From 214f1130165ada0ee47d2711aef6c11b6dad28c5 Mon Sep 17 00:00:00 2001
From: Arthur Baars <aibaars@github.com>
Date: Wed, 17 Feb 2021 13:36:01 +0100
Subject: [PATCH 1/8] AST: add getChild/getParent method

---
 ql/src/codeql_ruby/AST.qll              | 6 ++++++
 ql/src/codeql_ruby/ast/internal/AST.qll | 2 ++
 2 files changed, 8 insertions(+)

diff --git a/ql/src/codeql_ruby/AST.qll b/ql/src/codeql_ruby/AST.qll
index 11c41330aa4..28a05877c5f 100644
--- a/ql/src/codeql_ruby/AST.qll
+++ b/ql/src/codeql_ruby/AST.qll
@@ -36,4 +36,10 @@ class AstNode extends @ast_node {
 
   /** Gets the location of this node. */
   final Location getLocation() { result = range.getLocation() }
+
+  /** Gets a child node of this `AstNode`. */
+  final AstNode getAChild() { range.child(_, result) }
+
+  /** Gets the parent of this `AstNode`, if this node is not a root node. */
+  final AstNode getParent() { result.getAChild() = this }
 }
diff --git a/ql/src/codeql_ruby/ast/internal/AST.qll b/ql/src/codeql_ruby/ast/internal/AST.qll
index b09355148a1..8fb1159c83f 100644
--- a/ql/src/codeql_ruby/ast/internal/AST.qll
+++ b/ql/src/codeql_ruby/ast/internal/AST.qll
@@ -11,6 +11,8 @@ module AstNode {
     abstract string toString();
 
     Location getLocation() { result = generated.getLocation() }
+
+    predicate child(string label, AstNode::Range child) { none() }
   }
 
   // TODO: Remove

From e42d1ff936b5c9efef4c52999777194dfe037ca9 Mon Sep 17 00:00:00 2001
From: Arthur Baars <aibaars@github.com>
Date: Thu, 18 Feb 2021 13:19:22 +0100
Subject: [PATCH 2/8] Change Expr to LhsExpr for getVariableExpr

---
 ql/src/codeql_ruby/ast/Expr.qll          | 2 +-
 ql/src/codeql_ruby/ast/internal/Expr.qll | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/ql/src/codeql_ruby/ast/Expr.qll b/ql/src/codeql_ruby/ast/Expr.qll
index fa0bc6af7c9..7b6537e8166 100644
--- a/ql/src/codeql_ruby/ast/Expr.qll
+++ b/ql/src/codeql_ruby/ast/Expr.qll
@@ -177,7 +177,7 @@ class RescueClause extends Expr, @rescue {
    * end
    * ```
    */
-  final Expr getVariableExpr() { result = range.getVariableExpr() }
+  final LhsExpr getVariableExpr() { result = range.getVariableExpr() }
 
   /**
    * Gets the exception handler body.
diff --git a/ql/src/codeql_ruby/ast/internal/Expr.qll b/ql/src/codeql_ruby/ast/internal/Expr.qll
index fabab40880c..f258501e309 100644
--- a/ql/src/codeql_ruby/ast/internal/Expr.qll
+++ b/ql/src/codeql_ruby/ast/internal/Expr.qll
@@ -123,9 +123,9 @@ module RescueClause {
   class Range extends Expr::Range, @rescue {
     final override Generated::Rescue generated;
 
-    final LhsExpr getException(int n) { result = generated.getExceptions().getChild(n) }
+    final Expr getException(int n) { result = generated.getExceptions().getChild(n) }
 
-    final Expr getVariableExpr() { result = generated.getVariable() }
+    final LhsExpr getVariableExpr() { result = generated.getVariable().getChild() }
 
     final StmtSequence getBody() { result = generated.getBody() }
 

From 095eb803b3f7152838f00842f3ac770ef2ba2053 Mon Sep 17 00:00:00 2001
From: Arthur Baars <aibaars@github.com>
Date: Thu, 18 Feb 2021 13:43:14 +0100
Subject: [PATCH 3/8] AST: improve type of getDefaultValue

---
 ql/src/codeql_ruby/ast/Parameter.qll          | 6 ++----
 ql/src/codeql_ruby/ast/internal/Parameter.qll | 4 ++--
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/ql/src/codeql_ruby/ast/Parameter.qll b/ql/src/codeql_ruby/ast/Parameter.qll
index 76cba8c717f..88d77727488 100644
--- a/ql/src/codeql_ruby/ast/Parameter.qll
+++ b/ql/src/codeql_ruby/ast/Parameter.qll
@@ -120,9 +120,8 @@ class KeywordParameter extends @keyword_parameter, NamedParameter {
    * Gets the default value, i.e. the value assigned to the parameter when one
    * is not provided by the caller. If the parameter is mandatory and does not
    * have a default value, this predicate has no result.
-   * TODO: better return type (Expr?)
    */
-  final AstNode getDefaultValue() { result = range.getDefaultValue() }
+  final Expr getDefaultValue() { result = range.getDefaultValue() }
 
   /**
    * Holds if the parameter is optional. That is, there is a default value that
@@ -148,9 +147,8 @@ class OptionalParameter extends @optional_parameter, NamedParameter {
   /**
    * Gets the default value, i.e. the value assigned to the parameter when one
    * is not provided by the caller.
-   * TODO: better return type (Expr?)
    */
-  final AstNode getDefaultValue() { result = range.getDefaultValue() }
+  final Expr getDefaultValue() { result = range.getDefaultValue() }
 }
 
