| use reexport::*; |
| use rustc::hir::*; |
| use rustc::hir::def::Def; |
| use rustc::hir::def_id::DefId; |
| use rustc::hir::intravisit::{Visitor, walk_expr, walk_block, walk_decl, walk_pat, walk_stmt, NestedVisitorMap}; |
| use rustc::hir::map::Node::{NodeBlock, NodeExpr, NodeStmt}; |
| use rustc::lint::*; |
| use rustc::middle::const_val::ConstVal; |
| use rustc::middle::region::CodeExtent; |
| use rustc::ty::{self, Ty}; |
| use rustc::ty::subst::{Subst, Substs}; |
| use rustc_const_eval::ConstContext; |
| use std::collections::{HashMap, HashSet}; |
| use syntax::ast; |
| use utils::sugg; |
| |
| use utils::{snippet, span_lint, get_parent_expr, match_trait_method, match_type, multispan_sugg, in_external_macro, |
| is_refutable, span_help_and_lint, is_integer_literal, get_enclosing_block, span_lint_and_then, higher, |
| last_path_segment, span_lint_and_sugg}; |
| use utils::paths; |
| |
| /// **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 |
| /// for i in 0..vec.len() { |
| /// println!("{}", vec[i]); |
| /// } |
| /// ``` |
| declare_lint! { |
| pub NEEDLESS_RANGE_LOOP, |
| Warn, |
| "for-looping over a range of indices where an iterator over items would do" |
| } |
| |
| /// **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: |
| /// for x in y.iter() { .. } |
| /// ``` |
| declare_lint! { |
| pub EXPLICIT_ITER_LOOP, |
| Warn, |
| "for-looping over `_.iter()` or `_.iter_mut()` when `&_` or `&mut _` would do" |
| } |
| |
| /// **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 |
| /// // with `y` a `Vec` or slice: |
| /// for x in y.into_iter() { .. } |
| /// ``` |
| declare_lint! { |
| pub EXPLICIT_INTO_ITER_LOOP, |
| Warn, |
| "for-looping over `_.into_iter()` when `_` would do" |
| } |
| |
| /// **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:** |
| /// ```rust |
| /// for x in y.next() { .. } |
| /// ``` |
| declare_lint! { |
| pub ITER_NEXT_LOOP, |
| Warn, |
| "for-looping over `_.next()` which is probably not intended" |
| } |
| |
| /// **What it does:** Checks for `for` loops over `Option` values. |
| /// |
| /// **Why is this bad?** Readability. This is more clearly expressed as an `if |
| /// let`. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// for x in option { .. } |
| /// ``` |
| /// |
| /// This should be |
| /// ```rust |
| /// if let Some(x) = option { .. } |
| /// ``` |
| declare_lint! { |
| pub FOR_LOOP_OVER_OPTION, |
| Warn, |
| "for-looping over an `Option`, which is more clearly expressed as an `if let`" |
| } |
| |
| /// **What it does:** Checks for `for` loops over `Result` values. |
| /// |
| /// **Why is this bad?** Readability. This is more clearly expressed as an `if |
| /// let`. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// for x in result { .. } |
| /// ``` |
| /// |
| /// This should be |
| /// ```rust |
| /// if let Ok(x) = result { .. } |
| /// ``` |
| declare_lint! { |
| pub FOR_LOOP_OVER_RESULT, |
| Warn, |
| "for-looping over a `Result`, which is more clearly expressed as an `if let`" |
| } |
| |
| /// **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 |
| /// 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 |
| /// } |
| /// ``` |
| declare_lint! { |
| pub WHILE_LET_LOOP, |
| Warn, |
| "`loop { if let { ... } else break }`, which can be written as a `while let` loop" |
| } |
| |
| /// **What it does:** Checks for using `collect()` on an iterator without using |
| /// the result. |
| /// |
| /// **Why is this bad?** It is more idiomatic to use a `for` loop over the |
| /// iterator instead. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// vec.iter().map(|x| /* some operation returning () */).collect::<Vec<_>>(); |
| /// ``` |
| declare_lint! { |
| pub UNUSED_COLLECT, |
| Warn, |
| "`collect()`ing an iterator without using the result; this is usually better \ |
| written as a for loop" |
| } |
| |
| /// **What it does:** Checks for loops over ranges `x..y` where both `x` and `y` |
| /// are constant and `x` is greater or equal to `y`, unless the range is |
| /// reversed or has a negative `.step_by(_)`. |
| /// |
| /// **Why is it bad?** Such loops will either be skipped or loop until |
| /// wrap-around (in debug code, this may `panic!()`). Both options are probably |
| /// not intended. |
| /// |
| /// **Known problems:** The lint cannot catch loops over dynamically defined |
