Update lint documentation to use markdown headlines

[rust.git] / clippy_lints / src / minmax.rs

diff --git a/clippy_lints/src/minmax.rs b/clippy_lints/src/minmax.rs
index 8e6f3925d66050fd819b8fddfda818d609773590..dc2dd45e4edb6c1c096b141458f4e5b7e51421d5 100644 (file)
--- a/clippy_lints/src/minmax.rs
+++ b/clippy_lints/src/minmax.rs
@@ -1,23 +1,29 @@
-use crate::consts::{constant_simple, Constant};
-use crate::utils::{match_def_path, paths, span_lint};
+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 rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 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:**
+    /// ### Example
     /// ```ignore
     /// min(0, max(100, x))
     /// ```
+    /// or
+    /// ```ignore
+    /// 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`.
     pub MIN_MAX,
@@ -27,8 +33,8 @@
 
 declare_lint_pass!(MinMaxPass => [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, ie)) = min_max(cx, oe) {
                 if outer_max == inner_max {
@@ -36,7 +42,7 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
                 }
                 match (
                     outer_max,
-                    Constant::partial_cmp(cx.tcx, cx.tables().expr_ty(ie), &outer_c, &inner_c),
+                    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)) => (),
                     _ => {
@@ -53,53 +59,66 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
     }
 }
 
-#[derive(PartialEq, Eq, Debug)]
+#[derive(PartialEq, Eq, Debug, Clone, Copy)]
 enum MinMax {
     Min,
     Max,
 }
 
-fn min_max<'a>(cx: &LateContext<'_, '_>, expr: &'a Expr<'a>) -> Option<(MinMax, Constant, &'a Expr<'a>)> {
-    if let ExprKind::Call(ref path, ref args) = expr.kind {
-        if let ExprKind::Path(ref qpath) = path.kind {
-            cx.tables()
-                .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) {
+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| {
+                        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
+                        }
+                    })
+            } 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<'a>],
-    m: MinMax,
-) -> Option<(MinMax, Constant, &'a Expr<'a>)> {
+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
+            }
+        },
+    )
 }