 /**
diff --git a/ql/src/codeql_ruby/ast/internal/Parameter.qll b/ql/src/codeql_ruby/ast/internal/Parameter.qll
index a891df165f0..5d4026eda5c 100644
--- a/ql/src/codeql_ruby/ast/internal/Parameter.qll
+++ b/ql/src/codeql_ruby/ast/internal/Parameter.qll
@@ -100,7 +100,7 @@ module KeywordParameter {
       result = TLocalVariable(_, _, generated.getName())
     }
 
-    final Generated::AstNode getDefaultValue() { result = generated.getValue() }
+    final Expr::Range getDefaultValue() { result = generated.getValue() }
 
     final override string toString() { result = this.getName() }
 
@@ -116,7 +116,7 @@ module OptionalParameter {
       result = TLocalVariable(_, _, generated.getName())
     }
 
-    final Generated::AstNode getDefaultValue() { result = generated.getValue() }
+    final Expr::Range getDefaultValue() { result = generated.getValue() }
 
     final override string toString() { result = this.getName() }
 

From c0b5ac760adce486a90a2c8aba3a71035bfe26a1 Mon Sep 17 00:00:00 2001
From: Arthur Baars <aibaars@github.com>
Date: Thu, 18 Feb 2021 13:25:03 +0100
Subject: [PATCH 4/8] AST: rename getLhs/getRhs to
 getLeftOperand/getRightOperand

---
 ql/src/codeql_ruby/ast/Operation.qll             |  4 ++--
 ql/src/codeql_ruby/ast/Variable.qll              |  2 +-
 ql/src/codeql_ruby/ast/internal/Operation.qll    | 16 +++++++++-------
 ql/src/codeql_ruby/controlflow/CfgNodes.qll      |  4 ++--
 .../library-tests/ast/operations/assignment.ql   |  8 ++++----
 5 files changed, 18 insertions(+), 16 deletions(-)

diff --git a/ql/src/codeql_ruby/ast/Operation.qll b/ql/src/codeql_ruby/ast/Operation.qll
index 3544a9dd3f4..1b2458777f5 100644
--- a/ql/src/codeql_ruby/ast/Operation.qll
+++ b/ql/src/codeql_ruby/ast/Operation.qll
@@ -445,10 +445,10 @@ class Assignment extends Operation {
   override Assignment::Range range;
 
   /** Gets the left hand side of this assignment. */
-  final Expr getLhs() { result = range.getLhs() }
+  final Expr getLeftOperand() { result = range.getLeftOperand() }
 
   /** Gets the right hand side of this assignment. */
-  final Expr getRhs() { result = range.getRhs() }
+  final Expr getRightOperand() { result = range.getRightOperand() }
 }
 
 /**
diff --git a/ql/src/codeql_ruby/ast/Variable.qll b/ql/src/codeql_ruby/ast/Variable.qll
index 0159c63b6f0..6f283d813ed 100644
--- a/ql/src/codeql_ruby/ast/Variable.qll
+++ b/ql/src/codeql_ruby/ast/Variable.qll
@@ -156,7 +156,7 @@ class VariableReadAccess extends VariableAccess {
     not this instanceof VariableWriteAccess
     or
     // `x` in `x += y` is considered both a read and a write
-    this = any(AssignOperation a).getLhs()
+    this = any(AssignOperation a).getLeftOperand()
   }
 }
 
diff --git a/ql/src/codeql_ruby/ast/internal/Operation.qll b/ql/src/codeql_ruby/ast/internal/Operation.qll
index 0a0715961f3..c55af802ef8 100644
--- a/ql/src/codeql_ruby/ast/internal/Operation.qll
+++ b/ql/src/codeql_ruby/ast/internal/Operation.qll
@@ -218,11 +218,13 @@ module NoRegexMatchExpr {
 
 module Assignment {
   abstract class Range extends Operation::Range {
-    abstract Expr getLhs();
+    abstract Pattern getLeftOperand();
 
-    abstract Expr getRhs();
+    abstract Expr getRightOperand();
 
-    final override Expr getAnOperand() { result = this.getLhs() or result = this.getRhs() }
+    final override Expr getAnOperand() {
+      result = this.getLeftOperand() or result = this.getRightOperand()
+    }
 
     override string toString() { result = "... " + this.getOperator() + " ..." }
   }
@@ -232,9 +234,9 @@ module AssignExpr {
   class Range extends Assignment::Range, @assignment {
     final override Generated::Assignment generated;
 
-    final override Expr getLhs() { result = generated.getLeft() }
+    final override Pattern getLeftOperand() { result = generated.getLeft() }
 
-    final override Expr getRhs() { result = generated.getRight() }
+    final override Expr getRightOperand() { result = generated.getRight() }
 
     final override string getOperator() { result = "=" }
   }
@@ -246,9 +248,9 @@ module AssignOperation {
 
     final override string getOperator() { result = generated.getOperator() }
 
-    final override LhsExpr getLhs() { result = generated.getLeft() }
+    final override LhsExpr getLeftOperand() { result = generated.getLeft() }
 
