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New lint: (maybe_)infinite_iter

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This fixes #1870 (mostly, does not account for loops yet)
This commit is contained in:
Andre Bogus 2017-08-25 22:20:52 +02:00
parent 5cf3f8359f
commit df903edddd
7 changed files with 369 additions and 1 deletions
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2
CHANGELOG.md
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@ -481,6 +481,7 @@ All notable changes to this project will be documented in this file.
[`inconsistent_digit_grouping`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#inconsistent_digit_grouping
[`indexing_slicing`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#indexing_slicing
[`ineffective_bit_mask`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#ineffective_bit_mask
[`infinite_iter`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#infinite_iter
[`inline_always`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#inline_always
[`integer_arithmetic`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#integer_arithmetic
[`invalid_regex`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#invalid_regex
@ -508,6 +509,7 @@ All notable changes to this project will be documented in this file.
[`match_ref_pats`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#match_ref_pats
[`match_same_arms`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#match_same_arms
[`match_wild_err_arm`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#match_wild_err_arm
[`maybe_infinite_iter`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#maybe_infinite_iter
[`mem_forget`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#mem_forget
[`min_max`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#min_max
[`misrefactored_assign_op`]: https://github.com/rust-lang-nursery/rust-clippy/wiki#misrefactored_assign_op

4
README.md
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@ -180,7 +180,7 @@ transparently:
## Lints
There are 206 lints included in this crate:
There are 208 lints included in this crate:
name | default | triggers on
-----------------------------------------------------------------------------------------------------------------------------|---------|----------------------------------------------------------------------------------------------------------------------------------
@ -252,6 +252,7 @@ name
[inconsistent_digit_grouping](https://github.com/rust-lang-nursery/rust-clippy/wiki#inconsistent_digit_grouping) | warn | integer literals with digits grouped inconsistently
[indexing_slicing](https://github.com/rust-lang-nursery/rust-clippy/wiki#indexing_slicing) | allow | indexing/slicing usage
[ineffective_bit_mask](https://github.com/rust-lang-nursery/rust-clippy/wiki#ineffective_bit_mask) | warn | expressions where a bit mask will be rendered useless by a comparison, e.g. `(x | 1) > 2`
[infinite_iter](https://github.com/rust-lang-nursery/rust-clippy/wiki#infinite_iter) | warn | infinite iteration
[inline_always](https://github.com/rust-lang-nursery/rust-clippy/wiki#inline_always) | warn | use of `#[inline(always)]`
[integer_arithmetic](https://github.com/rust-lang-nursery/rust-clippy/wiki#integer_arithmetic) | allow | any integer arithmetic statement
[invalid_regex](https://github.com/rust-lang-nursery/rust-clippy/wiki#invalid_regex) | deny | invalid regular expressions
@ -279,6 +280,7 @@ name
[match_ref_pats](https://github.com/rust-lang-nursery/rust-clippy/wiki#match_ref_pats) | warn | a match or `if let` with all arms prefixed with `&` instead of deref-ing the match expression
[match_same_arms](https://github.com/rust-lang-nursery/rust-clippy/wiki#match_same_arms) | warn | `match` with identical arm bodies
[match_wild_err_arm](https://github.com/rust-lang-nursery/rust-clippy/wiki#match_wild_err_arm) | warn | a match with `Err(_)` arm and take drastic actions
[maybe_infinite_iter](https://github.com/rust-lang-nursery/rust-clippy/wiki#maybe_infinite_iter) | allow | possible infinite iteration
[mem_forget](https://github.com/rust-lang-nursery/rust-clippy/wiki#mem_forget) | allow | `mem::forget` usage on `Drop` types, likely to cause memory leaks
[min_max](https://github.com/rust-lang-nursery/rust-clippy/wiki#min_max) | warn | `min(_, max(_, _))` (or vice versa) with bounds clamping the result to a constant
[misrefactored_assign_op](https://github.com/rust-lang-nursery/rust-clippy/wiki#misrefactored_assign_op) | warn | having a variable on both sides of an assign op

