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Detect usage of (x + 1).ln() and suggest x.ln_1p() instead

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Krishna Veera Reddy 2019-12-20 20:07:03 -08:00 • committed by Krishna Sai Veera Reddy
parent a60ae5d31c
commit de07c84903
3 changed files with 84 additions and 24 deletions
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14
clippy_lints/src/floating_point_arithmetic.rs
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@ -94,16 +94,18 @@ fn check_log_base(cx: &LateContext<'_, '_>, expr: &Expr, args: &HirVec<Expr>) {
}
}
// TODO: Lint expressions of the form `(x + 1).ln()` and `(x + y).ln()`
// where y > 1 and suggest usage of `(x + (y - 1)).ln_1p()` instead
// TODO: Lint expressions of the form `(x + y).ln()` where y > 1 and
// suggest usage of `(x + (y - 1)).ln_1p()` instead
fn check_ln1p(cx: &LateContext<'_, '_>, expr: &Expr, args: &HirVec<Expr>) {
if_chain! {
if let ExprKind::Binary(op, ref lhs, ref rhs) = &args[0].kind;
if op.node == BinOpKind::Add;
if let Some((value, _)) = constant(cx, cx.tables, lhs);
if F32(1.0) == value || F64(1.0) == value;
then {
let arg = sugg::Sugg::hir(cx, rhs, "..").maybe_par();
let recv = match (constant(cx, cx.tables, lhs), constant(cx, cx.tables, rhs)) {
(Some((value, _)), _) if F32(1.0) == value || F64(1.0) == value => rhs,
(_, Some((value, _))) if F32(1.0) == value || F64(1.0) == value => lhs,
_ => return,
};
span_lint_and_sugg(
cx,
@ -111,7 +113,7 @@ fn check_ln1p(cx: &LateContext<'_, '_>, expr: &Expr, args: &HirVec<Expr>) {
expr.span,
"ln(1 + x) can be computed more accurately",
"consider using",
format!("{}.ln_1p()", arg),
format!("{}.ln_1p()", sugg::Sugg::hir(cx, recv, "..").maybe_par()),
Applicability::MachineApplicable,
);
}