From 55aefbd1371ec499fc43ca66a33ba7dd37ee714c Mon Sep 17 00:00:00 2001
From: Squirrel <gilescope@gmail.com>
Date: Tue, 10 Aug 2021 17:25:38 +0100
Subject: [PATCH] Use entry api to remove a lookup in deserialisation loop
 (#438)

* Use entry api to remove a lookup in a loop

* cargo fmt
---
 src/value.rs | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/value.rs b/src/value.rs
index 38dfe1f..9396856 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -15,7 +15,7 @@ use serde::ser;
 use crate::datetime::{self, DatetimeFromString};
 pub use crate::datetime::{Datetime, DatetimeParseError};
 
-pub use crate::map::Map;
+pub use crate::map::{Entry, Map};
 
 /// Representation of a TOML value.
 #[derive(PartialEq, Clone, Debug)]
@@ -526,12 +526,13 @@ impl<'de> de::Deserialize<'de> for Value {
                 }
                 let mut map = Map::new();
                 map.insert(key, visitor.next_value()?);
-                while let Some(key) = visitor.next_key()? {
-                    if map.contains_key(&key) {
+                while let Some(key) = visitor.next_key::<String>()? {
+                    if let Entry::Vacant(vacant) = map.entry(&key) {
+                        vacant.insert(visitor.next_value()?);
+                    } else {
                         let msg = format!("duplicate key: `{}`", key);
                         return Err(de::Error::custom(msg));
                     }
-                    map.insert(key, visitor.next_value()?);
                 }
                 Ok(Value::Table(map))
             }