From 5f6ccf61218fb98c2aa2cff0af83557d7ccaa5fd Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Tue, 23 Nov 2021 20:30:26 -0500
Subject: [PATCH] document BinOp behavior quirks in the corresponding enum

---
 compiler/rustc_middle/src/mir/mod.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 253ac266bed..4210e07d278 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -2246,8 +2246,12 @@ pub enum BinOp {
     /// The `*` operator (multiplication)
     Mul,
     /// The `/` operator (division)
+    ///
+    /// Division by zero is UB.
     Div,
     /// The `%` operator (modulus)
+    ///
+    /// Using zero as the modulus (second operand) is UB.
     Rem,
     /// The `^` operator (bitwise xor)
     BitXor,
@@ -2256,8 +2260,12 @@ pub enum BinOp {
     /// The `|` operator (bitwise or)
     BitOr,
     /// The `<<` operator (shift left)
+    ///
+    /// The offset is truncated to the size of the first operand before shifting.
     Shl,
     /// The `>>` operator (shift right)
+    ///
+    /// The offset is truncated to the size of the first operand before shifting.
     Shr,
     /// The `==` operator (equality)
     Eq,