From 222a45f07a7aa2d4ace50bb508935bc225e1d142 Mon Sep 17 00:00:00 2001
From: ridiculousfish <corydoras@ridiculousfish.com>
Date: Sun, 1 Apr 2018 16:10:59 -0700
Subject: [PATCH] Add acquire() to maybe_t

Easy way to pull the value out.
---
 src/fish_tests.cpp | 6 ++++++
 src/maybe.h        | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/src/fish_tests.cpp b/src/fish_tests.cpp
index d748e6e27..340d78b74 100644
--- a/src/fish_tests.cpp
+++ b/src/fish_tests.cpp
@@ -4491,6 +4491,12 @@ void test_maybe() {
     do_test(m4 && *m4 == "hi");
     maybe_t<std::string> m5 = m0;
     do_test(!m5);
+
+    maybe_t<std::string> acquire_test("def");
+    do_test(acquire_test);
+    std::string res = acquire_test.acquire();
+    do_test(!acquire_test);
+    do_test(res == "def");
 }
 
 void test_layout_cache() {
diff --git a/src/maybe.h b/src/maybe.h
index 898731f9d..9e8301ed5 100644
--- a/src/maybe.h
+++ b/src/maybe.h
@@ -64,6 +64,14 @@ class maybe_t {
         return *reinterpret_cast<const T *>(storage);
     }
 
+    // Transfer the value to the caller.
+    T acquire() {
+        assert(filled && "maybe_t does not have a value");
+        T res = std::move(value());
+        reset();
+        return res;
+    }
+
     // Clear the value.
     void reset() {
         if (filled) {