-    final override Expr getRhs() { result = generated.getRight() }
+    final override Expr getRightOperand() { result = generated.getRight() }
   }
 }
 
diff --git a/ql/src/codeql_ruby/controlflow/CfgNodes.qll b/ql/src/codeql_ruby/controlflow/CfgNodes.qll
index 58b0bf717df..2258f02c28b 100644
--- a/ql/src/codeql_ruby/controlflow/CfgNodes.qll
+++ b/ql/src/codeql_ruby/controlflow/CfgNodes.qll
@@ -218,10 +218,10 @@ module ExprNodes {
     final override Assignment getExpr() { result = ExprCfgNode.super.getExpr() }
 
     /** Gets the LHS of this assignment. */
-    final ExprCfgNode getLhs() { e.hasCfgChild(e.getLhs(), this, result) }
+    final ExprCfgNode getLhs() { e.hasCfgChild(e.getLeftOperand(), this, result) }
 
     /** Gets the RHS of this assignment. */
-    final ExprCfgNode getRhs() { e.hasCfgChild(e.getRhs(), this, result) }
+    final ExprCfgNode getRhs() { e.hasCfgChild(e.getRightOperand(), this, result) }
   }
 
   /** A control-flow node that wraps an `AssignExpr` AST expression. */
diff --git a/ql/test/library-tests/ast/operations/assignment.ql b/ql/test/library-tests/ast/operations/assignment.ql
index 83828da3ce7..3ff3b3f7684 100644
--- a/ql/test/library-tests/ast/operations/assignment.ql
+++ b/ql/test/library-tests/ast/operations/assignment.ql
@@ -2,8 +2,8 @@ import ruby
 
 query predicate assignments(Assignment a, string operator, Expr left, Expr right, string pClass) {
   operator = a.getOperator() and
-  left = a.getLhs() and
-  right = a.getRhs() and
+  left = a.getLeftOperand() and
+  right = a.getRightOperand() and
   pClass = a.getAPrimaryQlClass()
 }
 
@@ -11,8 +11,8 @@ query predicate assignOperations(
   AssignOperation o, string operator, Expr left, Expr right, string pClass
 ) {
   operator = o.getOperator() and
-  left = o.getLhs() and
-  right = o.getRhs() and
+  left = o.getLeftOperand() and
+  right = o.getRightOperand() and
   pClass = o.getAPrimaryQlClass()
 }
 

From 5659388ec087b2f297a38203be2dff6cc2d46609 Mon Sep 17 00:00:00 2001
From: Arthur Baars <aibaars@github.com>
Date: Thu, 18 Feb 2021 13:33:08 +0100
Subject: [PATCH 5/8] AST: implement AstNode::child

---
 ql/src/codeql_ruby/ast/internal/Call.qll      | 21 ++++++
 ql/src/codeql_ruby/ast/internal/Constant.qll  |  5 ++
 ql/src/codeql_ruby/ast/internal/Control.qll   | 73 +++++++++++++++++++
 ql/src/codeql_ruby/ast/internal/Expr.qll      | 39 ++++++++++
 ql/src/codeql_ruby/ast/internal/Literal.qll   | 22 ++++++
 ql/src/codeql_ruby/ast/internal/Method.qll    | 35 +++++++++
 ql/src/codeql_ruby/ast/internal/Module.qll    | 27 +++++++
 ql/src/codeql_ruby/ast/internal/Operation.qll | 37 +++++++++-
 ql/src/codeql_ruby/ast/internal/Parameter.qll |  6 ++
 ql/src/codeql_ruby/ast/internal/Pattern.qll   |  4 +
 ql/src/codeql_ruby/ast/internal/Statement.qll | 16 ++++
 ql/src/codeql_ruby/ast/internal/Variable.qll  |  2 +
 12 files changed, 286 insertions(+), 1 deletion(-)

diff --git a/ql/src/codeql_ruby/ast/internal/Call.qll b/ql/src/codeql_ruby/ast/internal/Call.qll
index b8eb59965d6..ca35a21e07c 100644
--- a/ql/src/codeql_ruby/ast/internal/Call.qll
+++ b/ql/src/codeql_ruby/ast/internal/Call.qll
@@ -1,4 +1,5 @@
 private import codeql_ruby.AST
+private import codeql_ruby.ast.internal.AST
 private import codeql_ruby.ast.internal.Expr
 private import codeql_ruby.ast.internal.TreeSitter
 private import codeql_ruby.ast.internal.Variable
@@ -14,6 +15,14 @@ module Call {
     abstract Block getBlock();
 
     override string toString() { result = "call to " + this.getMethodName() }
+
+    final override predicate child(string label, AstNode::Range child) {
+      label = "getReceiver" and child = getReceiver()
+      or
+      label = "getArgument" and child = getArgument(_)
+      or
+      label = "getBlock" and child = getBlock()
+    }
   }
 
   private class IdentifierCallRange extends Call::Range, @token_identifier {
@@ -144,6 +153,10 @@ module BlockArgument {
     final Expr getExpr() { result = generated.getChild() }
 
     final override string toString() { result = "&..." }
+
+    final override predicate child(string label, AstNode::Range child) {
+      label = "getExpr" and child = getExpr()
+    }
   }
 }
 
@@ -154,6 +167,10 @@ module SplatArgument {
     final Expr getExpr() { result = generated.getChild() }
 
     final override string toString() { result = "*..." }
+
+    final override predicate child(string label, AstNode::Range child) {
+      label = "getExpr" and child = getExpr()
+    }
   }
 }
 
