Move value-only methods to `InstallableValue`

These methods would previously fail on the other `Installable`s, so
moving them to this class is more correct as to where they actually
work.

Additionally, a `InstallableValueCommand` is created to make it easier
(or rather no worse than before) to write commands that just work on
`InstallableValue`s.

Besides being a cleanup to avoid failing default methods, this gets us
closer to https://github.com/NixOS/rfcs/pull/134.

1 files changed, 7 insertions, 5 deletions

diff --git a/src/nix/repl.cc b/src/nix/repl.cc
index 51d3074b4..c2d77ad5f 100644
--- a/src/nix/repl.cc
+++ b/src/nix/repl.cc
@@ -1,6 +1,7 @@
 #include "eval.hh"
 #include "globals.hh"
 #include "command.hh"
+#include "installable-value.hh"
 #include "repl.hh"
 
 namespace nix {
@@ -57,11 +58,12 @@ struct CmdRepl : RawInstallablesCommand
         auto getValues = [&]()->AbstractNixRepl::AnnotatedValues{
             auto installables = parseInstallables(store, rawInstallables);
             AbstractNixRepl::AnnotatedValues values;
-            for (auto & installable: installables){
-                auto what = installable->what();
+            for (auto & installable_: installables){
+                auto & installable = InstallableValue::require(*installable_);
+                auto what = installable.what();
                 if (file){
-                    auto [val, pos] = installable->toValue(*state);
-                    auto what = installable->what();
+                    auto [val, pos] = installable.toValue(*state);
+                    auto what = installable.what();
                     state->forceValue(*val, pos);
                     auto autoArgs = getAutoArgs(*state);
                     auto valPost = state->allocValue();
@@ -69,7 +71,7 @@ struct CmdRepl : RawInstallablesCommand
                     state->forceValue(*valPost, pos);
                     values.push_back( {valPost, what });
                 } else {
-                    auto [val, pos] = installable->toValue(*state);
+                    auto [val, pos] = installable.toValue(*state);
                     values.push_back( {val, what} );
                 }
             }