[flang][volatile] Get volatility of designators from base instead of component symbol (#138611)

The standard says in [8.5.20 VOLATILE attribute]:
If an object has the VOLATILE attribute, then all of its sub-objects
also have the VOLATILE attribute.

This code takes this into account and uses the volatility of the base of
the designator instead of that of the component. In fact, fields in a
structure are not allowed to have the volatile attribute. So given the
code, `A%B => t`, symbol `B` could never directly have the volatile
attribute, and the volatility of `A` indicates the volatility of `B`.


This PR should address [the
comments](#132486 (comment))
on this PR #132486

Author: akuhlens

flang/lib/Semantics/pointer-assignment.cpp

@@ -329,7 +329,6 @@ bool PointerAssignmentChecker::Check(const evaluate::Designator<T> &d) {
             " shape"_err_en_US;
     } else if (rhsType->corank() > 0 &&
         (isVolatile_ != last->attrs().test(Attr::VOLATILE))) { // C1020
-      // TODO: what if A is VOLATILE in A%B%C?  need a better test here
       if (isVolatile_) {
         msg = "Pointer may not be VOLATILE when target is a"
               " non-VOLATILE coarray"_err_en_US;
@@ -569,6 +568,12 @@ bool CheckPointerAssignment(SemanticsContext &context, const SomeExpr &lhs,
     return false; // error was reported
   }
   PointerAssignmentChecker checker{context, scope, *pointer};
+  const Symbol *base{GetFirstSymbol(lhs)};
+  if (base) {
+    // 8.5.20(4) If an object has the VOLATILE attribute, then all of its
+    // subobjects also have the VOLATILE attribute.
+    checker.set_isVolatile(base->attrs().test(Attr::VOLATILE));
+  }
   checker.set_isBoundsRemapping(isBoundsRemapping);
   checker.set_isAssumedRank(isAssumedRank);
   bool lhsOk{checker.CheckLeftHandSide(lhs)};

flang/test/Semantics/assign02.f90

@@ -8,9 +8,11 @@ module m1
   type t2
     sequence
     real :: t2Field
+    real, pointer :: t2FieldPtr
   end type
   type t3
     type(t2) :: t3Field
+    type(t2), pointer :: t3FieldPtr
   end type
 contains
 
@@ -198,6 +200,14 @@ subroutine s13
     q2 => y%t3Field
     !OK:
     q3 => y
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
+    p3%t3FieldPtr => y%t3Field
+    !ERROR: VOLATILE target associated with non-VOLATILE pointer
+    p3%t3FieldPtr%t2FieldPtr => y%t3Field%t2Field
+    !OK
+    q3%t3FieldPtr => y%t3Field
+    !OK
+    q3%t3FieldPtr%t2FieldPtr => y%t3Field%t2Field
   end
 end