[flang-commits] [flang] [flang] Non-generic interface must shadow outer generic (PR #164469)

[Peter Klausler via flang-commits]

https://github.com/klausler created https://github.com/llvm/llvm-project/pull/164469

A procedure defined in non-generic INTERFACE block must completely shadow any generic interface of the same name in an outer scope.

Fixes https://github.com/llvm/llvm-project/issues/164303.

>From 04959740c771b7d60f0bb3f295c0a718e4597a88 Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler at nvidia.com>
Date: Tue, 21 Oct 2025 11:05:27 -0700
Subject: [PATCH] [flang] Non-generic interface must shadow outer generic

A procedure defined in non-generic INTERFACE block must completely
shadow any generic interface of the same name in an outer scope.

Fixes https://github.com/llvm/llvm-project/issues/164303.
---
 flang/lib/Semantics/resolve-names.cpp |  6 +++++-
 flang/test/Semantics/bug164303.f90    | 31 +++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 flang/test/Semantics/bug164303.f90

diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index 0af1c94502bb4..d1160cc25a08b 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -5433,7 +5433,8 @@ void SubprogramVisitor::PushBlockDataScope(const parser::Name &name) {
   }
 }
 
-// If name is a generic, return specific subprogram with the same name.
+// If name is a generic in the same scope, return its specific subprogram with
+// the same name, if any.
 Symbol *SubprogramVisitor::GetSpecificFromGeneric(const parser::Name &name) {
   // Search for the name but don't resolve it
   if (auto *symbol{currScope().FindSymbol(name.source)}) {
@@ -5443,6 +5444,9 @@ Symbol *SubprogramVisitor::GetSpecificFromGeneric(const parser::Name &name) {
         // symbol doesn't inherit it and ruin the ability to check it.
         symbol->attrs().reset(Attr::MODULE);
       }
+    } else if (&symbol->owner() != &currScope() && inInterfaceBlock() &&
+        !isGeneric()) {
+      // non-generic interface shadows outer definition
     } else if (auto *details{symbol->detailsIf<GenericDetails>()}) {
       // found generic, want specific procedure
       auto *specific{details->specific()};
diff --git a/flang/test/Semantics/bug164303.f90 b/flang/test/Semantics/bug164303.f90
new file mode 100644
index 0000000000000..c356c07392577
--- /dev/null
+++ b/flang/test/Semantics/bug164303.f90
@@ -0,0 +1,31 @@
+!RUN: %flang -fc1 -fsyntax-only %s 2>&1 | FileCheck --allow-empty %s
+module foo_mod
+  use, intrinsic :: iso_fortran_env
+  use, intrinsic :: iso_c_binding
+  implicit none
+
+  interface new_foo
+    procedure :: foo_ctor
+  end interface
+
+contains
+
+function foo_ctor(options) result(retval)
+  implicit none
+  integer, intent(in) :: options
+  integer :: retval
+
+  interface
+!CHECK-NOT: error:
+    subroutine new_foo(f, opt) bind(c, name='new_foo')
+      import
+      implicit none
+      integer, intent(inout) :: f
+      integer(c_int), intent(in) :: opt
+    end subroutine
+  end interface
+
+  call new_foo(retval, options)
+end function
+
+end module