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Implements lint for order comparisons against bool

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This commit is contained in:
Lucas Lois 2018-12-06 21:50:16 -03:00
parent a416c5e0f7
commit bc48890b47
3 changed files with 148 additions and 25 deletions
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104
clippy_lints/src/needless_bool.rs
View File

@ -45,8 +45,9 @@
"if-statements with plain booleans in the then- and else-clause, e.g. `if p { true } else { false }`"
}
/// **What it does:** Checks for expressions of the form `x == true` and
/// `x != true` (or vice versa) and suggest using the variable directly.
/// **What it does:** Checks for expressions of the form `x == true`,
/// `x != true` and order comparisons such as `x < true` (or vice versa) and
/// suggest using the variable directly.
///
/// **Why is this bad?** Unnecessary code.
///
@ -143,22 +144,54 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
}
if let ExprKind::Binary(Spanned { node, .. }, ..) = e.node {
let ignore_case = None::<(fn(_) -> _, &str)>;
let ignore_no_literal = None::<(fn(_, _) -> _, &str)>;
match node {
BinOpKind::Eq => check_comparison(
BinOpKind::Eq => {
let true_case = Some((|h| h, "equality checks against true are unnecessary"));
let false_case = Some((
|h: Sugg<'_>| !h,
"equality checks against false can be replaced by a negation",
));
check_comparison(cx, e, true_case, false_case, true_case, false_case, ignore_no_literal)
},
BinOpKind::Ne => {
let true_case = Some((
|h: Sugg<'_>| !h,
"inequality checks against true can be replaced by a negation",
));
let false_case = Some((|h| h, "inequality checks against false are unnecessary"));
check_comparison(cx, e, true_case, false_case, true_case, false_case, ignore_no_literal)
},
BinOpKind::Lt => check_comparison(
cx,
e,
"equality checks against true are unnecessary",
"equality checks against false can be replaced by a negation",
|h| h,
|h| !h,
ignore_case,
Some((|h| h, "greater than checks against false are unnecessary")),
Some((
|h: Sugg<'_>| !h,
"less than comparison against true can be replaced by a negation",
)),
ignore_case,
Some((
|l: Sugg<'_>, r: Sugg<'_>| (!l).and(&r),
"order comparisons between booleans can be simplified",
)),
),
BinOpKind::Ne => check_comparison(
BinOpKind::Gt => check_comparison(
cx,
e,
"inequality checks against true can be replaced by a negation",
"inequality checks against false are unnecessary",
|h| !h,
|h| h,
Some((
|h: Sugg<'_>| !h,
"less than comparison against true can be replaced by a negation",
)),
ignore_case,
ignore_case,
Some((|h| h, "greater than checks against false are unnecessary")),
Some((
|l: Sugg<'_>, r: Sugg<'_>| l.and(&(!r)),
"order comparisons between booleans can be simplified",
)),
),
_ => (),
}
@ -169,22 +202,45 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
fn check_comparison<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
e: &'tcx Expr,
true_message: &str,
false_message: &str,
true_hint: impl FnOnce(Sugg<'_>) -> Sugg<'_>,
false_hint: impl FnOnce(Sugg<'_>) -> Sugg<'_>,
left_true: Option<(impl FnOnce(Sugg<'a>) -> Sugg<'a>, &str)>,
left_false: Option<(impl FnOnce(Sugg<'a>) -> Sugg<'a>, &str)>,
right_true: Option<(impl FnOnce(Sugg<'a>) -> Sugg<'a>, &str)>,
right_false: Option<(impl FnOnce(Sugg<'a>) -> Sugg<'a>, &str)>,
no_literal: Option<(impl FnOnce(Sugg<'a>, Sugg<'a>) -> Sugg<'a>, &str)>,
) {
use self::Expression::*;
if let ExprKind::Binary(_, ref left_side, ref right_side) = e.node {
let applicability = Applicability::MachineApplicable;
let mut applicability = Applicability::MachineApplicable;
match (fetch_bool_expr(left_side), fetch_bool_expr(right_side)) {
(Bool(true), Other) => suggest_bool_comparison(cx, e, right_side, applicability, true_message, true_hint),
(Other, Bool(true)) => suggest_bool_comparison(cx, e, left_side, applicability, true_message, true_hint),
(Bool(false), Other) => {
suggest_bool_comparison(cx, e, right_side, applicability, false_message, false_hint)
},
(Other, Bool(false)) => suggest_bool_comparison(cx, e, left_side, applicability, false_message, false_hint),
(Bool(true), Other) => left_true.map_or((), |(h, m)| {
suggest_bool_comparison(cx, e, right_side, applicability, m, h)
}),
(Other, Bool(true)) => right_true.map_or((), |(h, m)| {
suggest_bool_comparison(cx, e, left_side, applicability, m, h)
}),
(Bool(false), Other) => left_false.map_or((), |(h, m)| {
suggest_bool_comparison(cx, e, right_side, applicability, m, h)
}),
(Other, Bool(false)) => right_false.map_or((), |(h, m)| {
suggest_bool_comparison(cx, e, left_side, applicability, m, h)
}),
(Other, Other) => no_literal.map_or((), |(h, m)| {
let (l_ty, r_ty) = (cx.tables.expr_ty(left_side), cx.tables.expr_ty(right_side));
if l_ty.is_bool() && r_ty.is_bool() {
let left_side = Sugg::hir_with_applicability(cx, left_side, "..", &mut applicability);
let right_side = Sugg::hir_with_applicability(cx, right_side, "..", &mut applicability);
span_lint_and_sugg(
cx,
BOOL_COMPARISON,
e.span,
m,
"try simplifying it as shown",
h(left_side, right_side).to_string(),
applicability,
)
}
}),
_ => (),
}
}
@ -196,7 +252,7 @@ fn suggest_bool_comparison<'a, 'tcx>(
expr: &Expr,
mut applicability: Applicability,
message: &str,
conv_hint: impl FnOnce(Sugg<'_>) -> Sugg<'_>,
conv_hint: impl FnOnce(Sugg<'a>) -> Sugg<'a>,
) {
let hint = Sugg::hir_with_applicability(cx, expr, "..", &mut applicability);
span_lint_and_sugg(

