Ruby: Move language specific code out of FileSystem.qll (at least for now).

ruby/ql/lib/codeql/files/FileSystem.qll

@@ -2,7 +2,6 @@
 
 private import codeql.Locations
 private import codeql.util.FileSystem
-private import codeql.ruby.Diagnostics
 
 private module Input implements InputSig {
   abstract class ContainerBase extends @container {
@@ -35,20 +34,3 @@ class File extends Container, Impl::File {
   /** Holds if this file was extracted from ordinary source code. */
   predicate fromSource() { any() }
 }
-
-/**
- * A successfully extracted file, that is, a file that was extracted and
- * contains no extraction errors or warnings.
- */
-class SuccessfullyExtractedFile extends File {
-  SuccessfullyExtractedFile() {
-    not exists(Diagnostic d |
-      d.getLocation().getFile() = this and
-      (
-        d instanceof ExtractionError
-        or
-        d instanceof ExtractionWarning
-      )
-    )
-  }
-}

ruby/ql/lib/codeql/ruby/AST.qll

@@ -18,6 +18,7 @@ private import ast.internal.Scope
 private import ast.internal.Synthesis
 private import ast.internal.TreeSitter
 private import Customizations
+private import Diagnostics
 
 cached
 private module Cached {
@@ -166,3 +167,20 @@ class RubyFile extends File {
   /** Gets the number of lines of comments in this file. */
   int getNumberOfLinesOfComments() { result = count(int line | this.line(line, true)) }
 }
+
+/**
+ * A successfully extracted file, that is, a file that was extracted and
+ * contains no extraction errors or warnings.
+ */
+class SuccessfullyExtractedFile extends RubyFile {
+  SuccessfullyExtractedFile() {
+    not exists(Diagnostic d |
+      d.getLocation().getFile() = this and
+      (
+        d instanceof ExtractionError
+        or
+        d instanceof ExtractionWarning
+      )
+    )
+  }
+}