-use consts::{constant_simple, Constant};
-use rustc::lint::*;
-use rustc::hir::*;
-use std::cmp::{Ordering, PartialOrd};
-use utils::{match_def_path, opt_def_id, paths, span_lint};
+use clippy_utils::consts::{constant_simple, Constant};
+use clippy_utils::diagnostics::span_lint;
+use clippy_utils::{match_trait_method, paths};
+use if_chain::if_chain;
+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;
-/// **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
-/// the least it hurts readability of the code.
-///
-/// **Known problems:** None
-///
-/// **Example:**
-/// ```rust
-/// min(0, max(100, x))
-/// ```
-/// 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`.
declare_clippy_lint! {
+ /// ### 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
+ /// the least it hurts readability of the code.
+ ///
+ /// ### Example
+ /// ```rust,ignore
+ /// min(0, max(100, x))
+ ///
+ /// // 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"
}
-#[allow(missing_copy_implementations)]
-pub struct MinMaxPass;
+declare_lint_pass!(MinMaxPass => [MIN_MAX]);
-impl LintPass for MinMaxPass {
- fn get_lints(&self) -> LintArray {
- lint_array!(MIN_MAX)
- }
-}
-
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MinMaxPass {
- fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
+impl<'tcx> LateLintPass<'tcx> for MinMaxPass {
+ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let Some((outer_max, outer_c, oe)) = min_max(cx, expr) {
- if let Some((inner_max, inner_c, _)) = min_max(cx, oe) {
+ if let Some((inner_max, inner_c, ie)) = min_max(cx, oe) {
if outer_max == inner_max {
return;
}
- match (outer_max, outer_c.partial_cmp(&inner_c)) {
+ match (
+ outer_max,
+ Constant::partial_cmp(cx.tcx, cx.typeck_results().expr_ty(ie), &outer_c, &inner_c),
+ ) {
(_, None) | (MinMax::Max, Some(Ordering::Less)) | (MinMax::Min, Some(Ordering::Greater)) => (),
_ => {
- span_lint(cx, MIN_MAX, expr.span, "this min/max combination leads to constant result");
+ span_lint(
+ cx,
+ MIN_MAX,
+ expr.span,
+ "this `min`/`max` combination leads to constant result",
+ );
},
}
}
}
}
-#[derive(PartialEq, Eq, Debug)]
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
enum MinMax {
Min,
Max,
}
-fn min_max<'a>(cx: &LateContext, expr: &'a Expr) -> Option<(MinMax, Constant, &'a Expr)> {
- if let ExprCall(ref path, ref args) = expr.node {
- if let ExprPath(ref qpath) = path.node {
- opt_def_id(cx.tables.qpath_def(qpath, path.hir_id)).and_then(|def_id| {
- if match_def_path(cx.tcx, def_id, &paths::CMP_MIN) {
- fetch_const(cx, args, MinMax::Min)
- } else if match_def_path(cx.tcx, def_id, &paths::CMP_MAX) {
- fetch_const(cx, args, MinMax::Max)
+fn min_max<'a>(cx: &LateContext<'_>, expr: &'a Expr<'a>) -> Option<(MinMax, Constant, &'a Expr<'a>)> {
+ match expr.kind {
+ ExprKind::Call(path, args) => {
+ if let ExprKind::Path(ref qpath) = path.kind {
+ cx.typeck_results()
+ .qpath_res(qpath, path.hir_id)
+ .opt_def_id()
+ .and_then(|def_id| match cx.tcx.get_diagnostic_name(def_id) {
+ Some(sym::cmp_min) => fetch_const(cx, args, MinMax::Min),
+ Some(sym::cmp_max) => fetch_const(cx, 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
+ }
} else {
None
}
- })
- } else {
- None
- }
- } else {
- None
+ }
+ },
+ _ => None,
}
}
-fn fetch_const<'a>(cx: &LateContext, args: &'a [Expr], m: MinMax) -> Option<(MinMax, Constant, &'a Expr)> {
+fn fetch_const<'a>(cx: &LateContext<'_>, args: &'a [Expr<'a>], m: MinMax) -> Option<(MinMax, Constant, &'a Expr<'a>)> {
if args.len() != 2 {
return None;
}
- if let Some(c) = constant_simple(cx, cx.tables, &args[0]) {
- if constant_simple(cx, cx.tables, &args[1]).is_none() {
- // otherwise ignore
- Some((m, c, &args[1]))
- } else {
- None
- }
- } else if let Some(c) = constant_simple(cx, cx.tables, &args[1]) {
- Some((m, c, &args[0]))
- } else {
- 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])),
+ |c| {
+ if constant_simple(cx, cx.typeck_results(), &args[1]).is_none() {
+ // otherwise ignore
+ Some((m, c, &args[1]))
+ } else {
+ None
+ }
+ },
+ )
}