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Fix suggestions for `needless_bool`

This commit is contained in:
mcarton 2016-07-04 01:17:31 +02:00
parent 7778f314f2
commit 9b79b1022c
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GPG Key ID: 5E427C794CBA45E8
2 changed files with 50 additions and 17 deletions
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36
clippy_lints/src/needless_bool.rs
View File

@ -6,7 +6,8 @@ use rustc::lint::*;
use rustc::hir::*;
use syntax::ast::LitKind;
use syntax::codemap::Spanned;
use utils::{span_lint, span_lint_and_then, snippet, snippet_opt};
use utils::{span_lint, span_lint_and_then, snippet};
use utils::sugg::Sugg;
/// **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.
///
@ -49,11 +50,20 @@ impl LateLintPass for NeedlessBool {
fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
use self::Expression::*;
if let ExprIf(ref pred, ref then_block, Some(ref else_expr)) = e.node {
let reduce = |hint: &str, not| {
let hint = match snippet_opt(cx, pred.span) {
Some(pred_snip) => format!("`{}{}`", not, pred_snip),
None => hint.into(),
let reduce = |ret, not| {
let snip = Sugg::hir(cx, pred, "<predicate>");
let snip = if not {
!snip
} else {
snip
};
let hint = if ret {
format!("return {};", snip)
} else {
snip.to_string()
};
span_lint_and_then(cx,
NEEDLESS_BOOL,
e.span,
@ -77,10 +87,10 @@ impl LateLintPass for NeedlessBool {
e.span,
"this if-then-else expression will always return false");
}
(RetBool(true), RetBool(false)) => reduce("its predicate", "return "),
(Bool(true), Bool(false)) => reduce("its predicate", ""),
(RetBool(false), RetBool(true)) => reduce("`!` and its predicate", "return !"),
(Bool(false), Bool(true)) => reduce("`!` and its predicate", "!"),
(RetBool(true), RetBool(false)) => reduce(true, false),
(Bool(true), Bool(false)) => reduce(false, false),
(RetBool(false), RetBool(true)) => reduce(true, true),
(Bool(false), Bool(true)) => reduce(false, true),
_ => (),
}
}
@ -122,23 +132,23 @@ impl LateLintPass for BoolComparison {
});
}
(Bool(false), Other) => {
let hint = format!("!{}", snippet(cx, right_side.span, ".."));
let hint = Sugg::hir(cx, right_side, "..");
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);
db.span_suggestion(e.span, "try simplifying it as shown:", (!hint).to_string());
});
}
(Other, Bool(false)) => {
let hint = format!("!{}", snippet(cx, left_side.span, ".."));
let hint = Sugg::hir(cx, left_side, "..");
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);
db.span_suggestion(e.span, "try simplifying it as shown:", (!hint).to_string());
});
}
_ => (),

31
tests/compile-fail/needless_bool.rs
View File

@ -5,21 +5,28 @@
#[allow(if_same_then_else)]
fn main() {
let x = true;
let y = false;
if x { true } else { true }; //~ERROR this if-then-else expression will always return true
if x { false } else { false }; //~ERROR this if-then-else expression will always return false
if x { true } else { false };
//~^ ERROR this if-then-else expression returns a bool literal
//~| HELP you can reduce it to
//~| SUGGESTION `x`
//~| SUGGESTION x
if x { false } else { true };
//~^ ERROR this if-then-else expression returns a bool literal
//~| HELP you can reduce it to
//~| SUGGESTION `!x`
//~| SUGGESTION !x
if x && y { false } else { true };
//~^ ERROR this if-then-else expression returns a bool literal
//~| HELP you can reduce it to
//~| SUGGESTION !(x && y)
if x { x } else { false }; // would also be questionable, but we don't catch this yet
bool_ret(x);
bool_ret2(x);
bool_ret3(x);
bool_ret5(x, x);
bool_ret4(x);
bool_ret6(x, x);
}
#[allow(if_same_then_else, needless_return)]
@ -39,7 +46,15 @@ fn bool_ret3(x: bool) -> bool {
if x { return true } else { return false };
//~^ ERROR this if-then-else expression returns a bool literal
//~| HELP you can reduce it to
//~| SUGGESTION `return x`
//~| SUGGESTION return x
}
#[allow(needless_return)]
fn bool_ret5(x: bool, y: bool) -> bool {
if x && y { return true } else { return false };
//~^ ERROR this if-then-else expression returns a bool literal
//~| HELP you can reduce it to
//~| SUGGESTION return x && y
}
#[allow(needless_return)]
@ -47,5 +62,13 @@ fn bool_ret4(x: bool) -> bool {
if x { return false } else { return true };
//~^ ERROR this if-then-else expression returns a bool literal
//~| HELP you can reduce it to
//~| SUGGESTION `return !x`
//~| SUGGESTION return !x
}
#[allow(needless_return)]
fn bool_ret6(x: bool, y: bool) -> bool {
if x && y { return false } else { return true };
//~^ ERROR this if-then-else expression returns a bool literal
//~| HELP you can reduce it to
//~| SUGGESTION return !(x && y)
}