Implement class variables

ql/src/codeql_ruby/ast/internal/Variable.qll

@@ -22,6 +22,11 @@ private predicate instanceVariableAccess(
   else instance = false
 }
 
+private predicate classVariableAccess(Generated::ClassVariable var, string name, VariableScope scope) {
+  name = var.getValue() and
+  scope = enclosingModuleOrClass(var)
+}
+
 private VariableScope enclosingMethod(Generated::AstNode node) {
   exists(VariableScope scope, Callable c |
     scope = outerScope*(enclosingScope(node)) and
@@ -145,7 +150,14 @@ private module Cached {
   cached
   newtype TVariable =
     TGlobalVariable(string name) { name = any(Generated::GlobalVariable var).getValue() } or
-    TClassVariable(VariableScope scope, string name, Generated::AstNode decl) { none() } or
+    TClassVariable(VariableScope scope, string name, Generated::AstNode decl) {
+      decl =
+        min(Generated::ClassVariable other |
+          classVariableAccess(other, name, scope)
+        |
+          other order by other.getLocation().getStartLine(), other.getLocation().getStartColumn()
+        )
+    } or
     TInstanceVariable(VariableScope scope, string name, boolean instance, Generated::AstNode decl) {
       decl =
         min(Generated::InstanceVariable other |
@@ -549,7 +561,12 @@ module ClassVariableAccess {
   class Range extends VariableAccess::Range, @token_class_variable {
     ClassVariable variable;
 
-    Range() { this.(Generated::ClassVariable).getValue() = variable.getName() }
+    Range() {
+      exists(VariableScope scope, string name |
+        variable = TClassVariable(scope, name, _) and
+        classVariableAccess(this, name, scope)
+      )
+    }
 
     final override ClassVariable getVariable() { result = variable }
   }

ql/test/library-tests/variables/class_variables.rb

@@ -0,0 +1,29 @@
+@@x = 42
+
+p @@x
+
+def print
+ p @@x
+end
+
+class X
+  def b
+    p @@x
+  end
+  def self.s
+   p @@x
+  end
+end 
+
+class Y < BasicObject
+  @@x = 10
+end 
+
+module M
+  @@x = 12
+end
+
+module N
+  include M
+  p @@x
+end

ql/test/library-tests/variables/varaccess.expected

@@ -1,4 +1,12 @@
 variableAccess
+| class_variables.rb:1:1:1:3 | @@x | class_variables.rb:1:1:1:3 | @@x | class_variables.rb:1:1:29:4 | top-level scope |
+| class_variables.rb:3:3:3:5 | @@x | class_variables.rb:1:1:1:3 | @@x | class_variables.rb:1:1:29:4 | top-level scope |
+| class_variables.rb:6:4:6:6 | @@x | class_variables.rb:1:1:1:3 | @@x | class_variables.rb:1:1:29:4 | top-level scope |
+| class_variables.rb:11:7:11:9 | @@x | class_variables.rb:11:7:11:9 | @@x | class_variables.rb:9:1:16:3 | class scope |
+| class_variables.rb:14:6:14:8 | @@x | class_variables.rb:11:7:11:9 | @@x | class_variables.rb:9:1:16:3 | class scope |
+| class_variables.rb:19:3:19:5 | @@x | class_variables.rb:19:3:19:5 | @@x | class_variables.rb:18:1:20:3 | class scope |
+| class_variables.rb:23:3:23:5 | @@x | class_variables.rb:23:3:23:5 | @@x | class_variables.rb:22:1:24:3 | module scope |
+| class_variables.rb:28:5:28:7 | @@x | class_variables.rb:28:5:28:7 | @@x | class_variables.rb:26:1:29:3 | module scope |
 | instance_variables.rb:1:1:1:4 | @top | instance_variables.rb:1:1:1:4 | @top | instance_variables.rb:1:1:44:4 | top-level scope |
 | instance_variables.rb:4:3:4:6 | @foo | instance_variables.rb:4:3:4:6 | @foo | instance_variables.rb:1:1:44:4 | top-level scope |
 | instance_variables.rb:8:8:8:11 | @foo | instance_variables.rb:4:3:4:6 | @foo | instance_variables.rb:1:1:44:4 | top-level scope |
@@ -234,6 +242,14 @@ implicitWrite
 | ssa.rb:64:8:64:8 | a |
 | ssa.rb:66:15:66:15 | a |
 readAccess
+| class_variables.rb:1:1:1:3 | @@x |
+| class_variables.rb:3:3:3:5 | @@x |
+| class_variables.rb:6:4:6:6 | @@x |
+| class_variables.rb:11:7:11:9 | @@x |
+| class_variables.rb:14:6:14:8 | @@x |
+| class_variables.rb:19:3:19:5 | @@x |
+| class_variables.rb:23:3:23:5 | @@x |
+| class_variables.rb:28:5:28:7 | @@x |
 | instance_variables.rb:1:1:1:4 | @top |
 | instance_variables.rb:4:3:4:6 | @foo |
 | instance_variables.rb:8:8:8:11 | @foo |

ql/test/library-tests/variables/variable.expected

@@ -1,3 +1,8 @@
+| class_variables.rb:1:1:1:3 | @@x |
+| class_variables.rb:11:7:11:9 | @@x |
+| class_variables.rb:19:3:19:5 | @@x |
+| class_variables.rb:23:3:23:5 | @@x |
+| class_variables.rb:28:5:28:7 | @@x |
 | file://:0:0:0:0 | $0 |
 | file://:0:0:0:0 | $global |
 | instance_variables.rb:1:1:1:4 | @top |

ql/test/library-tests/variables/varscopes.expected

@@ -1,3 +1,11 @@
+| class_variables.rb:1:1:29:4 | top-level scope |
+| class_variables.rb:5:1:7:3 | method scope |
+| class_variables.rb:9:1:16:3 | class scope |
+| class_variables.rb:10:3:12:5 | method scope |
+| class_variables.rb:13:3:15:5 | method scope |
+| class_variables.rb:18:1:20:3 | class scope |
+| class_variables.rb:22:1:24:3 | module scope |
+| class_variables.rb:26:1:29:3 | module scope |
 | file://:0:0:0:0 | global scope |
 | instance_variables.rb:1:1:44:4 | top-level scope |
 | instance_variables.rb:3:1:5:3 | method scope |