31
tests/ui/bool_comparison.rs
View File

@ -50,4 +50,35 @@ fn main() {
} else {
"no"
};
if x < true {
"yes"
} else {
"no"
};
if false < x {
"yes"
} else {
"no"
};
if x > false {
"yes"
} else {
"no"
};
if true > x {
"yes"
} else {
"no"
};
let y = true;
if x < y {
"yes"
} else {
"no"
};
if x > y {
"yes"
} else {
"no"
};
}

38
tests/ui/bool_comparison.stderr
View File

@ -48,5 +48,41 @@ error: inequality checks against false are unnecessary
48 | if false != x {
| ^^^^^^^^^^ help: try simplifying it as shown: `x`
error: aborting due to 8 previous errors
error: less than comparison against true can be replaced by a negation
--> $DIR/bool_comparison.rs:53:8
|
53 | if x < true {
| ^^^^^^^^ help: try simplifying it as shown: `!x`
error: greater than checks against false are unnecessary
--> $DIR/bool_comparison.rs:58:8
|
58 | if false < x {
| ^^^^^^^^^ help: try simplifying it as shown: `x`
error: greater than checks against false are unnecessary
--> $DIR/bool_comparison.rs:63:8
|
63 | if x > false {
| ^^^^^^^^^ help: try simplifying it as shown: `x`
error: less than comparison against true can be replaced by a negation
--> $DIR/bool_comparison.rs:68:8
|
68 | if true > x {
| ^^^^^^^^ help: try simplifying it as shown: `!x`
error: order comparisons between booleans can be simplified
--> $DIR/bool_comparison.rs:74:8
|
74 | if x < y {
| ^^^^^ help: try simplifying it as shown: `!x && y`
error: order comparisons between booleans can be simplified
--> $DIR/bool_comparison.rs:79:8
|
79 | if x > y {
| ^^^^^ help: try simplifying it as shown: `x && !y`
error: aborting due to 14 previous errors