libexpr: Replace Value::mkPath with constructor calls

The pseudo-constructor `Value::mkPath` would previously be called on an
default-constructed (under-initialized) `Value` to create a properly
initialized `Value` that represents a path. This change
removes mkPath and constructs path `Value`s directly.

Change-Id: I9021de1ff59490828f9fec6866e083996a6a6964

lix/libexpr/eval-expr.cc

@@ -539,7 +539,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
                 .withFrame(env, *this)
                 .debugThrow();
         }
-        v.mkPath(CanonPath(canonPath(str())));
+        v = {NewValueAs::path, CanonPath(canonPath(str()))};
     } else {
         v.mkStringMove(gcStr(), context);
     }

lix/libexpr/primops.cc

@@ -1381,7 +1381,7 @@ static void prim_dirOf(EvalState & state, Value * * args, Value & v)
     state.forceValue(*args[0], noPos);
     if (args[0]->type() == nPath) {
         auto path = args[0]->path();
-        v.mkPath(path.canonical().isRoot() ? path : path.parent());
+        v = {NewValueAs::path, path.canonical().isRoot() ? path : path.parent()};
     } else {
         NixStringContext context;
         auto path = state.coerceToString(noPos, *args[0], context,
@@ -1479,9 +1479,12 @@ static void prim_findFile(EvalState & state, Value * * args, Value & v)
 
     auto path = state.forceStringNoCtx(*args[1], noPos, "while evaluating the second argument passed to builtins.findFile");
 
-    v.mkPath(state.ctx.paths.checkSourcePath(
-        state.aio.blockOn(state.ctx.paths.findFile(searchPath, path, noPos)).unwrap()
-    ));
+    v = {
+        NewValueAs::path,
+        state.ctx.paths.checkSourcePath(
+            state.aio.blockOn(state.ctx.paths.findFile(searchPath, path, noPos)).unwrap()
+        )
+    };
 }
 
 /* Return the cryptographic hash of a file in base-16. */
@@ -1536,8 +1539,7 @@ static void prim_readDir(EvalState & state, Value * * args, Value & v)
             // Some filesystems or operating systems may not be able to return
             // detailed node info quickly in this case we produce a thunk to
             // query the file type lazily.
-            Value epath;
-            epath.mkPath(path + name);
+            Value epath = {NewValueAs::path, path + name};
             if (!readFileType)
                 readFileType = &state.ctx.builtins.get("readFileType");
             attr = {NewValueAs::app, state.ctx.mem, *readFileType, epath};

lix/libexpr/value.cc

@@ -82,11 +82,6 @@ void Value::mkStringMove(Str * s, const NixStringContext & context)
     copyContextToValue(*block, context);
 }
 
-void Value::mkPath(const SourcePath & path)
-{
-    *this = Value(NewValueAs::path, path);
-}
-
 #ifndef __APPLE__
 [[gnu::section(".debug_gdb_scripts"), gnu::used, gnu::aligned(1)]]
 static const char printer_script[] =

lix/libexpr/value.hh

@@ -489,6 +489,18 @@ public:
         assert(str->isPath());
     }
 
+    /// Constructs a nix language value of type "path", with the value of the
+    /// C-string @ref path.
+    ///
+    /// The data from @ref path *is* copied, and this constructor performs a
+    /// dynamic (GC) allocation to do so.
+    Value(path_t, const char * path)
+    {
+        auto block = gcAllocType<String>();
+        *block = {.content = Str::gcCopy(path), .context = String::path};
+        raw = tag(tString, block);
+    }
+
     /// Constructs a nix language value of type "path", with the path
     /// @ref path.
     ///
@@ -774,15 +786,6 @@ public:
 
     void mkStringMove(Str * s, const NixStringContext & context);
 
-    void mkPath(const SourcePath & path);
-
-    inline void mkPath(const char * path)
-    {
-        auto block = gcAllocType<String>();
-        *block = {.content = Str::gcCopy(path), .context = String::path};
-        raw = tag(tString, block);
-    }
-
     inline void mkNull()
     {
         *this = {NewValueAs::null};

tests/unit/libexpr/json.cc

@@ -61,8 +61,7 @@ namespace nix {
     // C++ exception with description "error: operation 'addToStoreFromDump' is
     // not supported by store 'dummy'" thrown in the test body.
     TEST_F(JSONValueTest, DISABLED_Path) {
-        Value v;
-        v.mkPath("test");
+        Value v = {NewValueAs::path, "test"};
         ASSERT_EQ(getJSONValue(v), "\"/nix/store/g1w7hy3qg1w7hy3qg1w7hy3qg1w7hy3q-x\"");
     }
 } /* namespace nix */

tests/unit/libexpr/value/print.cc

@@ -45,8 +45,7 @@ TEST_F(ValuePrintingTests, tString)
 
 TEST_F(ValuePrintingTests, tPath)
 {
-    Value vPath;
-    vPath.mkPath("/foo");
+    Value vPath = {NewValueAs::path, "/foo"};
     test(vPath, "/foo");
 }
 
@@ -382,8 +381,7 @@ TEST_F(ValuePrintingTests, ansiColorsStringElided)
 
 TEST_F(ValuePrintingTests, ansiColorsPath)
 {
-    Value v;
-    v.mkPath(CanonPath("puppy"));
+    Value v = {NewValueAs::path, CanonPath("puppy")};
 
     test(v,
          ANSI_GREEN "/puppy" ANSI_NORMAL,