[flang] Fix crash in module file generation (#123859)

An assertion in module file generation didn't allow for a case that has
arisen in a test; remove it, extend commentary, and add a regression
test.

Fixes https://github.com/llvm/llvm-project/issues/123534.

1 files changed, 2 insertions, 2 deletions

diff --git a/flang/lib/Semantics/mod-file.cpp b/flang/lib/Semantics/mod-file.cpp
index 4367dd1..b45f1c0 100644
--- a/flang/lib/Semantics/mod-file.cpp
+++ b/flang/lib/Semantics/mod-file.cpp
@@ -1799,8 +1799,8 @@ bool SubprogramSymbolCollector::NeedImport(
     return found->has<UseDetails>() && found->owner() != scope_;
   } else {
     // "found" can be null in the case of a use-associated derived type's
-    // parent type
-    CHECK(symbol.has<DerivedTypeDetails>());
+    // parent type, and also in the case of an object (like a dummy argument)
+    // used to define a length or bound of a nested interface.
     return false;
   }
 }