flang] Accept SIZE(assumed-rank, DIM=n)

[klausler]

Summary

[Silence a bogus error message about an out-of-range DIM= argument
when the argument is assumed-rank. (More generally, don't pretend
to be able to discern a shape of known rank for an assumed-rank
object.)

[PeteSteinfeld]

Looks great!

flang/lib/Evaluate/shape.cpp

 }
 
 auto GetShapeHelper::operator()(const Symbol &symbol) const -> Result {
   return std::visit(
       common::visitors{
           [&](const semantics::ObjectEntityDetails &object) {
             if (IsImpliedShape(symbol) && object.init()) {
               return (*this)(object.init());
+            } else if (IsAssumedRank(symbol)) {
+              return Result{};
             } else {
               int n{object.shape().Rank()};
               NamedEntity base{symbol};
               return Result{CreateShape(n, base)};
             }
           },
           [](const semantics::EntityDetails &) {
             return ScalarShape(); // no dimensions seen
           },
           [&](const semantics::ProcEntityDetails &proc) {
             if (const Symbol * interface{proc.interface().symbol()}) {
               return (*this)(*interface);
             } else {
               return ScalarShape();
             }
           },
           [&](const semantics::AssocEntityDetails &assoc) {
-            if (!assoc.rank()) {
-              return (*this)(assoc.expr());
-            } else {
+            if (assoc.rank()) { // SELECT RANK case
               int n{assoc.rank().value()};
               NamedEntity base{symbol};
               return Result{CreateShape(n, base)};
+            } else {
+              return (*this)(assoc.expr());
             }
           },
           [&](const semantics::SubprogramDetails &subp) {
             if (subp.isFunction()) {
               return (*this)(subp.result());
             } else {
               return Result{};
             }