[flang] Compile the output of -fdebug-unparse-with-modules

flang/docs/ModFiles.md

@@ -98,7 +98,14 @@ Entities that have been included in a module by means of USE association
 are represented in the module file with `USE` statements.
 Name aliases are sometimes necessary when an entity from another
 module is needed for a declaration and conflicts with another
-entity of the same name.
+entity of the same name, or is `PRIVATE`.
+These aliases have currency symbols (`$`) in them.
+When a module
+is parsed from a module file, no error is emitted for associating
+such an alias with a `PRIVATE` name.
+A module parsed from another source file that is not a module file
+(notably, the output of the `-fdebug-unparse-with-modules` option)
+will emit only warnings.
 
 ## Reading and writing module files
 

flang/lib/Semantics/resolve-names.cpp

@@ -3325,9 +3325,19 @@ ModuleVisitor::SymbolRename ModuleVisitor::AddUse(
     // Privacy is not enforced in module files so that generic interfaces
     // can be resolved to private specific procedures in specification
     // expressions.
-    Say(useName, "'%s' is PRIVATE in '%s'"_err_en_US, MakeOpName(useName),
-        useModuleScope_->GetName().value());
-    return {};
+    // Local names that contain currency symbols ('$') are created by the
+    // module file writer when a private name in another module is needed to
+    // process a local declaration.  These can show up in the output of
+    // -fdebug-unparse-with-modules, too, so go easy on them.
+    if (currScope().IsModule() &&
+        localName.ToString().find("$") != std::string::npos) {
+      Say(useName, "'%s' is PRIVATE in '%s'"_warn_en_US, MakeOpName(useName),
+          useModuleScope_->GetName().value());
+    } else {
+      Say(useName, "'%s' is PRIVATE in '%s'"_err_en_US, MakeOpName(useName),
+          useModuleScope_->GetName().value());
+      return {};
+    }
   }
   auto &localSymbol{MakeSymbol(localName)};
   DoAddUse(useName, localName, localSymbol, *useSymbol);

flang/test/Semantics/resolve11.f90

@@ -86,3 +86,17 @@ subroutine s5
   use m5, only: foo, fun
   print *, fun() ! ok
 end
+
+module m6
+  !WARNING: 'foo' is PRIVATE in 'm5'
+  use m5, only: name$with$dollar => foo
+  !ERROR: 'foo' is PRIVATE in 'm5'
+  use m5, only: normal_name => foo
+end
+
+subroutine s6
+  !The special dispensation for USE association of private names to local
+  !aliases with '$' in them only applies to modules.
+  !ERROR: 'foo' is PRIVATE in 'm5'
+  use m5, only: name$with$dollar => foo
+end