//!
//! This lint is **warn** by default
+use crate::utils::sugg::Sugg;
+use crate::utils::{in_macro, span_lint, span_lint_and_sugg};
+use rustc::hir::*;
use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
use rustc::{declare_tool_lint, lint_array};
-use rustc::hir::*;
+use rustc_errors::Applicability;
use syntax::ast::LitKind;
use syntax::source_map::Spanned;
-use crate::utils::{snippet, span_lint, span_lint_and_sugg};
-use crate::utils::sugg::Sugg;
-/// **What it does:** Checks for expressions of the form `if c { true } else {
-/// false }`
-/// (or vice versa) and suggest using the condition directly.
-///
-/// **Why is this bad?** Redundant code.
-///
-/// **Known problems:** Maybe false positives: Sometimes, the two branches are
-/// painstakingly documented (which we of course do not detect), so they *may*
-/// have some value. Even then, the documentation can be rewritten to match the
-/// shorter code.
-///
-/// **Example:**
-/// ```rust
-/// if x { false } else { true }
-/// ```
declare_clippy_lint! {
+ /// **What it does:** Checks for expressions of the form `if c { true } else {
+ /// false }`
+ /// (or vice versa) and suggest using the condition directly.
+ ///
+ /// **Why is this bad?** Redundant code.
+ ///
+ /// **Known problems:** Maybe false positives: Sometimes, the two branches are
+ /// painstakingly documented (which we of course do not detect), so they *may*
+ /// have some value. Even then, the documentation can be rewritten to match the
+ /// shorter code.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// if x {
+ /// false
+ /// } else {
+ /// true
+ /// }
+ /// ```
pub NEEDLESS_BOOL,
complexity,
- "if-statements with plain booleans in the then- and else-clause, e.g. \
- `if p { true } else { false }`"
+ "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` (or vice
-/// versa) and suggest using the variable directly.
-///
-/// **Why is this bad?** Unnecessary code.
-///
-/// **Known problems:** None.
-///
-/// **Example:**
-/// ```rust
-/// if x == true { } // could be `if x { }`
-/// ```
declare_clippy_lint! {
+ /// **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.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// if x == true {} // could be `if x { }`
+ /// ```
pub BOOL_COMPARISON,
complexity,
- "comparing a variable to a boolean, e.g. `if x == true`"
+ "comparing a variable to a boolean, e.g., `if x == true` or `if x != true`"
}
#[derive(Copy, Clone)]
fn get_lints(&self) -> LintArray {
lint_array!(NEEDLESS_BOOL)
}
+
+ fn name(&self) -> &'static str {
+ "NeedlessBool"
+ }
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessBool {
use self::Expression::*;
if let ExprKind::If(ref pred, ref then_block, Some(ref else_expr)) = e.node {
let reduce = |ret, not| {
- let snip = Sugg::hir(cx, pred, "<predicate>");
- let snip = if not { !snip } else { snip };
+ let mut applicability = Applicability::MachineApplicable;
+ let snip = Sugg::hir_with_applicability(cx, pred, "<predicate>", &mut applicability);
+ let mut snip = if not { !snip } else { snip };
- let hint = if ret {
- format!("return {}", snip)
- } else {
- snip.to_string()
- };
+ if ret {
+ snip = snip.make_return();
+ }
+
+ if parent_node_is_if_expr(&e, &cx) {
+ snip = snip.blockify()
+ }
span_lint_and_sugg(
cx,
e.span,
"this if-then-else expression returns a bool literal",
"you can reduce it to",
- hint,
+ snip.to_string(),
+ applicability,
);
};
if let ExprKind::Block(ref then_block, _) = then_block.node {
}
}
+fn parent_node_is_if_expr<'a, 'b>(expr: &Expr, cx: &LateContext<'a, 'b>) -> bool {
+ let parent_id = cx.tcx.hir().get_parent_node_by_hir_id(expr.hir_id);
+ let parent_node = cx.tcx.hir().get_by_hir_id(parent_id);
+
+ if let rustc::hir::Node::Expr(e) = parent_node {
+ if let ExprKind::If(_, _, _) = e.node {
+ return true;
+ }
+ }
+
+ false
+}
+
#[derive(Copy, Clone)]
pub struct BoolComparison;
fn get_lints(&self) -> LintArray {
lint_array!(BOOL_COMPARISON)
}
+
+ fn name(&self) -> &'static str {
