From d2bcb0a129f1e60d291fe967426e3686d9ea0587 Mon Sep 17 00:00:00 2001
From: Mike Kashkarov <fruitclover@gmail.com>
Date: Tue, 1 Mar 2022 02:16:47 +0300
Subject: [PATCH] [flang] Allow IMPLICIT NONE(EXTERNAL) with GenericDetails

Restrictions of IMPLICIT NONE(EXTERNAL) prohibits usage of c_associated from
iso_c_binding (with explicit interface) without external definiton - relax
associated check.

Reviewed By: klausler

Differential Revision: https://reviews.llvm.org/D120971
---
 flang/lib/Semantics/resolve-names.cpp | 4 +++-
 flang/test/Semantics/implicit12.f90   | 8 ++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 flang/test/Semantics/implicit12.f90

diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index cf7bebcfd656..5b63f842d63f 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -6495,7 +6495,9 @@ void ResolveNamesVisitor::HandleProcedureName(
     if (!SetProcFlag(name, *symbol, flag)) {
       return; // reported error
     }
-    CheckImplicitNoneExternal(name.source, *symbol);
+    if (!symbol->has<GenericDetails>()) {
+      CheckImplicitNoneExternal(name.source, *symbol);
+    }
     if (symbol->has<SubprogramDetails>() &&
         symbol->attrs().test(Attr::ABSTRACT)) {
       Say(name, "Abstract interface '%s' may not be called"_err_en_US);
diff --git a/flang/test/Semantics/implicit12.f90 b/flang/test/Semantics/implicit12.f90
new file mode 100644
index 000000000000..bff2cb1545b1
--- /dev/null
+++ b/flang/test/Semantics/implicit12.f90
@@ -0,0 +1,8 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+use iso_c_binding, only: c_ptr, c_associated
+implicit none(external)
+type (c_ptr) :: cptr
+if (.not. c_associated (cptr)) then
+   return
+end if
+end