From e7208ae2799e2754c78d67f7f2b2dc0f3814a614 Mon Sep 17 00:00:00 2001
From: Florian Hartwig <florian.j.hartwig@gmail.com>
Date: Sun, 28 Oct 2018 20:30:13 +0100
Subject: [PATCH] Extend neg_multiply lint to *= assignments

---
 clippy_lints/src/neg_multiply.rs | 6 ++++++
 tests/ui/neg_multiply.rs         | 4 +++-
 tests/ui/neg_multiply.stderr     | 8 +++++++-
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/clippy_lints/src/neg_multiply.rs b/clippy_lints/src/neg_multiply.rs
index d3b72372c2f7..14da52fd5eae 100644
--- a/clippy_lints/src/neg_multiply.rs
+++ b/clippy_lints/src/neg_multiply.rs
@@ -53,6 +53,12 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NegMultiply {
                 _ => (),
             }
         }
+
+        if let ExprKind::AssignOp(Spanned {node: BinOpKind::Mul, .. }, _, ref rhs) = e.node {
+            if let ExprKind::Unary(UnNeg, ref lit) = rhs.node {
+                check_mul(cx, e.span, lit, rhs)
+            }
+        }
     }
 }
 
diff --git a/tests/ui/neg_multiply.rs b/tests/ui/neg_multiply.rs
index 446af7bbe948..2b7e7c3cab66 100644
--- a/tests/ui/neg_multiply.rs
+++ b/tests/ui/neg_multiply.rs
@@ -35,12 +35,14 @@ impl Mul<X> for isize {
 }
 
 fn main() {
-    let x = 0;
+    let mut x = 0;
 
     x * -1;
 
     -1 * x;
 
+    x *= -1;
+
     -1 * -1; // should be ok
 
     X * -1; // should be ok
diff --git a/tests/ui/neg_multiply.stderr b/tests/ui/neg_multiply.stderr
index ed96dd519ff6..14b3ee37d3e0 100644
--- a/tests/ui/neg_multiply.stderr
+++ b/tests/ui/neg_multiply.stderr
@@ -12,5 +12,11 @@ error: Negation by multiplying with -1
 42 |     -1 * x;
    |     ^^^^^^
 
-error: aborting due to 2 previous errors
+error: Negation by multiplying with -1
+  --> $DIR/neg_multiply.rs:44:5
+   |
+44 |     x *= -1;
+   |     ^^^^^^^
+
+error: aborting due to 3 previous errors