use itertools::Itertools;
use reexport::*;
use rustc::hir::*;
use rustc::hir::def::Def;
use rustc::hir::def_id;
use rustc::hir::intravisit::{walk_block, walk_decl, walk_expr, walk_pat, walk_stmt, NestedVisitorMap, Visitor};
use rustc::hir::map::Node::{NodeBlock, NodeExpr, NodeStmt};
use rustc::lint::*;
use rustc::middle::region;
use rustc::middle::expr_use_visitor::*;
use rustc::middle::mem_categorization::Categorization;
use rustc::middle::mem_categorization::cmt_;
use rustc::ty::{self, Ty};
use rustc::ty::subst::Subst;
use std::collections::{HashMap, HashSet};
use std::iter::{once, Iterator};
use syntax::ast;
use syntax::codemap::Span;
use utils::{sugg, sext};
use consts::{constant, Constant};
use utils::{get_enclosing_block, get_parent_expr, higher, in_external_macro, is_integer_literal, is_refutable,
last_path_segment, match_trait_method, match_type, match_var, multispan_sugg, snippet, snippet_opt,
span_help_and_lint, span_lint, span_lint_and_sugg, span_lint_and_then};
use utils::paths;
declare_clippy_lint! {
pub MANUAL_MEMCPY,
perf,
"manually copying items between slices"
}
declare_clippy_lint! {
pub NEEDLESS_RANGE_LOOP,
style,
"for-looping over a range of indices where an iterator over items would do"
}
declare_clippy_lint! {
pub EXPLICIT_ITER_LOOP,
style,
"for-looping over `_.iter()` or `_.iter_mut()` when `&_` or `&mut _` would do"
}
declare_clippy_lint! {
pub EXPLICIT_INTO_ITER_LOOP,
style,
"for-looping over `_.into_iter()` when `_` would do"
}
declare_clippy_lint! {
pub ITER_NEXT_LOOP,
correctness,
"for-looping over `_.next()` which is probably not intended"
}
declare_clippy_lint! {
pub FOR_LOOP_OVER_OPTION,
correctness,
"for-looping over an `Option`, which is more clearly expressed as an `if let`"
}
declare_clippy_lint! {
pub FOR_LOOP_OVER_RESULT,
correctness,
"for-looping over a `Result`, which is more clearly expressed as an `if let`"
}
declare_clippy_lint! {
pub WHILE_LET_LOOP,
complexity,
"`loop { if let { ... } else break }`, which can be written as a `while let` loop"
}
declare_clippy_lint! {
pub UNUSED_COLLECT,
perf,
"`collect()`ing an iterator without using the result; this is usually better \
written as a for loop"
}
declare_clippy_lint! {
pub REVERSE_RANGE_LOOP,
correctness,
"iteration over an empty range, such as `10..0` or `5..5`"
}
declare_clippy_lint! {
pub EXPLICIT_COUNTER_LOOP,
complexity,
"for-looping with an explicit counter when `_.enumerate()` would do"
}
declare_clippy_lint! {
pub EMPTY_LOOP,
style,
"empty `loop {}`, which should block or sleep"
}
declare_clippy_lint! {
pub WHILE_LET_ON_ITERATOR,
style,
"using a while-let loop instead of a for loop on an iterator"
}
declare_clippy_lint! {
pub FOR_KV_MAP,
style,
"looping on a map using `iter` when `keys` or `values` would do"
}
declare_clippy_lint! {
pub NEVER_LOOP,
correctness,
"any loop that will always `break` or `return`"
}
declare_clippy_lint! {
pub MUT_RANGE_BOUND,
complexity,
"for loop over a range where one of the bounds is a mutable variable"
}
declare_clippy_lint! {
pub WHILE_IMMUTABLE_CONDITION,
correctness,
"variables used within while expression are not mutated in the body"
}
#[derive(Copy, Clone)]
pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(
MANUAL_MEMCPY,
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,
MUT_RANGE_BOUND,
WHILE_IMMUTABLE_CONDITION,
)
}
}
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);
}
match expr.node {
ExprWhile(_, ref block, _) | ExprLoop(ref block, _, _) => {