| /// ranges. Doing this would require simulating all possible inputs and code |
| /// paths through the program, which would be complex and error-prone. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// for x in 5..10-5 { .. } // oops, stray `-` |
| /// ``` |
| declare_lint! { |
| pub REVERSE_RANGE_LOOP, |
| Warn, |
| "iteration over an empty range, such as `10..0` or `5..5`" |
| } |
| |
| /// **What it does:** Checks `for` loops over slices with an explicit counter |
| /// and suggests the use of `.enumerate()`. |
| /// |
| /// **Why is it bad?** Not only is the version using `.enumerate()` more |
| /// readable, the compiler is able to remove bounds checks which can lead to |
| /// faster code in some instances. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// for i in 0..v.len() { foo(v[i]); |
| /// for i in 0..v.len() { bar(i, v[i]); } |
| /// ``` |
| declare_lint! { |
| pub EXPLICIT_COUNTER_LOOP, |
| Warn, |
| "for-looping with an explicit counter when `_.enumerate()` would do" |
| } |
| |
| /// **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:** |
| /// ```rust |
| /// loop {} |
| /// ``` |
| declare_lint! { |
| pub EMPTY_LOOP, |
| Warn, |
| "empty `loop {}`, which should block or sleep" |
| } |
| |
| /// **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:** |
| /// ```rust |
| /// while let Some(val) = iter() { .. } |
| /// ``` |
| declare_lint! { |
| pub WHILE_LET_ON_ITERATOR, |
| Warn, |
| "using a while-let loop instead of a for loop on an iterator" |
| } |
| |
| /// **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:** |
| /// ```rust |
| /// for (k, _) in &map { .. } |
| /// ``` |
| /// |
| /// could be replaced by |
| /// |
| /// ```rust |
| /// for k in map.keys() { .. } |
| /// ``` |
| declare_lint! { |
| pub FOR_KV_MAP, |
| Warn, |
| "looping on a map using `iter` when `keys` or `values` would do" |
| } |
| |
| /// **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; } |
| /// ``` |
| declare_lint! { |
| pub NEVER_LOOP, |
| Warn, |
| "any loop that will always `break` or `return`" |
| } |
| |
| #[derive(Copy, Clone)] |
| pub struct Pass; |
| |
| impl LintPass for Pass { |
| fn get_lints(&self) -> LintArray { |
| lint_array!( |
| NEEDLESS_RANGE_LOOP, |
| EXPLICIT_ITER_LOOP, |
| EXPLICIT_INTO_ITER_LOOP, |
| ITER_NEXT_LOOP, |
| FOR_LOOP_OVER_RESULT, |
| FOR_LOOP_OVER_OPTION, |
| WHILE_LET_LOOP, |
| UNUSED_COLLECT, |
| REVERSE_RANGE_LOOP, |
| EXPLICIT_COUNTER_LOOP, |
| EMPTY_LOOP, |
| WHILE_LET_ON_ITERATOR, |
| FOR_KV_MAP, |
| NEVER_LOOP |
| ) |
| } |
| } |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass { |
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { |
| if let Some((pat, arg, body)) = higher::for_loop(expr) { |
| check_for_loop(cx, pat, arg, body, expr); |
| } |
| |
| // check for never_loop |
| match expr.node { |
| ExprWhile(_, ref block, _) | |
| ExprLoop(ref block, _, _) => { |
| if never_loop(block, &expr.id) { |
| span_lint(cx, NEVER_LOOP, expr.span, "this loop never actually loops"); |
| } |
| }, |
| _ => (), |
| } |
| |
| // 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 ExprLoop(ref block, _, LoopSource::Loop) = expr.node { |
| // also check for empty `loop {}` statements |
| if block.stmts.is_empty() && block.expr.is_none() { |
| 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 ExprMatch(ref matchexpr, ref arms, ref source) = inner.node { |
| // ensure "if let" compatible match structure |
| match *source { |
| MatchSource::Normal | |
| MatchSource::IfLetDesugar { .. } => { |
| if arms.len() == 2 && arms[0].pats.len() == 1 && arms[0].guard.is_none() && |
| arms[1].pats.len() == 1 && arms[1].guard.is_none() && |
| is_break_expr(&arms[1].body) |
| { |
| if in_external_macro(cx, expr.span) { |
| return; |
| } |
| |
| // NOTE: we used to make 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). |
| 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(cx, arms[0].pats[0].span, ".."), |
| snippet(cx, matchexpr.span, "..") |
| ), |
| ); |
| } |
| }, |
| _ => (), |
| } |
| } |
| } |
| } |
| if let ExprMatch(ref match_expr, ref arms, MatchSource::WhileLetDesugar) = expr.node { |
| let pat = &arms[0].pats[0].node; |
| if let (&PatKind::TupleStruct(ref qpath, ref pat_args, _), |
| &ExprMethodCall(ref method_path, _, ref method_args)) = (pat, &match_expr.node) |
| { |
| let iter_expr = &method_args[0]; |
| let lhs_constructor = last_path_segment(qpath); |
