[NF] Function evaluation fixes.

- Apply argument replacements recursively.
- Handle cat where all arguments are empty arrays.
- Handle diagonal of an empty array.
- Add EXP_NODE to InstNode.name for easier debugging.

OMCompiler/Compiler/NFFrontEnd/NFCeval.mo

@@ -2020,7 +2020,7 @@ function evalBuiltinCat
   input EvalTarget target;
   output Expression result;
 protected
-  Integer n, nd;
+  Integer n, nd, sz;
   Type ty;
   list<Expression> es;
   list<Integer> dims;
@@ -2037,8 +2037,11 @@ algorithm
   end if;
 
   es := list(e for e guard not Expression.isEmptyArray(e) in args);
+  sz := listLength(es);
 
-  if listLength(es) == 1 then
+  if sz == 0 then
+    result := listHead(args);
+  elseif sz == 1 then
     result := listHead(es);
   else
     (es,dims) := ExpressionSimplify.evalCat(n, es, getArrayContents=Expression.arrayElements, toString=Expression.toString);
@@ -2094,6 +2097,8 @@ protected
   Boolean e_lit, arg_lit = true;
 algorithm
   result := match arg
+    case Expression.ARRAY(elements = {}) then arg;
+
     case Expression.ARRAY(elements = elems)
       algorithm
         n := listLength(elems);

OMCompiler/Compiler/NFFrontEnd/NFEvalFunction.mo

@@ -390,6 +390,8 @@ algorithm
           ComponentRef.toString(cref), sourceInfo());
       end try;
     end if;
+
+    outExp := Expression.map(outExp, function applyReplacements2(repl = repl));
   end if;
 end applyReplacementCref;
 

OMCompiler/Compiler/NFFrontEnd/NFInstNode.mo

@@ -504,6 +504,7 @@ uniontype InstNode
       case REF_NODE() then "$REF[" + String(node.index) + "]";
       case NAME_NODE() then node.name;
       case IMPLICIT_SCOPE() then "$IMPLICIT";
+      case EXP_NODE() then "$EXP(" + Expression.toString(node.exp) + ")";
       case EMPTY_NODE() then "$EMPTY";
     end match;
   end name;