Rollup merge of rust-lang#5871 - wiomoc:feature/methodcall-minmax, r=flip1995

flip1995 · web-flow · commit ee8db50e13a7 · 2020-08-10T14:56:29.000+02:00
Lint .min(x).max(y) with x < y Fixes rust-lang#5854 changelog: Also lint `ord.min(a).max(b)`, where `a < b` in [`min_max`] lint
diff --git a/clippy_lints/src/minmax.rs b/clippy_lints/src/minmax.rs
@@ -1,5 +1,6 @@
 use crate::consts::{constant_simple, Constant};
-use crate::utils::{match_def_path, paths, span_lint};
+use crate::utils::{match_def_path, match_trait_method, paths, span_lint};
+use if_chain::if_chain;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
@@ -18,6 +19,10 @@ declare_clippy_lint! {
     /// ```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,
@@ -60,25 +65,43 @@ enum MinMax {
 }
 
 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.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) {
+    match expr.kind {
+        ExprKind::Call(ref path, ref 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(ref path, _, ref 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.as_str() == sym!(max).as_str() {
                         fetch_const(cx, args, MinMax::Max)
+                    } else if path.ident.as_str() == sym!(min).as_str() {
+                        fetch_const(cx, args, MinMax::Min)
                     } else {
                         None
                     }
-                })
-        } else {
-            None
-        }
-    } else {
-        None
+                } else {
+                    None
+                }
+            }
+        },
+        _ => None,
     }
 }
 
diff --git a/tests/ui/min_max.rs b/tests/ui/min_max.rs
@@ -6,6 +6,18 @@ use std::cmp::{max, min};
 
 const LARGE: usize = 3;
 
+struct NotOrd(u64);
+
+impl NotOrd {
+    fn min(self, x: u64) -> NotOrd {
+        NotOrd(x)
+    }
+
+    fn max(self, x: u64) -> NotOrd {
+        NotOrd(x)
+    }
+}
+
 fn main() {
     let x;
     x = 2usize;
@@ -30,4 +42,24 @@ fn main() {
     max(min(s, "Apple"), "Zoo");
 
     max("Apple", min(s, "Zoo")); // ok
+
+    let f = 3f32;
+    x.min(1).max(3);
+    x.max(3).min(1);
+    f.max(3f32).min(1f32);
+
+    x.max(1).min(3); // ok
+    x.min(3).max(1); // ok
+    f.min(3f32).max(1f32); // ok
+
+    max(x.min(1), 3);
+    min(x.max(1), 3); // ok
+
+    s.max("Zoo").min("Apple");
+    s.min("Apple").max("Zoo");
+
+    s.min("Zoo").max("Apple"); // ok
+
+    let not_ord = NotOrd(1);
+    not_ord.min(1).max(3); // ok
 }
diff --git a/tests/ui/min_max.stderr b/tests/ui/min_max.stderr
@@ -1,46 +1,82 @@
 error: this `min`/`max` combination leads to constant result
-  --> $DIR/min_max.rs:12:5
+  --> $DIR/min_max.rs:24:5
    |
 LL |     min(1, max(3, x));
    |     ^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::min-max` implied by `-D warnings`
 
 error: this `min`/`max` combination leads to constant result
-  --> $DIR/min_max.rs:13:5
+  --> $DIR/min_max.rs:25:5
    |
 LL |     min(max(3, x), 1);
    |     ^^^^^^^^^^^^^^^^^
 
 error: this `min`/`max` combination leads to constant result
-  --> $DIR/min_max.rs:14:5
+  --> $DIR/min_max.rs:26:5
    |
 LL |     max(min(x, 1), 3);
    |     ^^^^^^^^^^^^^^^^^
 
 error: this `min`/`max` combination leads to constant result
-  --> $DIR/min_max.rs:15:5
+  --> $DIR/min_max.rs:27:5
    |
 LL |     max(3, min(x, 1));
    |     ^^^^^^^^^^^^^^^^^
 
 error: this `min`/`max` combination leads to constant result
-  --> $DIR/min_max.rs:17:5
+  --> $DIR/min_max.rs:29:5
    |
 LL |     my_max(3, my_min(x, 1));
    |     ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this `min`/`max` combination leads to constant result
-  --> $DIR/min_max.rs:29:5
+  --> $DIR/min_max.rs:41:5
    |
 LL |     min("Apple", max("Zoo", s));
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this `min`/`max` combination leads to constant result
-  --> $DIR/min_max.rs:30:5
+  --> $DIR/min_max.rs:42:5
    |
 LL |     max(min(s, "Apple"), "Zoo");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 7 previous errors
+error: this `min`/`max` combination leads to constant result
+  --> $DIR/min_max.rs:47:5
+   |
+LL |     x.min(1).max(3);
+   |     ^^^^^^^^^^^^^^^
+
+error: this `min`/`max` combination leads to constant result
+  --> $DIR/min_max.rs:48:5
+   |
+LL |     x.max(3).min(1);
+   |     ^^^^^^^^^^^^^^^
+
+error: this `min`/`max` combination leads to constant result
+  --> $DIR/min_max.rs:49:5
+   |
+LL |     f.max(3f32).min(1f32);
+   |     ^^^^^^^^^^^^^^^^^^^^^
+
+error: this `min`/`max` combination leads to constant result
+  --> $DIR/min_max.rs:55:5
+   |
+LL |     max(x.min(1), 3);
+   |     ^^^^^^^^^^^^^^^^
+
+error: this `min`/`max` combination leads to constant result
+  --> $DIR/min_max.rs:58:5
+   |
+LL |     s.max("Zoo").min("Apple");
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: this `min`/`max` combination leads to constant result
+  --> $DIR/min_max.rs:59:5
+   |
+LL |     s.min("Apple").max("Zoo");
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 13 previous errors
 