| if method_path.name == "next" && match_trait_method(cx, match_expr, &paths::ITERATOR) && |
| lhs_constructor.name == "Some" && !is_refutable(cx, &pat_args[0]) && |
| !is_iterator_used_after_while_let(cx, iter_expr) && |
| !is_nested(cx, expr, &method_args[0]) |
| { |
| let iterator = snippet(cx, method_args[0].span, "_"); |
| let loop_var = snippet(cx, pat_args[0].span, "_"); |
| span_lint_and_sugg( |
| cx, |
| WHILE_LET_ON_ITERATOR, |
| expr.span, |
| "this loop could be written as a `for` loop", |
| "try", |
| format!("for {} in {} {{ .. }}", loop_var, iterator), |
| ); |
| } |
| } |
| } |
| } |
| |
| fn check_stmt(&mut self, cx: &LateContext<'a, 'tcx>, stmt: &'tcx Stmt) { |
| if let StmtSemi(ref expr, _) = stmt.node { |
| if let ExprMethodCall(ref method, _, ref args) = expr.node { |
| if args.len() == 1 && method.name == "collect" && match_trait_method(cx, expr, &paths::ITERATOR) { |
| span_lint( |
| cx, |
| UNUSED_COLLECT, |
| expr.span, |
| "you are collect()ing an iterator and throwing away the result. \ |
| Consider using an explicit for loop to exhaust the iterator", |
| ); |
| } |
| } |
| } |
| } |
| } |
| |
| fn never_loop(block: &Block, id: &NodeId) -> bool { |
| !contains_continue_block(block, id) && loop_exit_block(block) |
| } |
| |
| fn contains_continue_block(block: &Block, dest: &NodeId) -> bool { |
| block.stmts.iter().any(|e| contains_continue_stmt(e, dest)) || |
| block.expr.as_ref().map_or( |
| false, |
| |e| contains_continue_expr(e, dest), |
| ) |
| } |
| |
| fn contains_continue_stmt(stmt: &Stmt, dest: &NodeId) -> bool { |
| match stmt.node { |
| StmtSemi(ref e, _) | |
| StmtExpr(ref e, _) => contains_continue_expr(e, dest), |
| StmtDecl(ref d, _) => contains_continue_decl(d, dest), |
| } |
| } |
| |
| fn contains_continue_decl(decl: &Decl, dest: &NodeId) -> bool { |
| match decl.node { |
| DeclLocal(ref local) => { |
| local.init.as_ref().map_or( |
| false, |
| |e| contains_continue_expr(e, dest), |
| ) |
| }, |
| _ => false, |
| } |
| } |
| |
| fn contains_continue_expr(expr: &Expr, dest: &NodeId) -> bool { |
| match expr.node { |
| ExprRet(Some(ref e)) | |
| ExprBox(ref e) | |
| ExprUnary(_, ref e) | |
| ExprCast(ref e, _) | |
| ExprType(ref e, _) | |
| ExprField(ref e, _) | |
| ExprTupField(ref e, _) | |
| ExprAddrOf(_, ref e) | |
| ExprRepeat(ref e, _) => contains_continue_expr(e, dest), |
| ExprArray(ref es) | |
| ExprMethodCall(_, _, ref es) | |
| ExprTup(ref es) => es.iter().any(|e| contains_continue_expr(e, dest)), |
| ExprCall(ref e, ref es) => { |
| contains_continue_expr(e, dest) || es.iter().any(|e| contains_continue_expr(e, dest)) |
| }, |
| ExprBinary(_, ref e1, ref e2) | |
| ExprAssign(ref e1, ref e2) | |
| ExprAssignOp(_, ref e1, ref e2) | |
| ExprIndex(ref e1, ref e2) => [e1, e2].iter().any(|e| contains_continue_expr(e, dest)), |
| ExprIf(ref e, ref e2, ref e3) => { |
| [e, e2].iter().chain(e3.as_ref().iter()).any(|e| { |
| contains_continue_expr(e, dest) |
| }) |
| }, |
| ExprWhile(ref e, ref b, _) => contains_continue_expr(e, dest) || contains_continue_block(b, dest), |
| ExprMatch(ref e, ref arms, _) => { |
| contains_continue_expr(e, dest) || arms.iter().any(|a| contains_continue_expr(&a.body, dest)) |
| }, |
| ExprBlock(ref block) => contains_continue_block(block, dest), |
| ExprStruct(_, _, ref base) => { |
| base.as_ref().map_or( |
| false, |
| |e| contains_continue_expr(e, dest), |
| ) |
| }, |
| ExprAgain(d) => d.target_id.opt_id().map_or(false, |id| id == *dest), |
| _ => false, |
| } |
| } |
| |
| fn loop_exit_block(block: &Block) -> bool { |
| block.stmts.iter().any(|e| loop_exit_stmt(e)) || block.expr.as_ref().map_or(false, |e| loop_exit_expr(e)) |
| } |
| |
| fn loop_exit_stmt(stmt: &Stmt) -> bool { |
| match stmt.node { |
| StmtSemi(ref e, _) | |
| StmtExpr(ref e, _) => loop_exit_expr(e), |
| StmtDecl(ref d, _) => loop_exit_decl(d), |
| } |
| } |
| |
| fn loop_exit_decl(decl: &Decl) -> bool { |
| match decl.node { |
| DeclLocal(ref local) => local.init.as_ref().map_or(false, |e| loop_exit_expr(e)), |
| _ => false, |
| } |
| } |
| |
| fn loop_exit_expr(expr: &Expr) -> bool { |
| match expr.node { |
| ExprBox(ref e) | |
| ExprUnary(_, ref e) | |
| ExprCast(ref e, _) | |
| ExprType(ref e, _) | |
| ExprField(ref e, _) | |
| ExprTupField(ref e, _) | |
| ExprAddrOf(_, ref e) | |
| ExprRepeat(ref e, _) => loop_exit_expr(e), |
| ExprArray(ref es) | |
| ExprMethodCall(_, _, ref es) | |
