[Flang][OpenMP] Issue error if reduction clause has proc-pointer

Fixes #87915

Author: kiranchandramohan

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

@@ -2285,7 +2285,19 @@ void OmpStructureChecker::Enter(const parser::OmpClause::Reduction &x) {
   if (CheckReductionOperators(x)) {
     CheckReductionTypeList(x);
   }
+
+  SymbolSourceMap symbols;
+  const auto &ompObjectList{std::get<parser::OmpObjectList>(x.v.t)};
+  GetSymbolsInObjectList(ompObjectList, symbols);
+  for (auto &[symbol, source] : symbols) {
+    if (IsProcedurePointer(*symbol)) {
+      context_.Say(source,
+          "A procedure pointer '%s' must not appear in a REDUCTION clause."_err_en_US,
+          symbol->name());
+    }
+  }
 }
+
 bool OmpStructureChecker::CheckReductionOperators(
     const parser::OmpClause::Reduction &x) {
 

flang/test/Semantics/OpenMP/reduction12.f90

@@ -0,0 +1,16 @@
+! RUN: %python %S/../test_errors.py %s %flang_fc1 -fopenmp
+
+! OpenMP 5.2: Section 5.5.5 : A procedure pointer must not appear in a
+! reduction clause.
+
+  procedure(foo), pointer :: ptr
+  integer :: i
+  ptr => foo
+!ERROR: A procedure pointer 'ptr' must not appear in a REDUCTION clause.
+!$omp do reduction (+ : ptr)
+  do i = 1, 10
+  end do
+contains
+  subroutine foo
+  end subroutine
+end