[flang] Correct accessibility of name that is both generic and derive… (#85098)

…d type

When the same name is used for a derived type and generic interface in a
module, and no explicit PUBLIC or PRIVATE statement appears for the name
but the derived type definition does have an explicit accessibility,
that accessibility must also apply to the generic interface.

Author: klausler

flang/lib/Semantics/resolve-names.cpp

@@ -3391,12 +3391,25 @@ void ModuleVisitor::ApplyDefaultAccess() {
   const auto *moduleDetails{
       DEREF(currScope().symbol()).detailsIf<ModuleDetails>()};
   CHECK(moduleDetails);
+  Attr defaultAttr{
+      DEREF(moduleDetails).isDefaultPrivate() ? Attr::PRIVATE : Attr::PUBLIC};
   for (auto &pair : currScope()) {
     Symbol &symbol{*pair.second};
     if (!symbol.attrs().HasAny({Attr::PUBLIC, Attr::PRIVATE})) {
-      SetImplicitAttr(symbol,
-          DEREF(moduleDetails).isDefaultPrivate() ? Attr::PRIVATE
-                                                  : Attr::PUBLIC);
+      Attr attr{defaultAttr};
+      if (auto *generic{symbol.detailsIf<GenericDetails>()}) {
+        if (generic->derivedType()) {
+          // If a generic interface has a derived type of the same
+          // name that has an explicit accessibility attribute, then
+          // the generic must have the same accessibility.
+          if (generic->derivedType()->attrs().test(Attr::PUBLIC)) {
+            attr = Attr::PUBLIC;
+          } else if (generic->derivedType()->attrs().test(Attr::PRIVATE)) {
+            attr = Attr::PRIVATE;
+          }
+        }
+      }
+      SetImplicitAttr(symbol, attr);
     }
   }
 }

flang/test/Semantics/resolve11.f90

@@ -49,3 +49,40 @@ logical function gt(x, y)
   !ERROR: The accessibility of 'OPERATOR(.GT.)' has already been specified as PUBLIC
   private :: operator(.gt.)
 end
+
+module m4
+  private
+  type, public :: foo
+  end type
+  interface foo
+    procedure fun
+  end interface
+ contains
+  function fun
+  end
+end
+
+subroutine s4
+  !ERROR: 'fun' is PRIVATE in 'm4'
+  use m4, only: foo, fun
+  type(foo) x ! ok
+  print *, foo() ! ok
+end
+
+module m5
+  public
+  type, private :: foo
+  end type
+  interface foo
+    procedure fun
+  end interface
+ contains
+  function fun
+  end
+end
+
+subroutine s5
+  !ERROR: 'foo' is PRIVATE in 'm5'
+  use m5, only: foo, fun
+  print *, fun() ! ok
+end