Ruby: handle private module methods

`private` can be used in both classes and modules.

ruby/ql/lib/codeql/ruby/ast/Method.qll

@@ -49,7 +49,7 @@ private class Private extends MethodCall {
    * method named `name`.
    */
   pragma[noinline]
-  predicate isRef(ClassDeclaration c, string name) {
+  predicate isRef(Namespace c, string name) {
     this = c.getAStmt() and
     name = this.getMethod().(SymbolLiteral).getValueText()
   }
@@ -59,7 +59,7 @@ private class Private extends MethodCall {
    * and the call has no arguments.
    */
   pragma[noinline]
-  predicate hasNoArg(ClassDeclaration c, int i) {
+  predicate hasNoArg(Namespace c, int i) {
     this = c.getStmt(i) and
     not exists(this.getMethod())
   }
@@ -91,7 +91,7 @@ class Method extends MethodBase, TMethod {
   final predicate isSetter() { g.getName() instanceof Ruby::Setter }
 
   pragma[noinline]
-  private predicate isDeclaredIn(ClassDeclaration c, string name) {
+  private predicate isDeclaredIn(Namespace c, string name) {
     this = c.getAStmt() and
     name = this.getName()
   }
@@ -125,12 +125,12 @@ class Method extends MethodBase, TMethod {
   predicate isPrivate() {
     this = any(Private p).getMethod()
     or
-    exists(ClassDeclaration c, Private p, string name |
+    exists(Namespace c, Private p, string name |
       this.isDeclaredIn(c, name) and
       p.isRef(c, name)
     )
     or
-    exists(ClassDeclaration c, Private p, int i, int j |
+    exists(Namespace c, Private p, int i, int j |
       p.hasNoArg(c, i) and
       this = c.getStmt(j) and
       j > i

ruby/ql/test/library-tests/modules/callgraph.expected

@@ -85,6 +85,9 @@ getTarget
 | private.rb:28:1:28:5 | call to new | calls.rb:99:5:99:16 | new |
 | private.rb:28:1:28:12 | call to public | private.rb:5:3:6:5 | public |
 | private.rb:30:1:30:15 | call to private_on_main | private.rb:21:1:22:3 | private_on_main |
+| private.rb:33:3:34:5 | call to private | calls.rb:94:5:94:20 | private |
+| private.rb:41:3:41:19 | call to private | calls.rb:94:5:94:20 | private |
+| private.rb:43:3:43:9 | call to private | calls.rb:94:5:94:20 | private |
 unresolvedCall
 | calls.rb:19:5:19:14 | call to instance_m |
 | calls.rb:20:5:20:19 | call to instance_m |
@@ -127,3 +130,7 @@ privateMethod
 | private.rb:14:3:15:5 | private3 |
 | private.rb:17:3:18:5 | private4 |
 | private.rb:21:1:22:3 | private_on_main |
+| private.rb:33:11:34:5 | private1 |
+| private.rb:39:3:40:5 | private2 |
+| private.rb:45:3:46:5 | private3 |
+| private.rb:48:3:49:5 | private4 |

ruby/ql/test/library-tests/modules/private.rb

@@ -27,4 +27,24 @@ C.new.private3
 C.new.private4
 C.new.public
 
-private_on_main
+private_on_main
+
+module D
+  private def private1
+  end
+
+  def public
+  end
+
+  def private2
+  end
+  private :private2
+
+  private
+
+  def private3
+  end
+
+  def private4
+  end
+end