[flang] Fixed shape computation for elementals with optional dummys.

It looks like a regression after D151737: shape of the elemental
call became rank-0.

Reviewed By: klausler

Differential Revision: https://reviews.llvm.org/D156386

flang/lib/Evaluate/shape.cpp

@@ -811,13 +811,24 @@ auto GetShapeHelper::operator()(const ProcedureRef &call) const -> Result {
       if (auto chars{characteristics::Procedure::FromActuals(
               call.proc(), call.arguments(), *context_)}) {
         std::size_t j{0};
+        std::size_t anyArrayArgRank{0};
         for (const auto &arg : call.arguments()) {
-          if (arg && arg->Rank() > 0 && j < chars->dummyArguments.size() &&
-              !chars->dummyArguments[j].IsOptional()) {
-            return (*this)(*arg);
+          if (arg && arg->Rank() > 0 && j < chars->dummyArguments.size()) {
+            anyArrayArgRank = arg->Rank();
+            if (!chars->dummyArguments[j].IsOptional()) {
+              return (*this)(*arg);
+            }
           }
           ++j;
         }
+        if (anyArrayArgRank) {
+          // All dummy array arguments of the procedure are OPTIONAL.
+          // We cannot take the shape from just any array argument,
+          // because all of them might be OPTIONAL dummy arguments
+          // of the caller. Return unknown shape ranked according
+          // to the last actual array argument.
+          return Shape(anyArrayArgRank, MaybeExtentExpr{});
+        }
       }
     }
     return ScalarShape();

flang/test/Lower/shape-of-elemental-with-optional-arg.f90

@@ -0,0 +1,19 @@
+! Test that the shape of the elemental call is properly
+! computed as being rank 1, even though the only dummy
+! argument is optional.
+
+! RUN: bbc -emit-fir %s -o - | FileCheck %s
+! RUN: bbc -emit-hlfir %s -o - | FileCheck %s
+
+subroutine test
+  interface
+     elemental function callee(arg1)
+       integer, intent(in), optional :: arg1
+       integer                       :: fun
+     end function callee
+  end interface
+  integer :: arr(2)
+  print *, callee(arr)
+end subroutine test
+! The PRINT statement must be lowered into a ranked print:
+! CHECK: fir.call @_FortranAioOutputDescriptor