Handle empty arrays better during unit checking (#10064)

- Check for zero-dimensions instead of using `Expression.isEmptyArray`
  when checking if a unit expression is a non-empty array, since an
  array can be non-empty and still not contain any scalar elements (such
  as `{{}}`).
- Avoid having to evaluate `fill` calls when getting the unit string
  from an expression, all elements in the resulting array will be the
  same anyway so we can just take the fill argument directly instead.

Fixes #10057

OMCompiler/Compiler/NFFrontEnd/NFUnitCheck.mo

@@ -1023,9 +1023,15 @@ algorithm
     // A literal array. This happens for array variables, assume each variable
     // has the same unit for now.
     case Expression.ARRAY(literal = true)
-      guard Expression.isLiteral(unitExp) and not Expression.isEmptyArray(unitExp)
+      guard Expression.isLiteral(unitExp) and not Type.isEmptyArray(Expression.typeOf(unitExp))
       then getUnitStringFromExp(Expression.arrayFirstScalar(unitExp));
 
+    // A fill call. Will generate an array where all elements are the same, so
+    // no need to evaluate it.
+    case Expression.CALL(Call.TYPED_CALL(arguments = exp :: _))
+      guard Call.isNamed(unitExp.call, "fill")
+      then getUnitStringFromExp(exp);
+
     // A non-literal expression, evaluate it and try again if it could be evaluated.
     case _
       guard not Expression.isLiteral(unitExp)

testsuite/simulation/modelica/unitcheck/Makefile

@@ -23,6 +23,7 @@ UnitCheck19.mos \
 UnitCheck20.mos \
 UnitCheck21.mos \
 UnitCheck22.mos \
+UnitCheck23.mos \
 ticket3631.mos \
 
 

testsuite/simulation/modelica/unitcheck/UnitCheck22.mos

@@ -1,34 +1,34 @@
-// name: UnitCheck21
+// name: UnitCheck22
 // keywords: initialization
 // status: correct
 // cflags: -d=newInst --unitChecking -d=dumpUnits
 
 loadString("
-  model UnitCheck21
+  model UnitCheck22
     type Length = Real(unit = \"m\");
     type Area = Real(unit = \"m2\");
 
     Area A;
     Length L;
   equation
     A = L^3;
-  end UnitCheck21;
+  end UnitCheck22;
 "); getErrorString();
 
-instantiateModel(UnitCheck21); getErrorString();
+instantiateModel(UnitCheck22); getErrorString();
 
 // Result:
 // true
 // ""
 // (A, 1.0 * m^(2))
 // (L, 1.0 * m^(1))
 // ######## UnitCheck COMPLETED ########
-// "class UnitCheck21
+// "class UnitCheck22
 //   Real A(unit = \"m2\");
 //   Real L(unit = \"m\");
 // equation
 //   A = L ^ 3.0;
-// end UnitCheck21;
+// end UnitCheck22;
 // "
 // "[<interactive>:9:5-9:12:writable] Warning: The following equation is INCONSISTENT due to specified unit information: A = L ^ 3.0
 // Warning: The units of following sub-expressions need to be equal:

testsuite/simulation/modelica/unitcheck/UnitCheck23.mos

@@ -0,0 +1,24 @@
+// name: UnitCheck23
+// keywords: initialization
+// status: correct
+// cflags: -d=newInst --unitChecking -d=dumpUnits
+
+loadString("
+  model UnitCheck23
+    type MassFlowRate = Real(final unit = \"kg/s\");
+    MassFlowRate[1, 0] ports_mXi_flow;
+  end UnitCheck23;
+"); getErrorString();
+
+instantiateModel(UnitCheck23); getErrorString();
+
+// Result:
+// true
+// ""
+// (ports_mXi_flow, 1000.0 * s^(-1) * g^(1))
+// ######## UnitCheck COMPLETED ########
+// "class UnitCheck23
+// end UnitCheck23;
+// "
+// ""
+// endResult