, |
| perf, |
| "manually copying items between slices" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for looping over the range of `0..len` of some |
| /// collection just to get the values by index. |
| /// |
| /// **Why is this bad?** Just iterating the collection itself makes the intent |
| /// more clear and is probably faster. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let vec = vec!['a', 'b', 'c']; |
| /// for i in 0..vec.len() { |
| /// println!("{}", vec[i]); |
| /// } |
| /// ``` |
| /// Could be written as: |
| /// ```rust |
| /// let vec = vec!['a', 'b', 'c']; |
| /// for i in vec { |
| /// println!("{}", i); |
| /// } |
| /// ``` |
| pub NEEDLESS_RANGE_LOOP, |
| style, |
| "for-looping over a range of indices where an iterator over items would do" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for loops on `x.iter()` where `&x` will do, and |
| /// suggests the latter. |
| /// |
| /// **Why is this bad?** Readability. |
| /// |
| /// **Known problems:** False negatives. We currently only warn on some known |
| /// types. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// // with `y` a `Vec` or slice: |
| /// # let y = vec![1]; |
| /// for x in y.iter() { |
| /// // .. |
| /// } |
| /// ``` |
| /// can be rewritten to |
| /// ```rust |
| /// # let y = vec![1]; |
| /// for x in &y { |
| /// // .. |
| /// } |
| /// ``` |
| pub EXPLICIT_ITER_LOOP, |
| pedantic, |
| "for-looping over `_.iter()` or `_.iter_mut()` when `&_` or `&mut _` would do" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for loops on `y.into_iter()` where `y` will do, and |
| /// suggests the latter. |
| /// |
| /// **Why is this bad?** Readability. |
| /// |
| /// **Known problems:** None |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let y = vec![1]; |
| /// // with `y` a `Vec` or slice: |
| /// for x in y.into_iter() { |
| /// // .. |
| /// } |
| /// ``` |
| /// can be rewritten to |
| /// ```rust |
| /// # let y = vec![1]; |
| /// for x in y { |
| /// // .. |
| /// } |
| /// ``` |
| pub EXPLICIT_INTO_ITER_LOOP, |
| pedantic, |
| "for-looping over `_.into_iter()` when `_` would do" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for loops on `x.next()`. |
| /// |
| /// **Why is this bad?** `next()` returns either `Some(value)` if there was a |
| /// value, or `None` otherwise. The insidious thing is that `Option<_>` |
| /// implements `IntoIterator`, so that possibly one value will be iterated, |
| /// leading to some hard to find bugs. No one will want to write such code |
| /// [except to win an Underhanded Rust |
| /// Contest](https://www.reddit.com/r/rust/comments/3hb0wm/underhanded_rust_contest/cu5yuhr). |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```ignore |
| /// for x in y.next() { |
| /// .. |
| /// } |
| /// ``` |
| pub ITER_NEXT_LOOP, |
| correctness, |
| "for-looping over `_.next()` which is probably not intended" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for `for` loops over `Option` or `Result` values. |
| /// |
| /// **Why is this bad?** Readability. This is more clearly expressed as an `if |
| /// let`. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let opt = Some(1); |
| /// |
| /// // Bad |
| /// for x in opt { |
| /// // .. |
| /// } |
| /// |
| /// // Good |
| /// if let Some(x) = opt { |
| /// // .. |
| /// } |
| /// ``` |
| /// |
| /// // or |
| /// |
| /// ```rust |
| /// # let res: Result<i32, std::io::Error> = Ok(1); |
| /// |
| /// // Bad |
| /// for x in &res { |
| /// // .. |
| /// } |
| /// |
| /// // Good |
| /// if let Ok(x) = res { |
| /// // .. |
| /// } |
| /// ``` |
| pub FOR_LOOPS_OVER_FALLIBLES, |
| correctness, |
| "for-looping over an `Option` or a `Result`, which is more clearly expressed as an `if let`" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Detects `loop + match` combinations that are easier |
| /// written as a `while let` loop. |
| /// |
| /// **Why is this bad?** The `while let` loop is usually shorter and more |
| /// readable. |
| /// |
| /// **Known problems:** Sometimes the wrong binding is displayed (#383). |
| /// |
| /// **Example:** |
| /// ```rust,no_run |
| /// # let y = Some(1); |
| /// loop { |
| /// let x = match y { |
| /// Some(x) => x, |
| /// None => break, |
| /// }; |
| /// // .. do something with x |
| /// } |
| /// // is easier written as |
| /// while let Some(x) = y { |
| /// // .. do something with x |
| /// }; |
| /// ``` |
| pub WHILE_LET_LOOP, |
| complexity, |
| "`loop { if let { ... } else break }`, which can be written as a `while let` loop" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for functions collecting an iterator when collect |
| /// is not needed. |
| /// |
| /// **Why is this bad?** `collect` causes the allocation of a new data structure, |
| /// when this allocation may not be needed. |
| /// |
| /// **Known problems:** |
| /// None |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let iterator = vec![1].into_iter(); |
| /// let len = iterator.clone().collect::<Vec<_>>().len(); |
| /// // should be |
| /// let len = iterator.count(); |
| /// ``` |
| pub NEEDLESS_COLLECT, |
| perf, |
| "collecting an iterator when collect is not needed" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks `for` loops over slices with an explicit counter |
| /// and suggests the use of `.enumerate()`. |
| /// |
| /// **Why is it bad?** Using `.enumerate()` makes the intent more clear, |
| /// declutters the code and may be faster in some instances. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let v = vec![1]; |
| /// # fn bar(bar: usize, baz: usize) {} |
| /// let mut i = 0; |
| /// for item in &v { |
| /// bar(i, *item); |
| /// i += 1; |
| /// } |
| /// ``` |
| /// Could be written as |
| /// ```rust |
| /// # let v = vec![1]; |
| /// # fn bar(bar: usize, baz: usize) {} |
| /// for (i, item) in v.iter().enumerate() { bar(i, *item); } |
| /// ``` |
| pub EXPLICIT_COUNTER_LOOP, |
| complexity, |
| "for-looping with an explicit counter when `_.enumerate()` would do" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for empty `loop` expressions. |
| /// |
| /// **Why is this bad?** Those busy loops burn CPU cycles without doing |
| /// anything. Think of the environment and either block on something or at least |
| /// make the thread sleep for some microseconds. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```no_run |
| /// loop {} |
| /// ``` |
| pub EMPTY_LOOP, |
| style, |
| "empty `loop {}`, which should block or sleep" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for `while let` expressions on iterators. |
| /// |
| /// **Why is this bad?** Readability. A simple `for` loop is shorter and conveys |
| /// the intent better. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```ignore |
| /// while let Some(val) = iter() { |
| /// .. |
| /// } |
| /// ``` |
| pub WHILE_LET_ON_ITERATOR, |
| style, |
| "using a while-let loop instead of a for loop on an iterator" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for iterating a map (`HashMap` or `BTreeMap`) and |
| /// ignoring either the keys or values. |
| /// |
| /// **Why is this bad?** Readability. There are `keys` and `values` methods that |
| /// can be used to express that don't need the values or keys. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```ignore |
| /// for (k, _) in &map { |
| /// .. |
| /// } |
| /// ``` |
| /// |
| /// could be replaced by |
| /// |
| /// ```ignore |
| /// for k in map.keys() { |
| /// .. |
| /// } |
| /// ``` |
| pub FOR_KV_MAP, |
| style, |
| "looping on a map using `iter` when `keys` or `values` would do" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for loops that will always `break`, `return` or |
| /// `continue` an outer loop. |
| /// |
| /// **Why is this bad?** This loop never loops, all it does is obfuscating the |
| /// code. |
| /// |
| /// **Known problems:** None |
| /// |
| /// **Example:** |
| /// ```rust |
| /// loop { |
| /// ..; |
| /// break; |
| /// } |
| /// ``` |
| pub NEVER_LOOP, |
| correctness, |
| "any loop that will always `break` or `return`" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for loops which have a range bound that is a mutable variable |
| /// |
| /// **Why is this bad?** One might think that modifying the mutable variable changes the loop bounds |
| /// |
| /// **Known problems:** None |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let mut foo = 42; |
| /// for i in 0..foo { |
| /// foo -= 1; |
| /// println!("{}", i); // prints numbers from 0 to 42, not 0 to 21 |
| /// } |
| /// ``` |
| pub MUT_RANGE_BOUND, |
| complexity, |
| "for loop over a range where one of the bounds is a mutable variable" |
| } |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks whether variables used within while loop condition |
