[flang] Disallow BOZ literal constants as arguments of implicit interfaces

[PeteSteinfeld]

Summary

Since BOZ literal arguments are typeless, we cannot know how to pass them as
actual arguments to procedures with implicit interfaces. This change avoids
the problem by emitting an error message in such situations.

This change stemmed from the following issue --

https://github.com/flang-compiler/f18-llvm-project/issues/794

[klausler]

flang/lib/Semantics/check-call.cpp

51

Wording can be better; try something like "BOZ literal argument requires an explicit interface", like line #44 above.

flang/lib/Semantics/check-call.cpp

if (auto type{arg.GetType()}) {
     } else if (const DerivedTypeSpec * derived{GetDerivedTypeSpec(type)}) {
       if (!derived->parameters().empty()) {
         messages.Say(
             "Parameterized derived type argument requires an explicit interface"_err_en_US);
       }
     }
   }
   if (const auto *expr{arg.UnwrapExpr()}) {
+    if (std::holds_alternative<evaluate::BOZLiteralConstant>(expr->u)) {
+      messages.Say("BOZ argument requires an explicit interface"_err_en_US);
+    }
     if (auto named{evaluate::ExtractNamedEntity(*expr)}) {
       const Symbol &symbol{named->GetLastSymbol()};
       if (symbol.Corank() > 0) {
         messages.Say(
             "Coarray argument requires an explicit interface"_err_en_US);
       }
       if (const auto *details{symbol.detailsIf<ObjectEntityDetails>()}) {
         if (details->IsAssumedRank()) {

flang/test/Semantics/boz-literal-constants.f90

subroutine bozchecks
   res = MERGE_BITS(B"1101",3,11)
   !ERROR: Typeless (BOZ) not allowed for both 'i=' & 'j=' arguments
   res = MERGE_BITS(B"1101",B"0011",11)
   !ERROR: Typeless (BOZ) not allowed for both 'i=' & 'j=' arguments
   res = MERGE_BITS(B"1101",B"0011",B"1011")
   res = MERGE_BITS(B"1101",3,B"1011")
 
   res = REAL(B"1101")
+
+  !ERROR: BOZ argument requires an explicit interface
+  call implictSub(Z'12345')
 end subroutine