[flang][openacc] Fix unparsing of combined construct (bug 47659)

This patch fixes the bug report in https://bugs.llvm.org/show_bug.cgi?id=47659

Reviewed By: sameeranjoshi

Differential Revision: https://reviews.llvm.org/D88597

flang/lib/Parser/unparse.cpp

@@ -1903,8 +1903,8 @@ public:
     EndOpenACC();
     Walk(std::get<std::optional<DoConstruct>>(x.t));
     BeginOpenACC();
-    Walk("!$ACC END ", std::get<std::optional<DoConstruct>>(x.t));
-    Put("\n");
+    Walk("!$ACC END ", std::get<std::optional<AccEndCombinedDirective>>(x.t),
+        "\n");
     EndOpenACC();
   }
   void Unparse(const OpenACCRoutineConstruct &x) {

flang/test/Parser/acc-unparse.f90

@@ -0,0 +1,19 @@
+! RUN: %f18 -fopenacc -funparse %s | FileCheck %s
+
+! Test unparse does not crash with OpenACC directives.
+
+! Test bug 47659
+program bug47659
+  integer :: i, j
+  label1: do i = 1, 10
+    !$acc parallel loop
+    do j = 1, 10
+      if (j == 2) then
+        exit label1
+      end if
+    end do
+  end do label1
+end program
+
+!CHECK-LABEL: PROGRAM bug47659
+!CHECK: !$ACC PARALLEL LOOP