match never_loop_block(block, &expr.id) {
NeverLoopResult::AlwaysBreak =>
span_lint(cx, NEVER_LOOP, expr.span, "this loop never actually loops"),
NeverLoopResult::MayContinueMainLoop | NeverLoopResult::Otherwise => (),
}
},
_ => (),
}
if let ExprLoop(ref block, _, LoopSource::Loop) = expr.node {
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.",
);
}
let inner_stmt_expr = extract_expr_from_first_stmt(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 {
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_simple_break_expr(&arms[1].body)
{
if in_external_macro(cx, expr.span) {
return;
}
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),
);
}
}
}
if let ExprWhile(ref cond, ref block, _) = expr.node {
check_infinite_loop(cx, cond, block, expr);
}
}
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",
);
}
}
}
}
}
enum NeverLoopResult {
AlwaysBreak,
MayContinueMainLoop,
Otherwise,
}
fn absorb_break(arg: &NeverLoopResult) -> NeverLoopResult {
match *arg {
NeverLoopResult::AlwaysBreak |
NeverLoopResult::Otherwise => NeverLoopResult::Otherwise,
NeverLoopResult::MayContinueMainLoop => NeverLoopResult::MayContinueMainLoop,
}
}
fn combine_seq(first: NeverLoopResult, second: NeverLoopResult) -> NeverLoopResult {
match first {
NeverLoopResult::AlwaysBreak | NeverLoopResult::MayContinueMainLoop => first,
NeverLoopResult::Otherwise => second,
}
}
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,
}
}
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: &NodeId) -> NeverLoopResult {
let stmts = block.stmts.iter().map(stmt_to_expr);
let expr = once(block.expr.as_ref().map(|p| &**p));
let mut iter = stmts.chain(expr).filter_map(|e| e);
never_loop_expr_seq(&mut iter, main_loop_id)
}
fn stmt_to_expr(stmt: &Stmt) -> Option<&Expr> {
match stmt.node {
StmtSemi(ref e, ..) | StmtExpr(ref e, ..) => Some(e),
StmtDecl(ref d, ..) => decl_to_expr(d),
}
}
fn decl_to_expr(decl: &Decl) -> Option<&Expr> {
match decl.node {
DeclLocal(ref local) => local.init.as_ref().map(|p| &**p),
_ => None,
}
}
fn never_loop_expr(expr: &Expr, main_loop_id: &NodeId) -> NeverLoopResult {
match expr.node {
ExprBox(ref e) |
ExprUnary(_, ref e) |
ExprCast(ref e, _) |
ExprType(ref e, _) |
ExprField(ref e, _) |
ExprAddrOf(_, ref e) |
ExprStruct(_, _, Some(ref e)) |
ExprRepeat(ref e, _) => never_loop_expr(e, main_loop_id),
ExprArray(ref es) | ExprMethodCall(_, _, ref es) | ExprTup(ref es) => {
never_loop_expr_all(&mut es.iter(), main_loop_id)
},
ExprCall(ref e, ref es) => never_loop_expr_all(&mut once(&**e).chain(es.iter()), main_loop_id),
ExprBinary(_, ref e1, ref e2) |
ExprAssign(ref e1, ref e2) |
ExprAssignOp(_, ref e1, ref e2) |
ExprIndex(ref e1, ref e2) => never_loop_expr_all(&mut [&**e1, &**e2].iter().cloned(), main_loop_id),
ExprIf(ref e, ref e2, ref e3) => {
let e1 = never_loop_expr(e, main_loop_id);
let e2 = never_loop_expr(e2, main_loop_id);
let e3 = e3.as_ref().map_or(NeverLoopResult::Otherwise, |e| never_loop_expr(e, main_loop_id));
combine_seq(e1, combine_branches(e2, e3))
},
ExprLoop(ref b, _, _) => {
absorb_break(&never_loop_block(b, main_loop_id))
},
ExprWhile(ref e, ref b, _) => {
let e = never_loop_expr(e, main_loop_id);
let result = never_loop_block(b, main_loop_id);
combine_seq(e, absorb_break(&result))
},
ExprMatch(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)
}
},
ExprBlock(ref b, _) => never_loop_block(b, main_loop_id),
