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Manish Goregaokar 2016-02-10 10:20:23 +05:30
commit 1013026f18
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3
README.md
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@ -6,7 +6,7 @@ A collection of lints to catch common mistakes and improve your Rust code.
[Jump to usage instructions](#usage)
##Lints
There are 117 lints included in this crate:
There are 118 lints included in this crate:
name | default | meaning
---------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@ -15,6 +15,7 @@ name
[bad_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#bad_bit_mask) | warn | expressions of the form `_ & mask == select` that will only ever return `true` or `false` (because in the example `select` containing bits that `mask` doesn't have)
[block_in_if_condition_expr](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_expr) | warn | braces can be eliminated in conditions that are expressions, e.g `if { true } ...`
[block_in_if_condition_stmt](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_stmt) | warn | avoid complex blocks in conditions, instead move the block higher and bind it with 'let'; e.g: `if { let x = true; x } ...`
[bool_comparison](https://github.com/Manishearth/rust-clippy/wiki#bool_comparison) | warn | comparing a variable to a boolean, e.g. `if x == true`
[box_vec](https://github.com/Manishearth/rust-clippy/wiki#box_vec) | warn | usage of `Box<Vec<T>>`, vector elements are already on the heap
[boxed_local](https://github.com/Manishearth/rust-clippy/wiki#boxed_local) | warn | using Box<T> where unnecessary
[cast_possible_truncation](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_truncation) | allow | casts that may cause truncation of the value, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`

2
src/lib.rs
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@ -105,6 +105,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
reg.register_late_lint_pass(box bit_mask::BitMask);
reg.register_late_lint_pass(box ptr_arg::PtrArg);
reg.register_late_lint_pass(box needless_bool::NeedlessBool);
reg.register_late_lint_pass(box needless_bool::BoolComparison);
reg.register_late_lint_pass(box approx_const::ApproxConstant);
reg.register_late_lint_pass(box misc::FloatCmp);
reg.register_early_lint_pass(box precedence::Precedence);
@ -252,6 +253,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
misc_early::UNNEEDED_FIELD_PATTERN,
mut_reference::UNNECESSARY_MUT_PASSED,
mutex_atomic::MUTEX_ATOMIC,
needless_bool::BOOL_COMPARISON,
needless_bool::NEEDLESS_BOOL,
needless_features::UNSTABLE_AS_MUT_SLICE,
needless_features::UNSTABLE_AS_SLICE,

76
src/needless_bool.rs
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@ -6,8 +6,9 @@ use rustc::lint::*;
use rustc_front::hir::*;
use syntax::ast::Lit_;
use syntax::codemap::Spanned;
use utils::{span_lint, snippet};
use utils::{span_lint, span_lint_and_then, snippet};
/// **What it does:** This lint checks for expressions of the form `if c { true } else { false }` (or vice versa) and suggest using the condition directly.
///
@ -23,6 +24,20 @@ declare_lint! {
`if p { true } else { false }`"
}
/// **What it does:** This lint checks for expressions of the form `x == true` (or vice versa) and suggest using the variable directly.
///
/// **Why is this bad?** Unnecessary code.
///
/// **Known problems:** None.
///
/// **Example:** `if x == true { }` could be `if x { }`
declare_lint! {
pub BOOL_COMPARISON,
Warn,
"comparing a variable to a boolean, e.g. \
`if x == true`"
}
#[derive(Copy,Clone)]
pub struct NeedlessBool;
@ -78,6 +93,65 @@ impl LateLintPass for NeedlessBool {
}
}
#[derive(Copy,Clone)]
pub struct BoolComparison;
impl LintPass for BoolComparison {
fn get_lints(&self) -> LintArray {
lint_array!(BOOL_COMPARISON)
}
}
impl LateLintPass for BoolComparison {
fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
if let ExprBinary(Spanned{ node: BiEq, .. }, ref left_side, ref right_side) = e.node {
match (fetch_bool_expr(left_side), fetch_bool_expr(right_side)) {
(Some(true), None) => {
let hint = snippet(cx, right_side.span, "..").into_owned();
span_lint_and_then(cx,
BOOL_COMPARISON,
e.span,
"equality checks against true are unnecesary",
|db| {
db.span_suggestion(e.span, "try simplifying it as shown:", hint);
});
}
(None, Some(true)) => {
let hint = snippet(cx, left_side.span, "..").into_owned();
span_lint_and_then(cx,
BOOL_COMPARISON,
e.span,
"equality checks against true are unnecesary",
|db| {
db.span_suggestion(e.span, "try simplifying it as shown:", hint);
});
}
(Some(false), None) => {
let hint = format!("!{}", snippet(cx, right_side.span, ".."));
span_lint_and_then(cx,
BOOL_COMPARISON,
e.span,
"equality checks against false can be replaced by a negation",
|db| {
db.span_suggestion(e.span, "try simplifying it as shown:", hint);
});
}
(None, Some(false)) => {
let hint = format!("!{}", snippet(cx, left_side.span, ".."));
span_lint_and_then(cx,
BOOL_COMPARISON,
e.span,
"equality checks against false can be replaced by a negation",
|db| {
db.span_suggestion(e.span, "try simplifying it as shown:", hint);
});
}
_ => (),
}
}
}
}
fn fetch_bool_block(block: &Block) -> Option<bool> {
if block.stmts.is_empty() {
block.expr.as_ref().and_then(|e| fetch_bool_expr(e))

23
tests/compile-fail/bool_comparison.rs Normal file
View file

@ -0,0 +1,23 @@
#![feature(plugin)]
#![plugin(clippy)]
#[deny(bool_comparison)]
fn main() {
let x = true;
if x == true { "yes" } else { "no" };
//~^ ERROR equality checks against true are unnecesary
//~| HELP try simplifying it as shown:
//~| SUGGESTION if x { "yes" } else { "no" };
if x == false { "yes" } else { "no" };
//~^ ERROR equality checks against false can be replaced by a negation
//~| HELP try simplifying it as shown:
//~| SUGGESTION if !x { "yes" } else { "no" };
if true == x { "yes" } else { "no" };
//~^ ERROR equality checks against true are unnecesary
//~| HELP try simplifying it as shown:
//~| SUGGESTION if x { "yes" } else { "no" };
if false == x { "yes" } else { "no" };
//~^ ERROR equality checks against false can be replaced by a negation
//~| HELP try simplifying it as shown:
//~| SUGGESTION if !x { "yes" } else { "no" };
}