| ExprTup(ref es) => es.iter().any(|e| loop_exit_expr(e)), |
| ExprCall(ref e, ref es) => loop_exit_expr(e) || es.iter().any(|e| loop_exit_expr(e)), |
| ExprBinary(_, ref e1, ref e2) | |
| ExprAssign(ref e1, ref e2) | |
| ExprAssignOp(_, ref e1, ref e2) | |
| ExprIndex(ref e1, ref e2) => [e1, e2].iter().any(|e| loop_exit_expr(e)), |
| ExprIf(ref e, ref e2, ref e3) => { |
| loop_exit_expr(e) || e3.as_ref().map_or(false, |e| loop_exit_expr(e)) && loop_exit_expr(e2) |
| }, |
| ExprWhile(ref e, ref b, _) => loop_exit_expr(e) || loop_exit_block(b), |
| ExprMatch(ref e, ref arms, _) => loop_exit_expr(e) || arms.iter().all(|a| loop_exit_expr(&a.body)), |
| ExprBlock(ref b) => loop_exit_block(b), |
| ExprBreak(_, _) | ExprAgain(_) | ExprRet(_) => true, |
| _ => false, |
| } |
| } |
| |
| fn check_for_loop<'a, 'tcx>( |
| cx: &LateContext<'a, '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_reverse_range(cx, arg, expr); |
| check_for_loop_arg(cx, pat, arg, expr); |
| check_for_loop_explicit_counter(cx, arg, body, expr); |
| check_for_loop_over_map_kv(cx, pat, arg, body, expr); |
| } |
| |
| /// Check for looping over a range and then indexing a sequence with it. |
| /// The iteratee must be a range literal. |
| fn check_for_loop_range<'a, 'tcx>( |
| cx: &LateContext<'a, '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(arg) |
| { |
| // the var must be a single name |
| if let PatKind::Binding(_, def_id, ref ident, _) = pat.node { |
| let mut visitor = VarVisitor { |
| cx: cx, |
| var: def_id, |
| indexed: HashMap::new(), |
| referenced: HashSet::new(), |
| nonindex: false, |
| }; |
| walk_expr(&mut visitor, body); |
| |
| // linting condition: we only indexed one variable |
| if visitor.indexed.len() == 1 { |
| let (indexed, indexed_extent) = visitor.indexed.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(expr.id); |
| let parent_def_id = cx.tcx.hir.local_def_id(parent_id); |
| let region_maps = cx.tcx.region_maps(parent_def_id); |
| let pat_extent = region_maps.var_scope(pat.id); |
| if region_maps.is_subscope_of(indexed_extent, pat_extent) { |
| 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_literal(start, 0); |
| |
| let skip = if starts_at_zero { |
| "".to_owned() |
| } else { |
| format!(".skip({})", snippet(cx, start.span, "..")) |
| }; |
| |
| let take = if let Some(end) = *end { |
| if is_len_call(end, &indexed) { |
| "".to_owned() |
| } else { |
| match limits { |
| ast::RangeLimits::Closed => { |
| let end = sugg::Sugg::hir(cx, end, "<count>"); |
| format!(".take({})", end + sugg::ONE) |
| }, |
| ast::RangeLimits::HalfOpen => format!(".take({})", snippet(cx, end.span, "..")), |
| } |
| } |
| } else { |
| "".to_owned() |
| }; |
| |
| if visitor.nonindex { |
| span_lint_and_then(cx, |
| NEEDLESS_RANGE_LOOP, |
| expr.span, |
| &format!("the loop variable `{}` is used to index `{}`", ident.node, indexed), |
| |db| { |
| multispan_sugg(db, |
| "consider using an iterator".to_string(), |
| vec![(pat.span, format!("({}, <item>)", ident.node)), |
| (arg.span, format!("{}.iter().enumerate(){}{}", indexed, take, skip))]); |
| }); |
| } else { |
| let repl = if starts_at_zero && take.is_empty() { |
| format!("&{}", indexed) |
| } else { |
| format!("{}.iter(){}{}", indexed, take, skip) |
| }; |
| |
| span_lint_and_then(cx, |
| NEEDLESS_RANGE_LOOP, |
| expr.span, |
| &format!("the loop variable `{}` is only used to index `{}`.", |
| ident.node, |
| indexed), |
| |db| { |
| multispan_sugg(db, |
| "consider using an iterator".to_string(), |
| vec![(pat.span, "<item>".to_string()), (arg.span, repl)]); |
| }); |
| } |
| } |
| } |
| } |
| } |
| |
| fn is_len_call(expr: &Expr, var: &Name) -> bool { |
| if_let_chain! {[ |
| let ExprMethodCall(ref method, _, ref len_args) = expr.node, |
| len_args.len() == 1, |
| method.name == "len", |
| let ExprPath(QPath::Resolved(_, ref path)) = len_args[0].node, |
| path.segments.len() == 1, |
| path.segments[0].name == *var |
| ], { |
| return true; |
| }} |
| |
| false |
| } |
| |
| fn check_for_loop_reverse_range(cx: &LateContext, arg: &Expr, expr: &Expr) { |
| // if this for loop is iterating over a two-sided range... |
| if let Some(higher::Range { |
| start: Some(start), |
| end: Some(end), |
| limits, |
| }) = higher::range(arg) |
| { |
| // ...and both sides are compile-time constant integers... |
| let parent_item = cx.tcx.hir.get_parent(arg.id); |