| /// can be (and are) mutated in the body. |
| /// |
| /// **Why is this bad?** If the condition is unchanged, entering the body of the loop |
| /// will lead to an infinite loop. |
| /// |
| /// **Known problems:** If the `while`-loop is in a closure, the check for mutation of the |
| /// condition variables in the body can cause false negatives. For example when only `Upvar` `a` is |
| /// in the condition and only `Upvar` `b` gets mutated in the body, the lint will not trigger. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// let i = 0; |
| /// while i > 10 { |
| /// println!("let me loop forever!"); |
| /// } |
| /// ``` |
| pub WHILE_IMMUTABLE_CONDITION, |
| correctness, |
| "variables used within while expression are not mutated in the body" |
| } |
| |
| declare_lint_pass!(Loops => [ |
| MANUAL_MEMCPY, |
| NEEDLESS_RANGE_LOOP, |
| EXPLICIT_ITER_LOOP, |
| EXPLICIT_INTO_ITER_LOOP, |
| ITER_NEXT_LOOP, |
| FOR_LOOPS_OVER_FALLIBLES, |
| WHILE_LET_LOOP, |
| NEEDLESS_COLLECT, |
| EXPLICIT_COUNTER_LOOP, |
| EMPTY_LOOP, |
| WHILE_LET_ON_ITERATOR, |
| FOR_KV_MAP, |
| NEVER_LOOP, |
| MUT_RANGE_BOUND, |
| WHILE_IMMUTABLE_CONDITION, |
| ]); |
| |
| impl<'tcx> LateLintPass<'tcx> for Loops { |
| #[allow(clippy::too_many_lines)] |
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { |
| if let Some((pat, arg, body)) = higher::for_loop(expr) { |
| // we don't want to check expanded macros |
| // this check is not at the top of the function |
| // since higher::for_loop expressions are marked as expansions |
| if body.span.from_expansion() { |
| return; |
| } |
| check_for_loop(cx, pat, arg, body, expr); |
| } |
| |
| // we don't want to check expanded macros |
| if expr.span.from_expansion() { |
| return; |
| } |
| |
| // check for never_loop |
| if let ExprKind::Loop(ref block, _, _) = expr.kind { |
| match never_loop_block(block, expr.hir_id) { |
| NeverLoopResult::AlwaysBreak => span_lint(cx, NEVER_LOOP, expr.span, "this loop never actually loops"), |
| NeverLoopResult::MayContinueMainLoop | NeverLoopResult::Otherwise => (), |
| } |
| } |
| |
| // check for `loop { if let {} else break }` that could be `while let` |
| // (also matches an explicit "match" instead of "if let") |
| // (even if the "match" or "if let" is used for declaration) |
| if let ExprKind::Loop(ref block, _, LoopSource::Loop) = expr.kind { |
| // also check for empty `loop {}` statements |
| if block.stmts.is_empty() && block.expr.is_none() && !is_no_std_crate(cx.tcx.hir().krate()) { |
| span_lint( |
| cx, |
| EMPTY_LOOP, |
| expr.span, |
| "empty `loop {}` detected. You may want to either use `panic!()` or add \ |
| `std::thread::sleep(..);` to the loop body.", |
| ); |
| } |
| |
| // extract the expression from the first statement (if any) in a block |
| let inner_stmt_expr = extract_expr_from_first_stmt(block); |
| // or extract the first expression (if any) from the block |
| if let Some(inner) = inner_stmt_expr.or_else(|| extract_first_expr(block)) { |
| if let ExprKind::Match(ref matchexpr, ref arms, ref source) = inner.kind { |
| // ensure "if let" compatible match structure |
| match *source { |
| MatchSource::Normal | MatchSource::IfLetDesugar { .. } => { |
| if arms.len() == 2 |
| && arms[0].guard.is_none() |
| && arms[1].guard.is_none() |
| && is_simple_break_expr(&arms[1].body) |
| { |
| if in_external_macro(cx.sess(), expr.span) { |
| return; |
| } |
| |
| // NOTE: we used to build a body here instead of using |
| // ellipsis, this was removed because: |
| // 1) it was ugly with big bodies; |
| // 2) it was not indented properly; |
| // 3) it wasn’t very smart (see #675). |
| let mut applicability = Applicability::HasPlaceholders; |
| span_lint_and_sugg( |
| cx, |
| WHILE_LET_LOOP, |
| expr.span, |
| "this loop could be written as a `while let` loop", |
| "try", |
| format!( |
| "while let {} = {} {{ .. }}", |
| snippet_with_applicability(cx, arms[0].pat.span, "..", &mut applicability), |
| snippet_with_applicability(cx, matchexpr.span, "..", &mut applicability), |
| ), |
| applicability, |
| ); |
| } |
| }, |
| _ => (), |
| } |
| } |
| } |
| } |
| if let ExprKind::Match(ref match_expr, ref arms, MatchSource::WhileLetDesugar) = expr.kind { |
| let pat = &arms[0].pat.kind; |
| if let ( |
| &PatKind::TupleStruct(ref qpath, ref pat_args, _), |
| &ExprKind::MethodCall(ref method_path, _, ref method_args, _), |
| ) = (pat, &match_expr.kind) |
| { |
| let iter_expr = &method_args[0]; |
| |
| // Don't lint when the iterator is recreated on every iteration |
| if_chain! { |
| if let ExprKind::MethodCall(..) | ExprKind::Call(..) = iter_expr.kind; |
| if let Some(iter_def_id) = get_trait_def_id(cx, &paths::ITERATOR); |
| if implements_trait(cx, cx.tables().expr_ty(iter_expr), iter_def_id, &[]); |
| then { |
| return; |
| } |
| } |
| |
| let lhs_constructor = last_path_segment(qpath); |
| if method_path.ident.name == sym!(next) |
| && match_trait_method(cx, match_expr, &paths::ITERATOR) |
| && lhs_constructor.ident.name == sym!(Some) |
| && (pat_args.is_empty() |
| || !is_refutable(cx, &pat_args[0]) |
| && !is_used_inside(cx, iter_expr, &arms[0].body) |
| && !is_iterator_used_after_while_let(cx, iter_expr) |
| && !is_nested(cx, expr, &method_args[0])) |
| { |
| let mut applicability = Applicability::MachineApplicable; |
| let iterator = snippet_with_applicability(cx, method_args[0].span, "_", &mut applicability); |
| let loop_var = if pat_args.is_empty() { |
| "_".to_string() |
| } else { |
| snippet_with_applicability(cx, pat_args[0].span, "_", &mut applicability).into_owned() |
| }; |
| span_lint_and_sugg( |
| cx, |
| WHILE_LET_ON_ITERATOR, |
| expr.span.with_hi(match_expr.span.hi()), |
| "this loop could be written as a `for` loop", |
| "try", |
| format!("for {} in {}", loop_var, iterator), |
| applicability, |
| ); |
| } |
| } |
| } |
| |
| if let Some((cond, body)) = higher::while_loop(&expr) { |
| check_infinite_loop(cx, cond, body); |
| } |
| |
| check_needless_collect(expr, cx); |
| } |
| } |
| |
| enum NeverLoopResult { |
| // A break/return always get triggered but not necessarily for the main loop. |
| AlwaysBreak, |
| // A continue may occur for the main loop. |
| MayContinueMainLoop, |
| Otherwise, |
| } |
| |
| #[must_use] |
| fn absorb_break(arg: &NeverLoopResult) -> NeverLoopResult { |
| match *arg { |
| NeverLoopResult::AlwaysBreak | NeverLoopResult::Otherwise => NeverLoopResult::Otherwise, |
| NeverLoopResult::MayContinueMainLoop => NeverLoopResult::MayContinueMainLoop, |
| } |
| } |
| |
| // Combine two results for parts that are called in order. |
| #[must_use] |
| fn combine_seq(first: NeverLoopResult, second: NeverLoopResult) -> NeverLoopResult { |
| match first { |
| NeverLoopResult::AlwaysBreak | NeverLoopResult::MayContinueMainLoop => first, |
| NeverLoopResult::Otherwise => second, |
| } |
| } |
| |
| // Combine two results where both parts are called but not necessarily in order. |
| #[must_use] |
| fn combine_both(left: NeverLoopResult, right: NeverLoopResult) -> NeverLoopResult { |
| match (left, right) { |
| (NeverLoopResult::MayContinueMainLoop, _) | (_, NeverLoopResult::MayContinueMainLoop) => { |
| NeverLoopResult::MayContinueMainLoop |
| }, |
| (NeverLoopResult::AlwaysBreak, _) | (_, NeverLoopResult::AlwaysBreak) => NeverLoopResult::AlwaysBreak, |
| (NeverLoopResult::Otherwise, NeverLoopResult::Otherwise) => NeverLoopResult::Otherwise, |
| } |
| } |
| |
| // Combine two results where only one of the part may have been executed. |
| #[must_use] |
| fn combine_branches(b1: NeverLoopResult, b2: NeverLoopResult) -> NeverLoopResult { |
| match (b1, b2) { |
| (NeverLoopResult::AlwaysBreak, NeverLoopResult::AlwaysBreak) => NeverLoopResult::AlwaysBreak, |
| (NeverLoopResult::MayContinueMainLoop, _) | (_, NeverLoopResult::MayContinueMainLoop) => { |
| NeverLoopResult::MayContinueMainLoop |
| }, |
| (NeverLoopResult::Otherwise, _) | (_, NeverLoopResult::Otherwise) => NeverLoopResult::Otherwise, |
| } |
| } |
| |
| fn never_loop_block(block: &Block<'_>, main_loop_id: HirId) -> NeverLoopResult { |
| let stmts = block.stmts.iter().map(stmt_to_expr); |
| let expr = once(block.expr.as_deref()); |
| let mut iter = stmts.chain(expr).filter_map(|e| e); |
| never_loop_expr_seq(&mut iter, main_loop_id) |
| } |
| |
| fn stmt_to_expr<'tcx>(stmt: &Stmt<'tcx>) -> Option<&'tcx Expr<'tcx>> { |
| match stmt.kind { |
| StmtKind::Semi(ref e, ..) | StmtKind::Expr(ref e, ..) => Some(e), |
| StmtKind::Local(ref local) => local.init.as_deref(), |
| _ => None, |
| } |
| } |
| |
| fn never_loop_expr(expr: &Expr<'_>, main_loop_id: HirId) -> NeverLoopResult { |
| match expr.kind { |
| ExprKind::Box(ref e) |
| | ExprKind::Unary(_, ref e) |
| | ExprKind::Cast(ref e, _) |
| | ExprKind::Type(ref e, _) |
| | ExprKind::Field(ref e, _) |
| | ExprKind::AddrOf(_, _, ref e) |
