libexpr: remove templated forceAttrs

the callback is always called immediately, which defeats the purpose of
the callback and the purpose of the template itself. there seems to not
be any performance impact of this. optimizing Value::determinePos would
be nice, but it's not used nearly often enough to matter at this point.

Change-Id: I2aec6a38103630652112f4b273653f11d2404c04

lix/libcmd/repl.cc

@@ -1036,7 +1036,7 @@ Value * NixRepl::replInitInfo()
 
 void NixRepl::addAttrsToScope(Value & attrs)
 {
-    state.forceAttrs(attrs, [&]() { return attrs.determinePos(noPos); }, "while evaluating an attribute set to be merged in the global scope");
+    state.forceAttrs(attrs, attrs.determinePos(noPos), "while evaluating an attribute set to be merged in the global scope");
     if (displ + attrs.attrs->size() >= envSize)
         throw Error("environment full; cannot add more variables");
 

lix/libexpr/eval-inline.hh

@@ -89,15 +89,6 @@ void EvalState::forceValue(Value & v, const PosIdx pos)
 [[gnu::always_inline]]
 inline void EvalState::forceAttrs(Value & v, const PosIdx pos, std::string_view errorCtx)
 {
-    forceAttrs(v, [&]() { return pos; }, errorCtx);
-}
-
-
-template <typename Callable>
-[[gnu::always_inline]]
-inline void EvalState::forceAttrs(Value & v, Callable getPos, std::string_view errorCtx)
-{
-    PosIdx pos = getPos();
     forceValue(v, pos);
     if (v.type() != nAttrs) {
         error<TypeError>(

lix/libexpr/eval.cc

@@ -1099,7 +1099,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
            Hence we need __overrides.) */
         if (hasOverrides) {
             Value * vOverrides = (*v.attrs)[overrides->second.displ].value;
-            state.forceAttrs(*vOverrides, [&]() { return vOverrides->determinePos(noPos); }, "while evaluating the `__overrides` attribute");
+            state.forceAttrs(*vOverrides, vOverrides->determinePos(noPos), "while evaluating the `__overrides` attribute");
             Bindings * newBnds = state.mem.allocBindings(v.attrs->capacity() + vOverrides->attrs->size());
             for (auto & i : *v.attrs)
                 newBnds->push_back(i);

lix/libexpr/eval.hh

@@ -476,10 +476,6 @@ public:
     bool forceBool(Value & v, const PosIdx pos, std::string_view errorCtx);
 
     void forceAttrs(Value & v, const PosIdx pos, std::string_view errorCtx);
-
-    template <typename Callable>
-    inline void forceAttrs(Value & v, Callable getPos, std::string_view errorCtx);
-
     inline void forceList(Value & v, const PosIdx pos, std::string_view errorCtx);
     /**
      * @param v either lambda or primop