| let parent_def_id = cx.tcx.hir.local_def_id(parent_item); |
| let substs = Substs::identity_for_item(cx.tcx, parent_def_id); |
| let constcx = ConstContext::new(cx.tcx, cx.param_env.and(substs), cx.tables); |
| if let Ok(start_idx) = constcx.eval(start) { |
| if let Ok(end_idx) = constcx.eval(end) { |
| // ...and the start index is greater than the end index, |
| // this loop will never run. This is often confusing for developers |
| // who think that this will iterate from the larger value to the |
| // smaller value. |
| let (sup, eq) = match (start_idx, end_idx) { |
| (ConstVal::Integral(start_idx), ConstVal::Integral(end_idx)) => { |
| (start_idx > end_idx, start_idx == end_idx) |
| }, |
| _ => (false, false), |
| }; |
| |
| if sup { |
| let start_snippet = snippet(cx, start.span, "_"); |
| let end_snippet = snippet(cx, end.span, "_"); |
| let dots = if limits == ast::RangeLimits::Closed { |
| "..." |
| } else { |
| ".." |
| }; |
| |
| span_lint_and_then(cx, |
| REVERSE_RANGE_LOOP, |
| expr.span, |
| "this range is empty so this for loop will never run", |
| |db| { |
| db.span_suggestion(arg.span, |
| "consider using the following if you are attempting to iterate over this \ |
| range in reverse", |
| format!("({end}{dots}{start}).rev()", |
| end = end_snippet, |
| dots = dots, |
| start = start_snippet)); |
| }); |
| } else if eq && limits != ast::RangeLimits::Closed { |
| // if they are equal, it's also problematic - this loop |
| // will never run. |
| span_lint( |
| cx, |
| REVERSE_RANGE_LOOP, |
| expr.span, |
| "this range is empty so this for loop will never run", |
| ); |
| } |
| } |
| } |
| } |
| } |
| |
| fn lint_iter_method(cx: &LateContext, args: &[Expr], arg: &Expr, method_name: &str) { |
| let object = snippet(cx, args[0].span, "_"); |
| let muta = if method_name == "iter_mut" { |
| "mut " |
| } else { |
| "" |
| }; |
| span_lint_and_sugg( |
| cx, |
| EXPLICIT_ITER_LOOP, |
| arg.span, |
| "it is more idiomatic to loop over references to containers instead of using explicit \ |
| iteration methods", |
| "to write this more concisely, try", |
| format!("&{}{}", muta, object), |
| ) |
| } |
| |
| 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 ExprMethodCall(ref method, _, ref args) = arg.node { |
| // just the receiver, no arguments |
| if args.len() == 1 { |
| let method_name = &*method.name.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 def_id = cx.tables.type_dependent_defs[&arg.id].def_id(); |
| let substs = cx.tables.node_substs(arg.id); |
| let method_type = cx.tcx.type_of(def_id).subst(cx.tcx, substs); |
| |
| let fn_arg_tys = method_type.fn_sig(cx.tcx).inputs(); |
| assert_eq!(fn_arg_tys.skip_binder().len(), 1); |
| if fn_arg_tys.skip_binder()[0].is_region_ptr() { |
| lint_iter_method(cx, args, arg, method_name); |
| } else { |
| let object = snippet(cx, args[0].span, "_"); |
| span_lint_and_sugg( |
| cx, |
| EXPLICIT_INTO_ITER_LOOP, |
| arg.span, |
| "it is more idiomatic to loop over containers instead of using explicit \ |
| iteration methods`", |
| "to write this more concisely, try", |
| object.to_string(), |
| ); |
| } |
| } 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); |
| } |
| } |
| |
| /// Check for `for` loops over `Option`s and `Results` |
| fn check_arg_type(cx: &LateContext, pat: &Pat, arg: &Expr) { |
| let ty = cx.tables.expr_ty(arg); |
| if match_type(cx, ty, &paths::OPTION) { |
| span_help_and_lint( |
| cx, |
| FOR_LOOP_OVER_OPTION, |
| 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, "_") |
| ), |
| &format!( |
| "consider replacing `for {0} in {1}` with `if let Some({0}) = {1}`", |
| snippet(cx, pat.span, "_"), |
| snippet(cx, arg.span, "_") |
| ), |
| ); |
| } else if match_type(cx, ty, &paths::RESULT) { |
| span_help_and_lint( |
| cx, |
| FOR_LOOP_OVER_RESULT, |
| 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, "_") |
| ), |
| &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<'a, 'tcx>( |
| cx: &LateContext<'a, 'tcx>, |
| arg: &'tcx Expr, |
| body: &'tcx Expr, |
| expr: &'tcx Expr, |
| ) { |
| // Look for variables that are incremented once per loop iteration. |
| let mut visitor = IncrementVisitor { |
| cx: cx, |
| states: HashMap::new(), |
| 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. |
| let map = &cx.tcx.hir; |
| let parent_scope = map.get_enclosing_scope(expr.id).and_then(|id| { |
| map.get_enclosing_scope(id) |
| }); |
