unified: Add a basic facade AST

Author: asgerf

unified/ql/lib/codeql/unified/internal/FacadeAst.qll

@@ -0,0 +1,20 @@
+/**
+ * Provides facade AST classes, with additional hand-written members on top of the generated ones.
+ */
+overlay[local?]
+module;
+
+module Unified {
+  private import Ast::Unified as G
+  import G
+
+  class AstNode extends G::AstNode {
+    /** Holds if this AST node has a modifier with the given text. */
+    predicate hasModifier(string text) {
+      exists(Modifier mod |
+        mod.getParent() = this and
+        mod.getValue() = text
+      )
+    }
+  }
+}

unified/ql/lib/unified.qll

@@ -4,6 +4,6 @@
 
 import codeql.Locations
 import codeql.files.FileSystem
-import codeql.unified.Ast::Unified
+import codeql.unified.internal.FacadeAst::Unified
 import codeql.unified.internal.AstExtra::Public
 import codeql.unified.internal.Variables::Public