ExprAgain(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
}
},
ExprBreak(_, _) => {
NeverLoopResult::AlwaysBreak
},
ExprRet(ref e) => {
if let Some(ref e) = *e {
combine_seq(never_loop_expr(e, main_loop_id), NeverLoopResult::AlwaysBreak)
} else {
NeverLoopResult::AlwaysBreak
}
},
ExprStruct(_, _, None) |
ExprYield(_) |
ExprClosure(_, _, _, _, _) |
ExprInlineAsm(_, _, _) |
ExprPath(_) |
ExprLit(_) => NeverLoopResult::Otherwise,
}
}
fn never_loop_expr_seq<'a, T: Iterator<Item=&'a Expr>>(es: &mut T, main_loop_id: &NodeId) -> 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>>(es: &mut T, main_loop_id: &NodeId) -> 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>>(e: &mut T, main_loop_id: &NodeId) -> NeverLoopResult {
e.map(|e| never_loop_expr(e, main_loop_id))
.fold(NeverLoopResult::AlwaysBreak, combine_branches)
}
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_mut_range_bound(cx, arg, body);
detect_manual_memcpy(cx, pat, arg, body, expr);
}
fn same_var<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &Expr, var: ast::NodeId) -> bool {
if_chain! {
if let ExprPath(ref qpath) = expr.node;
if let QPath::Resolved(None, ref path) = *qpath;
if path.segments.len() == 1;
if let Def::Local(local_id) = cx.tables.qpath_def(qpath, expr.hir_id);
if local_id == var;
then {
return true;
}
}
false
}
struct Offset {
value: String,
negate: bool,
}
impl Offset {
fn negative(s: String) -> Self {
Self {
value: s,
negate: true,
}
}
fn positive(s: String) -> Self {
Self {
value: s,
negate: false,
}
}
}
struct FixedOffsetVar {
var_name: String,
offset: Offset,
}
fn is_slice_like<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ty: Ty) -> bool {
let is_slice = match ty.sty {
ty::TyRef(_, subty, _) => is_slice_like(cx, subty),
ty::TySlice(..) | ty::TyArray(..) => true,
_ => false,
};
is_slice || match_type(cx, ty, &paths::VEC) || match_type(cx, ty, &paths::VEC_DEQUE)
}
fn get_fixed_offset_var<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &Expr, var: ast::NodeId) -> Option<FixedOffsetVar> {
fn extract_offset<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, e: &Expr, var: ast::NodeId) -> Option<String> {
match e.node {
ExprLit(ref l) => match l.node {
ast::LitKind::Int(x, _ty) => Some(x.to_string()),
_ => None,
},
ExprPath(..) if !same_var(cx, e, var) => Some(snippet_opt(cx, e.span).unwrap_or_else(|| "??".into())),
_ => None,
}
}
if let ExprIndex(ref seqexpr, ref idx) = expr.node {
let ty = cx.tables.expr_ty(seqexpr);
if !is_slice_like(cx, ty) {
return None;
}
let offset = match idx.node {
ExprBinary(op, ref lhs, ref rhs) => match op.node {
BinOp_::BiAdd => {
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)
},
BinOp_::BiSub if same_var(cx, lhs, var) => extract_offset(cx, rhs, var).map(Offset::negative),
_ => None,
},
ExprPath(..) => if same_var(cx, idx, var) {
Some(Offset::positive("0".into()))
} else {
None
},
_ => None,
};
offset.map(|o| {
FixedOffsetVar {
var_name: snippet_opt(cx, seqexpr.span).unwrap_or_else(|| "???".into()),
offset: o,
}
})
} else {
None
}
}
fn fetch_cloned_fixed_offset_var<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
expr: &Expr,
var: ast::NodeId,
) -> Option<FixedOffsetVar> {
if_chain! {
if let ExprMethodCall(ref method, _, ref args) = expr.node;
if method.name == "clone";
if args.len() == 1;
if let Some(arg) = args.get(0);
then {
return get_fixed_offset_var(cx, arg, var);
}
}
get_fixed_offset_var(cx, expr, var)
}