@@ -164,5 +181,9 @@ module HashSplatArgument {
     final Expr getExpr() { result = generated.getChild() }
 
     final override string toString() { result = "**..." }
+
+    final override predicate child(string label, AstNode::Range child) {
+      label = "getExpr" and child = getExpr()
+    }
   }
 }
diff --git a/ql/src/codeql_ruby/ast/internal/Constant.qll b/ql/src/codeql_ruby/ast/internal/Constant.qll
index f40feda50b3..87082ae35c7 100644
--- a/ql/src/codeql_ruby/ast/internal/Constant.qll
+++ b/ql/src/codeql_ruby/ast/internal/Constant.qll
@@ -1,3 +1,4 @@
+private import codeql_ruby.ast.internal.AST
 private import codeql_ruby.ast.internal.Expr
 private import codeql_ruby.ast.internal.Pattern
 private import codeql_ruby.ast.internal.TreeSitter
@@ -12,6 +13,10 @@ module ConstantAccess {
     abstract Expr::Range getScopeExpr();
 
     abstract predicate hasGlobalScope();
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getScopeExpr" and child = getScopeExpr()
+    }
   }
 }
 
diff --git a/ql/src/codeql_ruby/ast/internal/Control.qll b/ql/src/codeql_ruby/ast/internal/Control.qll
index 518cb8e7505..c8a1e9d300c 100644
--- a/ql/src/codeql_ruby/ast/internal/Control.qll
+++ b/ql/src/codeql_ruby/ast/internal/Control.qll
@@ -1,4 +1,5 @@
 private import codeql_ruby.AST
+private import codeql_ruby.ast.internal.AST
 private import codeql_ruby.ast.internal.Expr
 private import codeql_ruby.ast.internal.Pattern
 private import codeql_ruby.ast.internal.TreeSitter
@@ -12,6 +13,12 @@ module ConditionalExpr {
     abstract Expr getCondition();
 
     abstract Expr getBranch(boolean cond);
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getCondition" and child = getCondition()
+      or
+      label = "getBranch" and child = getBranch(_)
+    }
   }
 }
 
@@ -24,6 +31,14 @@ module IfExpr {
     final override string toString() {
       if this instanceof @elsif then result = "elsif ..." else result = "if ..."
     }
+
+    override predicate child(string label, AstNode::Range child) {
+      super.child(label, child)
+      or
+      label = "getThen" and child = getThen()
+      or
+      label = "getElse" and child = getElse()
+    }
   }
 
   private class IfRange extends IfExpr::Range, @if {
@@ -76,6 +91,14 @@ module UnlessExpr {
     }
 
     final override string toString() { result = "unless ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      ConditionalExpr::Range.super.child(label, child)
+      or
+      label = "getThen" and child = getThen()
+      or
+      label = "getElse" and child = getElse()
+    }
   }
 }
 
@@ -90,6 +113,12 @@ module IfModifierExpr {
     final override Expr getBranch(boolean cond) { cond = true and result = getExpr() }
 
     final override string toString() { result = "... if ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      ConditionalExpr::Range.super.child(label, child)
+      or
+      label = "getExpr" and child = getExpr()
+    }
   }
 }
 
@@ -104,6 +133,12 @@ module UnlessModifierExpr {
     final override Expr getBranch(boolean cond) { cond = false and result = getExpr() }
 
     final override string toString() { result = "... unless ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      ConditionalExpr::Range.super.child(label, child)
+      or
+      label = "getExpr" and child = getExpr()
+    }
   }
 }
 
@@ -124,6 +159,14 @@ module TernaryIfExpr {
     }
 
     final override string toString() { result = "... ? ... : ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      ConditionalExpr::Range.super.child(label, child)
+      or
+      label = "getThen" and child = getThen()
+      or
+      label = "getElse" and child = getElse()
+    }
   }
 }
 
@@ -136,6 +179,12 @@ module CaseExpr {
     final Expr getBranch(int n) { result = generated.getChild(n) }
 
     final override string toString() { result = "case ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getValue" and child = getValue()
+      or
+      label = "getBranch" and child = getBranch(_)
+    }
   }
 }
 
@@ -148,18 +197,34 @@ module WhenExpr {
     final Expr getPattern(int n) { result = generated.getPattern(n).getChild() }
 
     final override string toString() { result = "when ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getBody" and child = getBody()
+      or
+      label = "getPattern" and child = getPattern(_)
+    }
   }
 }
 
 module Loop {
   abstract class Range extends ControlExpr::Range {
     abstract Expr getBody();
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getBody" and child = getBody()
+    }
   }
 }
 
 module ConditionalLoop {
   abstract class Range extends Loop::Range {
     abstract Expr getCondition();
+
+    override predicate child(string label, AstNode::Range child) {
+      super.child(label, child)
+      or
+      label = "getCondition" and child = getCondition()
+    }
   }
 }
 
@@ -222,5 +287,13 @@ module ForExpr {
     final Expr getValue() { result = generated.getValue().getChild() }
 
     final override string toString() { result = "for ... in ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      Loop::Range.super.child(label, child)
+      or
+      label = "getPattern" and child = getPattern()
+      or
+      label = "getValue" and child = getValue()
+    }
   }
 }
diff --git a/ql/src/codeql_ruby/ast/internal/Expr.qll b/ql/src/codeql_ruby/ast/internal/Expr.qll
index f258501e309..1d10bf85680 100644
--- a/ql/src/codeql_ruby/ast/internal/Expr.qll
+++ b/ql/src/codeql_ruby/ast/internal/Expr.qll
@@ -1,4 +1,5 @@
 private import codeql_ruby.AST
+private import codeql_ruby.ast.internal.AST
 private import codeql_ruby.ast.internal.Literal
 private import codeql_ruby.ast.internal.Statement
 private import codeql_ruby.ast.internal.TreeSitter
@@ -30,6 +31,10 @@ module StmtSequence {
         c > 1 and result = "...; ..."
       )
     }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getStmt" and child = getStmt(_)
+    }
   }
 }
 
