[flang-commits] [flang] [flang][Semantics] Resolve private PDT binding overrides (PR #218832)

[Eugene Epshteyn via flang-commits]

https://github.com/eugeneepshteyn created https://github.com/llvm/llvm-project/pull/218832

Use the selected binding declaration owner when determining the module in which a private binding may be overridden. A generic cloned into a PDT instantiation is owned by the instantiation scope, which can otherwise cause a legal same-module override to be skipped.

Add coverage for external, unrelated-module, module-owned, use-renamed, and cross-module private/public PDT cases.

Fixes #218683

Assisted-by: AI

>From 935e992d2cb64d1572a4da8ee7c338c7ce571aaf Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Tue, 25 Aug 2026 23:36:42 -0400
Subject: [PATCH] [flang][Semantics] Resolve private PDT binding overrides

Use the selected binding declaration owner when determining the module in which a private binding may be overridden. A generic cloned into a PDT instantiation is owned by the instantiation scope, which can otherwise cause a legal same-module override to be skipped.

Add coverage for external, unrelated-module, module-owned, use-renamed, and cross-module private/public PDT cases.

Fixes #218683
---
 flang/lib/Semantics/expression.cpp  |   2 +-
 flang/test/Semantics/bindings09.f90 | 134 ++++++++++++++++++++++++++++
 2 files changed, 135 insertions(+), 1 deletion(-)
 create mode 100644 flang/test/Semantics/bindings09.f90

diff --git a/flang/lib/Semantics/expression.cpp b/flang/lib/Semantics/expression.cpp
index efbf862a72c51..fa78379b7a4d0 100644
--- a/flang/lib/Semantics/expression.cpp
+++ b/flang/lib/Semantics/expression.cpp
@@ -2715,7 +2715,7 @@ auto ExpressionAnalyzer::AnalyzeProcedureComponentRef(
               latest{DEREF(dyType->GetDerivedTypeSpec().typeSymbol().scope())
                          .FindComponent(sym->name())}) {
             if (sym->attrs().test(semantics::Attr::PRIVATE)) {
-              const auto *bindingModule{FindModuleContaining(generic.owner())};
+              const auto *bindingModule{FindModuleContaining(sym->owner())};
               const Symbol *s{latest};
               while (s && FindModuleContaining(s->owner()) != bindingModule) {
                 if (const auto *parent{s->owner().GetDerivedTypeParent()}) {
diff --git a/flang/test/Semantics/bindings09.f90 b/flang/test/Semantics/bindings09.f90
new file mode 100644
index 0000000000000..0992ebc09bd6e
--- /dev/null
+++ b/flang/test/Semantics/bindings09.f90
@@ -0,0 +1,134 @@
+! RUN: %flang_fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
+
+! Ensure that generic resolution for a parameterized derived type uses the
+! module containing the selected binding, not the PDT instantiation site.
+
+module private_pdt
+  implicit none
+  integer, parameter :: sp = kind(1.0)
+
+  type, abstract :: base_t(k)
+    integer, kind :: k = sp
+  contains
+    procedure(private_interface), private, deferred :: binding
+    generic, public :: generic => binding
+  end type
+
+  type, extends(base_t) :: extension_t
+  contains
+    procedure, private :: binding => private_impl
+  end type
+
+  abstract interface
+    subroutine private_interface(x, n)
+      import base_t, sp
+      class(base_t(sp)), intent(inout) :: x
+      integer, intent(in) :: n
+    end subroutine
+  end interface
+
+  type(extension_t(sp)), public :: module_object
+
+contains
+  subroutine private_impl(x, n)
+    class(extension_t(sp)), intent(inout) :: x
+    integer, intent(in) :: n
+  end subroutine
+end module
+
+module third_module
+  use private_pdt
+  implicit none
+contains
+  subroutine call_from_third_module
+    type(extension_t(sp)) :: x
+    ! CHECK: CALL private_impl(x,1_4)
+    call x%generic(1)
+  end subroutine
+end module
+
+module use_renamed
+  use private_pdt, only: renamed_t => extension_t, sp
+  implicit none
+contains
+  subroutine call_use_renamed
+    type(renamed_t(sp)) :: x
+    ! CHECK: CALL private_impl(x,2_4)
+    call x%generic(2)
+  end subroutine
+end module
+
+module private_cross_module
+  use private_pdt
+  implicit none
+
+  ! The inherited private binding cannot be overridden in another module.
+  type, extends(extension_t) :: further_extension_t
+  contains
+    procedure :: binding => unrelated_impl
+  end type
+
+contains
+  subroutine unrelated_impl(x, n)
+    class(further_extension_t(sp)), intent(inout) :: x
+    integer, intent(in) :: n
+  end subroutine
+
+  subroutine call_private_cross_module
+    type(further_extension_t(sp)) :: x
+    ! CHECK: CALL private_impl(x,3_4)
+    call x%generic(3)
+  end subroutine
+end module
+
+module public_pdt
+  implicit none
+  integer, parameter :: sp = kind(1.0)
+
+  type :: base_t(k)
+    integer, kind :: k = sp
+  contains
+    procedure, public :: binding => public_base_impl
+    generic, public :: generic => binding
+  end type
+
+contains
+  subroutine public_base_impl(x, n)
+    class(base_t(sp)), intent(inout) :: x
+    integer, intent(in) :: n
+  end subroutine
+end module
+
+module public_cross_module
+  use public_pdt
+  implicit none
+
+  ! Unlike a private binding, the public binding remains overridable here.
+  type, extends(base_t) :: extension_t
+  contains
+    procedure :: binding => public_extension_impl
+  end type
+
+contains
+  subroutine public_extension_impl(x, n)
+    class(extension_t(sp)), intent(inout) :: x
+    integer, intent(in) :: n
+  end subroutine
+
+  subroutine call_public_cross_module
+    type(extension_t(sp)) :: x
+    ! CHECK: CALL public_extension_impl(x,4_4)
+    call x%generic(4)
+  end subroutine
+end module
+
+program test
+  use private_pdt
+  implicit none
+  type(extension_t(sp)) :: x
+
+  ! CHECK: CALL private_impl(x,5_4)
+  call x%generic(5)
+  ! CHECK: CALL private_impl(module_object,6_4)
+  call module_object%generic(6)
+end program