+ "BoolComparison"
+ }
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for BoolComparison {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
- use self::Expression::*;
- if let ExprKind::Binary(Spanned { node: BinOpKind::Eq, .. }, ref left_side, ref right_side) = e.node {
- match (fetch_bool_expr(left_side), fetch_bool_expr(right_side)) {
- (Bool(true), Other) => {
- let hint = snippet(cx, right_side.span, "..").into_owned();
- span_lint_and_sugg(
- cx,
- BOOL_COMPARISON,
- e.span,
- "equality checks against true are unnecessary",
- "try simplifying it as shown",
- hint,
- );
- },
- (Other, Bool(true)) => {
- let hint = snippet(cx, left_side.span, "..").into_owned();
- span_lint_and_sugg(
- cx,
- BOOL_COMPARISON,
- e.span,
- "equality checks against true are unnecessary",
- "try simplifying it as shown",
- hint,
- );
- },
- (Bool(false), Other) => {
- let hint = Sugg::hir(cx, right_side, "..");
- span_lint_and_sugg(
- cx,
- BOOL_COMPARISON,
- e.span,
+ if in_macro(e.span) {
+ return;
+ }
+
+ 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 => {
+ 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",
- "try simplifying it as shown",
- (!hint).to_string(),
- );
+ ));
+ 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)
},
- (Other, Bool(false)) => {
- let hint = Sugg::hir(cx, left_side, "..");
+ BinOpKind::Lt => check_comparison(
+ cx,
+ e,
+ 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).bit_and(&r),
+ "order comparisons between booleans can be simplified",
+ )),
+ ),
+ BinOpKind::Gt => check_comparison(
+ cx,
+ e,
+ 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.bit_and(&(!r)),
+ "order comparisons between booleans can be simplified",
+ )),
+ ),
+ _ => (),
+ }
+ }
+ }
+}
+
+fn check_comparison<'a, 'tcx>(
+ cx: &LateContext<'a, 'tcx>,
+ e: &'tcx Expr,
+ 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 (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 mut applicability = Applicability::MachineApplicable;
+ match (fetch_bool_expr(left_side), fetch_bool_expr(right_side)) {
+ (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 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,
- "equality checks against false can be replaced by a negation",
+ m,
"try simplifying it as shown",
- (!hint).to_string(),
- );
- },
+ h(left_side, right_side).to_string(),
+ applicability,
+ )
+ }),
_ => (),
}
}
}
}
+fn suggest_bool_comparison<'a, 'tcx>(
+ cx: &LateContext<'a, 'tcx>,
+ e: &'tcx Expr,
+ expr: &Expr,
+ mut applicability: Applicability,
+ message: &str,
+ conv_hint: impl FnOnce(Sugg<'a>) -> Sugg<'a>,
+) {
+ let hint = Sugg::hir_with_applicability(cx, expr, "..", &mut applicability);
+ span_lint_and_sugg(
+ cx,
+ BOOL_COMPARISON,
+ e.span,
+ message,
+ "try simplifying it as shown",
+ conv_hint(hint).to_string(),
+ applicability,
+ );
+}
+
enum Expression {
Bool(bool),
RetBool(bool),
fn fetch_bool_block(block: &Block) -> Expression {
match (&*block.stmts, block.expr.as_ref()) {
(&[], Some(e)) => fetch_bool_expr(&**e),
- (&[ref e], None) => if let StmtKind::Semi(ref e, _) = e.node {
- if let ExprKind::Ret(_) = e.node {
- fetch_bool_expr(&**e)
+ (&[ref e], None) => {
+ if let StmtKind::Semi(ref e) = e.node {
+ if let ExprKind::Ret(_) = e.node {
+ fetch_bool_expr(&**e)
+ } else {
+ Expression::Other
+ }
} else {
Expression::Other
}
- } else {
- Expression::Other
},
_ => Expression::Other,
}
fn fetch_bool_expr(expr: &Expr) -> Expression {
match expr.node {
ExprKind::Block(ref block, _) => fetch_bool_block(block),
- ExprKind::Lit(ref lit_ptr) => if let LitKind::Bool(value) = lit_ptr.node {
- Expression::Bool(value)
- } else {
- Expression::Other
+ ExprKind::Lit(ref lit_ptr) => {
+ if let LitKind::Bool(value) = lit_ptr.node {
+ Expression::Bool(value)
+ } else {
+ Expression::Other
+ }
},
ExprKind::Ret(Some(ref expr)) => match fetch_bool_expr(expr) {
Expression::Bool(value) => Expression::RetBool(value),
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