| | ExprKind::Struct(_, _, Some(ref e)) |
| | ExprKind::Repeat(ref e, _) |
| | ExprKind::DropTemps(ref e) => never_loop_expr(e, main_loop_id), |
| ExprKind::Array(ref es) | ExprKind::MethodCall(_, _, ref es, _) | ExprKind::Tup(ref es) => { |
| never_loop_expr_all(&mut es.iter(), main_loop_id) |
| }, |
| ExprKind::Call(ref e, ref es) => never_loop_expr_all(&mut once(&**e).chain(es.iter()), main_loop_id), |
| ExprKind::Binary(_, ref e1, ref e2) |
| | ExprKind::Assign(ref e1, ref e2, _) |
| | ExprKind::AssignOp(_, ref e1, ref e2) |
| | ExprKind::Index(ref e1, ref e2) => never_loop_expr_all(&mut [&**e1, &**e2].iter().cloned(), main_loop_id), |
| ExprKind::Loop(ref b, _, _) => { |
| // Break can come from the inner loop so remove them. |
| absorb_break(&never_loop_block(b, main_loop_id)) |
| }, |
| ExprKind::Match(ref e, ref arms, _) => { |
| let e = never_loop_expr(e, main_loop_id); |
| if arms.is_empty() { |
| e |
| } else { |
| let arms = never_loop_expr_branch(&mut arms.iter().map(|a| &*a.body), main_loop_id); |
| combine_seq(e, arms) |
| } |
| }, |
| ExprKind::Block(ref b, _) => never_loop_block(b, main_loop_id), |
| ExprKind::Continue(d) => { |
| let id = d |
| .target_id |
| .expect("target ID can only be missing in the presence of compilation errors"); |
| if id == main_loop_id { |
| NeverLoopResult::MayContinueMainLoop |
| } else { |
| NeverLoopResult::AlwaysBreak |
| } |
| }, |
| ExprKind::Break(_, ref e) | ExprKind::Ret(ref e) => { |
| if let Some(ref e) = *e { |
| combine_seq(never_loop_expr(e, main_loop_id), NeverLoopResult::AlwaysBreak) |
| } else { |
| NeverLoopResult::AlwaysBreak |
| } |
| }, |
| ExprKind::InlineAsm(ref asm) => asm |
| .operands |
| .iter() |
| .map(|o| match o { |
| InlineAsmOperand::In { expr, .. } |
| | InlineAsmOperand::InOut { expr, .. } |
| | InlineAsmOperand::Const { expr } |
| | InlineAsmOperand::Sym { expr } => never_loop_expr(expr, main_loop_id), |
| InlineAsmOperand::Out { expr, .. } => never_loop_expr_all(&mut expr.iter(), main_loop_id), |
| InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => { |
| never_loop_expr_all(&mut once(in_expr).chain(out_expr.iter()), main_loop_id) |
| }, |
| }) |
| .fold(NeverLoopResult::Otherwise, combine_both), |
| ExprKind::Struct(_, _, None) |
| | ExprKind::Yield(_, _) |
| | ExprKind::Closure(_, _, _, _, _) |
| | ExprKind::LlvmInlineAsm(_) |
| | ExprKind::Path(_) |
| | ExprKind::Lit(_) |
| | ExprKind::Err => NeverLoopResult::Otherwise, |
| } |
| } |
| |
| fn never_loop_expr_seq<'a, T: Iterator<Item = &'a Expr<'a>>>(es: &mut T, main_loop_id: HirId) -> NeverLoopResult { |
| es.map(|e| never_loop_expr(e, main_loop_id)) |
| .fold(NeverLoopResult::Otherwise, combine_seq) |
| } |
| |
| fn never_loop_expr_all<'a, T: Iterator<Item = &'a Expr<'a>>>(es: &mut T, main_loop_id: HirId) -> NeverLoopResult { |
| es.map(|e| never_loop_expr(e, main_loop_id)) |
| .fold(NeverLoopResult::Otherwise, combine_both) |
| } |
| |
| fn never_loop_expr_branch<'a, T: Iterator<Item = &'a Expr<'a>>>(e: &mut T, main_loop_id: HirId) -> NeverLoopResult { |
| e.map(|e| never_loop_expr(e, main_loop_id)) |
| .fold(NeverLoopResult::AlwaysBreak, combine_branches) |
| } |
| |
| fn check_for_loop<'tcx>( |
| cx: &LateContext<'tcx>, |
| pat: &'tcx Pat<'_>, |
| arg: &'tcx Expr<'_>, |
| body: &'tcx Expr<'_>, |
| expr: &'tcx Expr<'_>, |
| ) { |
| check_for_loop_range(cx, pat, arg, body, expr); |
| check_for_loop_arg(cx, pat, arg, expr); |
| check_for_loop_explicit_counter(cx, pat, arg, body, expr); |
| check_for_loop_over_map_kv(cx, pat, arg, body, expr); |
| check_for_mut_range_bound(cx, arg, body); |
| detect_manual_memcpy(cx, pat, arg, body, expr); |
| } |
| |
| fn same_var<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, var: HirId) -> bool { |
| if_chain! { |
| if let ExprKind::Path(qpath) = &expr.kind; |
| if let QPath::Resolved(None, path) = qpath; |
| if path.segments.len() == 1; |
| if let Res::Local(local_id) = qpath_res(cx, qpath, expr.hir_id); |
| then { |
| // our variable! |
| local_id == var |
| } else { |
| false |
| } |
| } |
| } |
| |
| #[derive(Clone, Copy)] |
| enum OffsetSign { |
| Positive, |
| Negative, |
| } |
| |
| struct Offset { |
| value: String, |
| sign: OffsetSign, |
| } |
| |
| impl Offset { |
| fn negative(value: String) -> Self { |
| Self { |
| value, |
| sign: OffsetSign::Negative, |
| } |
| } |
| |
| fn positive(value: String) -> Self { |
| Self { |
| value, |
| sign: OffsetSign::Positive, |
| } |
| } |
| } |
| |
| struct FixedOffsetVar<'hir> { |
| var: &'hir Expr<'hir>, |
| offset: Offset, |
| } |
| |
| fn is_slice_like<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'_>) -> bool { |
| let is_slice = match ty.kind { |
| ty::Ref(_, subty, _) => is_slice_like(cx, subty), |
| ty::Slice(..) | ty::Array(..) => true, |
| _ => false, |
| }; |
| |
| is_slice || is_type_diagnostic_item(cx, ty, sym!(vec_type)) || is_type_diagnostic_item(cx, ty, sym!(vecdeque_type)) |
| } |
| |
| fn fetch_cloned_expr<'tcx>(expr: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> { |
| if_chain! { |
| if let ExprKind::MethodCall(method, _, args, _) = expr.kind; |
| if method.ident.name == sym!(clone); |
| if args.len() == 1; |
| if let Some(arg) = args.get(0); |
| then { arg } else { expr } |
| } |
| } |
| |
| fn get_offset<'tcx>(cx: &LateContext<'tcx>, idx: &Expr<'_>, var: HirId) -> Option<Offset> { |
| fn extract_offset<'tcx>(cx: &LateContext<'tcx>, e: &Expr<'_>, var: HirId) -> Option<String> { |
| match &e.kind { |
| ExprKind::Lit(l) => match l.node { |
| ast::LitKind::Int(x, _ty) => Some(x.to_string()), |
| _ => None, |
| }, |
| ExprKind::Path(..) if !same_var(cx, e, var) => Some(snippet_opt(cx, e.span).unwrap_or_else(|| "??".into())), |
| _ => None, |
| } |
| } |
| |
| match idx.kind { |
| ExprKind::Binary(op, lhs, rhs) => match op.node { |
| BinOpKind::Add => { |
| let offset_opt = if same_var(cx, lhs, var) { |
| extract_offset(cx, rhs, var) |
| } else if same_var(cx, rhs, var) { |
| extract_offset(cx, lhs, var) |
| } else { |
| None |
| }; |
| |
| offset_opt.map(Offset::positive) |
| }, |
| BinOpKind::Sub if same_var(cx, lhs, var) => extract_offset(cx, rhs, var).map(Offset::negative), |
| _ => None, |
| }, |
| ExprKind::Path(..) if same_var(cx, idx, var) => Some(Offset::positive("0".into())), |
| _ => None, |
| } |
| } |
| |
| fn get_assignments<'tcx>(body: &'tcx Expr<'tcx>) -> impl Iterator<Item = Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)>> { |
| fn get_assignment<'tcx>(e: &'tcx Expr<'tcx>) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> { |
| if let ExprKind::Assign(lhs, rhs, _) = e.kind { |
| Some((lhs, rhs)) |
| } else { |
| None |
| } |
| } |
| |
| // This is one of few ways to return different iterators |
| // derived from: https://stackoverflow.com/questions/29760668/conditionally-iterate-over-one-of-several-possible-iterators/52064434#52064434 |
| let mut iter_a = None; |
| let mut iter_b = None; |
| |
| if let ExprKind::Block(b, _) = body.kind { |
| let Block { stmts, expr, .. } = *b; |
| |
| iter_a = stmts |
| .iter() |
| .filter_map(|stmt| match stmt.kind { |
| StmtKind::Local(..) | StmtKind::Item(..) => None, |
| StmtKind::Expr(e) | StmtKind::Semi(e) => Some(e), |
| }) |
| .chain(expr.into_iter()) |
| .map(get_assignment) |
| .into() |
| } else { |
| iter_b = Some(get_assignment(body)) |
| } |
| |
| iter_a.into_iter().flatten().chain(iter_b.into_iter()) |
| } |
| |
| fn build_manual_memcpy_suggestion<'tcx>( |
| cx: &LateContext<'tcx>, |
| start: &Expr<'_>, |
| end: &Expr<'_>, |
| limits: ast::RangeLimits, |
| dst_var: FixedOffsetVar<'_>, |
| src_var: FixedOffsetVar<'_>, |
| ) -> String { |
| fn print_sum(arg1: &str, arg2: &Offset) -> String { |
| match (arg1, &arg2.value[..], arg2.sign) { |
| ("0", "0", _) => "0".into(), |
| ("0", x, OffsetSign::Positive) | (x, "0", _) => x.into(), |
| ("0", x, OffsetSign::Negative) => format!("-{}", x), |
| (x, y, OffsetSign::Positive) => format!("({} + {})", x, y), |
| (x, y, OffsetSign::Negative) => { |
| if x == y { |
| "0".into() |
| } else { |
| format!("({} - {})", x, y) |
| } |
| }, |
| } |
| } |
| |
| fn print_offset(start_str: &str, inline_offset: &Offset) -> String { |
| let offset = print_sum(start_str, inline_offset); |
| if offset.as_str() == "0" { |
| "".into() |
| } else { |
| offset |
| } |
| } |
| |
| let print_limit = |end: &Expr<'_>, offset: Offset, var: &Expr<'_>| { |
| if_chain! { |
| if let ExprKind::MethodCall(method, _, len_args, _) = end.kind; |
| if method.ident.name == sym!(len); |
| if len_args.len() == 1; |
| if let Some(arg) = len_args.get(0); |
| if var_def_id(cx, arg) == var_def_id(cx, var); |
| then { |
| match offset.sign { |
| OffsetSign::Negative => format!("({} - {})", snippet(cx, end.span, "<src>.len()"), offset.value), |
| OffsetSign::Positive => "".into(), |
| } |
| } else { |
| let end_str = match limits { |
