From 6f300105d21e1f3bf7f0f92c2564c29f0cab8fb9 Mon Sep 17 00:00:00 2001
From: Tim Keith <tkeith@nvidia.com>
Date: Mon, 11 May 2020 13:28:05 -0700
Subject: [PATCH] [flang] Fix bug with IMPORT of USE of USE

When a module contained an import of a use-association of a
use-association, we weren't recognizing that the symbols was needed.
The fix is the follow all of the use-associations using `GetUltimate()`.

Differential Revision: https://reviews.llvm.org/D79737
---
 flang/lib/Semantics/mod-file.cpp   |  2 +-
 flang/test/Semantics/modfile36.f90 | 41 ++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)
 create mode 100644 flang/test/Semantics/modfile36.f90

diff --git a/flang/lib/Semantics/mod-file.cpp b/flang/lib/Semantics/mod-file.cpp
index d5b754816640..ca1704e8012c 100644
--- a/flang/lib/Semantics/mod-file.cpp
+++ b/flang/lib/Semantics/mod-file.cpp
@@ -833,7 +833,7 @@ void SubprogramSymbolCollector::Collect() {
   for (const auto &pair : scope_) {
     const Symbol &symbol{*pair.second};
     if (const auto *useDetails{symbol.detailsIf<UseDetails>()}) {
-      if (useSet_.count(useDetails->symbol()) > 0) {
+      if (useSet_.count(useDetails->symbol().GetUltimate()) > 0) {
         need_.push_back(symbol);
       }
     }
diff --git a/flang/test/Semantics/modfile36.f90 b/flang/test/Semantics/modfile36.f90
new file mode 100644
index 000000000000..b111d9eb7a6e
--- /dev/null
+++ b/flang/test/Semantics/modfile36.f90
@@ -0,0 +1,41 @@
+! RUN: %S/test_modfile.sh %s %t %f18
+
+! Check modfile that contains import of use-assocation of another use-association.
+
+module m1
+  interface
+     subroutine s(x)
+       use, intrinsic :: iso_c_binding, only: c_ptr
+       type(c_ptr) :: x
+     end subroutine
+  end interface
+end module
+!Expect: m1.mod
+!module m1
+! interface
+!  subroutine s(x)
+!   use iso_c_binding, only: c_ptr
+!   type(c_ptr) :: x
+!  end
+! end interface
+!end
+
+module m2
+  use, intrinsic :: iso_c_binding, only: c_ptr
+  interface
+     subroutine s(x)
+       import :: c_ptr
+       type(c_ptr) :: x
+     end subroutine
+  end interface
+end module
+!Expect: m2.mod
+!module m2
+! use iso_c_binding,only:c_ptr
+! interface
+!  subroutine s(x)
+!   import::c_ptr
+!   type(c_ptr)::x
+!  end
+! end interface
+!end