@@ -56,6 +61,16 @@ module BodyStatement {
     final StmtSequence getEnsure() { result = unique(Generated::Ensure s | s = getChild(_)) }
 
     abstract Generated::AstNode getChild(int i);
+
+    override predicate child(string label, AstNode::Range child) {
+      StmtSequence::Range.super.child(label, child)
+      or
+      label = "getRescue" and child = getRescue(_)
+      or
+      label = "getElse" and child = getElse()
+      or
+      label = "getEnsure" and child = getEnsure()
+    }
   }
 }
 
@@ -130,6 +145,14 @@ module RescueClause {
     final StmtSequence getBody() { result = generated.getBody() }
 
     final override string toString() { result = "rescue ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getException" and child = getException(_)
+      or
+      label = "getVariableExpr" and child = getVariableExpr()
+      or
+      label = "getBody" and child = getBody()
+    }
   }
 }
 
@@ -142,6 +165,12 @@ module RescueModifierExpr {
     final Stmt getHandler() { result = generated.getHandler() }
 
     final override string toString() { result = "... rescue ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getBody" and child = getBody()
+      or
+      label = "getHandler" and child = getHandler()
+    }
   }
 }
 
@@ -154,6 +183,12 @@ module Pair {
     final Expr getValue() { result = generated.getValue() }
 
     final override string toString() { result = "Pair" }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getKey" and child = getKey()
+      or
+      label = "getValue" and child = getValue()
+    }
   }
 }
 
@@ -164,5 +199,9 @@ module StringConcatenation {
     final StringLiteral::Range getString(int i) { result = generated.getChild(i) }
 
     final override string toString() { result = "\"...\" \"...\"" }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getString" and child = getString(_)
+    }
   }
 }
diff --git a/ql/src/codeql_ruby/ast/internal/Literal.qll b/ql/src/codeql_ruby/ast/internal/Literal.qll
index bd2243b93c5..2aab1ede55e 100644
--- a/ql/src/codeql_ruby/ast/internal/Literal.qll
+++ b/ql/src/codeql_ruby/ast/internal/Literal.qll
@@ -128,6 +128,10 @@ module StringInterpolationComponent {
     }
 
     final override string getValueText() { none() }
+
+    override predicate child(string label, AstNode::Range child) {
+      StmtSequence::Range.super.child(label, child)
+    }
   }
 }
 
@@ -176,6 +180,10 @@ module StringlikeLiteral {
         result = this.getStartDelimiter() + summary + this.getEndDelimiter()
       )
     }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getComponent" and child = getComponent(_)
+    }
   }
 }
 
@@ -340,6 +348,10 @@ module ArrayLiteral {
     final override string getValueText() { none() }
 
     abstract Expr getElement(int i);
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getElement" and child = getElement(_)
+    }
   }
 
   private class RegularArrayRange extends ArrayLiteral::Range, @array {
@@ -376,6 +388,10 @@ module HashLiteral {
     final Expr getElement(int i) { result = generated.getChild(i) }
 
     final override string toString() { result = "{...}" }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getElement" and child = getElement(_)
+    }
   }
 }
 
@@ -394,6 +410,12 @@ module RangeLiteral {
     final predicate isInclusive() { this instanceof @range_dotdot }
 
     final predicate isExclusive() { this instanceof @range_dotdotdot }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getBegin" and child = getBegin()
+      or
+      label = "getEnd" and child = getEnd()
+    }
   }
 }
 
diff --git a/ql/src/codeql_ruby/ast/internal/Method.qll b/ql/src/codeql_ruby/ast/internal/Method.qll
index f4d3779e639..49540f9b788 100644
--- a/ql/src/codeql_ruby/ast/internal/Method.qll
+++ b/ql/src/codeql_ruby/ast/internal/Method.qll
@@ -1,4 +1,5 @@
 private import codeql_ruby.AST
+private import codeql_ruby.ast.internal.AST
 private import codeql_ruby.ast.internal.Expr
 private import codeql_ruby.ast.internal.Parameter
 private import TreeSitter
@@ -6,6 +7,10 @@ private import TreeSitter
 module Callable {
   abstract class Range extends Expr::Range {
     abstract Parameter::Range getParameter(int n);
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getParameter" and child = getParameter(_)
+    }
   }
 }
 
@@ -25,6 +30,10 @@ module Method {
     final override Generated::AstNode getChild(int i) { result = generated.getChild(i) }
 
     final override string toString() { result = this.getName() }
+
+    override predicate child(string label, AstNode::Range child) {
+      Callable::Range.super.child(label, child) or BodyStatement::Range.super.child(label, child)
+    }
   }
 }
 