| ast::RangeLimits::Closed => { |
| let end = sugg::Sugg::hir(cx, end, "<count>"); |
| format!("{}", end + sugg::ONE) |
| }, |
| ast::RangeLimits::HalfOpen => format!("{}", snippet(cx, end.span, "..")), |
| }; |
| |
| print_sum(&end_str, &offset) |
| } |
| } |
| }; |
| |
| let start_str = snippet(cx, start.span, "").to_string(); |
| let dst_offset = print_offset(&start_str, &dst_var.offset); |
| let dst_limit = print_limit(end, dst_var.offset, dst_var.var); |
| let src_offset = print_offset(&start_str, &src_var.offset); |
| let src_limit = print_limit(end, src_var.offset, src_var.var); |
| |
| let dst_var_name = snippet_opt(cx, dst_var.var.span).unwrap_or_else(|| "???".into()); |
| let src_var_name = snippet_opt(cx, src_var.var.span).unwrap_or_else(|| "???".into()); |
| |
| let dst = if dst_offset == "" && dst_limit == "" { |
| dst_var_name |
| } else { |
| format!("{}[{}..{}]", dst_var_name, dst_offset, dst_limit) |
| }; |
| |
| format!( |
| "{}.clone_from_slice(&{}[{}..{}])", |
| dst, src_var_name, src_offset, src_limit |
| ) |
| } |
| /// Checks for for loops that sequentially copy items from one slice-like |
| /// object to another. |
| fn detect_manual_memcpy<'tcx>( |
| cx: &LateContext<'tcx>, |
| pat: &'tcx Pat<'_>, |
| arg: &'tcx Expr<'_>, |
| body: &'tcx Expr<'_>, |
| expr: &'tcx Expr<'_>, |
| ) { |
| if let Some(higher::Range { |
| start: Some(start), |
| end: Some(end), |
| limits, |
| }) = higher::range(cx, arg) |
| { |
| // the var must be a single name |
| if let PatKind::Binding(_, canonical_id, _, _) = pat.kind { |
| // The only statements in the for loops can be indexed assignments from |
| // indexed retrievals. |
| let big_sugg = get_assignments(body) |
| .map(|o| { |
| o.and_then(|(lhs, rhs)| { |
| let rhs = fetch_cloned_expr(rhs); |
| if_chain! { |
| if let ExprKind::Index(seqexpr_left, idx_left) = lhs.kind; |
| if let ExprKind::Index(seqexpr_right, idx_right) = rhs.kind; |
| if is_slice_like(cx, cx.tables().expr_ty(seqexpr_left)) |
| && is_slice_like(cx, cx.tables().expr_ty(seqexpr_right)); |
| if let Some(offset_left) = get_offset(cx, &idx_left, canonical_id); |
| if let Some(offset_right) = get_offset(cx, &idx_right, canonical_id); |
| |
| // Source and destination must be different |
| if var_def_id(cx, seqexpr_left) != var_def_id(cx, seqexpr_right); |
| then { |
| Some((FixedOffsetVar { var: seqexpr_left, offset: offset_left }, |
| FixedOffsetVar { var: seqexpr_right, offset: offset_right })) |
| } else { |
| None |
| } |
| } |
| }) |
| }) |
| .map(|o| o.map(|(dst, src)| build_manual_memcpy_suggestion(cx, start, end, limits, dst, src))) |
| .collect::<Option<Vec<_>>>() |
| .filter(|v| !v.is_empty()) |
| .map(|v| v.join("\n ")); |
| |
| if let Some(big_sugg) = big_sugg { |
| span_lint_and_sugg( |
| cx, |
| MANUAL_MEMCPY, |
| expr.span, |
| "it looks like you're manually copying between slices", |
| "try replacing the loop by", |
| big_sugg, |
| Applicability::Unspecified, |
| ); |
| } |
| } |
| } |
| } |
| |
| /// Checks for looping over a range and then indexing a sequence with it. |
| /// The iteratee must be a range literal. |
| #[allow(clippy::too_many_lines)] |
| fn check_for_loop_range<'tcx>( |
| cx: &LateContext<'tcx>, |
| pat: &'tcx Pat<'_>, |
| arg: &'tcx Expr<'_>, |
| body: &'tcx Expr<'_>, |
| expr: &'tcx Expr<'_>, |
| ) { |
| if let Some(higher::Range { |
| start: Some(start), |
| ref end, |
| limits, |
| }) = higher::range(cx, arg) |
| { |
| // the var must be a single name |
| if let PatKind::Binding(_, canonical_id, ident, _) = pat.kind { |
| let mut visitor = VarVisitor { |
| cx, |
| var: canonical_id, |
| indexed_mut: FxHashSet::default(), |
| indexed_indirectly: FxHashMap::default(), |
| indexed_directly: FxHashMap::default(), |
| referenced: FxHashSet::default(), |
| nonindex: false, |
| prefer_mutable: false, |
| }; |
| walk_expr(&mut visitor, body); |
| |
| // linting condition: we only indexed one variable, and indexed it directly |
| if visitor.indexed_indirectly.is_empty() && visitor.indexed_directly.len() == 1 { |
| let (indexed, (indexed_extent, indexed_ty)) = visitor |
| .indexed_directly |
| .into_iter() |
| .next() |
| .expect("already checked that we have exactly 1 element"); |
| |
| // ensure that the indexed variable was declared before the loop, see #601 |
| if let Some(indexed_extent) = indexed_extent { |
| let parent_id = cx.tcx.hir().get_parent_item(expr.hir_id); |
| let parent_def_id = cx.tcx.hir().local_def_id(parent_id); |
| let region_scope_tree = cx.tcx.region_scope_tree(parent_def_id); |
| let pat_extent = region_scope_tree.var_scope(pat.hir_id.local_id); |
| if region_scope_tree.is_subscope_of(indexed_extent, pat_extent) { |
| return; |
| } |
| } |
| |
| // don't lint if the container that is indexed does not have .iter() method |
| let has_iter = has_iter_method(cx, indexed_ty); |
| if has_iter.is_none() { |
| return; |
| } |
| |
| // don't lint if the container that is indexed into is also used without |
| // indexing |
| if visitor.referenced.contains(&indexed) { |
| return; |
| } |
| |
| let starts_at_zero = is_integer_const(cx, start, 0); |
| |
| let skip = if starts_at_zero { |
| String::new() |
| } else { |
| format!(".skip({})", snippet(cx, start.span, "..")) |
| }; |
| |
| let mut end_is_start_plus_val = false; |
| |
| let take = if let Some(end) = *end { |
| let mut take_expr = end; |
| |
| if let ExprKind::Binary(ref op, ref left, ref right) = end.kind { |
| if let BinOpKind::Add = op.node { |
| let start_equal_left = SpanlessEq::new(cx).eq_expr(start, left); |
| let start_equal_right = SpanlessEq::new(cx).eq_expr(start, right); |
| |
| if start_equal_left { |
| take_expr = right; |
| } else if start_equal_right { |
| take_expr = left; |
| } |
| |
| end_is_start_plus_val = start_equal_left | start_equal_right; |
| } |
| } |
| |
| if is_len_call(end, indexed) || is_end_eq_array_len(cx, end, limits, indexed_ty) { |
| String::new() |
| } else { |
| match limits { |
| ast::RangeLimits::Closed => { |
| let take_expr = sugg::Sugg::hir(cx, take_expr, "<count>"); |
| format!(".take({})", take_expr + sugg::ONE) |
| }, |
| ast::RangeLimits::HalfOpen => format!(".take({})", snippet(cx, take_expr.span, "..")), |
| } |
| } |
| } else { |
| String::new() |
| }; |
| |
| let (ref_mut, method) = if visitor.indexed_mut.contains(&indexed) { |
| ("mut ", "iter_mut") |
| } else { |
| ("", "iter") |
| }; |
| |
| let take_is_empty = take.is_empty(); |
| let mut method_1 = take; |
| let mut method_2 = skip; |
| |
| if end_is_start_plus_val { |
| mem::swap(&mut method_1, &mut method_2); |
| } |
| |
| if visitor.nonindex { |
| span_lint_and_then( |
| cx, |
| NEEDLESS_RANGE_LOOP, |
| expr.span, |
| &format!("the loop variable `{}` is used to index `{}`", ident.name, indexed), |
| |diag| { |
| multispan_sugg( |
| diag, |
| "consider using an iterator", |
| vec![ |
| (pat.span, format!("({}, <item>)", ident.name)), |
| ( |
| arg.span, |
| format!("{}.{}().enumerate(){}{}", indexed, method, method_1, method_2), |
| ), |
| ], |
| ); |
| }, |
| ); |
| } else { |
| let repl = if starts_at_zero && take_is_empty { |
| format!("&{}{}", ref_mut, indexed) |
| } else { |
| format!("{}.{}(){}{}", indexed, method, method_1, method_2) |
| }; |
| |
| span_lint_and_then( |
| cx, |
| NEEDLESS_RANGE_LOOP, |
| expr.span, |
| &format!( |
| "the loop variable `{}` is only used to index `{}`.", |
| ident.name, indexed |
| ), |
| |diag| { |
| multispan_sugg( |
| diag, |
| "consider using an iterator", |
| vec![(pat.span, "<item>".to_string()), (arg.span, repl)], |
| ); |
| }, |
| ); |
| } |
| } |
| } |
| } |
| } |
| |
| fn is_len_call(expr: &Expr<'_>, var: Name) -> bool { |
| if_chain! { |
| if let ExprKind::MethodCall(ref method, _, ref len_args, _) = expr.kind; |
| if len_args.len() == 1; |
| if method.ident.name == sym!(len); |
| if let ExprKind::Path(QPath::Resolved(_, ref path)) = len_args[0].kind; |
| if path.segments.len() == 1; |
| if path.segments[0].ident.name == var; |
| then { |
| return true; |
| } |
| } |
| |
| false |
| } |
| |
| fn is_end_eq_array_len<'tcx>( |
| cx: &LateContext<'tcx>, |
| end: &Expr<'_>, |
| limits: ast::RangeLimits, |
| indexed_ty: Ty<'tcx>, |
| ) -> bool { |
| if_chain! { |
| if let ExprKind::Lit(ref lit) = end.kind; |
| if let ast::LitKind::Int(end_int, _) = lit.node; |
| if let ty::Array(_, arr_len_const) = indexed_ty.kind; |
| if let Some(arr_len) = arr_len_const.try_eval_usize(cx.tcx, cx.param_env); |
| then { |
| return match limits { |
| ast::RangeLimits::Closed => end_int + 1 >= arr_len.into(), |
| ast::RangeLimits::HalfOpen => end_int >= arr_len.into(), |
| }; |
| } |
| } |
| |
| false |
| } |
| |
| fn lint_iter_method(cx: &LateContext<'_>, args: &[Expr<'_>], arg: &Expr<'_>, method_name: &str) { |
| let mut applicability = Applicability::MachineApplicable; |
