|
| 1 | +use std::cmp::Ordering; |
| 2 | + |
| 3 | +use super::UNNECESSARY_MIN_OR_MAX; |
| 4 | +use clippy_utils::diagnostics::span_lint_and_sugg; |
| 5 | + |
| 6 | +use clippy_utils::consts::{constant, constant_with_source, Constant, ConstantSource, FullInt}; |
| 7 | +use clippy_utils::source::snippet; |
| 8 | + |
| 9 | +use rustc_errors::Applicability; |
| 10 | +use rustc_hir::Expr; |
| 11 | +use rustc_lint::LateContext; |
| 12 | +use rustc_middle::ty; |
| 13 | +use rustc_span::Span; |
| 14 | + |
| 15 | +pub(super) fn check<'tcx>( |
| 16 | + cx: &LateContext<'tcx>, |
| 17 | + expr: &'tcx Expr<'_>, |
| 18 | + name: &str, |
| 19 | + recv: &'tcx Expr<'_>, |
| 20 | + arg: &'tcx Expr<'_>, |
| 21 | +) { |
| 22 | + let typeck_results = cx.typeck_results(); |
| 23 | + if let Some((left, ConstantSource::Local | ConstantSource::CoreConstant)) = |
| 24 | + constant_with_source(cx, typeck_results, recv) |
| 25 | + && let Some((right, ConstantSource::Local | ConstantSource::CoreConstant)) = |
| 26 | + constant_with_source(cx, typeck_results, arg) |
| 27 | + { |
| 28 | + let Some(ord) = Constant::partial_cmp(cx.tcx, typeck_results.expr_ty(recv), &left, &right) else { |
| 29 | + return; |
| 30 | + }; |
| 31 | + |
| 32 | + lint(cx, expr, name, recv.span, arg.span, ord); |
| 33 | + } else if let Some(extrema) = detect_extrema(cx, recv) { |
| 34 | + let ord = match extrema { |
| 35 | + Extrema::Minimum => Ordering::Less, |
| 36 | + Extrema::Maximum => Ordering::Greater, |
| 37 | + }; |
| 38 | + lint(cx, expr, name, recv.span, arg.span, ord); |
| 39 | + } else if let Some(extrema) = detect_extrema(cx, arg) { |
| 40 | + let ord = match extrema { |
| 41 | + Extrema::Minimum => Ordering::Greater, |
| 42 | + Extrema::Maximum => Ordering::Less, |
| 43 | + }; |
| 44 | + lint(cx, expr, name, recv.span, arg.span, ord); |
| 45 | + } |
| 46 | +} |
| 47 | + |
| 48 | +fn lint(cx: &LateContext<'_>, expr: &Expr<'_>, name: &str, lhs: Span, rhs: Span, order: Ordering) { |
| 49 | + let cmp_str = if order.is_ge() { "smaller" } else { "greater" }; |
| 50 | + |
| 51 | + let suggested_value = if (name == "min" && order.is_ge()) || (name == "max" && order.is_le()) { |
| 52 | + snippet(cx, rhs, "..") |
| 53 | + } else { |
| 54 | + snippet(cx, lhs, "..") |
| 55 | + }; |
| 56 | + |
| 57 | + span_lint_and_sugg( |
| 58 | + cx, |
| 59 | + UNNECESSARY_MIN_OR_MAX, |
| 60 | + expr.span, |
| 61 | + format!( |
| 62 | + "`{}` is never {} than `{}` and has therefore no effect", |
| 63 | + snippet(cx, lhs, ".."), |
| 64 | + cmp_str, |
| 65 | + snippet(cx, rhs, "..") |
| 66 | + ), |
| 67 | + "try", |
| 68 | + suggested_value.to_string(), |
| 69 | + Applicability::MachineApplicable, |
| 70 | + ); |
| 71 | +} |
| 72 | + |
| 73 | +#[derive(Debug)] |
| 74 | +enum Extrema { |
| 75 | + Minimum, |
| 76 | + Maximum, |
| 77 | +} |
| 78 | +fn detect_extrema<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<Extrema> { |
| 79 | + let ty = cx.typeck_results().expr_ty(expr); |
| 80 | + |
| 81 | + let cv = constant(cx, cx.typeck_results(), expr)?; |
| 82 | + |
| 83 | + match (cv.int_value(cx, ty)?, ty.kind()) { |
| 84 | + (FullInt::S(i), &ty::Int(ity)) if i == i128::MIN >> (128 - ity.bit_width()?) => Some(Extrema::Minimum), |
| 85 | + (FullInt::S(i), &ty::Int(ity)) if i == i128::MAX >> (128 - ity.bit_width()?) => Some(Extrema::Maximum), |
| 86 | + (FullInt::U(i), &ty::Uint(uty)) if i == u128::MAX >> (128 - uty.bit_width()?) => Some(Extrema::Maximum), |
| 87 | + (FullInt::U(0), &ty::Uint(_)) => Some(Extrema::Minimum), |
| 88 | + _ => None, |
| 89 | + } |
| 90 | +} |
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