[flang][OpenMP] Verify that arguments to COPYPRIVATE are variables (#141823)

The check if the arguments are variable list items was missing, leading
to a crash in lowering in some invalid situations.

This fixes the first testcase reported in
#141481

Author: kparzysz

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

@@ -390,6 +390,16 @@ std::optional<bool> OmpStructureChecker::IsContiguous(
       object.u);
 }
 
+void OmpStructureChecker::CheckVariableListItem(
+    const SymbolSourceMap &symbols) {
+  for (auto &[symbol, source] : symbols) {
+    if (!IsVariableListItem(*symbol)) {
+      context_.SayWithDecl(
+          *symbol, source, "'%s' must be a variable"_err_en_US, symbol->name());
+    }
+  }
+}
+
 void OmpStructureChecker::CheckMultipleOccurrence(
     semantics::UnorderedSymbolSet &listVars,
     const std::list<parser::Name> &nameList, const parser::CharBlock &item,
@@ -4587,6 +4597,7 @@ void OmpStructureChecker::Enter(const parser::OmpClause::Copyprivate &x) {
   CheckAllowedClause(llvm::omp::Clause::OMPC_copyprivate);
   SymbolSourceMap symbols;
   GetSymbolsInObjectList(x.v, symbols);
+  CheckVariableListItem(symbols);
   CheckIntentInPointer(symbols, llvm::omp::Clause::OMPC_copyprivate);
   CheckCopyingPolymorphicAllocatable(
       symbols, llvm::omp::Clause::OMPC_copyprivate);
@@ -4859,12 +4870,7 @@ void OmpStructureChecker::Enter(const parser::OmpClause::From &x) {
   const auto &objList{std::get<parser::OmpObjectList>(x.v.t)};
   SymbolSourceMap symbols;
   GetSymbolsInObjectList(objList, symbols);
-  for (const auto &[symbol, source] : symbols) {
-    if (!IsVariableListItem(*symbol)) {
-      context_.SayWithDecl(
-          *symbol, source, "'%s' must be a variable"_err_en_US, symbol->name());
-    }
-  }
+  CheckVariableListItem(symbols);
 
   // Ref: [4.5:109:19]
   // If a list item is an array section it must specify contiguous storage.
@@ -4904,12 +4910,7 @@ void OmpStructureChecker::Enter(const parser::OmpClause::To &x) {
   const auto &objList{std::get<parser::OmpObjectList>(x.v.t)};
   SymbolSourceMap symbols;
   GetSymbolsInObjectList(objList, symbols);
-  for (const auto &[symbol, source] : symbols) {
-    if (!IsVariableListItem(*symbol)) {
-      context_.SayWithDecl(
-          *symbol, source, "'%s' must be a variable"_err_en_US, symbol->name());
-    }
-  }
+  CheckVariableListItem(symbols);
 
   // Ref: [4.5:109:19]
   // If a list item is an array section it must specify contiguous storage.

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

@@ -174,6 +174,7 @@ class OmpStructureChecker
   bool IsExtendedListItem(const Symbol &sym);
   bool IsCommonBlock(const Symbol &sym);
   std::optional<bool> IsContiguous(const parser::OmpObject &object);
+  void CheckVariableListItem(const SymbolSourceMap &symbols);
   void CheckMultipleOccurrence(semantics::UnorderedSymbolSet &listVars,
       const std::list<parser::Name> &nameList, const parser::CharBlock &item,
       const std::string &clauseName);

flang/test/Semantics/OpenMP/copyprivate04.f90

@@ -70,6 +70,7 @@ program omp_copyprivate
   ! Named constants are shared.
   !$omp single
   !ERROR: COPYPRIVATE variable 'pi' is not PRIVATE or THREADPRIVATE in outer context
+  !ERROR: 'pi' must be a variable
   !$omp end single copyprivate(pi)
 
   !$omp parallel do

flang/test/Semantics/OpenMP/copyprivate05.f90

@@ -0,0 +1,12 @@
+!RUN: %python %S/../test_errors.py %s %flang_fc1 -fopenmp
+
+! The first testcase from https://github.com/llvm/llvm-project/issues/141481
+
+subroutine f00
+  type t
+  end type
+
+!ERROR: 't' must be a variable
+!$omp single copyprivate(t)
+!$omp end single
+end