Extend Rust FFI

Do idiomatic C++ copy and move constructors for a few things, so
wrapping structs' defaults can work.

src/libstore/derivations.hh

@@ -22,6 +22,9 @@ struct DerivationOutput
         , hashAlgo(std::move(hashAlgo))
         , hash(std::move(hash))
     { }
+    DerivationOutput(const DerivationOutput &) = default;
+    DerivationOutput(DerivationOutput &&) = default;
+    DerivationOutput & operator = (const DerivationOutput &) = default;
     void parseHashInfo(bool & recursive, Hash & hash) const;
 };
 

src/libstore/nar-info.cc

@@ -4,7 +4,7 @@
 namespace nix {
 
 NarInfo::NarInfo(const Store & store, const std::string & s, const std::string & whence)
-    : ValidPathInfo(StorePath::dummy.clone()) // FIXME: hack
+    : ValidPathInfo(StorePath::dummy) // FIXME: hack
 {
     auto corrupt = [&]() {
         throw Error(format("NAR info file '%1%' is corrupt") % whence);

src/libstore/path.hh

@@ -13,6 +13,7 @@ extern "C" {
     void ffi_StorePath_drop(void *);
     bool ffi_StorePath_less_than(const StorePath & a, const StorePath & b);
     bool ffi_StorePath_eq(const StorePath & a, const StorePath & b);
+    void ffi_StorePath_clone_to(const StorePath & _other, StorePath & _this);
     unsigned char * ffi_StorePath_hash_data(const StorePath & p);
 }
 
@@ -43,6 +44,19 @@ struct StorePath : rust::Value<3 * sizeof(void *) + 24, ffi_StorePath_drop>
         return !(*this == other);
     }
 
+    StorePath(StorePath && that) = default;
+
+    StorePath(const StorePath & that)
+    {
+        ffi_StorePath_clone_to(that, *this);
+    }
+
+    void operator = (const StorePath & that)
+    {
+        (rust::Value<3 * sizeof(void *) + 24, ffi_StorePath_drop>::operator = (that));
+        ffi_StorePath_clone_to(that, *this);
+    }
+
     StorePath clone() const;
 
     /* Check whether a file name ends with the extension for

src/libstore/store-api.cc

@@ -687,21 +687,6 @@ void copyClosure(ref<Store> srcStore, ref<Store> dstStore,
 }
 
 
-ValidPathInfo::ValidPathInfo(const ValidPathInfo & other)
-    : path(other.path.clone())
-    , deriver(other.deriver ? other.deriver->clone(): std::optional<StorePath>{})
-    , narHash(other.narHash)
-    , references(cloneStorePathSet(other.references))
-    , registrationTime(other.registrationTime)
-    , narSize(other.narSize)
-    , id(other.id)
-    , ultimate(other.ultimate)
-    , sigs(other.sigs)
-    , ca(other.ca)
-{
-}
-
-
 std::optional<ValidPathInfo> decodeValidPathInfo(const Store & store, std::istream & str, bool hashGiven)
 {
     std::string path;

src/libstore/store-api.hh

@@ -189,8 +189,9 @@ struct ValidPathInfo
 
     Strings shortRefs() const;
 
-    ValidPathInfo(StorePath && path) : path(std::move(path)) { }
-    explicit ValidPathInfo(const ValidPathInfo & other);
+    ValidPathInfo(StorePath && path) : path(std::move(path)) { };
+    ValidPathInfo(const StorePath & path) : path(path) { };
+    ValidPathInfo(const ValidPathInfo & other) = default;
 
     virtual ~ValidPathInfo() { }
 };