4 files changed, 10 insertions, 10 deletions

diff --git a/src/nix/build.cc b/src/nix/build.cc
index ce6df7df8..6e31757a2 100644
--- a/src/nix/build.cc
+++ b/src/nix/build.cc
@@ -66,12 +66,12 @@ struct CmdBuild : InstallablesCommand, MixDryRun, MixJSON, MixProfile
                 for (const auto & [_i, buildable] : enumerate(buildables)) {
                     auto i = _i;
                     std::visit(overloaded {
-                        [&](BuiltPath::Opaque bo) {
+                        [&](const BuiltPath::Opaque & bo) {
                             std::string symlink = outLink;
                             if (i) symlink += fmt("-%d", i);
                             store2->addPermRoot(bo.path, absPath(symlink));
                         },
-                        [&](BuiltPath::Built bfd) {
+                        [&](const BuiltPath::Built & bfd) {
                             for (auto & output : bfd.outputs) {
                                 std::string symlink = outLink;
                                 if (i) symlink += fmt("-%d", i);
diff --git a/src/nix/log.cc b/src/nix/log.cc
index 962c47525..fd3c1d787 100644
--- a/src/nix/log.cc
+++ b/src/nix/log.cc
@@ -35,10 +35,10 @@ struct CmdLog : InstallableCommand
         RunPager pager;
         for (auto & sub : subs) {
             auto log = std::visit(overloaded {
-                [&](DerivedPath::Opaque bo) {
+                [&](const DerivedPath::Opaque & bo) {
                     return sub->getBuildLog(bo.path);
                 },
-                [&](DerivedPath::Built bfd) {
+                [&](const DerivedPath::Built & bfd) {
                     return sub->getBuildLog(bfd.drvPath);
                 },
             }, b.raw());
diff --git a/src/nix/profile.cc b/src/nix/profile.cc
index bd5042d8f..916966997 100644
--- a/src/nix/profile.cc
+++ b/src/nix/profile.cc
@@ -269,11 +269,11 @@ struct CmdProfileInstall : InstallablesCommand, MixDefaultProfile
                     ProfileElement element;
 
                     std::visit(overloaded {
-                        [&](BuiltPath::Opaque bo) {
+                        [&](const BuiltPath::Opaque & bo) {
                             pathsToBuild.push_back(bo);
                             element.storePaths.insert(bo.path);
                         },
-                        [&](BuiltPath::Built bfd) {
+                        [&](const BuiltPath::Built & bfd) {
                             // TODO: Why are we querying if we know the output
                             // names already? Is it just to figure out what the
                             // default one is?
diff --git a/src/nix/show-derivation.cc b/src/nix/show-derivation.cc
index 2588a011d..c614be68d 100644
--- a/src/nix/show-derivation.cc
+++ b/src/nix/show-derivation.cc
@@ -65,18 +65,18 @@ struct CmdShowDerivation : InstallablesCommand
                     auto & outputName = _outputName; // work around clang bug
                     auto outputObj { outputsObj.object(outputName) };
                     std::visit(overloaded {
-                        [&](DerivationOutputInputAddressed doi) {
+                        [&](const DerivationOutputInputAddressed & doi) {
                             outputObj.attr("path", store->printStorePath(doi.path));
                         },
-                        [&](DerivationOutputCAFixed dof) {
+                        [&](const DerivationOutputCAFixed & dof) {
                             outputObj.attr("path", store->printStorePath(dof.path(*store, drv.name, outputName)));
                             outputObj.attr("hashAlgo", dof.hash.printMethodAlgo());
                             outputObj.attr("hash", dof.hash.hash.to_string(Base16, false));
                         },
-                        [&](DerivationOutputCAFloating dof) {
+                        [&](const DerivationOutputCAFloating & dof) {
                             outputObj.attr("hashAlgo", makeFileIngestionPrefix(dof.method) + printHashType(dof.hashType));
                         },
-                        [&](DerivationOutputDeferred) {},
+                        [&](const DerivationOutputDeferred &) {},
                     }, output.output);
                 }
             }