fn get_indexed_assignments<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
body: &Expr,
var: ast::NodeId,
) -> Vec<(FixedOffsetVar, FixedOffsetVar)> {
fn get_assignment<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
e: &Expr,
var: ast::NodeId,
) -> Option<(FixedOffsetVar, FixedOffsetVar)> {
if let Expr_::ExprAssign(ref lhs, ref rhs) = e.node {
match (get_fixed_offset_var(cx, lhs, var), fetch_cloned_fixed_offset_var(cx, rhs, var)) {
(Some(offset_left), Some(offset_right)) => {
if offset_left.var_name == offset_right.var_name {
None
} else {
Some((offset_left, offset_right))
}
},
_ => None,
}
} else {
None
}
}
if let Expr_::ExprBlock(ref b, _) = body.node {
let Block {
ref stmts,
ref expr,
..
} = **b;
stmts
.iter()
.map(|stmt| match stmt.node {
Stmt_::StmtDecl(..) => None,
Stmt_::StmtExpr(ref e, _node_id) | Stmt_::StmtSemi(ref e, _node_id) => Some(get_assignment(cx, e, var)),
})
.chain(
expr.as_ref()
.into_iter()
.map(|e| Some(get_assignment(cx, &*e, var))),
)
.filter_map(|op| op)
.collect::<Option<Vec<_>>>()
.unwrap_or_else(|| vec![])
} else {
get_assignment(cx, body, var).into_iter().collect()
}
}
fn detect_manual_memcpy<'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(cx, arg)
{
if let PatKind::Binding(_, canonical_id, _, _) = pat.node {
let print_sum = |arg1: &Offset, arg2: &Offset| -> String {
match (&arg1.value[..], arg1.negate, &arg2.value[..], arg2.negate) {
("0", _, "0", _) => "".into(),
("0", _, x, false) | (x, false, "0", false) => x.into(),
("0", _, x, true) | (x, false, "0", true) => format!("-{}", x),
(x, false, y, false) => format!("({} + {})", x, y),
(x, false, y, true) => format!("({} - {})", x, y),
(x, true, y, false) => format!("({} - {})", y, x),
(x, true, y, true) => format!("-({} + {})", x, y),
}
};
let print_limit = |end: &Option<&Expr>, offset: Offset, var_name: &str| if let Some(end) = *end {
if_chain! {
if let ExprMethodCall(ref method, _, ref len_args) = end.node;
if method.name == "len";
if len_args.len() == 1;
if let Some(arg) = len_args.get(0);
if snippet(cx, arg.span, "??") == var_name;
then {
return if offset.negate {
format!("({} - {})", snippet(cx, end.span, "<src>.len()"), offset.value)
} else {
"".to_owned()
};
}
}
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(&Offset::positive(end_str), &offset)
} else {
"..".into()
};
let manual_copies = get_indexed_assignments(cx, body, canonical_id);
let big_sugg = manual_copies
.into_iter()
.map(|(dst_var, src_var)| {
let start_str = Offset::positive(snippet_opt(cx, start.span).unwrap_or_else(|| "".into()));
let dst_offset = print_sum(&start_str, &dst_var.offset);
let dst_limit = print_limit(end, dst_var.offset, &dst_var.var_name);
let src_offset = print_sum(&start_str, &src_var.offset);
let src_limit = print_limit(end, src_var.offset, &src_var.var_name);
let dst = if dst_offset == "" && dst_limit == "" {
dst_var.var_name
} else {
format!("{}[{}..{}]", dst_var.var_name, dst_offset, dst_limit)
};
format!("{}.clone_from_slice(&{}[{}..{}])", dst, src_var.var_name, src_offset, src_limit)
})
.join("\n ");
if !big_sugg.is_empty() {
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,
);
}
}
}
}
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(cx, arg)
{
if let PatKind::Binding(_, canonical_id, ref ident, _) = pat.node {
let mut visitor = VarVisitor {
cx,
var: canonical_id,
indexed_mut: HashSet::new(),
indexed_indirectly: HashMap::new(),
indexed_directly: HashMap::new(),
referenced: HashSet::new(),
