[flang] Fix use-associated procedure in generic

[tskeith]

Summary

When a use-associated procedure was included in a generic, we weren't
correctly recording that fact. The ultimate symbol was added rather than
the local symbol.

Also, improve the message emitted for the specific procedure by
mentioning the module it came from.

This fixes one of the problems in https://bugs.llvm.org/show_bug.cgi?id=48648.

[PeteSteinfeld]

All builds, tests, and looks good.

flang/lib/Semantics/resolve-names.cpp

void InterfaceVisitor::ResolveSpecificsInGeneric(Symbol &generic) {
   for (auto it{range.first}; it != range.second; ++it) {
     auto *name{it->second.first};
     auto kind{it->second.second};
     const auto *symbol{FindSymbol(*name)};
     if (!symbol) {
       Say(*name, "Procedure '%s' not found"_err_en_US);
       continue;
     }
-    symbol = &symbol->GetUltimate();
     if (symbol == &generic) {
       if (auto *specific{generic.get<GenericDetails>().specific()}) {
         symbol = specific;
       }
     }
-    if (!symbol->has<SubprogramDetails>() &&
-        !symbol->has<SubprogramNameDetails>()) {
+    const Symbol &ultimate{symbol->GetUltimate()};
+    if (!ultimate.has<SubprogramDetails>() &&
+        !ultimate.has<SubprogramNameDetails>()) {
       Say(*name, "'%s' is not a subprogram"_err_en_US);
       continue;
     }
     if (kind == ProcedureKind::ModuleProcedure) {
-      if (const auto *nd{symbol->detailsIf<SubprogramNameDetails>()}) {
+      if (const auto *nd{ultimate.detailsIf<SubprogramNameDetails>()}) {
         if (nd->kind() != SubprogramKind::Module) {
           Say(*name, "'%s' is not a module procedure"_err_en_US);
         }
       } else {
         // USE-associated procedure
-        const auto *sd{symbol->detailsIf<SubprogramDetails>()};
+        const auto *sd{ultimate.detailsIf<SubprogramDetails>()};
         CHECK(sd);
-        if (symbol->owner().kind() != Scope::Kind::Module ||
+        if (ultimate.owner().kind() != Scope::Kind::Module ||
             sd->isInterface()) {
           Say(*name, "'%s' is not a module procedure"_err_en_US);
         }
       }
     }
-    if (!symbolsSeen.insert(*symbol).second) {
+    if (!symbolsSeen.insert(ultimate).second) {
+      if (symbol == &ultimate) {
         Say(name->source,
             "Procedure '%s' is already specified in generic '%s'"_err_en_US,
             name->source, MakeOpName(generic.name()));
+      } else {
+        Say(name->source,
+            "Procedure '%s' from module '%s' is already specified in generic '%s'"_err_en_US,
+            ultimate.name(), ultimate.owner().GetName().value(),
+            MakeOpName(generic.name()));
+      }
       continue;
     }
     details.AddSpecificProc(*symbol, name->source);
   }
   specificProcs_.erase(range.first, range.second);
 }
 
 // Check that the specific procedures are all functions or all subroutines.

flang/test/Semantics/modfile07.f90

 !Expect: m10d.mod
 !module m10d
 ! use m10c,only:operator(.ne.)
 ! use m10a,only:operator(.ne.)
 ! interface operator(.ne.)
 ! end interface
 ! private::operator(.ne.)
 !end
+
+module m11a
+contains
+  subroutine s1()
+  end
+end
+!Expect: m11a.mod
+!module m11a
+!contains
+! subroutine s1()
+! end
+!end
+
+module m11b
+  use m11a
+  interface g
+    module procedure s1
+  end interface
+end
+!Expect: m11b.mod
+!module m11b
+! use m11a,only:s1
+! interface g
+!  procedure::s1
+! end interface
+!end

flang/test/Semantics/resolve53.f90

module m20
   interface operator(+)
     procedure f
   end interface
 end module
 
 subroutine s1()
   use m20
   interface operator(.not.)
-    !ERROR: Procedure 'f' is already specified in generic 'OPERATOR(.NOT.)'
+    !ERROR: Procedure 'f' from module 'm20' is already specified in generic 'OPERATOR(.NOT.)'
     procedure f
   end interface
   interface operator(+)
-    !ERROR: Procedure 'f' is already specified in generic 'OPERATOR(+)'
+    !ERROR: Procedure 'f' from module 'm20' is already specified in generic 'OPERATOR(+)'
     procedure f
   end interface
 end subroutine s1