| if let Some(parent_id) = parent_scope { |
| if let NodeBlock(block) = map.get(parent_id) { |
| for (id, _) in visitor.states.iter().filter( |
| |&(_, v)| *v == VarState::IncrOnce, |
| ) |
| { |
| let mut visitor2 = InitializeVisitor { |
| cx: 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 { |
| span_lint( |
| cx, |
| EXPLICIT_COUNTER_LOOP, |
| expr.span, |
| &format!( |
| "the variable `{0}` is used as a loop counter. Consider using `for ({0}, \ |
| item) in {1}.enumerate()` or similar iterators", |
| name, |
| snippet(cx, arg.span, "_") |
| ), |
| ); |
| } |
| } |
| } |
| } |
| } |
| } |
| |
| /// Check for the `FOR_KV_MAP` lint. |
| fn check_for_loop_over_map_kv<'a, 'tcx>( |
| cx: &LateContext<'a, '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.node { |
| if pat.len() == 2 { |
| let arg_span = arg.span; |
| let (new_pat_span, kind, ty, mutbl) = match cx.tables.expr_ty(arg).sty { |
| ty::TyRef(_, ref tam) => { |
| match (&pat[0].node, &pat[1].node) { |
| (key, _) if pat_is_wild(key, body) => (pat[1].span, "value", tam.ty, tam.mutbl), |
| (_, value) if pat_is_wild(value, body) => (pat[0].span, "key", tam.ty, MutImmutable), |
| _ => return, |
| } |
| }, |
| _ => return, |
| }; |
| let mutbl = match mutbl { |
| MutImmutable => "", |
| MutMutable => "_mut", |
| }; |
| let arg = match arg.node { |
| ExprAddrOf(_, ref expr) => &**expr, |
| _ => arg, |
| }; |
| |
| if match_type(cx, ty, &paths::HASHMAP) || 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), |
| |db| { |
| let map = sugg::Sugg::hir(cx, arg, "map"); |
| multispan_sugg(db, |
| "use the corresponding method".into(), |
| vec![(pat_span, snippet(cx, new_pat_span, kind).into_owned()), |
| (arg_span, format!("{}.{}s{}()", map.maybe_par(), kind, mutbl))]); |
| }); |
| } |
| } |
| } |
| |
| } |
| |
| /// Return 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.node.as_str().starts_with('_') => { |
| let mut visitor = UsedVisitor { |
| var: ident.node, |
| used: false, |
| }; |
| walk_expr(&mut visitor, body); |
| !visitor.used |
| }, |
| _ => false, |
| } |
| } |
| |
| fn match_var(expr: &Expr, var: Name) -> bool { |
| if let ExprPath(QPath::Resolved(None, ref path)) = expr.node { |
| if path.segments.len() == 1 && path.segments[0].name == var { |
| return true; |
| } |
| } |
| false |
| } |
| |
| struct UsedVisitor { |
| var: ast::Name, // var to look for |
| used: bool, // has the var been used otherwise? |
| } |
| |
| impl<'tcx> Visitor<'tcx> for UsedVisitor { |
| fn visit_expr(&mut self, expr: &'tcx Expr) { |
| if match_var(expr, self.var) { |
| self.used = true; |
| return; |
| } |
| walk_expr(self, expr); |
| } |
| |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| struct VarVisitor<'a, 'tcx: 'a> { |
| /// context reference |
| cx: &'a LateContext<'a, 'tcx>, |
| /// var name to look for as index |
| var: DefId, |
| /// indexed variables, the extend is `None` for global |
| indexed: HashMap<Name, Option<CodeExtent>>, |
| /// Any names that are used outside an index operation. |
| /// Used to detect things like `&mut vec` used together with `vec[i]` |
| referenced: HashSet<Name>, |
| /// has the loop variable been used in expressions other than the index of |
| /// an index op? |
| nonindex: bool, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> { |
| fn visit_expr(&mut self, expr: &'tcx Expr) { |
| if_let_chain! {[ |
| // an index op |
| let ExprIndex(ref seqexpr, ref idx) = expr.node, |
| // directly indexing a variable |
| let ExprPath(ref qpath) = idx.node, |
| let QPath::Resolved(None, ref path) = *qpath, |
| path.segments.len() == 1, |
| // our variable! |
| self.cx.tables.qpath_def(qpath, expr.id).def_id() == self.var, |
| // the indexed container is referenced by a name |
| let ExprPath(ref seqpath) = seqexpr.node, |
| let QPath::Resolved(None, ref seqvar) = *seqpath, |
| seqvar.segments.len() == 1, |
| ], { |
| let def = self.cx.tables.qpath_def(seqpath, seqexpr.id); |
| match def { |
| Def::Local(..) | Def::Upvar(..) => { |
| let def_id = def.def_id(); |
| let node_id = self.cx.tcx.hir.as_local_node_id(def_id).expect("local/upvar are local nodes"); |
| |
| let parent_id = self.cx.tcx.hir.get_parent(expr.id); |
| let parent_def_id = self.cx.tcx.hir.local_def_id(parent_id); |
| let extent = self.cx.tcx.region_maps(parent_def_id).var_scope(node_id); |
| self.indexed.insert(seqvar.segments[0].name, Some(extent)); |
