Fixing #7479

Types converted:

- `NixStringContextElem`
- `OutputsSpec`
- `ExtendedOutputsSpec`
- `DerivationOutput`
- `DerivationType`

Existing ones mostly conforming the pattern cleaned up:

- `ContentAddressMethod`
- `ContentAddressWithReferences`

The `DerivationGoal::derivationType` field had a bogus initialization,
now caught, so I made it `std::optional`. I think #8829 can make it
non-optional again because it will ensure we always have the derivation
when we construct a `DerivationGoal`.

See that issue (#7479) for details on the general goal.

`git grep 'Raw::Raw'` indicates the two types I didn't yet convert
`DerivedPath` and `BuiltPath` (and their `Single` variants) . This is
because @roberth and I (can't find issue right now...) plan on reworking
them somewhat, so I didn't want to churn them more just yet.

Co-authored-by: Eelco Dolstra <edolstra@gmail.com>

8 files changed, 59 insertions, 71 deletions

diff --git a/src/libexpr/eval-cache.cc b/src/libexpr/eval-cache.cc
index 6a60ba87b..2c9aa5532 100644
--- a/src/libexpr/eval-cache.cc
+++ b/src/libexpr/eval-cache.cc
@@ -604,7 +604,7 @@ string_t AttrCursor::getStringWithContext()
                         [&](const NixStringContextElem::Opaque & o) -> const StorePath & {
                             return o.path;
                         },
-                    }, c.raw());
+                    }, c.raw);
                     if (!root->state.store->isValidPath(path)) {
                         valid = false;
                         break;
diff --git a/src/libexpr/eval.cc b/src/libexpr/eval.cc
index 79e2c4727..7e839dbe7 100644
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@@ -2364,7 +2364,7 @@ std::pair<SingleDerivedPath, std::string_view> EvalState::coerceToSingleDerivedP
         [&](NixStringContextElem::Built && b) -> SingleDerivedPath {
             return std::move(b);
         },
-    }, ((NixStringContextElem &&) *context.begin()).raw());
+    }, ((NixStringContextElem &&) *context.begin()).raw);
     return {
         std::move(derivedPath),
         std::move(s),
diff --git a/src/libexpr/flake/flakeref.cc b/src/libexpr/flake/flakeref.cc
index d3fa1d557..e1bce90bc 100644
--- a/src/libexpr/flake/flakeref.cc
+++ b/src/libexpr/flake/flakeref.cc
@@ -246,7 +246,7 @@ std::tuple<FlakeRef, std::string, ExtendedOutputsSpec> parseFlakeRefWithFragment
 {
     auto [prefix, extendedOutputsSpec] = ExtendedOutputsSpec::parse(url);
     auto [flakeRef, fragment] = parseFlakeRefWithFragment(std::string { prefix }, baseDir, allowMissing, isFlake);
-    return {std::move(flakeRef), fragment, extendedOutputsSpec};
+    return {std::move(flakeRef), fragment, std::move(extendedOutputsSpec)};
 }
 
 }
diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc
index 283f99a48..5067da449 100644
--- a/src/libexpr/primops.cc
+++ b/src/libexpr/primops.cc
@@ -69,7 +69,7 @@ StringMap EvalState::realiseContext(const NixStringContext & context)
                 res.insert_or_assign(ctxS, ctxS);
                 ensureValid(d.drvPath);
             },
-        }, c.raw());
+        }, c.raw);
     }
 
     if (drvs.empty()) return {};
@@ -1265,7 +1265,7 @@ drvName, Bindings * attrs, Value & v)
             [&](const NixStringContextElem::Opaque & o) {
                 drv.inputSrcs.insert(o.path);
             },
-        }, c.raw());
+        }, c.raw);
     }
 
