[flang] Allow INQUIRE() on a child unit in user-defined I/O procedure

[klausler]

Summary

A procedure that implements a user-defined derived type I/O operation
is allowed to perform an INQUIRE statement on its unit.

[mleair]

LGTM

flang/runtime/io-api.cpp

   }
   ExternalFileUnit &unit{ExternalFileUnit::LookUpOrCreateAnonymous(
       unitNumber, DIR, false /*!unformatted*/, terminator)};
+  if (!unit.isUnformatted.has_value()) {
+    unit.isUnformatted = false;
+  }
+  if (*unit.isUnformatted) {
+    terminator.Crash("%s attempted on unformatted file", what);
+    return nullptr;
+  }
   if (ChildIo * child{unit.GetChildIo()}) {
     return child->CheckFormattingAndDirection(terminator, what, false, DIR)
         ? &child->BeginIoStatement<ChildListIoStatementState<DIR>>(

       terminator.Crash("%s attempted on direct access file", what);
       return nullptr;
     }
-    if (!unit.isUnformatted.has_value()) {
-      unit.isUnformatted = false;
-    }
-    if (*unit.isUnformatted) {
-      terminator.Crash("%s attempted on unformatted file", what);
-      return nullptr;
-    }
     IoErrorHandler handler{terminator};
     unit.SetDirection(DIR, handler);
     IoStatementState &io{unit.BeginIoStatement<STATE<DIR>>(

   }
   ExternalFileUnit &unit{ExternalFileUnit::LookUpOrCreateAnonymous(
       unitNumber, DIR, false /*!unformatted*/, terminator)};
+  if (!unit.isUnformatted.has_value()) {
+    unit.isUnformatted = false;
+  }
+  if (*unit.isUnformatted) {
+    terminator.Crash("Formatted I/O attempted on unformatted file");
+    return nullptr;
+  }
   if (ChildIo * child{unit.GetChildIo()}) {
     return child->CheckFormattingAndDirection(terminator,
                DIR == Direction::Output ? "formatted output"

               *child, sourceFile, sourceLine)
         : nullptr;
   } else {
-    if (!unit.isUnformatted.has_value()) {
-      unit.isUnformatted = false;
-    }
-    if (*unit.isUnformatted) {
-      terminator.Crash("Formatted I/O attempted on unformatted file");
-      return nullptr;
-    }
     IoErrorHandler handler{terminator};
     unit.SetDirection(DIR, handler);
     IoStatementState &io{

   Terminator terminator{sourceFile, sourceLine};
   ExternalFileUnit &unit{ExternalFileUnit::LookUpOrCreateAnonymous(
       unitNumber, DIR, true /*unformatted*/, terminator)};
+  if (!unit.isUnformatted.has_value()) {
+    unit.isUnformatted = true;
+  }
+  if (!*unit.isUnformatted) {
+    terminator.Crash("Unformatted I/O attempted on formatted file");
+  }
   if (ChildIo * child{unit.GetChildIo()}) {
     return child->CheckFormattingAndDirection(terminator,
                DIR == Direction::Output ? "unformatted output"

               *child, sourceFile, sourceLine)
         : nullptr;
   } else {
-    if (!unit.isUnformatted.has_value()) {
-      unit.isUnformatted = true;
-    }
-    if (!*unit.isUnformatted) {
-      terminator.Crash("Unformatted I/O attempted on formatted file");
-    }
     IoStatementState &io{
         unit.BeginIoStatement<ExternalUnformattedIoStatementState<DIR>>(
             unit, sourceFile, sourceLine)};

 Cookie IONAME(BeginInquireUnit)(
     ExternalUnit unitNumber, const char *sourceFile, int sourceLine) {
   if (ExternalFileUnit * unit{ExternalFileUnit::LookUp(unitNumber)}) {
-    return &unit->BeginIoStatement<InquireUnitState>(
-        *unit, sourceFile, sourceLine);
+    if (ChildIo * child{unit->GetChildIo()}) {
+      return &child->BeginIoStatement<InquireUnitState>(
+          *unit, sourceFile, sourceLine);
+    } else {
+      return &unit->BeginIoStatement<InquireUnitState>(
+          *unit, sourceFile, sourceLine);
+    }
   } else {
     // INQUIRE(UNIT=unrecognized unit)
     Terminator oom{sourceFile, sourceLine};

flang/runtime/unit.h

       ChildListIoStatementState<Direction::Output>,
       ChildListIoStatementState<Direction::Input>,
       ChildUnformattedIoStatementState<Direction::Output>,
-      ChildUnformattedIoStatementState<Direction::Input>>
+      ChildUnformattedIoStatementState<Direction::Input>, InquireUnitState>
       u_;
   std::optional<IoStatementState> io_;
 };