| return; // no need to walk further |
| } |
| Def::Static(..) | Def::Const(..) => { |
| self.indexed.insert(seqvar.segments[0].name, None); |
| return; // no need to walk further |
| } |
| _ => (), |
| } |
| }} |
| |
| if_let_chain! {[ |
| // directly indexing a variable |
| let ExprPath(ref qpath) = expr.node, |
| let QPath::Resolved(None, ref path) = *qpath, |
| path.segments.len() == 1, |
| ], { |
| if self.cx.tables.qpath_def(qpath, expr.id).def_id() == self.var { |
| // we are not indexing anything, record that |
| self.nonindex = true; |
| } else { |
| // not the correct variable, but still a variable |
| self.referenced.insert(path.segments[0].name); |
| } |
| }} |
| |
| walk_expr(self, expr); |
| } |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| fn is_iterator_used_after_while_let<'a, 'tcx: 'a>(cx: &LateContext<'a, '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: cx, |
| def_id: def_id, |
| iter_expr_id: iter_expr.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: 'a> { |
| cx: &'a LateContext<'a, 'tcx>, |
| def_id: NodeId, |
| iter_expr_id: NodeId, |
| past_while_let: bool, |
| var_used_after_while_let: bool, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for VarUsedAfterLoopVisitor<'a, '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.id { |
| self.past_while_let = true; |
| } |
| walk_expr(self, expr); |
| } |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| |
| /// Return true if the type of expr is one that provides `IntoIterator` impls |
| /// for `&T` and `&mut T`, such as `Vec`. |
| #[cfg_attr(rustfmt, 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) || |
| match_type(cx, ty, &paths::VEC) || |
| match_type(cx, ty, &paths::LINKED_LIST) || |
| match_type(cx, ty, &paths::HASHMAP) || |
| match_type(cx, ty, &paths::HASHSET) || |
| match_type(cx, ty, &paths::VEC_DEQUE) || |
| match_type(cx, ty, &paths::BINARY_HEAP) || |
| match_type(cx, ty, &paths::BTREEMAP) || |
| match_type(cx, ty, &paths::BTREESET) |
| } |
| |
| fn is_iterable_array(ty: Ty) -> bool { |
| // IntoIterator is currently only implemented for array sizes <= 32 in rustc |
| match ty.sty { |
| ty::TyArray(_, 0...32) => true, |
| _ => false, |
| } |
| } |
| |
| /// If a block begins with a statement (possibly a `let` binding) and has an |
| /// expression, return it. |
| fn extract_expr_from_first_stmt(block: &Block) -> Option<&Expr> { |
| if block.stmts.is_empty() { |
| return None; |
| } |
| if let StmtDecl(ref decl, _) = block.stmts[0].node { |
| if let DeclLocal(ref local) = decl.node { |
| if let Some(ref expr) = local.init { |
| Some(expr) |
| } else { |
| None |
| } |
| } else { |
| None |
| } |
| } else { |
| None |
| } |
| } |
| |
| /// If a block begins with an expression (with or without semicolon), return it. |
| fn extract_first_expr(block: &Block) -> Option<&Expr> { |
| match block.expr { |
| Some(ref expr) if block.stmts.is_empty() => Some(expr), |
| None if !block.stmts.is_empty() => { |
| match block.stmts[0].node { |
| StmtExpr(ref expr, _) | |
| StmtSemi(ref expr, _) => Some(expr), |
| StmtDecl(..) => None, |
| } |
| }, |
| _ => None, |
| } |
| } |
| |
| /// Return true if expr contains a single break expr (maybe within a block). |
| fn is_break_expr(expr: &Expr) -> bool { |
| match expr.node { |
| ExprBreak(dest, _) if dest.ident.is_none() => true, |
| ExprBlock(ref b) => { |
| match extract_first_expr(b) { |
| Some(subexpr) => is_break_expr(subexpr), |
| None => false, |
| } |
| }, |
| _ => 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(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: 'a> { |
| cx: &'a LateContext<'a, 'tcx>, // context reference |
| states: HashMap<NodeId, VarState>, // incremented variables |
| depth: u32, // depth of conditional expressions |
| done: bool, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for IncrementVisitor<'a, '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.node { |
| ExprAssignOp(op, ref lhs, ref rhs) => { |
| if lhs.id == expr.id { |
| if op.node == BiAdd && is_integer_literal(rhs, 1) { |
| *state = match *state { |
| VarState::Initial if self.depth == 0 => VarState::IncrOnce, |
| _ => VarState::DontWarn, |
| }; |
| } else { |
| // Assigned some other value |
| *state = VarState::DontWarn; |
| } |
| } |
| }, |
| ExprAssign(ref lhs, _) if lhs.id == expr.id => *state = VarState::DontWarn, |