nonindex: false,
prefer_mutable: false,
};
walk_expr(&mut visitor, body);
if visitor.indexed_indirectly.is_empty() && visitor.indexed_directly.len() == 1 {
let (indexed, indexed_extent) = visitor
.indexed_directly
.into_iter()
.next()
.expect("already checked that we have exactly 1 element");
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_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;
}
}
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()
};
let (ref_mut, method) = if visitor.indexed_mut.contains(&indexed) {
("mut ", "iter_mut")
} else {
("", "iter")
};
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!("{}.{}().enumerate(){}{}", indexed, method, take, skip)),
],
);
},
);
} else {
let repl = if starts_at_zero && take.is_empty() {
format!("&{}{}", ref_mut, indexed)
} else {
format!("{}.{}(){}{}", indexed, method, 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_chain! {
if let ExprMethodCall(ref method, _, ref len_args) = expr.node;
if len_args.len() == 1;
if method.name == "len";
if let ExprPath(QPath::Resolved(_, ref path)) = len_args[0].node;
if path.segments.len() == 1;
if path.segments[0].name == *var;
then {
return true;
}
}
false
}
fn check_for_loop_reverse_range<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, arg: &'tcx Expr, expr: &'tcx Expr) {
if let Some(higher::Range {
start: Some(start),
end: Some(end),
limits,
}) = higher::range(cx, arg)
{
if let Some((start_idx, _)) = constant(cx, cx.tables, start) {
if let Some((end_idx, _)) = constant(cx, cx.tables, end) {
let ty = cx.tables.expr_ty(start);
let (sup, eq) = match (start_idx, end_idx) {
(
Constant::Int(start_idx),
Constant::Int(end_idx),
) => (match ty.sty {
ty::TyInt(ity) => sext(cx.tcx, start_idx, ity) > sext(cx.tcx, end_idx, ity),
ty::TyUint(_) => start_idx > end_idx,
_ => false,
}, 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 {
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; if let ExprMethodCall(ref method, _, ref args) = arg.node {
if args.len() == 1 {
let method_name = &*method.name.as_str();
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.hir_id].def_id();
let substs = cx.tables.node_substs(arg.hir_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() {
match cx.tables.expr_ty(&args[0]).sty {
ty::TypeVariants::TyArray(_, size) if size.assert_usize(cx.tcx).expect("array size") > 32 => (),
_ => 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);
}
}
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,
) {
let mut visitor = IncrementVisitor {
cx,
states: HashMap::new(),
depth: 0,
done: false,
};
walk_expr(&mut visitor, body);
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,
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, "_")
),
);
}
}
}
}
}
}
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(_, ty, mutbl) => match (&pat[0].node, &pat[1].node) {
(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, 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)),
],
);
},
);
}
}
}
}
struct MutatePairDelegate {
node_id_low: Option<NodeId>,
node_id_high: Option<NodeId>,
span_low: Option<Span>,
span_high: Option<Span>,
}
impl<'tcx> Delegate<'tcx> for MutatePairDelegate {
fn consume(&mut self, _: NodeId, _: Span, _: &cmt_<'tcx>, _: ConsumeMode) {}
fn matched_pat(&mut self, _: &Pat, _: &cmt_<'tcx>, _: MatchMode) {}
fn consume_pat(&mut self, _: &Pat, _: &cmt_<'tcx>, _: ConsumeMode) {}
fn borrow(&mut self, _: NodeId, sp: Span, cmt: &cmt_<'tcx>, _: ty::Region, bk: ty::BorrowKind, _: LoanCause) {
