libexpr: Replace Value::mkNull with Value::VNULL

A small step towards fixing #744

Change-Id: If8304d4de20bae07b33eb7825f781e0f6a6a6964

lix/libexpr/eval.cc

@@ -862,7 +862,7 @@ void EvalState::mkPos(Value & v, PosIdx p)
         std::tie(line, col) = makePositionThunks(*this, p);
         v = {NewValueAs::attrs, attrs};
     } else
-        v.mkNull();
+        v = Value::VNULL;
 }
 
 Value EvalPaths::mkStorePathString(const StorePath & p)

lix/libexpr/json-to-value.cc

@@ -94,7 +94,7 @@ public:
 
     bool null() override
     {
-        rs->value().mkNull();
+        rs->value() = Value::VNULL;
         rs->add();
         return true;
     }

lix/libexpr/primops.cc

@@ -1899,7 +1899,7 @@ static void prim_unsafeGetAttrPos(EvalState & state, Value * * args, Value & v)
     state.forceAttrs(*args[1], noPos, "while evaluating the second argument passed to builtins.unsafeGetAttrPos");
     auto i = args[1]->attrs()->get(state.ctx.symbols.create(attr));
     if (!i) {
-        v.mkNull();
+        v = Value::VNULL;
     } else {
         state.mkPos(v, i->pos);
     }
@@ -2853,7 +2853,7 @@ void prim_match(EvalState & state, Value * * args, Value & v)
 
         std::cmatch match;
         if (!std::regex_match(str.begin(), str.end(), match, regex)) {
-            v.mkNull();
+            v = Value::VNULL;
             return;
         }
 
@@ -2863,7 +2863,7 @@ void prim_match(EvalState & state, Value * * args, Value & v)
         v = {NewValueAs::list, result};
         for (size_t i = 0; i < len; ++i) {
             if (!match[i+1].matched)
-                result->elems[i].mkNull();
+                result->elems[i] = Value::VNULL;
             else
                 result->elems[i] = {NewValueAs::string, match[i + 1].str()};
         }
@@ -2916,7 +2916,7 @@ void prim_split(EvalState & state, Value * * args, Value & v)
             elem = {NewValueAs::list, content};
             for (size_t si = 0; si < slen; ++si) {
                 if (!match[si + 1].matched)
-                    content->elems[si].mkNull();
+                    content->elems[si] = Value::VNULL;
                 else
                     content->elems[si] = {NewValueAs::string, match[si + 1].str()};
             }

lix/libexpr/primops/fromTOML.cc

@@ -57,7 +57,7 @@ void prim_fromTOML(EvalState & state, Value ** args, Value & val)
             throw std::runtime_error("Dates and times are not supported");
             break;
         case toml::value_t::empty:
-            v.mkNull();
+            v = Value::VNULL;
             break;
         }
     };

lix/libexpr/value.hh

@@ -766,11 +766,6 @@ public:
      */
     inline ValueType type(bool invalidIsThunk = false) const;
 
-    inline void mkNull()
-    {
-        *this = {NewValueAs::null};
-    }
-
     bool isList() const
     {
         return internalType() == tList;

tests/functional/plugins/plugintest.cc

@@ -29,7 +29,7 @@ static void prim_anotherNull (EvalState & state, Value ** args, Value & v)
 {
     assert(entryCalled);
     if (mySettings.settingSet)
-        v.mkNull();
+        v = Value::VNULL;
     else
         v = {NewValueAs::boolean, false};
 }

tests/unit/libexpr/json.cc

@@ -15,8 +15,7 @@ namespace nix {
     };
 
     TEST_F(JSONValueTest, null) {
-        Value v;
-        v.mkNull();
+        Value v = Value::VNULL;
         ASSERT_EQ(getJSONValue(v), "null");
     }
 

tests/unit/libexpr/value/print.cc

@@ -48,8 +48,7 @@ TEST_F(ValuePrintingTests, tPath)
 
 TEST_F(ValuePrintingTests, tNull)
 {
-    Value vNull;
-    vNull.mkNull();
+    Value vNull = Value::VNULL;
     test(vNull, "null");
 }
 
@@ -95,7 +94,7 @@ TEST_F(ValuePrintingTests, vThunk)
 TEST_F(ValuePrintingTests, vApp)
 {
     EvalMemory mem;
-    Value vFn{NewValueAs::null};
+    Value vFn = Value::VNULL;
     Value vApp{NewValueAs::app, mem, vFn, vFn};
 
     test(vApp, "«thunk»");
@@ -368,8 +367,7 @@ TEST_F(ValuePrintingTests, ansiColorsPath)
 
 TEST_F(ValuePrintingTests, ansiColorsNull)
 {
-    Value v;
-    v.mkNull();
+    Value v = Value::VNULL;
 
     test(v,
          ANSI_CYAN "null" ANSI_NORMAL,