[flang-commits] [flang] c82db77 - [flang] Handle indirect USE of ancestor module into submodule (#124969)

[via flang-commits]

Author: Peter Klausler
Date: 2025-01-31T10:54:25-08:00
New Revision: c82db773f47fce978c6ec5c567caeefa27e6521b

URL: https://github.com/llvm/llvm-project/commit/c82db773f47fce978c6ec5c567caeefa27e6521b
DIFF: https://github.com/llvm/llvm-project/commit/c82db773f47fce978c6ec5c567caeefa27e6521b.diff

LOG: [flang] Handle indirect USE of ancestor module into submodule (#124969)

A USE statement within a submodule (possibly in a nested scope) is not
allowed to USE the submodule's ancestor module directly, but it is
permissible to USE that ancestor module indirectly via another unrelated
module. Don't emit "already present in scope" errors for this case.

Fixes https://github.com/llvm/llvm-project/issues/124731.

Added: 
    flang/test/Semantics/bug124731.f90

Modified: 
    flang/lib/Semantics/resolve-names.cpp
    flang/test/Semantics/self-use.f90

Removed: 
    


################################################################################
diff  --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index a586b8e969ec61..cb95db89ca08e6 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -3354,6 +3354,15 @@ void ModuleVisitor::DoAddUse(SourceName location, SourceName localName,
     // use-associating the same symbol again -- ok
     return;
   }
+  if (useUltimate.owner().IsModule() && localUltimate.owner().IsSubmodule() &&
+      DoesScopeContain(&useUltimate.owner(), localUltimate)) {
+    // Within a submodule, USE'ing a symbol that comes indirectly
+    // from the ancestor module, e.g. foo in:
+    //  MODULE m1; INTERFACE; MODULE SUBROUTINE foo; END INTERFACE; END
+    //  MODULE m2; USE m1; END
+    //  SUBMODULE m1(sm); USE m2; CONTAINS; MODULE PROCEDURE foo; END; END
+    return; // ok, ignore it
+  }
 
   if (localUltimate.name() == useUltimate.name() &&
       localUltimate.owner().IsModule() && useUltimate.owner().IsModule() &&

diff  --git a/flang/test/Semantics/bug124731.f90 b/flang/test/Semantics/bug124731.f90
new file mode 100644
index 00000000000000..924b41dd1db48c
--- /dev/null
+++ b/flang/test/Semantics/bug124731.f90
@@ -0,0 +1,24 @@
+!RUN: %flang_fc1 -fsyntax-only %s  2>&1 | FileCheck %s --allow-empty
+!CHECK-NOT: error:
+module m1
+  interface
+    module subroutine foo
+    end
+  end interface
+  real x
+end
+module m2
+  use m1
+end
+submodule(m1) sm1
+  use m2 ! ok
+ contains
+  module procedure foo
+  end
+end
+submodule(m1) sm2
+ contains
+  subroutine bar
+    use m2 ! ok
+  end
+end

diff  --git a/flang/test/Semantics/self-use.f90 b/flang/test/Semantics/self-use.f90
index 4bc66a24343c6a..12433732fc3300 100644
--- a/flang/test/Semantics/self-use.f90
+++ b/flang/test/Semantics/self-use.f90
@@ -15,7 +15,6 @@ subroutine modsub
  contains
   module subroutine separate
     !ERROR: Module 'm' cannot USE itself from its own submodule 'submod1'
-    !ERROR: Cannot use-associate 'separate'; it is already declared in this scope
     use m
   end
 end