Swift: add QLdoc to AST consistency checks

Author: redsun82

swift/ql/lib/codeql/swift/printast/Consistency.qll

@@ -1,5 +1,17 @@
+/** Provides a set of checks that the AST is actually a tree. */
+
 private import codeql.swift.printast.PrintAstNode
 
+/** Checks that no child has more than one parent. */
+query predicate doubleParents(
+  PrintAstNode parent1, string label1, PrintAstNode parent2, string label2, PrintAstNode child
+) {
+  parent1 != parent2 and
+  parent1.hasChild(child, _, label1) and
+  parent2.hasChild(child, _, label2)
+}
+
+/** Checks that no two children share the same index. */
 query predicate doubleChildren(
   PrintAstNode parent, int index, string label1, PrintAstNode child1, string label2,
   PrintAstNode child2
@@ -9,6 +21,7 @@ query predicate doubleChildren(
   parent.hasChild(child2, index, label2)
 }
 
+/** Checks that no child is under different indexes. */
 query predicate doubleIndexes(
   PrintAstNode parent, int index1, string label1, int index2, string label2, PrintAstNode child
 ) {
@@ -17,18 +30,11 @@ query predicate doubleIndexes(
   parent.hasChild(child, index2, label2)
 }
 
-query predicate doubleParents(
-  PrintAstNode parent1, string label1, PrintAstNode parent2, string label2, PrintAstNode child
-) {
-  parent1 != parent2 and
-  parent1.hasChild(child, _, label1) and
-  parent2.hasChild(child, _, label2)
-}
-
 private predicate isChildOf(PrintAstNode parent, PrintAstNode child) {
   parent.hasChild(child, _, _)
 }
 
+/** Checks that there is no back edge. */
 query predicate parentChildLoops(PrintAstNode parent, PrintAstNode child) {
   isChildOf(parent, child) and isChildOf*(child, parent)
 }