Rust: Add get(Immediate)Child predicate

Author: hvitved

misc/codegen/templates/ql_parent.mustache

@@ -79,6 +79,11 @@ Element getImmediateParent(Element e) {
     result = unique(Element x | e = Impl::getImmediateChild(x, _, _) | x)
 }
 
+/**
+* Gets the immediate child indexed at `index`. Indexes are not guaranteed to be contiguous, but are guaranteed to be distinct.
+*/
+Element getImmediateChild(Element e, int index) { result = Impl::getImmediateChild(e, index, _) }
+
 /**
 * Gets the immediate child indexed at `index`. Indexes are not guaranteed to be contiguous, but are guaranteed to be distinct. `accessor` is bound the member predicate call resulting in the given child.
 */
@@ -92,3 +97,10 @@ Element getImmediateChildAndAccessor(Element e, int index, string accessor) {
 Element getChildAndAccessor(Element e, int index, string accessor) {
     exists(string partialAccessor | result = Impl::getImmediateChild(e, index, partialAccessor).resolve() and accessor = "get" + partialAccessor)
 }
+
+/**
+* Gets the child indexed at `index`. Indexes are not guaranteed to be contiguous, but are guaranteed to be distinct. `accessor` is bound the member predicate call resulting in the given child.
+*/
+Element getChild(Element e, int index) {
+    result = Impl::getImmediateChild(e, index, _).resolve()
+}

rust/ql/.generated.list

@@ -236,13 +236,11 @@ module Impl {
       this instanceof VariableScope or
       this instanceof VariableAccessCand or
       this instanceof LetStmt or
-      getImmediateChildAndAccessor(this, _, _) instanceof RelevantElement
+      getImmediateChild(this, _) instanceof RelevantElement
     }
 
     pragma[nomagic]
-    private RelevantElement getChild(int index) {
-      result = getImmediateChildAndAccessor(this, index, _)
-    }
+    private RelevantElement getChild(int index) { result = getImmediateChild(this, index) }
 
     pragma[nomagic]
     private RelevantElement getImmediateChildMin(int index) {

rust/ql/lib/codeql/rust/elements/internal/VariableImpl.qll

@@ -38,7 +38,7 @@ query predicate multiplePrimaryQlClasses(Element e, string s) {
   s = strictconcat(e.getPrimaryQlClasses(), ", ")
 }
 
-private Element getParent(Element child) { child = getChildAndAccessor(result, _, _) }
+private Element getParent(Element child) { child = getChild(result, _) }
 
 private predicate multipleParents(Element child) { strictcount(getParent(child)) > 1 }
 
@@ -54,8 +54,8 @@ query predicate multipleParents(Element child, string childClass, Element parent
 
 /** Holds if `parent` has multiple children at the same index. */
 query predicate multipleChildren(Element parent, int index, Element child1, Element child2) {
-  child1 = getChildAndAccessor(parent, index, _) and
-  child2 = getChildAndAccessor(parent, index, _) and
+  child1 = getChild(parent, index) and
+  child2 = getChild(parent, index) and
   child1 != child2
 }