@@ -45,6 +54,14 @@ module SingletonMethod {
     final override Generated::AstNode getChild(int i) { result = generated.getChild(i) }
 
     final override string toString() { result = this.getName() }
+
+    override predicate child(string label, AstNode::Range child) {
+      Callable::Range.super.child(label, child)
+      or
+      BodyStatement::Range.super.child(label, child)
+      or
+      label = "getObject" and child = getObject()
+    }
   }
 }
 
@@ -62,12 +79,24 @@ module Lambda {
     }
 
     final override string toString() { result = "-> { ... }" }
+
+    override predicate child(string label, AstNode::Range child) {
+      Callable::Range.super.child(label, child)
+      or
+      BodyStatement::Range.super.child(label, child)
+    }
   }
 }
 
 module Block {
   abstract class Range extends Callable::Range, StmtSequence::Range {
     Range() { not generated.getParent() instanceof Generated::Lambda }
+
+    override predicate child(string label, AstNode::Range child) {
+      Callable::Range.super.child(label, child)
+      or
+      StmtSequence::Range.super.child(label, child)
+    }
   }
 }
 
@@ -82,6 +111,12 @@ module DoBlock {
     }
 
     final override string toString() { result = "do ... end" }
+
+    override predicate child(string label, AstNode::Range child) {
+      Block::Range.super.child(label, child)
+      or
+      BodyStatement::Range.super.child(label, child)
+    }
   }
 }
 
diff --git a/ql/src/codeql_ruby/ast/internal/Module.qll b/ql/src/codeql_ruby/ast/internal/Module.qll
index 3897435bf4b..79bb29429cd 100644
--- a/ql/src/codeql_ruby/ast/internal/Module.qll
+++ b/ql/src/codeql_ruby/ast/internal/Module.qll
@@ -1,4 +1,5 @@
 private import codeql_ruby.AST
+private import codeql_ruby.ast.internal.AST
 private import codeql_ruby.ast.internal.Constant
 private import codeql_ruby.ast.internal.Expr
 private import codeql_ruby.ast.internal.TreeSitter
@@ -23,6 +24,12 @@ module Toplevel {
     }
 
     final override string toString() { result = generated.getLocation().getFile().getBaseName() }
+
+    override predicate child(string label, AstNode::Range child) {
+      ModuleBase::Range.super.child(label, child)
+      or
+      label = "getBeginBlock" and child = getBeginBlock(_)
+    }
   }
 }
 
@@ -52,6 +59,14 @@ module Class {
     final Expr getSuperclassExpr() { result = generated.getSuperclass().getChild() }
 
     final override string toString() { result = this.getName() }
+
+    override predicate child(string label, AstNode::Range child) {
+      ModuleBase::Range.super.child(label, child)
+      or
+      ConstantWriteAccess::Range.super.child(label, child)
+      or
+      label = "getSuperclassExpr" and child = getSuperclassExpr()
+    }
   }
 }
 
@@ -64,6 +79,12 @@ module SingletonClass {
     final Expr getValue() { result = generated.getValue() }
 
     final override string toString() { result = "class << ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      ModuleBase::Range.super.child(label, child)
+      or
+      label = "getValue" and child = getValue()
+    }
   }
 }
 
@@ -91,5 +112,11 @@ module Module {
     }
 
     final override string toString() { result = this.getName() }
+
+    override predicate child(string label, AstNode::Range child) {
+      ModuleBase::Range.super.child(label, child)
+      or
+      ConstantWriteAccess::Range.super.child(label, child)
+    }
   }
 }
diff --git a/ql/src/codeql_ruby/ast/internal/Operation.qll b/ql/src/codeql_ruby/ast/internal/Operation.qll
index c55af802ef8..f6ad5e158d0 100644
--- a/ql/src/codeql_ruby/ast/internal/Operation.qll
+++ b/ql/src/codeql_ruby/ast/internal/Operation.qll
@@ -1,4 +1,5 @@
-import codeql_ruby.AST
+private import codeql_ruby.AST
+private import codeql_ruby.ast.internal.AST
 private import codeql_ruby.ast.internal.TreeSitter
 private import codeql_ruby.ast.internal.Expr
 
@@ -7,6 +8,10 @@ module Operation {
     abstract string getOperator();
 
     abstract Expr getAnOperand();
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getAnOperand" and child = getAnOperand()
+    }
   }
 }
 
@@ -21,6 +26,12 @@ module UnaryOperation {
     final override Expr getAnOperand() { result = this.getOperand() }
 
     override string toString() { result = this.getOperator() + " ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      Operation::Range.super.child(label, child)
+      or
+      label = "getOperand" and child = getOperand()
+    }
   }
 }
 
@@ -73,6 +84,14 @@ module BinaryOperation {
     }
 
     override string toString() { result = "... " + this.getOperator() + " ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      Operation::Range.super.child(label, child)
+      or
+      label = "getLeftOperand" and child = getLeftOperand()
+      or
+      label = "getRightOperand" and child = getRightOperand()
+    }
   }
 }
 
@@ -169,6 +188,14 @@ module RelationalOperation {
     abstract Expr getGreaterOperand();
 
     abstract Expr getLesserOperand();
+
+    override predicate child(string label, AstNode::Range child) {
+      ComparisonOperation::Range.super.child(label, child)
+      or
+      label = "getGreaterOperand" and child = getGreaterOperand()
+      or
+      label = "getLesserOperand" and child = getLesserOperand()
+    }
   }
 }
 
