Added negative test cases and ran cargo dev fmt

4 files changed, 100 insertions, 45 deletions

diff --git a/clippy_lints/src/sort_by_key_reverse.rs b/clippy_lints/src/sort_by_key_reverse.rs
index 31629a1dbc1..ea850955db1 100644
--- a/clippy_lints/src/sort_by_key_reverse.rs
+++ b/clippy_lints/src/sort_by_key_reverse.rs
@@ -3,7 +3,7 @@ use crate::utils::paths;
 use crate::utils::sugg::Sugg;
 use if_chain::if_chain;
 use rustc_errors::Applicability;
-use rustc_hir::*;
+use rustc_hir::{Expr, ExprKind, Mutability, Param, Pat, PatKind, Path, QPath};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::symbol::Ident;
@@ -43,64 +43,105 @@ struct LintTrigger {
 
 /// Detect if the two expressions are mirrored (identical, except one
 /// contains a and the other replaces it with b)
-fn mirrored_exprs(cx: &LateContext<'_, '_>, a_expr: &Expr<'_>, a_ident: &Ident, b_expr: &Expr<'_>, b_ident: &Ident) -> bool {
+fn mirrored_exprs(
+    cx: &LateContext<'_, '_>,
+    a_expr: &Expr<'_>,
+    a_ident: &Ident,
+    b_expr: &Expr<'_>,
+    b_ident: &Ident,
+) -> bool {
     match (&a_expr.kind, &b_expr.kind) {
         // Two boxes with mirrored contents
-        (ExprKind::Box(left_expr), ExprKind::Box(right_expr)) => mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident),
+        (ExprKind::Box(left_expr), ExprKind::Box(right_expr)) => {
+            mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
+        },
         // Two arrays with mirrored contents
-        (ExprKind::Array(left_exprs), ExprKind::Array(right_exprs))
-            => left_exprs.iter().zip(right_exprs.iter()).all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)),
+        (ExprKind::Array(left_exprs), ExprKind::Array(right_exprs)) => left_exprs
+            .iter()
+            .zip(right_exprs.iter())
+            .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)),
         // The two exprs are function calls.
         // Check to see that the function itself and its arguments are mirrored
-        (ExprKind::Call(left_expr, left_args), ExprKind::Call(right_expr, right_args))
-            => {
-                // println!("{:?}\n{:?}\n", left_expr, left_args);
-                // println!("{:?}\n{:?}\n", right_expr, right_args);
-                mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
-                && left_args.iter().zip(right_args.iter()).all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
-            },
+        (ExprKind::Call(left_expr, left_args), ExprKind::Call(right_expr, right_args)) => {
+            mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
+                && left_args
+                    .iter()
+                    .zip(right_args.iter())
+                    .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
+        },
         // The two exprs are method calls.
         // Check to see that the function is the same and the arguments are mirrored
         // This is enough because the receiver of the method is listed in the arguments
-        (ExprKind::MethodCall(left_segment, _, left_args), ExprKind::MethodCall(right_segment, _, right_args))
-            => left_segment.ident == right_segment.ident
-                && left_args.iter().zip(right_args.iter()).all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)),
+        (ExprKind::MethodCall(left_segment, _, left_args), ExprKind::MethodCall(right_segment, _, right_args)) => {
+            left_segment.ident == right_segment.ident
+                && left_args
+                    .iter()
+                    .zip(right_args.iter())
+                    .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
+        },
         // Two tuples with mirrored contents
-        (ExprKind::Tup(left_exprs), ExprKind::Tup(right_exprs))
-            => left_exprs.iter().zip(right_exprs.iter()).all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)),
+        (ExprKind::Tup(left_exprs), ExprKind::Tup(right_exprs)) => left_exprs
+            .iter()
+            .zip(right_exprs.iter())
+            .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)),
         // Two binary ops, which are the same operation and which have mirrored arguments
-        (ExprKind::Binary(left_op, left_left, left_right), ExprKind::Binary(right_op, right_left, right_right))
-            => left_op.node == right_op.node
+        (ExprKind::Binary(left_op, left_left, left_right), ExprKind::Binary(right_op, right_left, right_right)) => {
+            left_op.node == right_op.node
                 && mirrored_exprs(cx, left_left, a_ident, right_left, b_ident)
