[flang] Enforce C15104(5) for coindexed values (#130203)

A object's value can't be copied from another image by means of an
intrinsic assignment statement if it has a derived type that contains a
pointer subobject ultimate component.

Author: klausler

flang/lib/Semantics/assignment.cpp

@@ -134,10 +134,16 @@ static std::optional<std::string> GetPointerComponentDesignatorName(
 // Checks C1594(5,6); false if check fails
 bool CheckCopyabilityInPureScope(parser::ContextualMessages &messages,
     const SomeExpr &expr, const Scope &scope) {
-  if (const Symbol * base{GetFirstSymbol(expr)}) {
-    if (const char *why{
-            WhyBaseObjectIsSuspicious(base->GetUltimate(), scope)}) {
-      if (auto pointer{GetPointerComponentDesignatorName(expr)}) {
+  if (auto pointer{GetPointerComponentDesignatorName(expr)}) {
+    if (const Symbol * base{GetFirstSymbol(expr)}) {
+      const char *why{WhyBaseObjectIsSuspicious(base->GetUltimate(), scope)};
+      if (!why) {
+        if (auto coarray{evaluate::ExtractCoarrayRef(expr)}) {
+          base = &coarray->GetLastSymbol();
+          why = "coindexed";
+        }
+      }
+      if (why) {
         evaluate::SayWithDeclaration(messages, *base,
             "A pure subprogram may not copy the value of '%s' because it is %s"
             " and has the POINTER potential subobject component '%s'"_err_en_US,

flang/test/Semantics/call12.f90

@@ -104,4 +104,11 @@ pure subroutine internal
       localhp = hasPtr(z%a)
     end subroutine
   end function
+  pure subroutine test2(hpd, hhpd)
+    use used
+    type(hasHiddenPtr), intent(in out) :: hpd, hhpd[*]
+    hpd = hhpd ! ok
+    !ERROR: A pure subprogram may not copy the value of 'hhpd' because it is coindexed and has the POINTER potential subobject component '%a%p'
+    hpd = hhpd[1]
+  end subroutine
 end module