| let object = snippet_with_applicability(cx, args[0].span, "_", &mut applicability); |
| let muta = if method_name == "iter_mut" { "mut " } else { "" }; |
| span_lint_and_sugg( |
| cx, |
| EXPLICIT_ITER_LOOP, |
| arg.span, |
| "it is more concise to loop over references to containers instead of using explicit \ |
| iteration methods", |
| "to write this more concisely, try", |
| format!("&{}{}", muta, object), |
| applicability, |
| ) |
| } |
| |
| fn check_for_loop_arg(cx: &LateContext<'_>, pat: &Pat<'_>, arg: &Expr<'_>, expr: &Expr<'_>) { |
| let mut next_loop_linted = false; // whether or not ITER_NEXT_LOOP lint was used |
| if let ExprKind::MethodCall(ref method, _, ref args, _) = arg.kind { |
| // just the receiver, no arguments |
| if args.len() == 1 { |
| let method_name = &*method.ident.as_str(); |
| // check for looping over x.iter() or x.iter_mut(), could use &x or &mut x |
| if method_name == "iter" || method_name == "iter_mut" { |
| if is_ref_iterable_type(cx, &args[0]) { |
| lint_iter_method(cx, args, arg, method_name); |
| } |
| } else if method_name == "into_iter" && match_trait_method(cx, arg, &paths::INTO_ITERATOR) { |
| let receiver_ty = cx.tables().expr_ty(&args[0]); |
| let receiver_ty_adjusted = cx.tables().expr_ty_adjusted(&args[0]); |
| if TyS::same_type(receiver_ty, receiver_ty_adjusted) { |
| let mut applicability = Applicability::MachineApplicable; |
| let object = snippet_with_applicability(cx, args[0].span, "_", &mut applicability); |
| span_lint_and_sugg( |
| cx, |
| EXPLICIT_INTO_ITER_LOOP, |
| arg.span, |
| "it is more concise to loop over containers instead of using explicit \ |
| iteration methods", |
| "to write this more concisely, try", |
| object.to_string(), |
| applicability, |
| ); |
| } else { |
| let ref_receiver_ty = cx.tcx.mk_ref( |
| cx.tcx.lifetimes.re_erased, |
| ty::TypeAndMut { |
| ty: receiver_ty, |
| mutbl: Mutability::Not, |
| }, |
| ); |
| if TyS::same_type(receiver_ty_adjusted, ref_receiver_ty) { |
| lint_iter_method(cx, args, arg, method_name) |
| } |
| } |
| } else if method_name == "next" && match_trait_method(cx, arg, &paths::ITERATOR) { |
| span_lint( |
| cx, |
| ITER_NEXT_LOOP, |
| expr.span, |
| "you are iterating over `Iterator::next()` which is an Option; this will compile but is \ |
| probably not what you want", |
| ); |
| next_loop_linted = true; |
| } |
| } |
| } |
| if !next_loop_linted { |
| check_arg_type(cx, pat, arg); |
| } |
| } |
| |
| /// Checks for `for` loops over `Option`s and `Result`s. |
| fn check_arg_type(cx: &LateContext<'_>, pat: &Pat<'_>, arg: &Expr<'_>) { |
| let ty = cx.tables().expr_ty(arg); |
| if is_type_diagnostic_item(cx, ty, sym!(option_type)) { |
| span_lint_and_help( |
| cx, |
| FOR_LOOPS_OVER_FALLIBLES, |
| arg.span, |
| &format!( |
| "for loop over `{0}`, which is an `Option`. This is more readably written as an \ |
| `if let` statement.", |
| snippet(cx, arg.span, "_") |
| ), |
| None, |
| &format!( |
| "consider replacing `for {0} in {1}` with `if let Some({0}) = {1}`", |
| snippet(cx, pat.span, "_"), |
| snippet(cx, arg.span, "_") |
| ), |
| ); |
| } else if is_type_diagnostic_item(cx, ty, sym!(result_type)) { |
| span_lint_and_help( |
| cx, |
| FOR_LOOPS_OVER_FALLIBLES, |
| arg.span, |
| &format!( |
| "for loop over `{0}`, which is a `Result`. This is more readably written as an \ |
| `if let` statement.", |
| snippet(cx, arg.span, "_") |
| ), |
| None, |
| &format!( |
| "consider replacing `for {0} in {1}` with `if let Ok({0}) = {1}`", |
| snippet(cx, pat.span, "_"), |
| snippet(cx, arg.span, "_") |
| ), |
| ); |
| } |
| } |
| |
| fn check_for_loop_explicit_counter<'tcx>( |
| cx: &LateContext<'tcx>, |
| pat: &'tcx Pat<'_>, |
| arg: &'tcx Expr<'_>, |
| body: &'tcx Expr<'_>, |
| expr: &'tcx Expr<'_>, |
| ) { |
| // Look for variables that are incremented once per loop iteration. |
| let mut visitor = IncrementVisitor { |
| cx, |
| states: FxHashMap::default(), |
| depth: 0, |
| done: false, |
| }; |
| walk_expr(&mut visitor, body); |
| |
| // For each candidate, check the parent block to see if |
| // it's initialized to zero at the start of the loop. |
| if let Some(block) = get_enclosing_block(&cx, expr.hir_id) { |
| for (id, _) in visitor.states.iter().filter(|&(_, v)| *v == VarState::IncrOnce) { |
| let mut visitor2 = InitializeVisitor { |
| cx, |
| end_expr: expr, |
| var_id: *id, |
| state: VarState::IncrOnce, |
| name: None, |
| depth: 0, |
| past_loop: false, |
| }; |
| walk_block(&mut visitor2, block); |
| |
| if visitor2.state == VarState::Warn { |
| if let Some(name) = visitor2.name { |
| let mut applicability = Applicability::MachineApplicable; |
| |
| // for some reason this is the only way to get the `Span` |
| // of the entire `for` loop |
| let for_span = if let ExprKind::Match(_, arms, _) = &expr.kind { |
| arms[0].body.span |
| } else { |
| unreachable!() |
| }; |
| |
| span_lint_and_sugg( |
| cx, |
| EXPLICIT_COUNTER_LOOP, |
| for_span.with_hi(arg.span.hi()), |
| &format!("the variable `{}` is used as a loop counter.", name), |
| "consider using", |
| format!( |
| "for ({}, {}) in {}.enumerate()", |
| name, |
| snippet_with_applicability(cx, pat.span, "item", &mut applicability), |
| make_iterator_snippet(cx, arg, &mut applicability), |
| ), |
| applicability, |
| ); |
| } |
| } |
| } |
| } |
| } |
| |
| /// If `arg` was the argument to a `for` loop, return the "cleanest" way of writing the |
| /// actual `Iterator` that the loop uses. |
| fn make_iterator_snippet(cx: &LateContext<'_>, arg: &Expr<'_>, applic_ref: &mut Applicability) -> String { |
| let impls_iterator = get_trait_def_id(cx, &paths::ITERATOR) |
| .map_or(false, |id| implements_trait(cx, cx.tables().expr_ty(arg), id, &[])); |
| if impls_iterator { |
| format!( |
| "{}", |
| sugg::Sugg::hir_with_applicability(cx, arg, "_", applic_ref).maybe_par() |
| ) |
| } else { |
| // (&x).into_iter() ==> x.iter() |
| // (&mut x).into_iter() ==> x.iter_mut() |
| match &arg.kind { |
| ExprKind::AddrOf(BorrowKind::Ref, mutability, arg_inner) |
| if has_iter_method(cx, cx.tables().expr_ty(&arg_inner)).is_some() => |
| { |
| let meth_name = match mutability { |
| Mutability::Mut => "iter_mut", |
| Mutability::Not => "iter", |
| }; |
| format!( |
| "{}.{}()", |
| sugg::Sugg::hir_with_applicability(cx, &arg_inner, "_", applic_ref).maybe_par(), |
| meth_name, |
| ) |
| } |
| _ => format!( |
| "{}.into_iter()", |
| sugg::Sugg::hir_with_applicability(cx, arg, "_", applic_ref).maybe_par() |
| ), |
| } |
| } |
| } |
| |
| /// Checks for the `FOR_KV_MAP` lint. |
| fn check_for_loop_over_map_kv<'tcx>( |
| cx: &LateContext<'tcx>, |
| pat: &'tcx Pat<'_>, |
| arg: &'tcx Expr<'_>, |
| body: &'tcx Expr<'_>, |
| expr: &'tcx Expr<'_>, |
| ) { |
| let pat_span = pat.span; |
| |
| if let PatKind::Tuple(ref pat, _) = pat.kind { |
| if pat.len() == 2 { |
| let arg_span = arg.span; |
| let (new_pat_span, kind, ty, mutbl) = match cx.tables().expr_ty(arg).kind { |
| ty::Ref(_, ty, mutbl) => match (&pat[0].kind, &pat[1].kind) { |
| (key, _) if pat_is_wild(key, body) => (pat[1].span, "value", ty, mutbl), |
| (_, value) if pat_is_wild(value, body) => (pat[0].span, "key", ty, Mutability::Not), |
| _ => return, |
| }, |
| _ => return, |
| }; |
| let mutbl = match mutbl { |
| Mutability::Not => "", |
| Mutability::Mut => "_mut", |
| }; |
| let arg = match arg.kind { |
| ExprKind::AddrOf(BorrowKind::Ref, _, ref expr) => &**expr, |
| _ => arg, |
| }; |
| |
| if is_type_diagnostic_item(cx, ty, sym!(hashmap_type)) || match_type(cx, ty, &paths::BTREEMAP) { |
| span_lint_and_then( |
| cx, |
| FOR_KV_MAP, |
| expr.span, |
| &format!("you seem to want to iterate on a map's {}s", kind), |
| |diag| { |
| let map = sugg::Sugg::hir(cx, arg, "map"); |
| multispan_sugg( |
| diag, |
| "use the corresponding method", |
| vec![ |
| (pat_span, snippet(cx, new_pat_span, kind).into_owned()), |
| (arg_span, format!("{}.{}s{}()", map.maybe_par(), kind, mutbl)), |
| ], |
| ); |
| }, |
| ); |
| } |
| } |
| } |
| } |
| |
| struct MutatePairDelegate<'a, 'tcx> { |
| cx: &'a LateContext<'tcx>, |
| hir_id_low: Option<HirId>, |
| hir_id_high: Option<HirId>, |
| span_low: Option<Span>, |
| span_high: Option<Span>, |
| } |
| |
| impl<'tcx> Delegate<'tcx> for MutatePairDelegate<'_, 'tcx> { |
| fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: ConsumeMode) {} |
| |
| fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, bk: ty::BorrowKind) { |
| if let ty::BorrowKind::MutBorrow = bk { |
| if let PlaceBase::Local(id) = cmt.place.base { |
| if Some(id) == self.hir_id_low { |
| self.span_low = Some(self.cx.tcx.hir().span(cmt.hir_id)) |
| } |
| if Some(id) == self.hir_id_high { |
| self.span_high = Some(self.cx.tcx.hir().span(cmt.hir_id)) |
| } |
| } |
| } |
| } |
| |
| fn mutate(&mut self, cmt: &PlaceWithHirId<'tcx>) { |