@@ -227,6 +254,14 @@ module Assignment {
     }
 
     override string toString() { result = "... " + this.getOperator() + " ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      Operation::Range.super.child(label, child)
+      or
+      label = "getLeftOperand" and child = getLeftOperand()
+      or
+      label = "getRightOperand" and child = getRightOperand()
+    }
   }
 }
 
diff --git a/ql/src/codeql_ruby/ast/internal/Parameter.qll b/ql/src/codeql_ruby/ast/internal/Parameter.qll
index 5d4026eda5c..d73339e4da4 100644
--- a/ql/src/codeql_ruby/ast/internal/Parameter.qll
+++ b/ql/src/codeql_ruby/ast/internal/Parameter.qll
@@ -1,6 +1,7 @@
 private import codeql_ruby.AST
 private import TreeSitter
 private import codeql_ruby.ast.internal.AST
+private import codeql_ruby.ast.internal.Expr
 private import codeql_ruby.ast.internal.Variable
 private import codeql_ruby.ast.internal.Method
 private import codeql_ruby.ast.internal.Pattern
@@ -61,6 +62,11 @@ module TuplePatternParameter {
     override LocalVariable getAVariable() { result = TuplePattern::Range.super.getAVariable() }
 
     override string toString() { result = TuplePattern::Range.super.toString() }
+
+    override predicate child(string label, AstNode::Range child) {
+      PatternParameter::Range.super.child(label, child) or
+      TuplePattern::Range.super.child(label, child)
+    }
   }
 }
 
diff --git a/ql/src/codeql_ruby/ast/internal/Pattern.qll b/ql/src/codeql_ruby/ast/internal/Pattern.qll
index 205439881d2..44ea94e2704 100644
--- a/ql/src/codeql_ruby/ast/internal/Pattern.qll
+++ b/ql/src/codeql_ruby/ast/internal/Pattern.qll
@@ -101,5 +101,9 @@ module TuplePattern {
     override Variable getAVariable() { result = this.getElement(_).getAVariable() }
 
     override string toString() { result = "(..., ...)" }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getElement" and child = getElement(_)
+    }
   }
 }
diff --git a/ql/src/codeql_ruby/ast/internal/Statement.qll b/ql/src/codeql_ruby/ast/internal/Statement.qll
index 7c0aee758bd..8fd7291b503 100644
--- a/ql/src/codeql_ruby/ast/internal/Statement.qll
+++ b/ql/src/codeql_ruby/ast/internal/Statement.qll
@@ -12,6 +12,8 @@ module EmptyStmt {
     final override Generated::EmptyStatement generated;
 
     final override string toString() { result = ";" }
+
+    override predicate child(string label, AstNode::Range child) { none() }
   }
 }
 
@@ -32,6 +34,10 @@ module UndefStmt {
     final MethodName getMethodName(int n) { result = generated.getChild(n) }
 
     final override string toString() { result = "undef ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getMethodName" and child = getMethodName(_)
+    }
   }
 }
 
@@ -44,6 +50,12 @@ module AliasStmt {
     final MethodName getOldName() { result = generated.getAlias() }
 
     final override string toString() { result = "alias ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getNewName" and child = getNewName()
+      or
+      label = "getOldName" and child = getOldName()
+    }
   }
 }
 
@@ -60,6 +72,10 @@ module ReturningStmt {
         result = a and c > 1
       )
     }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getValue" and child = getValue()
+    }
   }
 }
 
diff --git a/ql/src/codeql_ruby/ast/internal/Variable.qll b/ql/src/codeql_ruby/ast/internal/Variable.qll
index 24f1cb1e733..a0e2ea83056 100644
--- a/ql/src/codeql_ruby/ast/internal/Variable.qll
+++ b/ql/src/codeql_ruby/ast/internal/Variable.qll
@@ -578,6 +578,8 @@ module VariableAccess {
     abstract Variable getVariable();
 
     final override string toString() { result = this.getVariable().getName() }
+
+    override predicate child(string label, AstNode::Range child) { none() }
   }
 }
 

From 3ee83870b6def22a1cf75ed1b01b81149b407271 Mon Sep 17 00:00:00 2001
From: Arthur Baars <aibaars@github.com>
Date: Thu, 18 Feb 2021 13:41:47 +0100
Subject: [PATCH 6/8] AST: add begin expressions

---
 ql/src/codeql_ruby/ast/Statement.qll          | 16 ++++++++++++++-
 ql/src/codeql_ruby/ast/internal/Expr.qll      | 10 ----------
 ql/src/codeql_ruby/ast/internal/Statement.qll | 20 +++++++++++++++++++
 3 files changed, 35 insertions(+), 11 deletions(-)

diff --git a/ql/src/codeql_ruby/ast/Statement.qll b/ql/src/codeql_ruby/ast/Statement.qll
index e30f0c15fd7..2e6e6c37509 100644
--- a/ql/src/codeql_ruby/ast/Statement.qll
+++ b/ql/src/codeql_ruby/ast/Statement.qll
@@ -36,7 +36,21 @@ class EmptyStmt extends Stmt, @token_empty_statement {
 }
 