     /* Do we have all required attributes? */
@@ -1334,13 +1334,13 @@ drvName, Bindings * attrs, Value & v)
             if (isImpure)
                 drv.outputs.insert_or_assign(i,
                     DerivationOutput::Impure {
-                        .method = method.raw,
+                        .method = method,
                         .hashType = ht,
                     });
             else
                 drv.outputs.insert_or_assign(i,
                     DerivationOutput::CAFloating {
-                        .method = method.raw,
+                        .method = method,
                         .hashType = ht,
                     });
         }
@@ -1373,7 +1373,7 @@ drvName, Bindings * attrs, Value & v)
                 drv.env[i] = state.store->printStorePath(outPath);
                 drv.outputs.insert_or_assign(
                     i,
-                    DerivationOutputInputAddressed {
+                    DerivationOutput::InputAddressed {
                         .path = std::move(outPath),
                     });
             }
@@ -1381,7 +1381,7 @@ drvName, Bindings * attrs, Value & v)
             ;
         case DrvHash::Kind::Deferred:
             for (auto & i : outputs) {
-                drv.outputs.insert_or_assign(i, DerivationOutputDeferred {});
+                drv.outputs.insert_or_assign(i, DerivationOutput::Deferred {});
             }
         }
     }
@@ -2054,7 +2054,7 @@ static void prim_toFile(EvalState & state, const PosIdx pos, Value * * args, Val
     StorePathSet refs;
 
     for (auto c : context) {
-        if (auto p = std::get_if<NixStringContextElem::Opaque>(&c))
+        if (auto p = std::get_if<NixStringContextElem::Opaque>(&c.raw))
             refs.insert(p->path);
         else
             state.debugThrowLastTrace(EvalError({
diff --git a/src/libexpr/primops/context.cc b/src/libexpr/primops/context.cc
index bfc731744..e8542503a 100644
--- a/src/libexpr/primops/context.cc
+++ b/src/libexpr/primops/context.cc
@@ -51,13 +51,13 @@ static void prim_unsafeDiscardOutputDependency(EvalState & state, const PosIdx p
 
     NixStringContext context2;
     for (auto && c : context) {
-        if (auto * ptr = std::get_if<NixStringContextElem::DrvDeep>(&c)) {
+        if (auto * ptr = std::get_if<NixStringContextElem::DrvDeep>(&c.raw)) {
             context2.emplace(NixStringContextElem::Opaque {
                 .path = ptr->drvPath
             });
         } else {
             /* Can reuse original item */
-            context2.emplace(std::move(c));
+            context2.emplace(std::move(c).raw);
         }
     }
 
@@ -114,7 +114,7 @@ static void prim_getContext(EvalState & state, const PosIdx pos, Value * * args,
             [&](NixStringContextElem::Opaque && o) {
                 contextInfos[std::move(o.path)].path = true;
             },
-        }, ((NixStringContextElem &&) i).raw());
+        }, ((NixStringContextElem &&) i).raw);
     }
 
     auto attrs = state.buildBindings(contextInfos.size());
diff --git a/src/libexpr/tests/value/context.cc b/src/libexpr/tests/value/context.cc
index c56b50b59..19407d071 100644
--- a/src/libexpr/tests/value/context.cc
+++ b/src/libexpr/tests/value/context.cc
@@ -47,7 +47,7 @@ TEST(NixStringContextElemTest, slash_invalid) {
 TEST(NixStringContextElemTest, opaque) {
     std::string_view opaque = "g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x";
     auto elem = NixStringContextElem::parse(opaque);
-    auto * p = std::get_if<NixStringContextElem::Opaque>(&elem);
+    auto * p = std::get_if<NixStringContextElem::Opaque>(&elem.raw);
     ASSERT_TRUE(p);
     ASSERT_EQ(p->path, StorePath { opaque });
     ASSERT_EQ(elem.to_string(), opaque);
@@ -60,7 +60,7 @@ TEST(NixStringContextElemTest, opaque) {
 TEST(NixStringContextElemTest, drvDeep) {
     std::string_view drvDeep = "=g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x.drv";
     auto elem = NixStringContextElem::parse(drvDeep);
-    auto * p = std::get_if<NixStringContextElem::DrvDeep>(&elem);
+    auto * p = std::get_if<NixStringContextElem::DrvDeep>(&elem.raw);
     ASSERT_TRUE(p);
     ASSERT_EQ(p->drvPath, StorePath { drvDeep.substr(1) });
     ASSERT_EQ(elem.to_string(), drvDeep);
@@ -73,7 +73,7 @@ TEST(NixStringContextElemTest, drvDeep) {
 TEST(NixStringContextElemTest, built_opaque) {
     std::string_view built = "!foo!g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x.drv";
     auto elem = NixStringContextElem::parse(built);
-    auto * p = std::get_if<NixStringContextElem::Built>(&elem);
+    auto * p = std::get_if<NixStringContextElem::Built>(&elem.raw);
     ASSERT_TRUE(p);
     ASSERT_EQ(p->output, "foo");
     ASSERT_EQ(*p->drvPath, ((SingleDerivedPath) SingleDerivedPath::Opaque {
@@ -96,7 +96,7 @@ TEST(NixStringContextElemTest, built_built) {
 