| if let PlaceBase::Local(id) = cmt.place.base { |
| if Some(id) == self.hir_id_low { |
| self.span_low = Some(self.cx.tcx.hir().span(cmt.hir_id)) |
| } |
| if Some(id) == self.hir_id_high { |
| self.span_high = Some(self.cx.tcx.hir().span(cmt.hir_id)) |
| } |
| } |
| } |
| } |
| |
| impl MutatePairDelegate<'_, '_> { |
| fn mutation_span(&self) -> (Option<Span>, Option<Span>) { |
| (self.span_low, self.span_high) |
| } |
| } |
| |
| fn check_for_mut_range_bound(cx: &LateContext<'_>, arg: &Expr<'_>, body: &Expr<'_>) { |
| if let Some(higher::Range { |
| start: Some(start), |
| end: Some(end), |
| .. |
| }) = higher::range(cx, arg) |
| { |
| let mut_ids = vec![check_for_mutability(cx, start), check_for_mutability(cx, end)]; |
| if mut_ids[0].is_some() || mut_ids[1].is_some() { |
| let (span_low, span_high) = check_for_mutation(cx, body, &mut_ids); |
| mut_warn_with_span(cx, span_low); |
| mut_warn_with_span(cx, span_high); |
| } |
| } |
| } |
| |
| fn mut_warn_with_span(cx: &LateContext<'_>, span: Option<Span>) { |
| if let Some(sp) = span { |
| span_lint( |
| cx, |
| MUT_RANGE_BOUND, |
| sp, |
| "attempt to mutate range bound within loop; note that the range of the loop is unchanged", |
| ); |
| } |
| } |
| |
| fn check_for_mutability(cx: &LateContext<'_>, bound: &Expr<'_>) -> Option<HirId> { |
| if_chain! { |
| if let ExprKind::Path(ref qpath) = bound.kind; |
| if let QPath::Resolved(None, _) = *qpath; |
| then { |
| let res = qpath_res(cx, qpath, bound.hir_id); |
| if let Res::Local(hir_id) = res { |
| let node_str = cx.tcx.hir().get(hir_id); |
| if_chain! { |
| if let Node::Binding(pat) = node_str; |
| if let PatKind::Binding(bind_ann, ..) = pat.kind; |
| if let BindingAnnotation::Mutable = bind_ann; |
| then { |
| return Some(hir_id); |
| } |
| } |
| } |
| } |
| } |
| None |
| } |
| |
| fn check_for_mutation<'tcx>( |
| cx: &LateContext<'tcx>, |
| body: &Expr<'_>, |
| bound_ids: &[Option<HirId>], |
| ) -> (Option<Span>, Option<Span>) { |
| let mut delegate = MutatePairDelegate { |
| cx, |
| hir_id_low: bound_ids[0], |
| hir_id_high: bound_ids[1], |
| span_low: None, |
| span_high: None, |
| }; |
| let def_id = body.hir_id.owner.to_def_id(); |
| cx.tcx.infer_ctxt().enter(|infcx| { |
| ExprUseVisitor::new(&mut delegate, &infcx, def_id.expect_local(), cx.param_env, cx.tables()).walk_expr(body); |
| }); |
| delegate.mutation_span() |
| } |
| |
| /// Returns `true` if the pattern is a `PatWild` or an ident prefixed with `_`. |
| fn pat_is_wild<'tcx>(pat: &'tcx PatKind<'_>, body: &'tcx Expr<'_>) -> bool { |
| match *pat { |
| PatKind::Wild => true, |
| PatKind::Binding(.., ident, None) if ident.as_str().starts_with('_') => is_unused(&ident, body), |
| _ => false, |
| } |
| } |
| |
| struct LocalUsedVisitor<'a, 'tcx> { |
| cx: &'a LateContext<'tcx>, |
| local: HirId, |
| used: bool, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for LocalUsedVisitor<'a, 'tcx> { |
| type Map = Map<'tcx>; |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| if same_var(self.cx, expr, self.local) { |
| self.used = true; |
| } else { |
| walk_expr(self, expr); |
| } |
| } |
| |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| struct VarVisitor<'a, 'tcx> { |
| /// context reference |
| cx: &'a LateContext<'tcx>, |
| /// var name to look for as index |
| var: HirId, |
| /// indexed variables that are used mutably |
| indexed_mut: FxHashSet<Name>, |
| /// indirectly indexed variables (`v[(i + 4) % N]`), the extend is `None` for global |
| indexed_indirectly: FxHashMap<Name, Option<region::Scope>>, |
| /// subset of `indexed` of vars that are indexed directly: `v[i]` |
| /// this will not contain cases like `v[calc_index(i)]` or `v[(i + 4) % N]` |
| indexed_directly: FxHashMap<Name, (Option<region::Scope>, Ty<'tcx>)>, |
| /// Any names that are used outside an index operation. |
| /// Used to detect things like `&mut vec` used together with `vec[i]` |
| referenced: FxHashSet<Name>, |
| /// has the loop variable been used in expressions other than the index of |
| /// an index op? |
| nonindex: bool, |
| /// Whether we are inside the `$` in `&mut $` or `$ = foo` or `$.bar`, where bar |
| /// takes `&mut self` |
| prefer_mutable: bool, |
| } |
| |
| impl<'a, 'tcx> VarVisitor<'a, 'tcx> { |
| fn check(&mut self, idx: &'tcx Expr<'_>, seqexpr: &'tcx Expr<'_>, expr: &'tcx Expr<'_>) -> bool { |
| if_chain! { |
| // the indexed container is referenced by a name |
| if let ExprKind::Path(ref seqpath) = seqexpr.kind; |
| if let QPath::Resolved(None, ref seqvar) = *seqpath; |
| if seqvar.segments.len() == 1; |
| then { |
| let index_used_directly = same_var(self.cx, idx, self.var); |
| let indexed_indirectly = { |
| let mut used_visitor = LocalUsedVisitor { |
| cx: self.cx, |
| local: self.var, |
| used: false, |
| }; |
| walk_expr(&mut used_visitor, idx); |
| used_visitor.used |
| }; |
| |
| if indexed_indirectly || index_used_directly { |
| if self.prefer_mutable { |
| self.indexed_mut.insert(seqvar.segments[0].ident.name); |
| } |
| let res = qpath_res(self.cx, seqpath, seqexpr.hir_id); |
| match res { |
| Res::Local(hir_id) => { |
| let parent_id = self.cx.tcx.hir().get_parent_item(expr.hir_id); |
| let parent_def_id = self.cx.tcx.hir().local_def_id(parent_id); |
| let extent = self.cx.tcx.region_scope_tree(parent_def_id).var_scope(hir_id.local_id); |
| if indexed_indirectly { |
| self.indexed_indirectly.insert(seqvar.segments[0].ident.name, Some(extent)); |
| } |
| if index_used_directly { |
| self.indexed_directly.insert( |
| seqvar.segments[0].ident.name, |
| (Some(extent), self.cx.tables().node_type(seqexpr.hir_id)), |
| ); |
| } |
| return false; // no need to walk further *on the variable* |
| } |
| Res::Def(DefKind::Static | DefKind::Const, ..) => { |
| if indexed_indirectly { |
| self.indexed_indirectly.insert(seqvar.segments[0].ident.name, None); |
| } |
| if index_used_directly { |
| self.indexed_directly.insert( |
| seqvar.segments[0].ident.name, |
| (None, self.cx.tables().node_type(seqexpr.hir_id)), |
| ); |
| } |
| return false; // no need to walk further *on the variable* |
| } |
| _ => (), |
| } |
| } |
| } |
| } |
| true |
| } |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> { |
| type Map = Map<'tcx>; |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| if_chain! { |
| // a range index op |
| if let ExprKind::MethodCall(ref meth, _, ref args, _) = expr.kind; |
| if (meth.ident.name == sym!(index) && match_trait_method(self.cx, expr, &paths::INDEX)) |
| || (meth.ident.name == sym!(index_mut) && match_trait_method(self.cx, expr, &paths::INDEX_MUT)); |
| if !self.check(&args[1], &args[0], expr); |
| then { return } |
| } |
| |
| if_chain! { |
| // an index op |
| if let ExprKind::Index(ref seqexpr, ref idx) = expr.kind; |
| if !self.check(idx, seqexpr, expr); |
| then { return } |
| } |
| |
| if_chain! { |
| // directly using a variable |
| if let ExprKind::Path(ref qpath) = expr.kind; |
| if let QPath::Resolved(None, ref path) = *qpath; |
| if path.segments.len() == 1; |
| then { |
| if let Res::Local(local_id) = qpath_res(self.cx, qpath, expr.hir_id) { |
| if local_id == self.var { |
| self.nonindex = true; |
| } else { |
| // not the correct variable, but still a variable |
| self.referenced.insert(path.segments[0].ident.name); |
| } |
| } |
| } |
| } |
| |
| let old = self.prefer_mutable; |
| match expr.kind { |
| ExprKind::AssignOp(_, ref lhs, ref rhs) | ExprKind::Assign(ref lhs, ref rhs, _) => { |
| self.prefer_mutable = true; |
| self.visit_expr(lhs); |
| self.prefer_mutable = false; |
| self.visit_expr(rhs); |
| }, |
| ExprKind::AddrOf(BorrowKind::Ref, mutbl, ref expr) => { |
| if mutbl == Mutability::Mut { |
| self.prefer_mutable = true; |
| } |
| self.visit_expr(expr); |
| }, |
| ExprKind::Call(ref f, args) => { |
| self.visit_expr(f); |
| for expr in args { |
| let ty = self.cx.tables().expr_ty_adjusted(expr); |
| self.prefer_mutable = false; |
| if let ty::Ref(_, _, mutbl) = ty.kind { |
| if mutbl == Mutability::Mut { |
| self.prefer_mutable = true; |
| } |
| } |
| self.visit_expr(expr); |
| } |
| }, |
| ExprKind::MethodCall(_, _, args, _) => { |
| let def_id = self.cx.tables().type_dependent_def_id(expr.hir_id).unwrap(); |
| for (ty, expr) in self.cx.tcx.fn_sig(def_id).inputs().skip_binder().iter().zip(args) { |
| self.prefer_mutable = false; |
| if let ty::Ref(_, _, mutbl) = ty.kind { |
| if mutbl == Mutability::Mut { |
| self.prefer_mutable = true; |
| } |
| } |
| self.visit_expr(expr); |
| } |
| }, |
| ExprKind::Closure(_, _, body_id, ..) => { |
| let body = self.cx.tcx.hir().body(body_id); |
| self.visit_expr(&body.value); |
| }, |
| _ => walk_expr(self, expr), |
| } |
| self.prefer_mutable = old; |
| } |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| fn is_used_inside<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, container: &'tcx Expr<'_>) -> bool { |