if let ty::BorrowKind::MutBorrow = bk {
if let Categorization::Local(id) = cmt.cat {
if Some(id) == self.node_id_low {
self.span_low = Some(sp)
}
if Some(id) == self.node_id_high {
self.span_high = Some(sp)
}
}
}
}
fn mutate(&mut self, _: NodeId, sp: Span, cmt: &cmt_<'tcx>, _: MutateMode) {
if let Categorization::Local(id) = cmt.cat {
if Some(id) == self.node_id_low {
self.span_low = Some(sp)
}
if Some(id) == self.node_id_high {
self.span_high = Some(sp)
}
}
}
fn decl_without_init(&mut self, _: NodeId, _: Span) {}
}
impl<'tcx> 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<NodeId> {
if_chain! {
if let ExprPath(ref qpath) = bound.node;
if let QPath::Resolved(None, _) = *qpath;
then {
let def = cx.tables.qpath_def(qpath, bound.hir_id);
if let Def::Local(node_id) = def {
let node_str = cx.tcx.hir.get(node_id);
if_chain! {
if let map::Node::NodeBinding(pat) = node_str;
if let PatKind::Binding(bind_ann, _, _, _) = pat.node;
if let BindingAnnotation::Mutable = bind_ann;
then {
return Some(node_id);
}
}
}
}
}
None
}
fn check_for_mutation(cx: &LateContext, body: &Expr, bound_ids: &[Option<NodeId>]) -> (Option<Span>, Option<Span>) {
let mut delegate = MutatePairDelegate {
node_id_low: bound_ids[0],
node_id_high: bound_ids[1],
span_low: None,
span_high: None,
};
let def_id = def_id::DefId::local(body.hir_id.owner);
let region_scope_tree = &cx.tcx.region_scope_tree(def_id);
ExprUseVisitor::new(&mut delegate, cx.tcx, cx.param_env, region_scope_tree, cx.tables, None).walk_expr(body);
delegate.mutation_span()
}
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,
}
}
struct UsedVisitor {
var: ast::Name, used: bool, }
impl<'tcx> Visitor<'tcx> for UsedVisitor {
fn visit_expr(&mut self, expr: &'tcx Expr) {
if match_var(expr, self.var) {
self.used = true;
} else {
walk_expr(self, expr);
}
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}
struct LocalUsedVisitor<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>,
local: ast::NodeId,
used: bool,
}
impl<'a, 'tcx: 'a> Visitor<'tcx> for LocalUsedVisitor<'a, '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<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}
struct VarVisitor<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>,
var: ast::NodeId,
indexed_mut: HashSet<Name>,
indexed_indirectly: HashMap<Name, Option<region::Scope>>,
indexed_directly: HashMap<Name, Option<region::Scope>>,
referenced: HashSet<Name>,
nonindex: bool,
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! {
if let ExprPath(ref seqpath) = seqexpr.node;
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].name);
}
let def = self.cx.tables.qpath_def(seqpath, seqexpr.hir_id);
match def {
Def::Local(node_id) | Def::Upvar(node_id, ..) => {
let hir_id = self.cx.tcx.hir.node_to_hir_id(node_id);
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_scope_tree(parent_def_id).var_scope(hir_id.local_id);
if indexed_indirectly {
self.indexed_indirectly.insert(seqvar.segments[0].name, Some(extent));
}
if index_used_directly {
self.indexed_directly.insert(seqvar.segments[0].name, Some(extent));
}
return false; }
Def::Static(..) | Def::Const(..) => {
if indexed_indirectly {
self.indexed_indirectly.insert(seqvar.segments[0].name, None);
}
if index_used_directly {
self.indexed_directly.insert(seqvar.segments[0].name, None);
}
return false; }
_ => (),
}
}
}
}
true
}
}
impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr) {