 /**
- * An `BEGIN` block.
+ * A `begin` statement.
+ * ```rb
+ * begin
+ *  puts "hello world"
+ * end
+ * ```
+ */
+class BeginExpr extends BodyStatement, @begin {
+  final override Begin::Range range;
+
+  final override string getAPrimaryQlClass() { result = "BeginExpr" }
+}
+
+/**
+ * A `BEGIN` block.
  * ```rb
  * BEGIN { puts "starting ..." }
  * ```
diff --git a/ql/src/codeql_ruby/ast/internal/Expr.qll b/ql/src/codeql_ruby/ast/internal/Expr.qll
index 1d10bf85680..337589a5653 100644
--- a/ql/src/codeql_ruby/ast/internal/Expr.qll
+++ b/ql/src/codeql_ruby/ast/internal/Expr.qll
@@ -90,16 +90,6 @@ module ParenthesizedExpr {
   }
 }
 
-module BeginBlock {
-  class Range extends StmtSequence::Range, @begin_block {
-    final override Generated::BeginBlock generated;
-
-    final override Stmt getStmt(int n) { result = generated.getChild(n) }
-
-    final override string toString() { result = "BEGIN { ... }" }
-  }
-}
-
 module ThenExpr {
   class Range extends StmtSequence::Range, @then {
     final override Generated::Then generated;
diff --git a/ql/src/codeql_ruby/ast/internal/Statement.qll b/ql/src/codeql_ruby/ast/internal/Statement.qll
index 8fd7291b503..08d5d2a19bc 100644
--- a/ql/src/codeql_ruby/ast/internal/Statement.qll
+++ b/ql/src/codeql_ruby/ast/internal/Statement.qll
@@ -17,6 +17,26 @@ module EmptyStmt {
   }
 }
 
+module Begin {
+  class Range extends BodyStatement::Range, @begin {
+    final override Generated::Begin generated;
+
+    final override Generated::AstNode getChild(int n) { result = generated.getChild(n) }
+
+    final override string toString() { result = "begin ... " }
+  }
+}
+
+module BeginBlock {
+  class Range extends StmtSequence::Range, @begin_block {
+    final override Generated::BeginBlock generated;
+
+    final override Stmt getStmt(int n) { result = generated.getChild(n) }
+
+    final override string toString() { result = "BEGIN { ... }" }
+  }
+}
+
 module EndBlock {
   class Range extends StmtSequence::Range, @end_block {
     final override Generated::EndBlock generated;

From c877eb46428020f6a46ad36b04a84a85d4af5a4b Mon Sep 17 00:00:00 2001
From: Arthur Baars <aibaars@github.com>
Date: Thu, 18 Feb 2021 13:42:52 +0100
Subject: [PATCH 7/8] AST: add additional token-types to variable patterns

---
 ql/src/codeql_ruby/ast/Pattern.qll          | 2 +-
 ql/src/codeql_ruby/ast/internal/Pattern.qll | 7 +++++--
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/ql/src/codeql_ruby/ast/Pattern.qll b/ql/src/codeql_ruby/ast/Pattern.qll
index 4be8084c198..82ed5d1ff90 100644
--- a/ql/src/codeql_ruby/ast/Pattern.qll
+++ b/ql/src/codeql_ruby/ast/Pattern.qll
@@ -35,7 +35,7 @@ class LhsExpr extends Pattern, Expr {
 }
 
 /** A simple variable pattern. */
-class VariablePattern extends Pattern {
+class VariablePattern extends Pattern, VariablePattern::VariableToken {
   override VariablePattern::Range range;
 
   /** Gets the variable used in (or introduced by) this pattern. */
diff --git a/ql/src/codeql_ruby/ast/internal/Pattern.qll b/ql/src/codeql_ruby/ast/internal/Pattern.qll
index 44ea94e2704..275e483107a 100644
--- a/ql/src/codeql_ruby/ast/internal/Pattern.qll
+++ b/ql/src/codeql_ruby/ast/internal/Pattern.qll
@@ -64,8 +64,11 @@ module LhsExpr {
 }
 
 module VariablePattern {
-  class Range extends LhsExpr::Range, @token_identifier {
-    override Generated::Identifier generated;
+  class VariableToken =
+    @token_identifier or @token_instance_variable or @token_class_variable or @token_global_variable;
+
+  class Range extends LhsExpr::Range, VariableToken {
+    override Generated::Token generated;
 
     string getVariableName() { result = generated.getValue() }
 

From 1c8a76f44a71f781e648c6a083a6ec9b389c2a61 Mon Sep 17 00:00:00 2001
From: Arthur Baars <aibaars@github.com>
Date: Thu, 18 Feb 2021 18:14:55 +0100
Subject: [PATCH 8/8] AST: make Assignment::getLeftOperand a Pattern again

---
 ql/src/codeql_ruby/ast/internal/Operation.qll | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ql/src/codeql_ruby/ast/internal/Operation.qll b/ql/src/codeql_ruby/ast/internal/Operation.qll
index f6ad5e158d0..9144598e139 100644
--- a/ql/src/codeql_ruby/ast/internal/Operation.qll
+++ b/ql/src/codeql_ruby/ast/internal/Operation.qll
@@ -245,7 +245,7 @@ module NoRegexMatchExpr {
 
 module Assignment {
   abstract class Range extends Operation::Range {
-    abstract Pattern getLeftOperand();
+    abstract Expr getLeftOperand();
 
     abstract Expr getRightOperand();
 
@@ -269,7 +269,7 @@ module AssignExpr {
   class Range extends Assignment::Range, @assignment {
     final override Generated::Assignment generated;
 
-    final override Pattern getLeftOperand() { result = generated.getLeft() }
+    final override Expr getLeftOperand() { result = generated.getLeft() }
 
     final override Expr getRightOperand() { result = generated.getRight() }