add consistency test that parents are unique (and fix non-unique parents)

ql/ql/src/codeql_ql/ast/Ast.qll

@@ -162,6 +162,8 @@ class QLDoc extends TQLDoc, AstNode {
   string getContents() { result = qldoc.getValue() }
 
   override string getAPrimaryQlClass() { result = "QLDoc" }
+
+  override AstNode getParent() { result.getQLDoc() = this }
 }
 
 class BlockComment extends TBlockComment, AstNode {
@@ -2313,7 +2315,7 @@ class Annotation extends TAnnotation, AstNode {
   /** Gets the node corresponding to the field `name`. */
   string getName() { result = annot.getName().getValue() }
 
-  override AstNode getParent() { result = AstNode.super.getParent() }
+  override AstNode getParent() { result.getAnAnnotation() = this }
 
   override AstNode getAChild(string pred) {
     result = super.getAChild(pred)

ql/ql/src/codeql_ql/ast/internal/AstNodes.qll

@@ -231,4 +231,6 @@ module AstConsistency {
     not node instanceof YAML::YAMLNode and // parents for YAML doens't work
     not (node instanceof QLDoc and node.getLocation().getFile().getExtension() = "dbscheme") // qldoc in dbschemes are not hooked up
   }
+
+  query predicate nonUniqueParent(AstNode node) { count(node.getParent()) >= 2 }
 }

ql/ql/src/queries/diagnostics/EmptyConsistencies.ql

@@ -31,7 +31,9 @@ where
   TypeConsistency::multiplePrimitivesExpr(node, _, _) and
   msg = "TypeConsistency::multiplePrimitivesExpr"
   or
-  AstConsistency::nonTotalGetParent(node) and msg = "AstConsistency::nonTotalGetParent" // TODO: unique parent
+  AstConsistency::nonTotalGetParent(node) and msg = "AstConsistency::nonTotalGetParent"
+  or
+  AstConsistency::nonUniqueParent(node) and msg = "AstConsistency::nonUniqueParent"
   or
   TypeConsistency::noResolve(node) and msg = "TypeConsistency::noResolve"
   or
@@ -47,4 +49,3 @@ where
   or
   VarConsistency::noVarDef(node) and msg = "VarConsistency::noVarDef"
 select node, msg
-// TODO: vardef consistency.