if_chain! {
if let ExprMethodCall(ref meth, _, ref args) = expr.node;
if (meth.name == "index" && match_trait_method(self.cx, expr, &paths::INDEX))
|| (meth.name == "index_mut" && match_trait_method(self.cx, expr, &paths::INDEX_MUT));
if !self.check(&args[1], &args[0], expr);
then { return }
}
if_chain! {
if let ExprIndex(ref seqexpr, ref idx) = expr.node;
if !self.check(idx, seqexpr, expr);
then { return }
}
if_chain! {
if let ExprPath(ref qpath) = expr.node;
if let QPath::Resolved(None, ref path) = *qpath;
if path.segments.len() == 1;
if let Def::Local(local_id) = self.cx.tables.qpath_def(qpath, expr.hir_id);
then {
if local_id == self.var {
self.nonindex = true;
} else {
self.referenced.insert(path.segments[0].name);
}
}
}
let old = self.prefer_mutable;
match expr.node {
ExprAssignOp(_, ref lhs, ref rhs) |
ExprAssign(ref lhs, ref rhs) => {
self.prefer_mutable = true;
self.visit_expr(lhs);
self.prefer_mutable = false;
self.visit_expr(rhs);
},
ExprAddrOf(mutbl, ref expr) => {
if mutbl == MutMutable {
self.prefer_mutable = true;
}
self.visit_expr(expr);
},
ExprCall(ref f, ref 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::TyRef(_, _, mutbl) = ty.sty {
if mutbl == MutMutable {
self.prefer_mutable = true;
}
}
self.visit_expr(expr);
}
},
ExprMethodCall(_, _, ref args) => {
let def_id = self.cx.tables.type_dependent_defs()[expr.hir_id].def_id();
for (ty, expr) in self.cx.tcx.fn_sig(def_id).inputs().skip_binder().iter().zip(args) {
self.prefer_mutable = false;
if let ty::TyRef(_, _, mutbl) = ty.sty {
if mutbl == MutMutable {
self.prefer_mutable = true;
}
}
self.visit_expr(expr);
}
},
_ => walk_expr(self, expr),
}
self.prefer_mutable = old;
}
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,
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
}
}
#[cfg_attr(rustfmt, rustfmt_skip)]
fn is_ref_iterable_type(cx: &LateContext, e: &Expr) -> bool {
let ty = cx.tables.expr_ty(e);
is_iterable_array(ty, cx) ||
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, cx: &LateContext) -> bool {
match ty.sty {
ty::TyArray(_, n) => (0..=32).contains(&n.assert_usize(cx.tcx).expect("array length")),
_ => false,
}
}
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
}
}
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,
}
}
fn is_simple_break_expr(expr: &Expr) -> bool {
match expr.node {
ExprBreak(dest, ref passed_expr) if dest.label.is_none() && passed_expr.is_none() => true,
ExprBlock(ref b, _) => match extract_first_expr(b) {
Some(subexpr) => is_simple_break_expr(subexpr),
None => false,
},
_ => false,
}
}
#[derive(PartialEq)]
enum VarState {
Initial, IncrOnce, Declared, Warn,
DontWarn,
}
struct IncrementVisitor<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>, states: HashMap<NodeId, VarState>, depth: u32, done: bool,
}
impl<'a, 'tcx> Visitor<'tcx> for IncrementVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx Expr) {
if self.done {
return;
}
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 {
*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
}
}
struct InitializeVisitor<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>, end_expr: &'tcx Expr, var_id: NodeId,
state: VarState,
name: Option<Name>,
depth: u32, past_loop: bool,
}
impl<'a, 'tcx> Visitor<'tcx> for InitializeVisitor<'a, 'tcx> {
fn visit_decl(&mut self, decl: &'tcx Decl) {
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;
}
if self.state == VarState::IncrOnce {