| let def_id = match var_def_id(cx, expr) { |
| Some(id) => id, |
| None => return false, |
| }; |
| if let Some(used_mutably) = mutated_variables(container, cx) { |
| if used_mutably.contains(&def_id) { |
| return true; |
| } |
| } |
| false |
| } |
| |
| fn is_iterator_used_after_while_let<'tcx>(cx: &LateContext<'tcx>, iter_expr: &'tcx Expr<'_>) -> bool { |
| let def_id = match var_def_id(cx, iter_expr) { |
| Some(id) => id, |
| None => return false, |
| }; |
| let mut visitor = VarUsedAfterLoopVisitor { |
| cx, |
| def_id, |
| iter_expr_id: iter_expr.hir_id, |
| past_while_let: false, |
| var_used_after_while_let: false, |
| }; |
| if let Some(enclosing_block) = get_enclosing_block(cx, def_id) { |
| walk_block(&mut visitor, enclosing_block); |
| } |
| visitor.var_used_after_while_let |
| } |
| |
| struct VarUsedAfterLoopVisitor<'a, 'tcx> { |
| cx: &'a LateContext<'tcx>, |
| def_id: HirId, |
| iter_expr_id: HirId, |
| past_while_let: bool, |
| var_used_after_while_let: bool, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for VarUsedAfterLoopVisitor<'a, 'tcx> { |
| type Map = Map<'tcx>; |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| if self.past_while_let { |
| if Some(self.def_id) == var_def_id(self.cx, expr) { |
| self.var_used_after_while_let = true; |
| } |
| } else if self.iter_expr_id == expr.hir_id { |
| self.past_while_let = true; |
| } |
| walk_expr(self, expr); |
| } |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| /// Returns `true` if the type of expr is one that provides `IntoIterator` impls |
| /// for `&T` and `&mut T`, such as `Vec`. |
| #[rustfmt::skip] |
| fn is_ref_iterable_type(cx: &LateContext<'_>, e: &Expr<'_>) -> bool { |
| // no walk_ptrs_ty: calling iter() on a reference can make sense because it |
| // will allow further borrows afterwards |
| let ty = cx.tables().expr_ty(e); |
| is_iterable_array(ty, cx) || |
| is_type_diagnostic_item(cx, ty, sym!(vec_type)) || |
| match_type(cx, ty, &paths::LINKED_LIST) || |
| is_type_diagnostic_item(cx, ty, sym!(hashmap_type)) || |
| is_type_diagnostic_item(cx, ty, sym!(hashset_type)) || |
| is_type_diagnostic_item(cx, ty, sym!(vecdeque_type)) || |
| match_type(cx, ty, &paths::BINARY_HEAP) || |
| match_type(cx, ty, &paths::BTREEMAP) || |
| match_type(cx, ty, &paths::BTREESET) |
| } |
| |
| fn is_iterable_array<'tcx>(ty: Ty<'tcx>, cx: &LateContext<'tcx>) -> bool { |
| // IntoIterator is currently only implemented for array sizes <= 32 in rustc |
| match ty.kind { |
| ty::Array(_, n) => { |
| if let Some(val) = n.try_eval_usize(cx.tcx, cx.param_env) { |
| (0..=32).contains(&val) |
| } else { |
| false |
| } |
| }, |
| _ => false, |
| } |
| } |
| |
| /// If a block begins with a statement (possibly a `let` binding) and has an |
| /// expression, return it. |
| fn extract_expr_from_first_stmt<'tcx>(block: &Block<'tcx>) -> Option<&'tcx Expr<'tcx>> { |
| if block.stmts.is_empty() { |
| return None; |
| } |
| if let StmtKind::Local(ref local) = block.stmts[0].kind { |
| if let Some(expr) = local.init { |
| Some(expr) |
| } else { |
| None |
| } |
| } else { |
| None |
| } |
| } |
| |
| /// If a block begins with an expression (with or without semicolon), return it. |
| fn extract_first_expr<'tcx>(block: &Block<'tcx>) -> Option<&'tcx Expr<'tcx>> { |
| match block.expr { |
| Some(ref expr) if block.stmts.is_empty() => Some(expr), |
| None if !block.stmts.is_empty() => match block.stmts[0].kind { |
| StmtKind::Expr(ref expr) | StmtKind::Semi(ref expr) => Some(expr), |
| StmtKind::Local(..) | StmtKind::Item(..) => None, |
| }, |
| _ => None, |
| } |
| } |
| |
| /// Returns `true` if expr contains a single break expr without destination label |
| /// and |
| /// passed expression. The expression may be within a block. |
| fn is_simple_break_expr(expr: &Expr<'_>) -> bool { |
| match expr.kind { |
| ExprKind::Break(dest, ref passed_expr) if dest.label.is_none() && passed_expr.is_none() => true, |
| ExprKind::Block(ref b, _) => extract_first_expr(b).map_or(false, |subexpr| is_simple_break_expr(subexpr)), |
| _ => false, |
| } |
| } |
| |
| // To trigger the EXPLICIT_COUNTER_LOOP lint, a variable must be |
| // incremented exactly once in the loop body, and initialized to zero |
| // at the start of the loop. |
| #[derive(Debug, PartialEq)] |
| enum VarState { |
| Initial, // Not examined yet |
| IncrOnce, // Incremented exactly once, may be a loop counter |
| Declared, // Declared but not (yet) initialized to zero |
| Warn, |
| DontWarn, |
| } |
| |
| /// Scan a for loop for variables that are incremented exactly once. |
| struct IncrementVisitor<'a, 'tcx> { |
| cx: &'a LateContext<'tcx>, // context reference |
| states: FxHashMap<HirId, VarState>, // incremented variables |
| depth: u32, // depth of conditional expressions |
| done: bool, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for IncrementVisitor<'a, 'tcx> { |
| type Map = Map<'tcx>; |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| if self.done { |
| return; |
| } |
| |
| // If node is a variable |
| if let Some(def_id) = var_def_id(self.cx, expr) { |
| if let Some(parent) = get_parent_expr(self.cx, expr) { |
| let state = self.states.entry(def_id).or_insert(VarState::Initial); |
| |
| match parent.kind { |
| ExprKind::AssignOp(op, ref lhs, ref rhs) => { |
| if lhs.hir_id == expr.hir_id { |
| if op.node == BinOpKind::Add && is_integer_const(self.cx, rhs, 1) { |
| *state = match *state { |
| VarState::Initial if self.depth == 0 => VarState::IncrOnce, |
| _ => VarState::DontWarn, |
| }; |
| } else { |
| // Assigned some other value |
| *state = VarState::DontWarn; |
| } |
| } |
| }, |
| ExprKind::Assign(ref lhs, _, _) if lhs.hir_id == expr.hir_id => *state = VarState::DontWarn, |
| ExprKind::AddrOf(BorrowKind::Ref, mutability, _) if mutability == Mutability::Mut => { |
| *state = VarState::DontWarn |
| }, |
| _ => (), |
| } |
| } |
| } else if is_loop(expr) || is_conditional(expr) { |
| self.depth += 1; |
| walk_expr(self, expr); |
| self.depth -= 1; |
| return; |
| } else if let ExprKind::Continue(_) = expr.kind { |
| self.done = true; |
| return; |
| } |
| walk_expr(self, expr); |
| } |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| /// Checks whether a variable is initialized to zero at the start of a loop. |
| struct InitializeVisitor<'a, 'tcx> { |
| cx: &'a LateContext<'tcx>, // context reference |
| end_expr: &'tcx Expr<'tcx>, // the for loop. Stop scanning here. |
| var_id: HirId, |
| state: VarState, |
| name: Option<Name>, |
| depth: u32, // depth of conditional expressions |
| past_loop: bool, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for InitializeVisitor<'a, 'tcx> { |
| type Map = Map<'tcx>; |
| |
| fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) { |
| // Look for declarations of the variable |
| if let StmtKind::Local(ref local) = stmt.kind { |
| if local.pat.hir_id == self.var_id { |
| if let PatKind::Binding(.., ident, _) = local.pat.kind { |
| self.name = Some(ident.name); |
| |
| self.state = if let Some(ref init) = local.init { |
| if is_integer_const(&self.cx, init, 0) { |
| VarState::Warn |
| } else { |
| VarState::Declared |
| } |
| } else { |
| VarState::Declared |
| } |
| } |
| } |
| } |
| walk_stmt(self, stmt); |
| } |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| if self.state == VarState::DontWarn { |
| return; |
| } |
| if expr.hir_id == self.end_expr.hir_id { |
| self.past_loop = true; |
| return; |
| } |
| // No need to visit expressions before the variable is |
| // declared |
| if self.state == VarState::IncrOnce { |
| return; |
| } |
| |
| // If node is the desired variable, see how it's used |
| if var_def_id(self.cx, expr) == Some(self.var_id) { |
| if let Some(parent) = get_parent_expr(self.cx, expr) { |
| match parent.kind { |
| ExprKind::AssignOp(_, ref lhs, _) if lhs.hir_id == expr.hir_id => { |
| self.state = VarState::DontWarn; |
| }, |
| ExprKind::Assign(ref lhs, ref rhs, _) if lhs.hir_id == expr.hir_id => { |
| self.state = if is_integer_const(&self.cx, rhs, 0) && self.depth == 0 { |
| VarState::Warn |
| } else { |
| VarState::DontWarn |
| } |
| }, |
| ExprKind::AddrOf(BorrowKind::Ref, mutability, _) if mutability == Mutability::Mut => { |
| self.state = VarState::DontWarn |
| }, |
| _ => (), |
| } |
| } |
| |
| if self.past_loop { |
| self.state = VarState::DontWarn; |
| return; |
| } |
| } else if !self.past_loop && is_loop(expr) { |
| self.state = VarState::DontWarn; |
| return; |
| } else if is_conditional(expr) { |
| self.depth += 1; |
| walk_expr(self, expr); |
| self.depth -= 1; |
| return; |
| } |
| walk_expr(self, expr); |
| } |
| |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::OnlyBodies(self.cx.tcx.hir()) |
| } |
| } |
| |
| fn var_def_id(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<HirId> { |
