[flang] Catch assumed-length interoperability error (#124179)

An assumed-length character dummy argument is interoperable only if it
is neither a pointer nor allocatable.

Author: klausler

flang/lib/Semantics/check-declarations.cpp

@@ -3089,16 +3089,17 @@ parser::Messages CheckHelper::WhyNotInteroperableObject(
       }
     }
     if (type->IsAssumedType()) { // ok
-    } else if (IsAssumedLengthCharacter(symbol)) {
+    } else if (IsAssumedLengthCharacter(symbol) &&
+        !IsAllocatableOrPointer(symbol)) {
     } else if (IsAllocatableOrPointer(symbol) &&
         type->category() == DeclTypeSpec::Character &&
         type->characterTypeSpec().length().isDeferred()) {
       // ok; F'2023 18.3.7 p2(6)
     } else if (derived) { // type has been checked
     } else if (auto dyType{evaluate::DynamicType::From(*type)}; dyType &&
-               evaluate::IsInteroperableIntrinsicType(*dyType,
-                   InModuleFile() ? nullptr : &context_.languageFeatures())
-                   .value_or(false)) {
+        evaluate::IsInteroperableIntrinsicType(
+            *dyType, InModuleFile() ? nullptr : &context_.languageFeatures())
+            .value_or(false)) {
       // F'2023 18.3.7 p2(4,5)
       // N.B. Language features are not passed to IsInteroperableIntrinsicType
       // when processing a module file, since the module file might have been

flang/test/Semantics/bind-c06.f90

@@ -95,4 +95,13 @@ program main
     real :: x(0)
   end type
 
+  interface
+    subroutine badAssumedLen(x,y,z) bind(c)
+      !ERROR: A BIND(C) object must have an interoperable type
+      character(*), pointer :: x
+      !ERROR: A BIND(C) object must have an interoperable type
+      character(*), allocatable :: y
+      character(*) z ! ok
+    end
+  end interface
 end