return;
}
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.hir_id);
if let Def::Local(node_id) = path_res {
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_chain! {
if let Some(loop_block) = get_enclosing_block(cx, match_expr.id);
if let Some(map::Node::NodeExpr(loop_expr)) = cx.tcx.hir.find(cx.tcx.hir.get_parent_node(loop_block.id));
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.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,
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, RuledOut, LookFurther, }
use self::Nesting::{LookFurther, RuledOut, Unknown};
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
}
fn check_infinite_loop<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, cond: &'tcx Expr, block: &'tcx Block, expr: &'tcx Expr) {
if constant(cx, cx.tables, cond).is_some() {
return;
}
let mut mut_var_visitor = VarCollectorVisitor {
cx,
ids: HashMap::new(),
skip: false,
};
walk_expr(&mut mut_var_visitor, expr);
if mut_var_visitor.skip {
return;
}
let mut delegate = MutVarsDelegate {
used_mutably: mut_var_visitor.ids,
skip: false,
};
let def_id = def_id::DefId::local(block.hir_id.owner);
let region_scope_tree = &cx.tcx.region_scope_tree(def_id);
ExprUseVisitor::new(&mut delegate, cx.tcx, cx.param_env, region_scope_tree, cx.tables, None).walk_expr(expr);
if delegate.skip {
return;
}
if !delegate.used_mutably.iter().any(|(_, v)| *v) {
span_lint(
cx,
WHILE_IMMUTABLE_CONDITION,
cond.span,
"Variable in the condition are not mutated in the loop body. This either leads to an infinite or to a never running loop.",
);
}
}
struct VarCollectorVisitor<'a, 'tcx: 'a> {
cx: &'a LateContext<'a, 'tcx>,
ids: HashMap<NodeId, bool>,
skip: bool,
}
impl<'a, 'tcx> VarCollectorVisitor<'a, 'tcx> {
fn insert_def_id(&mut self, ex: &'tcx Expr) {
if_chain! {
if let ExprPath(ref qpath) = ex.node;
if let QPath::Resolved(None, _) = *qpath;
let def = self.cx.tables.qpath_def(qpath, ex.hir_id);
then {
match def {
Def::Local(node_id) | Def::Upvar(node_id, ..) => {
self.ids.insert(node_id, false);
},
_ => {},
}
}
}
}
}
impl<'a, 'tcx> Visitor<'tcx> for VarCollectorVisitor<'a, 'tcx> {
fn visit_expr(&mut self, ex: &'tcx Expr) {
match ex.node {
ExprPath(_) => self.insert_def_id(ex),
ExprCall(..) | ExprMethodCall(..) => self.skip = true,
_ => walk_expr(self, ex),
}
}
fn visit_block(&mut self, _b: &'tcx Block) {}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}
struct MutVarsDelegate {
used_mutably: HashMap<NodeId, bool>,
skip: bool,
}
impl<'tcx> MutVarsDelegate {
fn update(&mut self, cat: &'tcx Categorization) {
match *cat {
Categorization::Local(id) =>
if let Some(used) = self.used_mutably.get_mut(&id) {
*used = true;
},
Categorization::Upvar(_) => {
self.skip = true
},
Categorization::Deref(ref cmt, _) | Categorization::Interior(ref cmt, _) => self.update(&cmt.cat),
_ => {}
}
}
}
impl<'tcx> Delegate<'tcx> for MutVarsDelegate {
fn consume(&mut self, _: NodeId, _: Span, _: &cmt_<'tcx>, _: ConsumeMode) {}
fn matched_pat(&mut self, _: &Pat, _: &cmt_<'tcx>, _: MatchMode) {}
fn consume_pat(&mut self, _: &Pat, _: &cmt_<'tcx>, _: ConsumeMode) {}
fn borrow(&mut self, _: NodeId, _: Span, cmt: &cmt_<'tcx>, _: ty::Region, bk: ty::BorrowKind, _: LoanCause) {
if let ty::BorrowKind::MutBorrow = bk {
self.update(&cmt.cat)
}
}
fn mutate(&mut self, _: NodeId, _: Span, cmt: &cmt_<'tcx>, _: MutateMode) {
self.update(&cmt.cat)
}
fn decl_without_init(&mut self, _: NodeId, _: Span) {}
}