     std::string_view built = "!foo!bar!g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x.drv";
     auto elem = NixStringContextElem::parse(built, mockXpSettings);
-    auto * p = std::get_if<NixStringContextElem::Built>(&elem);
+    auto * p = std::get_if<NixStringContextElem::Built>(&elem.raw);
     ASSERT_TRUE(p);
     ASSERT_EQ(p->output, "foo");
     auto * drvPath = std::get_if<SingleDerivedPath::Built>(&*p->drvPath);
diff --git a/src/libexpr/value/context.cc b/src/libexpr/value/context.cc
index d8116011e..22361d8fa 100644
--- a/src/libexpr/value/context.cc
+++ b/src/libexpr/value/context.cc
@@ -99,7 +99,7 @@ std::string NixStringContextElem::to_string() const
             res += '=';
             res += d.drvPath.to_string();
         },
-    }, raw());
+    }, raw);
 
     return res;
 }
diff --git a/src/libexpr/value/context.hh b/src/libexpr/value/context.hh
index a1b71695b..9f1d59317 100644
--- a/src/libexpr/value/context.hh
+++ b/src/libexpr/value/context.hh
@@ -4,8 +4,7 @@
 #include "util.hh"
 #include "comparator.hh"
 #include "derived-path.hh"
-
-#include <variant>
+#include "variant-wrapper.hh"
 
 #include <nlohmann/json_fwd.hpp>
 
@@ -26,58 +25,47 @@ public:
     }
 };
 
-/**
- * Plain opaque path to some store object.
- *
- * Encoded as just the path: ‘<path>’.
- */
-typedef SingleDerivedPath::Opaque NixStringContextElem_Opaque;
-
-/**
- * Path to a derivation and its entire build closure.
- *
- * The path doesn't just refer to derivation itself and its closure, but
- * also all outputs of all derivations in that closure (including the
- * root derivation).
- *
- * Encoded in the form ‘=<drvPath>’.
- */
-struct NixStringContextElem_DrvDeep {
-    StorePath drvPath;
-
-    GENERATE_CMP(NixStringContextElem_DrvDeep, me->drvPath);
-};
+struct NixStringContextElem {
+    /**
+     * Plain opaque path to some store object.
+     *
+     * Encoded as just the path: ‘<path>’.
+     */
+    using Opaque = SingleDerivedPath::Opaque;
 
-/**
- * Derivation output.
- *
- * Encoded in the form ‘!<output>!<drvPath>’.
- */
-typedef SingleDerivedPath::Built NixStringContextElem_Built;
-
-using _NixStringContextElem_Raw = std::variant<
-    NixStringContextElem_Opaque,
-    NixStringContextElem_DrvDeep,
-    NixStringContextElem_Built
->;
-
-struct NixStringContextElem : _NixStringContextElem_Raw {
-    using Raw = _NixStringContextElem_Raw;
-    using Raw::Raw;
-
-    using Opaque = NixStringContextElem_Opaque;
-    using DrvDeep = NixStringContextElem_DrvDeep;
-    using Built = NixStringContextElem_Built;
-
-    inline const Raw & raw() const & {
-        return static_cast<const Raw &>(*this);
-    }
-    inline Raw & raw() & {
-        return static_cast<Raw &>(*this);
-    }
-    inline Raw && raw() && {
-        return static_cast<Raw &&>(*this);
-    }
+    /**
+     * Path to a derivation and its entire build closure.
+     *
+     * The path doesn't just refer to derivation itself and its closure, but
+     * also all outputs of all derivations in that closure (including the
+     * root derivation).
+     *
+     * Encoded in the form ‘=<drvPath>’.
+     */
+    struct DrvDeep {
+        StorePath drvPath;
+
+        GENERATE_CMP(DrvDeep, me->drvPath);
+    };
+
+    /**
+     * Derivation output.
+     *
+     * Encoded in the form ‘!<output>!<drvPath>’.
+     */
+    using Built = SingleDerivedPath::Built;
+
+    using Raw = std::variant<
+        Opaque,
+        DrvDeep,
+        Built
+    >;
+
+    Raw raw;
+
+    GENERATE_CMP(NixStringContextElem, me->raw);
+
+    MAKE_WRAPPER_CONSTRUCTOR(NixStringContextElem);
 
     /**
      * Decode a context string, one of: