From fb20b5152822462de2b5482f590c8f18078ec70b Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <japaricious@gmail.com>
Date: Wed, 12 Apr 2017 10:43:36 -0500
Subject: [PATCH] add `claim_mut`

---
 src/lib.rs               | 13 +++++++++++++
 tests/cfail/claim_mut.rs | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 tests/cfail/claim_mut.rs

diff --git a/src/lib.rs b/src/lib.rs
index dfc5e5226e..7b170fc65b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -83,6 +83,19 @@ where
         unsafe { &*self.data.get() }
     }
 
+    /// Like [Resource.claim](struct.Resource.html#method.claim) but returns a
+    /// `&mut-` reference
+    pub fn claim_mut<'task, PRIORITY>(
+        &'static self,
+        _priority: &'task mut P<PRIORITY>,
+    ) -> &'task mut T
+    where
+        CEILING: Cmp<PRIORITY, Output = Equal>,
+        P<PRIORITY>: Priority,
+    {
+        unsafe { &mut *self.data.get() }
+    }
+
     /// Locks the resource for the duration of the critical section `f`
     ///
     /// For the duration of the critical section, tasks whose priority level is
diff --git a/tests/cfail/claim_mut.rs b/tests/cfail/claim_mut.rs
new file mode 100644
index 0000000000..0d1dffd5aa
--- /dev/null
+++ b/tests/cfail/claim_mut.rs
@@ -0,0 +1,34 @@
+#![feature(const_fn)]
+
+extern crate cortex_m_srp;
+
+use cortex_m_srp::{C2, P2, Resource};
+
+static R1: Resource<i32, C2> = Resource::new(0);
+
+fn j1(mut prio: P2) {
+    // OK only one `&mut-` reference to the data
+    let r1: &mut i32 = R1.claim_mut(&mut prio);
+}
+
+fn j2(prio: P2) {
+    // OK two `&-` references to the same data
+    let r1: &i32 = R1.claim(&prio);
+    let another_r1: &i32 = R1.claim(&prio);
+}
+
+fn j3(mut prio: P2) {
+    // CAN'T have a `&-` reference and a `&mut-` reference to the same data
+    let r1: &i32 = R1.claim(&prio);
+    let another_r1: &mut i32 = R1.claim_mut(&mut prio);
+    //~^ error
+}
+
+fn j4(mut prio: P2) {
+    // CAN'T have two `&mut-` references to the same data
+    let r1: &mut i32 = R1.claim_mut(&mut prio);
+    let another_r1: &mut i32 = R1.claim_mut(&mut prio);
+    //~^ error
+}
+
+fn main() {}