-                && mirrored_exprs(cx, left_right, a_ident, right_right, b_ident),
+                && mirrored_exprs(cx, left_right, a_ident, right_right, b_ident)
+        },
         // Two unary ops, which are the same operation and which have the same argument
-        (ExprKind::Unary(left_op, left_expr), ExprKind::Unary(right_op, right_expr))
-            => left_op == right_op && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident),
+        (ExprKind::Unary(left_op, left_expr), ExprKind::Unary(right_op, right_expr)) => {
+            left_op == right_op && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
+        },
         // The two exprs are literals of some kind
         (ExprKind::Lit(left_lit), ExprKind::Lit(right_lit)) => left_lit.node == right_lit.node,
-        (ExprKind::Cast(left_expr, left_ty), ExprKind::Cast(right_expr, right_ty))
-            => mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident),
-        (ExprKind::DropTemps(left), ExprKind::DropTemps(right)) => mirrored_exprs(cx, left, a_ident, right, b_ident),
-        (ExprKind::Field(left_expr, left_ident), ExprKind::Field(right_expr, right_ident))
-            => left_ident.name == right_ident.name && mirrored_exprs(cx, left_expr, a_ident, right_expr, right_ident),
+        (ExprKind::Cast(left, _), ExprKind::Cast(right, _)) => mirrored_exprs(cx, left, a_ident, right, b_ident),
+        (ExprKind::DropTemps(left_block), ExprKind::DropTemps(right_block)) => {
+            mirrored_exprs(cx, left_block, a_ident, right_block, b_ident)
+        },
+        (ExprKind::Field(left_expr, left_ident), ExprKind::Field(right_expr, right_ident)) => {
+            left_ident.name == right_ident.name && mirrored_exprs(cx, left_expr, a_ident, right_expr, right_ident)
+        },
         // Two paths: either one is a and the other is b, or they're identical to each other
-        (ExprKind::Path(QPath::Resolved(_, Path { segments: left_segments, .. })),
-         ExprKind::Path(QPath::Resolved(_, Path { segments: right_segments, .. })))
-            => (left_segments.iter().zip(right_segments.iter()).all(|(left, right)| left.ident == right.ident)
-                 && left_segments.iter().all(|seg| &seg.ident != a_ident && &seg.ident != b_ident))
-                || (left_segments.len() == 1 && &left_segments[0].ident == a_ident && right_segments.len() == 1 && &right_segments[0].ident == b_ident),
+        (
+            ExprKind::Path(QPath::Resolved(
+                _,
+                Path {
+                    segments: left_segments,
+                    ..
+                },
+            )),
+            ExprKind::Path(QPath::Resolved(
+                _,
+                Path {
+                    segments: right_segments,
+                    ..
+                },
+            )),
+        ) => {
+            (left_segments
+                .iter()
+                .zip(right_segments.iter())
+                .all(|(left, right)| left.ident == right.ident)
+                && left_segments
+                    .iter()
+                    .all(|seg| &seg.ident != a_ident && &seg.ident != b_ident))
+                || (left_segments.len() == 1
+                    && &left_segments[0].ident == a_ident
+                    && right_segments.len() == 1
+                    && &right_segments[0].ident == b_ident)
+        },
         // Matching expressions, but one or both is borrowed
-        (ExprKind::AddrOf(left_kind, Mutability::Not, left_expr), ExprKind::AddrOf(right_kind, Mutability::Not, right_expr))
-            => left_kind == right_kind && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident),
-        (_, ExprKind::AddrOf(_, Mutability::Not, right_expr))
-            => mirrored_exprs(cx, a_expr, a_ident, right_expr, b_ident),
-        (ExprKind::AddrOf(_, Mutability::Not, left_expr), _)
-            => mirrored_exprs(cx, left_expr, a_ident, b_expr, b_ident),
+        (
+            ExprKind::AddrOf(left_kind, Mutability::Not, left_expr),
+            ExprKind::AddrOf(right_kind, Mutability::Not, right_expr),
+        ) => left_kind == right_kind && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident),
+        (_, ExprKind::AddrOf(_, Mutability::Not, right_expr)) => {
+            mirrored_exprs(cx, a_expr, a_ident, right_expr, b_ident)
+        },
+        (ExprKind::AddrOf(_, Mutability::Not, left_expr), _) => mirrored_exprs(cx, left_expr, a_ident, b_expr, b_ident),
         _ => false,
-        // (left, right) => {
-            // println!("{:?}\n{:?}", left, right);
-            // false
-        // },
     }
 }
 
