[flang] More error checking for ASSOCIATED()

[klausler]

Summary

The TARGET= argument of the ASSOCIATED() intrinsic function must be a valid
pointer assignment statement target. Ensure that it does not contain a vector
subscript or any coindexing, either of which would imply a data copy into
temporary storage.

[clementval]

LGTM

flang/lib/Evaluate/intrinsics.cpp

                     *targetProcDesignator, context);
                 targetName = targetProcDesignator->GetName();
               } else if (targetSymbol) {
-                // proc that's not a call
                 if (IsProcedure(*targetSymbol)) {
+                  // proc that's not a call
                   targetProc = characteristics::Procedure::Characterize(
                       *targetSymbol, context);
                 }

                   for (SymbolRef ref : symbols) {
                     msg = AttachDeclaration(msg, *ref);
                   }
+                } else if (HasVectorSubscript(*targetExpr) ||
+                    ExtractCoarrayRef(*targetExpr)) {
+                  context.messages().Say(targetArg->sourceLocation(),
+                      "TARGET= argument '%s' may not have a vector subscript or coindexing"_err_en_US,
+                      targetExpr->AsFortran());
                 }
                 if (const auto pointerType{pointerArg->GetType()}) {
                   if (const auto targetType{targetArg->GetType()}) {

flang/test/Semantics/associated.f90

     type(t1), target :: t1xtarget
     type(t2) :: t2x
     type(t2), target :: t2xtarget
+    integer, target :: targetIntArr(2)
+    integer, target :: targetIntCoarray[*]
+    integer, pointer :: intPointerArr(:)
 
     !ERROR: missing mandatory 'pointer=' argument
     lVar = associated()

     cannotBeCalledfromImplicitPointer => externalProc
     !WARNING: Procedure pointer 'cannotbecalledfromimplicitpointer' with explicit interface that cannot be called via an implicit interface cannot be associated with procedure designator with an implicit interface
     lvar = associated(cannotBeCalledfromImplicitPointer, externalProc)
+    !ERROR: TARGET= argument 'targetintarr([INTEGER(8)::2_8,1_8])' may not have a vector subscript or coindexing
+    lvar = associated(intPointerArr, targetIntArr([2,1]))
+    !ERROR: TARGET= argument 'targetintcoarray[1_8]' may not have a vector subscript or coindexing
+    lvar = associated(intPointerVar1, targetIntCoarray[1])
   end subroutine test
 end subroutine assoc