From c4ada76e860a595e3f034b89f27374ce79513d9f Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sat, 1 Aug 2020 16:22:50 +0000
Subject: [PATCH] Fix error message and avoid recalculation

---
 src/libfetchers/fetchers.cc | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/libfetchers/fetchers.cc b/src/libfetchers/fetchers.cc
index 08b83b0db..9c69fc564 100644
--- a/src/libfetchers/fetchers.cc
+++ b/src/libfetchers/fetchers.cc
@@ -203,8 +203,8 @@ std::optional<Hash> Input::getNarHash() const
     if (auto s = maybeGetStrAttr(attrs, "narHash")) {
         auto hash = s->empty() ? Hash(htSHA256) : Hash::parseSRI(*s);
         if (hash.type != htSHA256)
-            throw UsageError("narHash must be specified with SRI notation");
-        return newHashAllowEmpty(*s, htSHA256);
+            throw UsageError("narHash must use SHA-256");
+        return hash;
     }
     return {};
 }