From 5be7f8a666daee086042da0650b595a0938e3da2 Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler@nvidia.com>
Date: Fri, 17 Feb 2023 17:12:14 -0800
Subject: [PATCH] [flang] Catch attempt to misuse an abstract procedure in a
 generic interface

A procedure defined in an ABSTRACT INTERFACE may not appear as
a specific procedure in a generic interface.

Differential Revision: https://reviews.llvm.org/D145102
---
 flang/lib/Semantics/check-declarations.cpp | 8 ++++++++
 flang/test/Semantics/generic02.f90         | 6 ++++++
 2 files changed, 14 insertions(+)

diff --git a/flang/lib/Semantics/check-declarations.cpp b/flang/lib/Semantics/check-declarations.cpp
index 8321bbc..8c38d0f 100644
--- a/flang/lib/Semantics/check-declarations.cpp
+++ b/flang/lib/Semantics/check-declarations.cpp
@@ -1374,6 +1374,14 @@ void CheckHelper::CheckSpecificsAreDistinguishable(
   GenericKind kind{details.kind()};
   DistinguishabilityHelper helper{context_};
   for (const Symbol &specific : details.specificProcs()) {
+    if (specific.attrs().test(Attr::ABSTRACT)) {
+      if (auto *msg{messages_.Say(generic.name(),
+              "Generic interface '%s' must not use abstract interface '%s' as a specific procedure"_err_en_US,
+              generic.name(), specific.name())}) {
+        msg->Attach(
+            specific.name(), "Definition of '%s'"_en_US, specific.name());
+      }
+    }
     if (const Procedure *procedure{Characterize(specific)}) {
       if (procedure->HasExplicitInterface()) {
         helper.Add(generic, kind, specific, *procedure);
diff --git a/flang/test/Semantics/generic02.f90 b/flang/test/Semantics/generic02.f90
index e4f7fe6..551b897 100644
--- a/flang/test/Semantics/generic02.f90
+++ b/flang/test/Semantics/generic02.f90
@@ -1,10 +1,16 @@
 ! RUN: %python %S/test_errors.py %s %flang_fc1
 program test
+  !ERROR: Generic interface 'generic' must not use abstract interface 'abstract' as a specific procedure
   interface generic
     subroutine explicit(n)
       integer, intent(in) :: n
     end subroutine
     procedure implicit
+    procedure abstract
+  end interface
+  abstract interface
+    subroutine abstract
+    end subroutine
   end interface
 !ERROR: Specific procedure 'implicit' of generic interface 'generic' must have an explicit interface
   external implicit
-- 
2.7.4