-use consts::{Constant, constant_simple};
-use rustc::lint::*;
+// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use crate::consts::{constant_simple, Constant};
+use crate::utils::{match_def_path, opt_def_id, paths, span_lint};
use rustc::hir::*;
-use std::cmp::{PartialOrd, Ordering};
-use syntax::ptr::P;
-use utils::{match_def_path, paths, span_lint};
+use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use rustc::{declare_tool_lint, lint_array};
+use std::cmp::Ordering;
-/// **What it does:** This lint checks for expressions where `std::cmp::min` and `max` are used to clamp values, but switched so that the result is constant.
+/// **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.
+/// **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:** `min(0, max(100, x))` 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_lint! {
- pub MIN_MAX, Warn,
+/// **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! {
+ pub MIN_MAX,
+ correctness,
"`min(_, max(_, _))` (or vice versa) with bounds clamping the result to a constant"
}
-#[allow(missing_copy_implementations)]
pub struct MinMaxPass;
impl LintPass for MinMaxPass {
}
}
-impl LateLintPass for MinMaxPass {
- fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MinMaxPass {
+ fn check_expr(&mut self, cx: &LateContext<'a, '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)) {
- (_, None) |
- (MinMax::Max, Some(Ordering::Less)) |
- (MinMax::Min, Some(Ordering::Greater)) => (),
+ match (
+ outer_max,
+ Constant::partial_cmp(cx.tcx, cx.tables.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",
+ );
+ },
}
}
}
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(None, _) = path.node {
- let def_id = cx.tcx.expect_def(path.id).def_id();
-
- if match_def_path(cx, def_id, &paths::CMP_MIN) {
- fetch_const(args, MinMax::Min)
- } else if match_def_path(cx, def_id, &paths::CMP_MAX) {
- fetch_const(args, MinMax::Max)
- } else {
- None
- }
+fn min_max<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr) -> Option<(MinMax, Constant, &'a Expr)> {
+ if let ExprKind::Call(ref path, ref args) = expr.node {
+ if let ExprKind::Path(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)
+ } else {
+ None
+ }
+ })
} else {
None
}
}
}
-fn fetch_const(args: &[P<Expr>], m: MinMax) -> Option<(MinMax, Constant, &Expr)> {
+fn fetch_const<'a>(cx: &LateContext<'_, '_>, args: &'a [Expr], m: MinMax) -> Option<(MinMax, Constant, &'a Expr)> {
if args.len() != 2 {
return None;
}
- if let Some(c) = constant_simple(&args[0]) {
- if let None = constant_simple(&args[1]) {
+ 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(&args[1]) {
+ } else if let Some(c) = constant_simple(cx, cx.tables, &args[1]) {
Some((m, c, &args[0]))
} else {
None