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https://github.com/rust-lang/rust-clippy
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Suggest for loop instead of while-let when looping over iterators
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4 changed files with 37 additions and 3 deletions
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@ -6,7 +6,8 @@ A collection of lints to catch common mistakes and improve your Rust code.
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[Jump to usage instructions](#usage)
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##Lints
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There are 68 lints included in this crate:
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There are 69 lints included in this crate:
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There are 65 lints included in this crate:
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name | default | meaning
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-------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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@ -74,6 +75,7 @@ name
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[unstable_as_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_slice) | warn | as_slice is not stable and can be replaced by & v[..]see https://github.com/rust-lang/rust/issues/27729
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[unused_collect](https://github.com/Manishearth/rust-clippy/wiki#unused_collect) | warn | `collect()`ing an iterator without using the result; this is usually better written as a for loop
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[while_let_loop](https://github.com/Manishearth/rust-clippy/wiki#while_let_loop) | warn | `loop { if let { ... } else break }` can be written as a `while let` loop
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[while_let_on_iterator](https://github.com/Manishearth/rust-clippy/wiki#while_let_on_iterator) | warn | using a while-let loop instead of a for loop on an iterator
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[wrong_pub_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_pub_self_convention) | allow | defining a public method named with an established prefix (like "into_") that takes `self` with the wrong convention
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[wrong_self_convention](https://github.com/Manishearth/rust-clippy/wiki#wrong_self_convention) | warn | defining a method named with an established prefix (like "into_") that takes `self` with the wrong convention
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[zero_divided_by_zero](https://github.com/Manishearth/rust-clippy/wiki#zero_divided_by_zero) | warn | usage of `0.0 / 0.0` to obtain NaN instead of std::f32::NaN or std::f64::NaN
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@ -138,6 +138,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
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loops::REVERSE_RANGE_LOOP,
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loops::UNUSED_COLLECT,
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loops::WHILE_LET_LOOP,
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loops::WHILE_LET_ON_ITERATOR,
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matches::MATCH_BOOL,
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matches::MATCH_REF_PATS,
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matches::SINGLE_MATCH,
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16
src/loops.rs
16
src/loops.rs
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@ -38,6 +38,8 @@ declare_lint!{ pub EXPLICIT_COUNTER_LOOP, Warn,
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declare_lint!{ pub EMPTY_LOOP, Warn, "empty `loop {}` detected" }
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declare_lint!{ pub WHILE_LET_ON_ITERATOR, Warn, "using a while-let loop instead of a for loop on an iterator" }
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#[derive(Copy, Clone)]
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pub struct LoopsPass;
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@ -45,7 +47,8 @@ impl LintPass for LoopsPass {
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fn get_lints(&self) -> LintArray {
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lint_array!(NEEDLESS_RANGE_LOOP, EXPLICIT_ITER_LOOP, ITER_NEXT_LOOP,
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WHILE_LET_LOOP, UNUSED_COLLECT, REVERSE_RANGE_LOOP,
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EXPLICIT_COUNTER_LOOP, EMPTY_LOOP)
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EXPLICIT_COUNTER_LOOP, EMPTY_LOOP,
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WHILE_LET_ON_ITERATOR)
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}
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}
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@ -228,6 +231,17 @@ impl LateLintPass for LoopsPass {
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}
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}
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}
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if let ExprMatch(ref expr, ref arms, MatchSource::WhileLetDesugar) = expr.node {
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let pat = &arms[0].pats[0].node;
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if let (&PatEnum(ref path, _), &ExprMethodCall(method_name, _, _)) = (pat, &expr.node) {
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if method_name.node.as_str() == "next" &&
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match_trait_method(cx, expr, &["core", "iter", "Iterator"]) &&
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path.segments.last().unwrap().identifier.name.as_str() == "Some" {
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span_lint(cx, WHILE_LET_ON_ITERATOR, expr.span,
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"this loop could be written as a `for` loop");
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}
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}
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}
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}
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fn check_stmt(&mut self, cx: &LateContext, stmt: &Stmt) {
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@ -1,7 +1,7 @@
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#![feature(plugin)]
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#![plugin(clippy)]
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#![deny(while_let_loop, empty_loop)]
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#![deny(while_let_loop, empty_loop, while_let_on_iterator)]
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#![allow(dead_code, unused)]
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fn main() {
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@ -53,6 +53,23 @@ fn main() {
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while let Some(x) = y { // no error, obviously
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println!("{}", x);
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}
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while let Option::Some(x) = (1..20).next() { //~ERROR this loop could be written as a `for` loop
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println!("{}", x);
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}
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while let Some(x) = (1..20).next() { //~ERROR this loop could be written as a `for` loop
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println!("{}", x);
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}
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while let Some(_) = (1..20).next() {} //~ERROR this loop could be written as a `for` loop
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while let None = (1..20).next() {} // this is fine (if nonsensical)
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if let Some(x) = (1..20).next() { // also fine
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println!("{}", x)
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}
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}
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// regression test (#360)
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