[NF] Improve handling of scalar().

- Implement expansion of size(x).
- Try to expand the argument to scalar and retrieve the result directly
  instead of creating a call to scalar, since scalar isn't implemented
  in the runtime.

Belonging to [master]:
  - #2539
  - OpenModelica/OpenModelica-testsuite#985

Author: perost

Compiler/NFFrontEnd/NFBuiltinCall.mo

@@ -58,6 +58,7 @@ protected
   import TypeCheck = NFTypeCheck;
   import Typing = NFTyping;
   import Util;
+  import ExpandExp = NFExpandExp;
 
 public
   function needSpecialHandling
@@ -885,6 +886,7 @@ protected
     Expression arg;
     Variability var;
     Function fn;
+    Boolean expanded;
   algorithm
     Call.UNTYPED_CALL(ref = fn_ref, arguments = args, named_args = named_args) := call;
     assertNoNamedParams("scalar", named_args, info);
@@ -904,9 +906,22 @@ protected
       end if;
     end for;
 
+    (arg, expanded) := ExpandExp.expand(arg);
     ty := Type.arrayElementType(ty);
-    {fn} := Function.typeRefCache(fn_ref);
-    callExp := Expression.CALL(Call.makeTypedCall(fn, {arg}, variability, ty));
+
+    if expanded then
+      args := Expression.arrayScalarElements(arg);
+
+      if listLength(args) <> 1 then
+        Error.assertion(false, getInstanceName() + " failed to expand scalar(" +
+          Expression.toString(arg) + ") correctly", info);
+      end if;
+
+      callExp := listHead(args);
+    else
+      {fn} := Function.typeRefCache(fn_ref);
+      callExp := Expression.CALL(Call.makeTypedCall(fn, {arg}, variability, ty));
+    end if;
   end typeScalarCall;
 
   function typeVectorCall

Compiler/NFFrontEnd/NFExpandExp.mo

@@ -68,6 +68,7 @@ public
       case Expression.ARRAY() then (exp, true);
       case Expression.RANGE() then expandRange(exp);
       case Expression.CALL() then expandCall(exp.call, exp);
+      case Expression.SIZE() then expandSize(exp);
       case Expression.BINARY() then expandBinary(exp, exp.operator);
       case Expression.UNARY() then expandUnary(exp.exp, exp.operator);
       case Expression.LBINARY() then expandLogicalBinary(exp);
@@ -338,6 +339,31 @@ public
     end if;
   end expandReduction2;
 
+  function expandSize
+    input Expression exp;
+    output Expression outExp;
+    output Boolean expanded = true;
+  algorithm
+    outExp := match exp
+      local
+        Integer dims;
+        Expression e;
+        Type ty;
+        list<Expression> expl;
+
+      case Expression.SIZE(exp = e, dimIndex = NONE())
+        algorithm
+          ty := Expression.typeOf(e);
+          dims := Type.dimensionCount(ty);
+          expl := list(Expression.SIZE(e, SOME(Expression.INTEGER(i))) for i in 1:dims);
+        then
+          Expression.ARRAY(Type.ARRAY(ty, {Dimension.fromInteger(dims)}), expl);
+
+      // Size with an index is scalar, and thus already maximally expanded.
+      else exp;
+    end match;
+  end expandSize;
+
   function expandBinary
     input Expression exp;
     input Operator op;