218
clippy_lints/src/infinite_iter.rs Normal file
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@ -0,0 +1,218 @@
use rustc::hir::*;
use rustc::lint::*;
use utils::{get_trait_def_id, implements_trait, higher, match_path, paths, span_lint};
/// **What it does:** Checks for iteration that is guaranteed to be infinite.
///
/// **Why is this bad?** While there may be places where this is acceptable
/// (e.g. in event streams), in most cases this is simply an error.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// repeat(1_u8).iter().collect::<Vec<_>>()
/// ```
declare_lint! {
pub INFINITE_ITER,
Warn,
"infinite iteration"
}
/// **What it does:** Checks for iteration that may be infinite.
///
/// **Why is this bad?** While there may be places where this is acceptable
/// (e.g. in event streams), in most cases this is simply an error.
///
/// **Known problems:** The code may have a condition to stop iteration, but
/// this lint is not clever enough to analyze it.
///
/// **Example:**
/// ```rust
/// [0..].iter().zip(infinite_iter.take_while(|x| x > 5))
/// ```
declare_lint! {
pub MAYBE_INFINITE_ITER,
Allow,
"possible infinite iteration"
}
#[derive(Copy, Clone)]
pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(INFINITE_ITER, MAYBE_INFINITE_ITER)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
let (lint, msg) = match complete_infinite_iter(cx, expr) {
True => (INFINITE_ITER, "infinite iteration detected"),
Unknown => (MAYBE_INFINITE_ITER,
"possible infinite iteration detected"),
False => { return; }
};
span_lint(cx, lint, expr.span, msg)
}
}
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
enum TriState {
True,
Unknown,
False
}
use self::TriState::{True, Unknown, False};
impl TriState {
fn and(self, b: Self) -> Self {
match (self, b) {
(False, _) | (_, False) => False,
(Unknown, _) | (_, Unknown) => Unknown,
_ => True
}
}
fn or(self, b: Self) -> Self {
match (self, b) {
(True, _) | (_, True) => True,
(Unknown, _) | (_, Unknown) => Unknown,
_ => False
}
}
}
impl From<bool> for TriState {
fn from(b: bool) -> Self {
if b { True } else { False }
}
}
#[derive(Copy, Clone)]
enum Heuristic {
Always,
First,
Any,
All
}
use self::Heuristic::{Always, First, Any, All};
// here we use the `TriState` as (Finite, Possible Infinite, Infinite)
static HEURISTICS : &[(&str, usize, Heuristic, TriState)] = &[
("zip", 2, All, True),
("chain", 2, Any, True),
("cycle", 1, Always, True),
("map", 2, First, True),
("by_ref", 1, First, True),
("cloned", 1, First, True),
("rev", 1, First, True),
("inspect", 1, First, True),
("enumerate", 1, First, True),
("peekable", 2, First, True),
("fuse", 1, First, True),
("skip", 2, First, True),
("skip_while", 1, First, True),
("filter", 2, First, True),
("filter_map", 2, First, True),
("flat_map", 2, First, True),
("unzip", 1, First, True),
("take_while", 2, First, Unknown),
("scan", 3, First, Unknown)
];
fn is_infinite(cx: &LateContext, expr: &Expr) -> TriState {
match expr.node {
ExprMethodCall(ref method, _, ref args) => {
for &(name, len, heuristic, cap) in HEURISTICS.iter() {
if method.name == name && args.len() == len {
return (match heuristic {
Always => True,
First => is_infinite(cx, &args[0]),
Any => is_infinite(cx, &args[0]).or(is_infinite(cx, &args[1])),
All => is_infinite(cx, &args[0]).and(is_infinite(cx, &args[1])),
}).and(cap);
}
}
if method.name == "flat_map" && args.len() == 2 {
if let ExprClosure(_, _, body_id, _) = args[1].node {
let body = cx.tcx.hir.body(body_id);
return is_infinite(cx, &body.value);
}
}
False
},
ExprBlock(ref block) =>
block.expr.as_ref().map_or(False, |e| is_infinite(cx, e)),
ExprBox(ref e) | ExprAddrOf(_, ref e) => is_infinite(cx, e),
ExprCall(ref path, _) => {
if let ExprPath(ref qpath) = path.node {
match_path(qpath, &paths::REPEAT).into()
} else { False }
},
ExprStruct(..) => {
higher::range(expr).map_or(false, |r| r.end.is_none()).into()
},
_ => False
}
}
static POSSIBLY_COMPLETING_METHODS : &[(&str, usize)] = &[
("find", 2),
("rfind", 2),
("position", 2),
("rposition", 2),
("any", 2),
("all", 2)
];
static COMPLETING_METHODS : &[(&str, usize)] = &[
("count", 1),
("collect", 1),
("fold", 3),
("for_each", 2),
("partition", 2),
("max", 1),
("max_by", 2),
("max_by_key", 2),
("min", 1),
("min_by", 2),
("min_by_key", 2),
("sum", 1),
("product", 1)
];
fn complete_infinite_iter(cx: &LateContext, expr: &Expr) -> TriState {
match expr.node {
ExprMethodCall(ref method, _, ref args) => {
for &(name, len) in COMPLETING_METHODS.iter() {
if method.name == name && args.len() == len {
return is_infinite(cx, &args[0]);
}
}
for &(name, len) in POSSIBLY_COMPLETING_METHODS.iter() {
if method.name == name && args.len() == len {
return Unknown.and(is_infinite(cx, &args[0]));
}
}
if method.name == "last" && args.len() == 1 &&
get_trait_def_id(cx, &paths::DOUBLE_ENDED_ITERATOR).map_or(false,
|id| !implements_trait(cx,
cx.tables.expr_ty(&args[0]),
id,
&[])) {
return is_infinite(cx, &args[0]);
}
},
ExprBinary(op, ref l, ref r) => {
if op.node.is_comparison() {
return is_infinite(cx, l).and(is_infinite(cx, r)).and(Unknown)
}
}, //TODO: ExprLoop + Match
_ => ()
}
False
}