| if let ExprKind::Path(ref qpath) = expr.kind { |
| let path_res = qpath_res(cx, qpath, expr.hir_id); |
| if let Res::Local(hir_id) = path_res { |
| return Some(hir_id); |
| } |
| } |
| None |
| } |
| |
| fn is_loop(expr: &Expr<'_>) -> bool { |
| match expr.kind { |
| ExprKind::Loop(..) => true, |
| _ => false, |
| } |
| } |
| |
| fn is_conditional(expr: &Expr<'_>) -> bool { |
| match expr.kind { |
| ExprKind::Match(..) => true, |
| _ => false, |
| } |
| } |
| |
| fn is_nested(cx: &LateContext<'_>, match_expr: &Expr<'_>, iter_expr: &Expr<'_>) -> bool { |
| if_chain! { |
| if let Some(loop_block) = get_enclosing_block(cx, match_expr.hir_id); |
| let parent_node = cx.tcx.hir().get_parent_node(loop_block.hir_id); |
| if let Some(Node::Expr(loop_expr)) = cx.tcx.hir().find(parent_node); |
| then { |
| return is_loop_nested(cx, loop_expr, iter_expr) |
| } |
| } |
| false |
| } |
| |
| fn is_loop_nested(cx: &LateContext<'_>, loop_expr: &Expr<'_>, iter_expr: &Expr<'_>) -> bool { |
| let mut id = loop_expr.hir_id; |
| let iter_name = if let Some(name) = path_name(iter_expr) { |
| name |
| } else { |
| return true; |
| }; |
| loop { |
| let parent = cx.tcx.hir().get_parent_node(id); |
| if parent == id { |
| return false; |
| } |
| match cx.tcx.hir().find(parent) { |
| Some(Node::Expr(expr)) => { |
| if let ExprKind::Loop(..) = expr.kind { |
| return true; |
| }; |
| }, |
| Some(Node::Block(block)) => { |
| let mut block_visitor = LoopNestVisitor { |
| hir_id: id, |
| iterator: iter_name, |
| nesting: Unknown, |
| }; |
| walk_block(&mut block_visitor, block); |
| if block_visitor.nesting == RuledOut { |
| return false; |
| } |
| }, |
| Some(Node::Stmt(_)) => (), |
| _ => { |
| return false; |
| }, |
| } |
| id = parent; |
| } |
| } |
| |
| #[derive(PartialEq, Eq)] |
| enum Nesting { |
| Unknown, // no nesting detected yet |
| RuledOut, // the iterator is initialized or assigned within scope |
| LookFurther, // no nesting detected, no further walk required |
| } |
| |
| use self::Nesting::{LookFurther, RuledOut, Unknown}; |
| |
| struct LoopNestVisitor { |
| hir_id: HirId, |
| iterator: Name, |
| nesting: Nesting, |
| } |
| |
| impl<'tcx> Visitor<'tcx> for LoopNestVisitor { |
| type Map = Map<'tcx>; |
| |
| fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) { |
| if stmt.hir_id == self.hir_id { |
| self.nesting = LookFurther; |
| } else if self.nesting == Unknown { |
| walk_stmt(self, stmt); |
| } |
| } |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| if self.nesting != Unknown { |
| return; |
| } |
| if expr.hir_id == self.hir_id { |
| self.nesting = LookFurther; |
| return; |
| } |
| match expr.kind { |
| ExprKind::Assign(ref path, _, _) | ExprKind::AssignOp(_, ref path, _) => { |
| if match_var(path, self.iterator) { |
| self.nesting = RuledOut; |
| } |
| }, |
| _ => walk_expr(self, expr), |
| } |
| } |
| |
| fn visit_pat(&mut self, pat: &'tcx Pat<'_>) { |
| if self.nesting != Unknown { |
| return; |
| } |
| if let PatKind::Binding(.., span_name, _) = pat.kind { |
| if self.iterator == span_name.name { |
| self.nesting = RuledOut; |
| return; |
| } |
| } |
| walk_pat(self, pat) |
| } |
| |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| fn path_name(e: &Expr<'_>) -> Option<Name> { |
| if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.kind { |
| let segments = &path.segments; |
| if segments.len() == 1 { |
| return Some(segments[0].ident.name); |
| } |
| }; |
| None |
| } |
| |
| fn check_infinite_loop<'tcx>(cx: &LateContext<'tcx>, cond: &'tcx Expr<'_>, expr: &'tcx Expr<'_>) { |
| if constant(cx, cx.tables(), cond).is_some() { |
| // A pure constant condition (e.g., `while false`) is not linted. |
| return; |
| } |
| |
| let mut var_visitor = VarCollectorVisitor { |
| cx, |
| ids: FxHashSet::default(), |
| def_ids: FxHashMap::default(), |
| skip: false, |
| }; |
| var_visitor.visit_expr(cond); |
| if var_visitor.skip { |
| return; |
| } |
| let used_in_condition = &var_visitor.ids; |
| let no_cond_variable_mutated = if let Some(used_mutably) = mutated_variables(expr, cx) { |
| used_in_condition.is_disjoint(&used_mutably) |
| } else { |
| return; |
| }; |
| let mutable_static_in_cond = var_visitor.def_ids.iter().any(|(_, v)| *v); |
| |
| let mut has_break_or_return_visitor = HasBreakOrReturnVisitor { |
| has_break_or_return: false, |
| }; |
| has_break_or_return_visitor.visit_expr(expr); |
| let has_break_or_return = has_break_or_return_visitor.has_break_or_return; |
| |
| if no_cond_variable_mutated && !mutable_static_in_cond { |
| span_lint_and_then( |
| cx, |
| WHILE_IMMUTABLE_CONDITION, |
| cond.span, |
| "variables in the condition are not mutated in the loop body", |
| |diag| { |
| diag.note("this may lead to an infinite or to a never running loop"); |
| |
| if has_break_or_return { |
| diag.note("this loop contains `return`s or `break`s"); |
| diag.help("rewrite it as `if cond { loop { } }`"); |
| } |
| }, |
| ); |
| } |
| } |
| |
| struct HasBreakOrReturnVisitor { |
| has_break_or_return: bool, |
| } |
| |
| impl<'tcx> Visitor<'tcx> for HasBreakOrReturnVisitor { |
| type Map = Map<'tcx>; |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| if self.has_break_or_return { |
| return; |
| } |
| |
| match expr.kind { |
| ExprKind::Ret(_) | ExprKind::Break(_, _) => { |
| self.has_break_or_return = true; |
| return; |
| }, |
| _ => {}, |
| } |
| |
| walk_expr(self, expr); |
| } |
| |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| /// Collects the set of variables in an expression |
| /// Stops analysis if a function call is found |
| /// Note: In some cases such as `self`, there are no mutable annotation, |
| /// All variables definition IDs are collected |
| struct VarCollectorVisitor<'a, 'tcx> { |
| cx: &'a LateContext<'tcx>, |
| ids: FxHashSet<HirId>, |
| def_ids: FxHashMap<def_id::DefId, bool>, |
| skip: bool, |
| } |
| |
| impl<'a, 'tcx> VarCollectorVisitor<'a, 'tcx> { |
| fn insert_def_id(&mut self, ex: &'tcx Expr<'_>) { |
| if_chain! { |
| if let ExprKind::Path(ref qpath) = ex.kind; |
| if let QPath::Resolved(None, _) = *qpath; |
| let res = qpath_res(self.cx, qpath, ex.hir_id); |
| then { |
| match res { |
| Res::Local(hir_id) => { |
| self.ids.insert(hir_id); |
| }, |
| Res::Def(DefKind::Static, def_id) => { |
| let mutable = self.cx.tcx.is_mutable_static(def_id); |
| self.def_ids.insert(def_id, mutable); |
| }, |
| _ => {}, |
| } |
| } |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for VarCollectorVisitor<'a, 'tcx> { |
| type Map = Map<'tcx>; |
| |
| fn visit_expr(&mut self, ex: &'tcx Expr<'_>) { |
| match ex.kind { |
| ExprKind::Path(_) => self.insert_def_id(ex), |
| // If there is any function/method call… we just stop analysis |
| ExprKind::Call(..) | ExprKind::MethodCall(..) => self.skip = true, |
| |
| _ => walk_expr(self, ex), |
| } |
| } |
| |
| fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| const NEEDLESS_COLLECT_MSG: &str = "avoid using `collect()` when not needed"; |
| |
| fn check_needless_collect<'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; |
| if chain_method.ident.name == sym!(collect) && match_trait_method(cx, &args[0], &paths::ITERATOR); |
| if let Some(ref generic_args) = chain_method.args; |
| if let Some(GenericArg::Type(ref ty)) = generic_args.args.get(0); |
| then { |
| let ty = cx.tables().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::BTREEMAP) || |
| is_type_diagnostic_item(cx, ty, sym!(hashmap_type)) { |
| if method.ident.name == sym!(len) { |
| let span = shorten_span(expr, sym!(collect)); |
| span_lint_and_sugg( |
| cx, |
| NEEDLESS_COLLECT, |
| span, |
| NEEDLESS_COLLECT_MSG, |
| "replace with", |
| "count()".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| } |
| if method.ident.name == sym!(is_empty) { |
| let span = shorten_span(expr, sym!(iter)); |
| span_lint_and_sugg( |
| cx, |
| NEEDLESS_COLLECT, |
| span, |
| NEEDLESS_COLLECT_MSG, |
| "replace with", |
| "get(0).is_none()".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| } |
| if method.ident.name == sym!(contains) { |
| let contains_arg = snippet(cx, args[1].span, "??"); |
| let span = shorten_span(expr, sym!(collect)); |
| span_lint_and_then( |
| cx, |
| NEEDLESS_COLLECT, |
| span, |
| NEEDLESS_COLLECT_MSG, |
| |diag| { |
| let (arg, pred) = if contains_arg.starts_with('&') { |
| ("x", &contains_arg[1..]) |
| } else { |
| ("&x", &*contains_arg) |
| }; |
| diag.span_suggestion( |
| span, |
| "replace with", |
| format!( |
| "any(|{}| x == {})", |
| arg, pred |
| ), |
| Applicability::MachineApplicable, |
| ); |
| } |
| ); |
| } |
| } |
| } |
| } |
| } |
| |
| 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 { |
| if path.ident.name == target_fn_name { |
| return expr.span.with_lo(span.lo()); |
| } |
| current_expr = &args[0]; |
| } |
| unreachable!() |
| } |
