[flang] Allow LOCK_TYPE & al. to associate with INTENT(IN OUT) (#121413)

We're emitting a bogus semantic error message about an actual argument
being undefinable when associating LOCK_TYPE, EVENT_TYPE, and someday
NOTIFY_TYPE with an INTENT(IN OUT) dummy argument. These types indeed
make many definition contexts invalid, and the actual argument
associated with an INTENT(IN OUT) dummy argument must indeed be
definable, but the argument association itself is not a problem.

Author: klausler

flang/lib/Semantics/assignment.cpp

@@ -66,8 +66,13 @@ void AssignmentContext::Analyze(const parser::AssignmentStmt &stmt) {
     const SomeExpr &rhs{assignment->rhs};
     auto lhsLoc{std::get<parser::Variable>(stmt.t).GetSource()};
     const Scope &scope{context_.FindScope(lhsLoc)};
-    if (auto whyNot{WhyNotDefinable(lhsLoc, scope,
-            DefinabilityFlags{DefinabilityFlag::VectorSubscriptIsOk}, lhs)}) {
+    DefinabilityFlags flags{DefinabilityFlag::VectorSubscriptIsOk};
+    bool isDefinedAssignment{
+        std::holds_alternative<evaluate::ProcedureRef>(assignment->u)};
+    if (isDefinedAssignment) {
+      flags.set(DefinabilityFlag::AllowEventLockOrNotifyType);
+    }
+    if (auto whyNot{WhyNotDefinable(lhsLoc, scope, flags, lhs)}) {
       if (whyNot->IsFatal()) {
         if (auto *msg{Say(lhsLoc,
                 "Left-hand side of assignment is not definable"_err_en_US)}) {
@@ -79,9 +84,7 @@ void AssignmentContext::Analyze(const parser::AssignmentStmt &stmt) {
       }
     }
     auto rhsLoc{std::get<parser::Expr>(stmt.t).source};
-    if (std::holds_alternative<evaluate::ProcedureRef>(assignment->u)) {
-      // it's a defined ASSIGNMENT(=)
-    } else {
+    if (!isDefinedAssignment) {
       CheckForPureContext(rhs, rhsLoc);
     }
     if (whereDepth_ > 0) {

flang/lib/Semantics/check-call.cpp

@@ -703,12 +703,14 @@ static void CheckExplicitDataArg(const characteristics::DummyDataObject &dummy,
   // Problems with polymorphism are caught in the callee's definition.
   if (scope) {
     std::optional<parser::MessageFixedText> undefinableMessage;
-    if (dummy.intent == common::Intent::Out) {
-      undefinableMessage =
-          "Actual argument associated with INTENT(OUT) %s is not definable"_err_en_US;
-    } else if (dummy.intent == common::Intent::InOut) {
+    DefinabilityFlags flags{DefinabilityFlag::PolymorphicOkInPure};
+    if (dummy.intent == common::Intent::InOut) {
+      flags.set(DefinabilityFlag::AllowEventLockOrNotifyType);
       undefinableMessage =
           "Actual argument associated with INTENT(IN OUT) %s is not definable"_err_en_US;
+    } else if (dummy.intent == common::Intent::Out) {
+      undefinableMessage =
+          "Actual argument associated with INTENT(OUT) %s is not definable"_err_en_US;
     } else if (context.ShouldWarn(common::LanguageFeature::
                        UndefinableAsynchronousOrVolatileActual)) {
       if (dummy.attrs.test(
@@ -722,7 +724,6 @@ static void CheckExplicitDataArg(const characteristics::DummyDataObject &dummy,
       }
     }
     if (undefinableMessage) {
-      DefinabilityFlags flags{DefinabilityFlag::PolymorphicOkInPure};
       if (isElemental) { // 15.5.2.4(21)
         flags.set(DefinabilityFlag::VectorSubscriptIsOk);
       }

flang/lib/Semantics/definable.cpp

@@ -204,7 +204,8 @@ static std::optional<parser::Message> WhyNotDefinableLast(parser::CharBlock at,
     }
     return std::nullopt; // pointer assignment - skip following checks
   }
-  if (IsOrContainsEventOrLockComponent(ultimate)) {
+  if (!flags.test(DefinabilityFlag::AllowEventLockOrNotifyType) &&
+      IsOrContainsEventOrLockComponent(ultimate)) {
     return BlameSymbol(at,
         "'%s' is an entity with either an EVENT_TYPE or LOCK_TYPE"_en_US,
         original);

flang/lib/Semantics/definable.h

@@ -32,7 +32,8 @@ ENUM_CLASS(DefinabilityFlag,
     AcceptAllocatable, // treat allocatable as if it were a pointer
     SourcedAllocation, // ALLOCATE(a,SOURCE=)
     PolymorphicOkInPure, // don't check for polymorphic type in pure subprogram
-    DoNotNoteDefinition) // context does not imply definition
+    DoNotNoteDefinition, // context does not imply definition
+    AllowEventLockOrNotifyType)
 
 using DefinabilityFlags =
     common::EnumSet<DefinabilityFlag, DefinabilityFlag_enumSize>;

flang/test/Semantics/definable01.f90

@@ -109,7 +109,29 @@ pure function test6(lp)
   end
   pure subroutine test7(lp)
     type(list), pointer :: lp
-    !CHECK-NOT: error:
-    lp%next%next => null()
+    lp%next%next => null() ! ok
   end
 end module
+program main
+  use iso_fortran_env, only: lock_type
+  type(lock_type) lock
+  interface
+    subroutine inlock(lock)
+      import lock_type
+      type(lock_type), intent(in) :: lock
+    end
+    subroutine outlock(lock)
+      import lock_type
+      !CHECK: error: An INTENT(OUT) dummy argument may not be, or contain, EVENT_TYPE or LOCK_TYPE
+      type(lock_type), intent(out) :: lock
+    end
+    subroutine inoutlock(lock)
+      import lock_type
+      type(lock_type), intent(in out) :: lock
+    end
+  end interface
+  call inlock(lock) ! ok
+  call inoutlock(lock) ! ok
+  !CHECK: error: Actual argument associated with INTENT(OUT) dummy argument 'lock=' is not definable
+  call outlock(lock)
+end