From: Nicholas Nethercote <nnethercote@mozilla.com>
Date: Mon, 23 Mar 2020 00:21:27 +0000 (+1100)
Subject: Add a comment to `parse_bool`.
X-Git-Url: https://git.lizzy.rs/?a=commitdiff_plain;h=8818eace09b05f07afcfe03d838a214e2afa47b4;hp=c55c682e9ba2be16d5de4264d1b626e70f00de9d;p=rust.git

Add a comment to `parse_bool`.

It's behaviour can be surprising.
---

diff --git a/src/librustc_session/options.rs b/src/librustc_session/options.rs
index a1ecf4e8528..9fd7b7e2e9b 100644
--- a/src/librustc_session/options.rs
+++ b/src/librustc_session/options.rs
@@ -299,6 +299,9 @@ pub fn $opt(cg: &mut $struct_name, v: Option<&str>) -> bool {
             }
         )*
 
+        /// Set a flag to true. Note that it cannot set the flag to false, so
+        /// using this parser in combination with a flag that defaults to true
+        /// is useless; the flag will always be true.
         fn parse_bool(slot: &mut bool, v: Option<&str>) -> bool {
             match v {
                 Some(..) => false,