use clippy_utils::consts::{constant_simple, Constant};
use clippy_utils::diagnostics::span_lint;
-use clippy_utils::{match_def_path, match_trait_method, paths};
-use if_chain::if_chain;
+use clippy_utils::is_trait_method;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::sym;
use std::cmp::Ordering;
declare_clippy_lint! {
- /// **What it does:** Checks for expressions where `std::cmp::min` and `max` are
+ /// ### What it does
+ /// Checks for expressions where `std::cmp::min` and `max` are
/// used to clamp values, but switched so that the result is constant.
///
- /// **Why is this bad?** This is in all probability not the intended outcome. At
+ /// ### Why is this bad?
+ /// This is in all probability not the intended outcome. At
/// the least it hurts readability of the code.
///
- /// **Known problems:** None
- ///
- /// **Example:**
- /// ```ignore
+ /// ### Example
+ /// ```rust,ignore
/// min(0, max(100, x))
- /// ```
- /// or
- /// ```ignore
+ ///
+ /// // or
+ ///
/// x.max(100).min(0)
/// ```
/// It will always be equal to `0`. Probably the author meant to clamp the value
/// between 0 and 100, but has erroneously swapped `min` and `max`.
+ #[clippy::version = "pre 1.29.0"]
pub MIN_MAX,
correctness,
"`min(_, max(_, _))` (or vice versa) with bounds clamping the result to a constant"
cx.typeck_results()
.qpath_res(qpath, path.hir_id)
.opt_def_id()
- .and_then(|def_id| {
- if match_def_path(cx, def_id, &paths::CMP_MIN) {
- fetch_const(cx, args, MinMax::Min)
- } else if match_def_path(cx, def_id, &paths::CMP_MAX) {
- fetch_const(cx, args, MinMax::Max)
- } else {
- None
- }
+ .and_then(|def_id| match cx.tcx.get_diagnostic_name(def_id) {
+ Some(sym::cmp_min) => fetch_const(cx, None, args, MinMax::Min),
+ Some(sym::cmp_max) => fetch_const(cx, None, args, MinMax::Max),
+ _ => None,
})
} else {
None
}
},
- ExprKind::MethodCall(path, _, args, _) => {
- if_chain! {
- if let [obj, _] = args;
- if cx.typeck_results().expr_ty(obj).is_floating_point() || match_trait_method(cx, expr, &paths::ORD);
- then {
- if path.ident.name == sym!(max) {
- fetch_const(cx, args, MinMax::Max)
- } else if path.ident.name == sym!(min) {
- fetch_const(cx, args, MinMax::Min)
- } else {
- None
- }
+ ExprKind::MethodCall(path, receiver, args @ [_], _) => {
+ if cx.typeck_results().expr_ty(receiver).is_floating_point() || is_trait_method(cx, expr, sym::Ord) {
+ if path.ident.name == sym!(max) {
+ fetch_const(cx, Some(receiver), args, MinMax::Max)
+ } else if path.ident.name == sym!(min) {
+ fetch_const(cx, Some(receiver), args, MinMax::Min)
} else {
None
}
+ } else {
+ None
}
},
_ => None,
}
}
-fn fetch_const<'a>(cx: &LateContext<'_>, args: &'a [Expr<'a>], m: MinMax) -> Option<(MinMax, Constant, &'a Expr<'a>)> {
- if args.len() != 2 {
+fn fetch_const<'a>(
+ cx: &LateContext<'_>,
+ receiver: Option<&'a Expr<'a>>,
+ args: &'a [Expr<'a>],
+ m: MinMax,
+) -> Option<(MinMax, Constant, &'a Expr<'a>)> {
+ let mut args = receiver.into_iter().chain(args);
+ let first_arg = args.next()?;
+ let second_arg = args.next()?;
+ if args.next().is_some() {
return None;
}
- constant_simple(cx, cx.typeck_results(), &args[0]).map_or_else(
- || constant_simple(cx, cx.typeck_results(), &args[1]).map(|c| (m, c, &args[0])),
+ constant_simple(cx, cx.typeck_results(), first_arg).map_or_else(
+ || constant_simple(cx, cx.typeck_results(), second_arg).map(|c| (m, c, first_arg)),
|c| {
- if constant_simple(cx, cx.typeck_results(), &args[1]).is_none() {
+ if constant_simple(cx, cx.typeck_results(), second_arg).is_none() {
// otherwise ignore
- Some((m, c, &args[1]))
+ Some((m, c, second_arg))
} else {
None
}