| ExprAddrOf(mutability, _) if mutability == MutMutable => *state = VarState::DontWarn, |
| _ => (), |
| } |
| } |
| } else if is_loop(expr) { |
| self.states.clear(); |
| self.done = true; |
| 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<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| /// Check whether a variable is initialized to zero at the start of a loop. |
| struct InitializeVisitor<'a, 'tcx: 'a> { |
| cx: &'a LateContext<'a, 'tcx>, // context reference |
| end_expr: &'tcx Expr, // the for loop. Stop scanning here. |
| var_id: NodeId, |
| state: VarState, |
| name: Option<Name>, |
| depth: u32, // depth of conditional expressions |
| past_loop: bool, |
| } |
| |
| impl<'a, 'tcx> Visitor<'tcx> for InitializeVisitor<'a, 'tcx> { |
| fn visit_decl(&mut self, decl: &'tcx Decl) { |
| // Look for declarations of the variable |
| if let DeclLocal(ref local) = decl.node { |
| if local.pat.id == self.var_id { |
| if let PatKind::Binding(_, _, ref ident, _) = local.pat.node { |
| self.name = Some(ident.node); |
| |
| self.state = if let Some(ref init) = local.init { |
| if is_integer_literal(init, 0) { |
| VarState::Warn |
| } else { |
| VarState::Declared |
| } |
| } else { |
| VarState::Declared |
| } |
| } |
| } |
| } |
| walk_decl(self, decl); |
| } |
| |
| fn visit_expr(&mut self, expr: &'tcx Expr) { |
| if self.state == VarState::DontWarn { |
| return; |
| } |
| if expr == self.end_expr { |
| 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.node { |
| ExprAssignOp(_, ref lhs, _) if lhs.id == expr.id => { |
| self.state = VarState::DontWarn; |
| }, |
| ExprAssign(ref lhs, ref rhs) if lhs.id == expr.id => { |
| self.state = if is_integer_literal(rhs, 0) && self.depth == 0 { |
| VarState::Warn |
| } else { |
| VarState::DontWarn |
| } |
| }, |
| ExprAddrOf(mutability, _) if mutability == MutMutable => 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<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| fn var_def_id(cx: &LateContext, expr: &Expr) -> Option<NodeId> { |
| if let ExprPath(ref qpath) = expr.node { |
| let path_res = cx.tables.qpath_def(qpath, expr.id); |
| if let Def::Local(def_id) = path_res { |
| let node_id = cx.tcx.hir.as_local_node_id(def_id).expect( |
| "That DefId should be valid", |
| ); |
| return Some(node_id); |
| } |
| } |
| None |
| } |
| |
| fn is_loop(expr: &Expr) -> bool { |
| match expr.node { |
| ExprLoop(..) | ExprWhile(..) => true, |
| _ => false, |
| } |
| } |
| |
| fn is_conditional(expr: &Expr) -> bool { |
| match expr.node { |
| ExprIf(..) | ExprMatch(..) => true, |
| _ => false, |
| } |
| } |
| |
| fn is_nested(cx: &LateContext, match_expr: &Expr, iter_expr: &Expr) -> bool { |
| if_let_chain! {[ |
| let Some(loop_block) = get_enclosing_block(cx, match_expr.id), |
| let Some(map::Node::NodeExpr(loop_expr)) = cx.tcx.hir.find(cx.tcx.hir.get_parent_node(loop_block.id)), |
| ], { |
| 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.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(NodeExpr(expr)) => { |
| match expr.node { |
| ExprLoop(..) | ExprWhile(..) => { |
| return true; |
| }, |
| _ => (), |
| } |
| }, |
| Some(NodeBlock(block)) => { |
| let mut block_visitor = LoopNestVisitor { |
| id: id, |
| iterator: iter_name, |
| nesting: Unknown, |
| }; |
| walk_block(&mut block_visitor, block); |
| if block_visitor.nesting == RuledOut { |
| return false; |
| } |
| }, |
| Some(NodeStmt(_)) => (), |
| _ => { |
| 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::{Unknown, RuledOut, LookFurther}; |
| |
| struct LoopNestVisitor { |
| id: NodeId, |
| iterator: Name, |
| nesting: Nesting, |
| } |
| |
| impl<'tcx> Visitor<'tcx> for LoopNestVisitor { |
| fn visit_stmt(&mut self, stmt: &'tcx Stmt) { |
| if stmt.node.id() == self.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.id == self.id { |
| self.nesting = LookFurther; |
| return; |
| } |
| match expr.node { |
| ExprAssign(ref path, _) | |
| ExprAssignOp(_, 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.node { |
| if self.iterator == span_name.node { |
| self.nesting = RuledOut; |
| return; |
| } |
| } |
| walk_pat(self, pat) |
| } |
| |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| } |
| |
| fn path_name(e: &Expr) -> Option<Name> { |
| if let ExprPath(QPath::Resolved(_, ref path)) = e.node { |
| let segments = &path.segments; |
| if segments.len() == 1 { |
| return Some(segments[0].name); |
| } |
| }; |
| None |
| } |
