Add a new "short_circuit_statement" lint (fixes #1194)

This commit is contained in:
Samuel Tardieu 2016-12-30 00:00:55 +01:00
parent e0ab332303
commit 82b2f5663f
8 changed files with 76 additions and 8 deletions

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@ -372,6 +372,7 @@ All notable changes to this project will be documented in this file.
[`shadow_reuse`]: https://github.com/Manishearth/rust-clippy/wiki#shadow_reuse [`shadow_reuse`]: https://github.com/Manishearth/rust-clippy/wiki#shadow_reuse
[`shadow_same`]: https://github.com/Manishearth/rust-clippy/wiki#shadow_same [`shadow_same`]: https://github.com/Manishearth/rust-clippy/wiki#shadow_same
[`shadow_unrelated`]: https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated [`shadow_unrelated`]: https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated
[`short_circuit_statement`]: https://github.com/Manishearth/rust-clippy/wiki#short_circuit_statement
[`should_implement_trait`]: https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait [`should_implement_trait`]: https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait
[`similar_names`]: https://github.com/Manishearth/rust-clippy/wiki#similar_names [`similar_names`]: https://github.com/Manishearth/rust-clippy/wiki#similar_names
[`single_char_pattern`]: https://github.com/Manishearth/rust-clippy/wiki#single_char_pattern [`single_char_pattern`]: https://github.com/Manishearth/rust-clippy/wiki#single_char_pattern

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@ -179,7 +179,7 @@ transparently:
## Lints ## Lints
There are 181 lints included in this crate: There are 182 lints included in this crate:
name | default | triggers on name | default | triggers on
-----------------------------------------------------------------------------------------------------------------------|---------|---------------------------------------------------------------------------------------------------------------------------------- -----------------------------------------------------------------------------------------------------------------------|---------|----------------------------------------------------------------------------------------------------------------------------------
@ -320,6 +320,7 @@ name
[shadow_reuse](https://github.com/Manishearth/rust-clippy/wiki#shadow_reuse) | allow | rebinding a name to an expression that re-uses the original value, e.g. `let x = x + 1` [shadow_reuse](https://github.com/Manishearth/rust-clippy/wiki#shadow_reuse) | allow | rebinding a name to an expression that re-uses the original value, e.g. `let x = x + 1`
[shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same) | allow | rebinding a name to itself, e.g. `let mut x = &mut x` [shadow_same](https://github.com/Manishearth/rust-clippy/wiki#shadow_same) | allow | rebinding a name to itself, e.g. `let mut x = &mut x`
[shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated) | allow | rebinding a name without even using the original value [shadow_unrelated](https://github.com/Manishearth/rust-clippy/wiki#shadow_unrelated) | allow | rebinding a name without even using the original value
[short_circuit_statement](https://github.com/Manishearth/rust-clippy/wiki#short_circuit_statement) | warn | using a short circuit boolean condition as a statement
[should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait) | warn | defining a method that should be implementing a std trait [should_implement_trait](https://github.com/Manishearth/rust-clippy/wiki#should_implement_trait) | warn | defining a method that should be implementing a std trait
[similar_names](https://github.com/Manishearth/rust-clippy/wiki#similar_names) | allow | similarly named items and bindings [similar_names](https://github.com/Manishearth/rust-clippy/wiki#similar_names) | allow | similarly named items and bindings
[single_char_pattern](https://github.com/Manishearth/rust-clippy/wiki#single_char_pattern) | warn | using a single-character str where a char could be used, e.g. `_.split("x")` [single_char_pattern](https://github.com/Manishearth/rust-clippy/wiki#single_char_pattern) | warn | using a single-character str where a char could be used, e.g. `_.split("x")`

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@ -421,6 +421,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
misc::FLOAT_CMP, misc::FLOAT_CMP,
misc::MODULO_ONE, misc::MODULO_ONE,
misc::REDUNDANT_PATTERN, misc::REDUNDANT_PATTERN,
misc::SHORT_CIRCUIT_STATEMENT,
misc::TOPLEVEL_REF_ARG, misc::TOPLEVEL_REF_ARG,
misc_early::BUILTIN_TYPE_SHADOW, misc_early::BUILTIN_TYPE_SHADOW,
misc_early::DOUBLE_NEG, misc_early::DOUBLE_NEG,

