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Merge pull request #1061 from Manishearth/double_neg

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new lint: double_neg
This commit is contained in:
Manish Goregaokar 2016-06-30 10:05:11 +05:30 committed by GitHub
commit b5b6945755
5 changed files with 53 additions and 16 deletions
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3
CHANGELOG.md
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@ -2,7 +2,7 @@
All notable changes to this project will be documented in this file.
## 0.0.78 - TBA
* New lints: [`wrong_transmute`]
* New lints: [`wrong_transmute`, `double_neg`]
* For compatibility, `cargo clippy` does not defines the `clippy` feature
introduced in 0.0.76 anymore
* [`collapsible_if`] now considers `if let`
@ -153,6 +153,7 @@ All notable changes to this project will be documented in this file.
[`deprecated_semver`]: https://github.com/Manishearth/rust-clippy/wiki#deprecated_semver
[`derive_hash_xor_eq`]: https://github.com/Manishearth/rust-clippy/wiki#derive_hash_xor_eq
[`doc_markdown`]: https://github.com/Manishearth/rust-clippy/wiki#doc_markdown
[`double_neg`]: https://github.com/Manishearth/rust-clippy/wiki#double_neg
[`drop_ref`]: https://github.com/Manishearth/rust-clippy/wiki#drop_ref
[`duplicate_underscore_argument`]: https://github.com/Manishearth/rust-clippy/wiki#duplicate_underscore_argument
[`empty_loop`]: https://github.com/Manishearth/rust-clippy/wiki#empty_loop

3
README.md
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@ -17,7 +17,7 @@ Table of contents:
## Lints
There are 156 lints included in this crate:
There are 157 lints included in this crate:
name | default | meaning
---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@ -49,6 +49,7 @@ name
[deprecated_semver](https://github.com/Manishearth/rust-clippy/wiki#deprecated_semver) | warn | `Warn` on `#[deprecated(since = "x")]` where x is not semver
[derive_hash_xor_eq](https://github.com/Manishearth/rust-clippy/wiki#derive_hash_xor_eq) | warn | deriving `Hash` but implementing `PartialEq` explicitly
[doc_markdown](https://github.com/Manishearth/rust-clippy/wiki#doc_markdown) | warn | checks for the presence of `_`, `::` or camel-case outside ticks in documentation
[double_neg](https://github.com/Manishearth/rust-clippy/wiki#double_neg) | warn | `--x` is a double negation of `x` and not a pre-decrement as in C or C++
[drop_ref](https://github.com/Manishearth/rust-clippy/wiki#drop_ref) | warn | call to `std::mem::drop` with a reference instead of an owned value, which will not call the `Drop::drop` method on the underlying value
[duplicate_underscore_argument](https://github.com/Manishearth/rust-clippy/wiki#duplicate_underscore_argument) | warn | Function arguments having names which only differ by an underscore
[empty_loop](https://github.com/Manishearth/rust-clippy/wiki#empty_loop) | warn | empty `loop {}` detected

1
clippy_lints/src/lib.rs
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@ -369,6 +369,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
misc::MODULO_ONE,
misc::REDUNDANT_PATTERN,
misc::TOPLEVEL_REF_ARG,
misc_early::DOUBLE_NEG,
misc_early::DUPLICATE_UNDERSCORE_ARGUMENT,
misc_early::REDUNDANT_CLOSURE_CALL,
misc_early::UNNEEDED_FIELD_PATTERN,

52
clippy_lints/src/misc_early.rs
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@ -40,12 +40,25 @@ declare_lint! {
"Closures should not be called in the expression they are defined"
}
/// **What it does:** This lint detects expressions of the form `--x`
///
/// **Why is this bad?** It can mislead C/C++ programmers to think `x` was decremented.
///
/// **Known problems:** None.
///
/// **Example:** `--x;`
declare_lint! {
pub DOUBLE_NEG, Warn,
"`--x` is a double negation of `x` and not a pre-decrement as in C or C++"
}
#[derive(Copy, Clone)]
pub struct MiscEarly;
impl LintPass for MiscEarly {
fn get_lints(&self) -> LintArray {
lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT, REDUNDANT_CLOSURE_CALL)
lint_array!(UNNEEDED_FIELD_PATTERN, DUPLICATE_UNDERSCORE_ARGUMENT, REDUNDANT_CLOSURE_CALL, DOUBLE_NEG)
}
}
@ -126,21 +139,32 @@ impl EarlyLintPass for MiscEarly {
}
fn check_expr(&mut self, cx: &EarlyContext, expr: &Expr) {
if let ExprKind::Call(ref paren, _) = expr.node {
if let ExprKind::Paren(ref closure) = paren.node {
if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node {
span_lint_and_then(cx,
REDUNDANT_CLOSURE_CALL,
expr.span,
"Try not to call a closure in the expression where it is declared.",
|db| {
if decl.inputs.is_empty() {
let hint = format!("{}", snippet(cx, block.span, ".."));
db.span_suggestion(expr.span, "Try doing something like: ", hint);
}
});
match expr.node {
ExprKind::Call(ref paren, _) => {
if let ExprKind::Paren(ref closure) = paren.node {
if let ExprKind::Closure(_, ref decl, ref block, _) = closure.node {
span_lint_and_then(cx,
REDUNDANT_CLOSURE_CALL,
expr.span,
"Try not to call a closure in the expression where it is declared.",
|db| {
if decl.inputs.is_empty() {
let hint = format!("{}", snippet(cx, block.span, ".."));
db.span_suggestion(expr.span, "Try doing something like: ", hint);
}
});
}
}
}
ExprKind::Unary(UnOp::Neg, ref inner) => {
if let ExprKind::Unary(UnOp::Neg, _) = inner.node {
span_lint(cx,
DOUBLE_NEG,
expr.span,
"`--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op");
}
}
_ => ()
}
}

10
tests/compile-fail/double_neg.rs Normal file
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@ -0,0 +1,10 @@
#![feature(plugin)]
#![plugin(clippy)]
#[deny(double_neg)]
fn main() {
let x = 1;
-x;
-(-x);
--x; //~ERROR: `--x` could be misinterpreted as pre-decrement by C programmers, is usually a no-op
}