From 76325ce5cda8b4ea3654b58590cce0aed5f4127f Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Mon, 29 Apr 2019 22:11:14 +0200
Subject: [PATCH] DerivationOutput::parseHashInfo: Return a tuple

---
 src/libstore/build.cc       |  3 +--
 src/libstore/derivations.cc | 12 +++++-------
 src/libstore/derivations.hh |  2 +-
 src/libstore/local-store.cc |  3 +--
 4 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index 53a0c743b..7fa82ae74 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -3106,8 +3106,7 @@ void DerivationGoal::registerOutputs()
            hash). */
         if (fixedOutput) {
 
-            bool recursive; Hash h;
-            i.second.parseHashInfo(recursive, h);
+            auto [recursive, h] = i.second.parseHashInfo();
 
             if (!recursive) {
                 /* The output path should be a regular file without
diff --git a/src/libstore/derivations.cc b/src/libstore/derivations.cc
index 3961126ff..3c5205a87 100644
--- a/src/libstore/derivations.cc
+++ b/src/libstore/derivations.cc
@@ -9,21 +9,19 @@
 namespace nix {
 
 
-void DerivationOutput::parseHashInfo(bool & recursive, Hash & hash) const
+std::pair<bool, Hash> DerivationOutput::parseHashInfo() const
 {
-    recursive = false;
+    bool recursive = false;
     string algo = hashAlgo;
 
-    if (string(algo, 0, 2) == "r:") {
+    if (string(algo, 0, 2) == "r:")
         recursive = true;
-        algo = string(algo, 2);
-    }
 
-    HashType hashType = parseHashType(algo);
+    HashType hashType = parseHashType(recursive ? string(algo, 2) : algo);
     if (hashType == htUnknown)
         throw Error(format("unknown hash algorithm '%1%'") % algo);
 
-    hash = Hash(this->hash, hashType);
+    return {recursive, Hash(this->hash, hashType)};
 }
 
 
diff --git a/src/libstore/derivations.hh b/src/libstore/derivations.hh
index 9753e796d..b21713bad 100644
--- a/src/libstore/derivations.hh
+++ b/src/libstore/derivations.hh
@@ -30,7 +30,7 @@ struct DerivationOutput
         this->hashAlgo = hashAlgo;
         this->hash = hash;
     }
-    void parseHashInfo(bool & recursive, Hash & hash) const;
+    std::pair<bool, Hash> parseHashInfo() const;
 };
 
 typedef std::map<string, DerivationOutput> DerivationOutputs;
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 485fdd691..0bf1831e4 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -548,8 +548,7 @@ void LocalStore::checkDerivationOutputs(const Path & drvPath, const Derivation &
         if (out == drv.outputs.end())
             throw Error(format("derivation '%1%' does not have an output named 'out'") % drvPath);
 
-        bool recursive; Hash h;
-        out->second.parseHashInfo(recursive, h);
+        auto [recursive, h] = out->second.parseHashInfo();
         Path outPath = makeFixedOutputPath(recursive, h, drvName);
 
         StringPairs::const_iterator j = drv.env.find("out");