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@ -154,6 +154,25 @@ declare_lint! {
"using a binding which is prefixed with an underscore" "using a binding which is prefixed with an underscore"
} }
/// **What it does:** Checks for the use of short circuit boolean conditions as a
/// statement.
///
/// **Why is this bad?** Using a short circuit boolean condition as a statement may
/// hide the fact that the second part is executed or not depending on the outcome of
/// the first part.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// f() && g(); // We should write `if f() { g(); }`.
/// ```
declare_lint! {
pub SHORT_CIRCUIT_STATEMENT,
Warn,
"using a short circuit boolean condition as a statement"
}
#[derive(Copy, Clone)] #[derive(Copy, Clone)]
pub struct Pass; pub struct Pass;
@ -165,7 +184,8 @@ impl LintPass for Pass {
CMP_OWNED, CMP_OWNED,
MODULO_ONE, MODULO_ONE,
REDUNDANT_PATTERN, REDUNDANT_PATTERN,
USED_UNDERSCORE_BINDING) USED_UNDERSCORE_BINDING,
SHORT_CIRCUIT_STATEMENT)
} }
} }
@ -224,7 +244,23 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
initref=initref)); initref=initref));
} }
); );
}} }};
if_let_chain! {[
let StmtSemi(ref expr, _) = s.node,
let Expr_::ExprBinary(ref binop, ref a, ref b) = expr.node,
binop.node == BiAnd || binop.node == BiOr,
let Some(sugg) = Sugg::hir_opt(cx, a),
], {
span_lint_and_then(cx,
SHORT_CIRCUIT_STATEMENT,
s.span,
"boolean short circuit operator in statement may be clearer using an explicit test",
|db| {
let sugg = if binop.node == BiOr { !sugg } else { sugg };
db.span_suggestion(s.span, "replace it with",
format!("if {} {{ {}; }}", sugg, &snippet(cx, b.span, "..")));
});
}};
} }
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {

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@ -1,6 +1,6 @@
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use rustc::hir::def::Def; use rustc::hir::def::Def;
use rustc::hir::{Expr, Expr_, Stmt, StmtSemi, BlockCheckMode, UnsafeSource}; use rustc::hir::{Expr, Expr_, Stmt, StmtSemi, BlockCheckMode, UnsafeSource, BiAnd, BiOr};
use utils::{in_macro, span_lint, snippet_opt, span_lint_and_then}; use utils::{in_macro, span_lint, snippet_opt, span_lint_and_then};
use std::ops::Deref; use std::ops::Deref;
@ -134,8 +134,10 @@ fn reduce_expression<'a>(cx: &LateContext, expr: &'a Expr) -> Option<Vec<&'a Exp
return None; return None;
} }
match expr.node { match expr.node {
Expr_::ExprIndex(ref a, ref b) | Expr_::ExprIndex(ref a, ref b) => Some(vec![&**a, &**b]),
Expr_::ExprBinary(_, ref a, ref b) => Some(vec![&**a, &**b]), Expr_::ExprBinary(ref binop, ref a, ref b) if binop.node != BiAnd && binop.node != BiOr => {
Some(vec![&**a, &**b])
},
Expr_::ExprArray(ref v) | Expr_::ExprArray(ref v) |
Expr_::ExprTup(ref v) => Some(v.iter().collect()), Expr_::ExprTup(ref v) => Some(v.iter().collect()),
Expr_::ExprRepeat(ref inner, _) | Expr_::ExprRepeat(ref inner, _) |

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@ -12,7 +12,7 @@ impl A {
fn foo(&self) -> ! { diverge() } fn foo(&self) -> ! { diverge() }
} }
#[allow(unused_variables, unnecessary_operation)] #[allow(unused_variables, unnecessary_operation, short_circuit_statement)]
fn main() { fn main() {
let b = true; let b = true;
b || diverge(); //~ ERROR sub-expression diverges b || diverge(); //~ ERROR sub-expression diverges

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@ -3,7 +3,7 @@
#[deny(eq_op)] #[deny(eq_op)]
#[allow(identity_op, double_parens)] #[allow(identity_op, double_parens)]
#[allow(no_effect, unused_variables, unnecessary_operation)] #[allow(no_effect, unused_variables, unnecessary_operation, short_circuit_statement)]
#[deny(nonminimal_bool)] #[deny(nonminimal_bool)]
fn main() { fn main() {
// simple values and comparisons // simple values and comparisons

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@ -0,0 +1,27 @@
#![feature(plugin)]
#![plugin(clippy)]
#![deny(short_circuit_statement)]
fn main() {
f() && g();
//~^ ERROR boolean short circuit operator
//~| HELP replace it with
//~| SUGGESTION if f() { g(); }
f() || g();
//~^ ERROR boolean short circuit operator
//~| HELP replace it with
//~| SUGGESTION if !f() { g(); }
1 == 2 || g();
//~^ ERROR boolean short circuit operator
//~| HELP replace it with
//~| SUGGESTION if !(1 == 2) { g(); }
}
fn f() -> bool {
true
}
fn g() -> bool {
false
}