[flang][OpenMP] Add diagnostic for ATOMIC WRITE with pointer to non-intrinsic type

Fixes #161932

Author: Krish Gupta

flang/lib/Semantics/check-omp-atomic.cpp

@@ -539,7 +539,6 @@ void OmpStructureChecker::CheckAtomicType(
     return;
   }
 
-  // Variable is a pointer.
   if (typeSpec->IsPolymorphic()) {
     context_.Say(source,
         "Atomic variable %s cannot be a pointer to a polymorphic type"_err_en_US,
@@ -829,6 +828,32 @@ void OmpStructureChecker::CheckAtomicWriteAssignment(
   if (!IsVarOrFunctionRef(atom)) {
     ErrorShouldBeVariable(atom, rsrc);
   } else {
+    // For intrinsic assignment (x = expr), check if the variable is a pointer
+    // to a non-intrinsic type, which is not allowed in ATOMIC WRITE
+    if (!IsPointerAssignment(write)) {
+      std::vector<SomeExpr> dsgs{GetAllDesignators(atom)};
+      if (!dsgs.empty()) {
+        evaluate::SymbolVector syms{evaluate::GetSymbolVector(dsgs.front())};
+        if (!syms.empty() && IsPointer(syms.back())) {
+          SymbolRef sym = syms.back();
+          if (const DeclTypeSpec *typeSpec{sym->GetType()}) {
+            using Category = DeclTypeSpec::Category;
+            Category cat{typeSpec->category()};
+            if (cat != Category::Numeric && cat != Category::Logical) {
+              std::string details = " has the POINTER attribute";
+              if (const auto *derived{typeSpec->AsDerived()}) {
+                details +=
+                    " and derived type '"s + derived->name().ToString() + "'";
+              }
+              context_.Say(lsrc,
+                  "ATOMIC WRITE requires an intrinsic scalar variable; '%s'%s"_err_en_US,
+                  sym->name(), details);
+              return;
+            }
+          }
+        }
+      }
+    }
     CheckAtomicVariable(atom, lsrc);
     CheckStorageOverlap(atom, {write.rhs}, source);
   }

flang/test/Semantics/OpenMP/omp-atomic-write-pointer-derived.f90

@@ -0,0 +1,8 @@
+! RUN: not %flang_fc1 -fopenmp -fsyntax-only %s 2>&1 | FileCheck %s
+type t
+end type
+type(t), pointer :: a1, a2
+!$omp atomic write
+a1 = a2
+! CHECK: error: ATOMIC WRITE requires an intrinsic scalar variable; 'a1' has the POINTER attribute and derived type 't'
+end