diff --git a/tests/ui/sort_by_key_reverse.fixed b/tests/ui/sort_by_key_reverse.fixed
index d536dc385d5..722675a6b71 100644
--- a/tests/ui/sort_by_key_reverse.fixed
+++ b/tests/ui/sort_by_key_reverse.fixed
@@ -12,4 +12,11 @@ fn main() {
     vec.sort_by_key(|&b| Reverse(b));
     vec.sort_by_key(|&b| Reverse((b + 5).abs()));
     vec.sort_by_key(|&b| Reverse(id(-b)));
+    // Negative examples (shouldn't be changed)
+    let c = &7;
+    vec.sort_by(|a, b| (b - a).cmp(&(a - b)));
+    vec.sort_by(|_, b| b.cmp(&5));
+    vec.sort_by(|_, b| b.cmp(c));
+    vec.sort_by(|a, _| a.cmp(c));
+    vec.sort_by(|a, b| a.cmp(b));
 }
diff --git a/tests/ui/sort_by_key_reverse.rs b/tests/ui/sort_by_key_reverse.rs
index 9c42d401755..601621ffa9f 100644
--- a/tests/ui/sort_by_key_reverse.rs
+++ b/tests/ui/sort_by_key_reverse.rs
@@ -10,6 +10,13 @@ fn id(x: isize) -> isize {
 fn main() {
     let mut vec: Vec<isize> = vec![3, 6, 1, 2, 5];
     vec.sort_by(|a, b| b.cmp(a));
-    vec.sort_by(|a, b| (b + 5).abs().cmp(&(a+5).abs()));
+    vec.sort_by(|a, b| (b + 5).abs().cmp(&(a + 5).abs()));
     vec.sort_by(|a, b| id(-b).cmp(&id(-a)));
+    // Negative examples (shouldn't be changed)
+    let c = &7;
+    vec.sort_by(|a, b| (b - a).cmp(&(a - b)));
+    vec.sort_by(|_, b| b.cmp(&5));
+    vec.sort_by(|_, b| b.cmp(c));
+    vec.sort_by(|a, _| a.cmp(c));
+    vec.sort_by(|a, b| a.cmp(b));
 }
diff --git a/tests/ui/sort_by_key_reverse.stderr b/tests/ui/sort_by_key_reverse.stderr
index 3d26ddae78a..b757c8a6176 100644
--- a/tests/ui/sort_by_key_reverse.stderr
+++ b/tests/ui/sort_by_key_reverse.stderr
@@ -9,8 +9,8 @@ LL |     vec.sort_by(|a, b| b.cmp(a));
 error: use Vec::sort_by_key here instead
   --> $DIR/sort_by_key_reverse.rs:13:5
    |
-LL |     vec.sort_by(|a, b| (b + 5).abs().cmp(&(a+5).abs()));
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec.sort_by_key(|&b| Reverse((b + 5).abs()))`
+LL |     vec.sort_by(|a, b| (b + 5).abs().cmp(&(a + 5).abs()));
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `vec.sort_by_key(|&b| Reverse((b + 5).abs()))`
 
 error: use Vec::sort_by_key here instead
   --> $DIR/sort_by_key_reverse.rs:14:5