4
clippy_lints/src/lib.rs
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@ -97,6 +97,7 @@ pub mod functions;
pub mod identity_op;
pub mod if_let_redundant_pattern_matching;
pub mod if_not_else;
pub mod infinite_iter;
pub mod items_after_statements;
pub mod large_enum_variant;
pub mod len_zero;
@ -323,6 +324,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
reg.register_early_lint_pass(box literal_digit_grouping::LiteralDigitGrouping);
reg.register_late_lint_pass(box use_self::UseSelf);
reg.register_late_lint_pass(box bytecount::ByteCount);
reg.register_late_lint_pass(box infinite_iter::Pass);
reg.register_lint_group("clippy_restrictions", vec![
arithmetic::FLOAT_ARITHMETIC,
@ -338,6 +340,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
enum_variants::PUB_ENUM_VARIANT_NAMES,
enum_variants::STUTTER,
if_not_else::IF_NOT_ELSE,
infinite_iter::MAYBE_INFINITE_ITER,
items_after_statements::ITEMS_AFTER_STATEMENTS,
matches::SINGLE_MATCH_ELSE,
mem_forget::MEM_FORGET,
@ -422,6 +425,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
functions::TOO_MANY_ARGUMENTS,
identity_op::IDENTITY_OP,
if_let_redundant_pattern_matching::IF_LET_REDUNDANT_PATTERN_MATCHING,
infinite_iter::INFINITE_ITER,
large_enum_variant::LARGE_ENUM_VARIANT,
len_zero::LEN_WITHOUT_IS_EMPTY,
len_zero::LEN_ZERO,

2
clippy_lints/src/utils/paths.rs
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@ -21,6 +21,7 @@ pub const CSTRING_NEW: [&'static str; 5] = ["std", "ffi", "c_str", "CString", "n
pub const DEBUG_FMT_METHOD: [&'static str; 4] = ["core", "fmt", "Debug", "fmt"];
pub const DEFAULT_TRAIT: [&'static str; 3] = ["core", "default", "Default"];
pub const DISPLAY_FMT_METHOD: [&'static str; 4] = ["core", "fmt", "Display", "fmt"];
pub const DOUBLE_ENDED_ITERATOR: [&'static str; 4] = ["core", "iter", "traits", "DoubleEndedIterator"];
pub const DROP: [&'static str; 3] = ["core", "mem", "drop"];
pub const FMT_ARGUMENTS_NEWV1: [&'static str; 4] = ["core", "fmt", "Arguments", "new_v1"];
pub const FMT_ARGUMENTV1_NEW: [&'static str; 4] = ["core", "fmt", "ArgumentV1", "new"];
@ -65,6 +66,7 @@ pub const REGEX_BYTES_NEW: [&'static str; 4] = ["regex", "re_bytes", "Regex", "n
pub const REGEX_BYTES_SET_NEW: [&'static str; 5] = ["regex", "re_set", "bytes", "RegexSet", "new"];
pub const REGEX_NEW: [&'static str; 4] = ["regex", "re_unicode", "Regex", "new"];
pub const REGEX_SET_NEW: [&'static str; 5] = ["regex", "re_set", "unicode", "RegexSet", "new"];
pub const REPEAT: [&'static str; 3] = ["core", "iter", "repeat"];
pub const RESULT: [&'static str; 3] = ["core", "result", "Result"];
pub const RESULT_ERR: [&'static str; 4] = ["core", "result", "Result", "Err"];
pub const RESULT_OK: [&'static str; 4] = ["core", "result", "Result", "Ok"];

40
tests/ui/infinite_iter.rs Normal file
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@ -0,0 +1,40 @@
#![feature(plugin)]
#![feature(iterator_for_each)]
#![plugin(clippy)]
use std::iter::repeat;
fn square_is_lower_64(x: &u32) -> bool { x * x < 64 }
#[allow(maybe_infinite_iter)]
#[deny(infinite_iter)]
fn infinite_iters() {
repeat(0_u8).collect::<Vec<_>>(); // infinite iter
(0..8_u32).take_while(square_is_lower_64).cycle().count(); // infinite iter
(0..8_u64).chain(0..).max(); // infinite iter
(0_usize..).chain([0usize, 1, 2].iter().cloned()).skip_while(|x| *x != 42).min(); // infinite iter
(0..8_u32).rev().cycle().map(|x| x + 1_u32).for_each(|x| println!("{}", x)); // infinite iter
(0..3_u32).flat_map(|x| x..).sum::<u32>(); // infinite iter
(0_usize..).flat_map(|x| 0..x).product::<usize>(); // infinite iter
(0_u64..).filter(|x| x % 2 == 0).last(); // infinite iter
(0..42_u64).by_ref().last(); // not an infinite, because ranges are double-ended
(0..).next(); // iterator is not exhausted
}
#[deny(maybe_infinite_iter)]
fn potential_infinite_iters() {
(0..).zip((0..).take_while(square_is_lower_64)).count(); // maybe infinite iter
repeat(42).take_while(|x| *x == 42).chain(0..42).max(); // maybe infinite iter
(1..).scan(0, |state, x| { *state += x; Some(*state) }).min(); // maybe infinite iter
(0..).find(|x| *x == 24); // maybe infinite iter
(0..).position(|x| x == 24); // maybe infinite iter
(0..).any(|x| x == 24); // maybe infinite iter
(0..).all(|x| x == 24); // maybe infinite iter
(0..).zip(0..42).take_while(|&(x, _)| x != 42).count(); // not infinite
repeat(42).take_while(|x| *x == 42).next(); // iterator is not exhausted
}
fn main() {
infinite_iters();
potential_infinite_iters();
}

100
tests/ui/infinite_iter.stderr Normal file
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@ -0,0 +1,100 @@
error: you are collect()ing an iterator and throwing away the result. Consider using an explicit for loop to exhaust the iterator
--> $DIR/infinite_iter.rs:11:5
|
11 | repeat(0_u8).collect::<Vec<_>>(); // infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: `-D unused-collect` implied by `-D warnings`
error: infinite iteration detected
--> $DIR/infinite_iter.rs:11:5
|
11 | repeat(0_u8).collect::<Vec<_>>(); // infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: lint level defined here
--> $DIR/infinite_iter.rs:9:8
|
9 | #[deny(infinite_iter)]
| ^^^^^^^^^^^^^
error: infinite iteration detected
--> $DIR/infinite_iter.rs:12:5
|
12 | (0..8_u32).take_while(square_is_lower_64).cycle().count(); // infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: infinite iteration detected
--> $DIR/infinite_iter.rs:13:5
|
13 | (0..8_u64).chain(0..).max(); // infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: infinite iteration detected
--> $DIR/infinite_iter.rs:15:5
|
15 | (0..8_u32).rev().cycle().map(|x| x + 1_u32).for_each(|x| println!("{}", x)); // infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: infinite iteration detected
--> $DIR/infinite_iter.rs:17:5
|
17 | (0_usize..).flat_map(|x| 0..x).product::<usize>(); // infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: infinite iteration detected
--> $DIR/infinite_iter.rs:18:5
|
18 | (0_u64..).filter(|x| x % 2 == 0).last(); // infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: possible infinite iteration detected
--> $DIR/infinite_iter.rs:25:5
|
25 | (0..).zip((0..).take_while(square_is_lower_64)).count(); // maybe infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: lint level defined here
--> $DIR/infinite_iter.rs:23:8
|
23 | #[deny(maybe_infinite_iter)]
| ^^^^^^^^^^^^^^^^^^^
error: possible infinite iteration detected
--> $DIR/infinite_iter.rs:26:5
|
26 | repeat(42).take_while(|x| *x == 42).chain(0..42).max(); // maybe infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: possible infinite iteration detected
--> $DIR/infinite_iter.rs:27:5
|
27 | (1..).scan(0, |state, x| { *state += x; Some(*state) }).min(); // maybe infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: possible infinite iteration detected
--> $DIR/infinite_iter.rs:28:5
|
28 | (0..).find(|x| *x == 24); // maybe infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^
error: possible infinite iteration detected
--> $DIR/infinite_iter.rs:29:5
|
29 | (0..).position(|x| x == 24); // maybe infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: possible infinite iteration detected
--> $DIR/infinite_iter.rs:30:5
|
30 | (0..).any(|x| x == 24); // maybe infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^
error: possible infinite iteration detected
--> $DIR/infinite_iter.rs:31:5
|
31 | (0..).all(|x| x == 24); // maybe infinite iter
| ^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 14 previous errors