C++: Add 'expectsBooleanChild' predicate which we will need later.

Author: MathiasVP

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedElement.qll

@@ -978,6 +978,12 @@ abstract class TranslatedElement extends TTranslatedElement {
    */
   predicate hasAnImplicitDestructorCall() { none() }
 
+  /**
+   * Holds if `child` is a child element of this `TranslatedElement` and
+   * `child` is expected to return a Boolean result.
+   */
+  predicate expectsBooleanChild(TranslatedExpr child) { none() }
+
   /**
    * Gets the child index of the first destructor call that should be executed after this `TranslatedElement`
    */

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedExpr.qll

@@ -72,6 +72,11 @@ abstract class TranslatedExpr extends TranslatedElement {
    */
   Type getExprType() { result = expr.getType() }
 
+  final override predicate expectsBooleanChild(TranslatedExpr child) {
+    child = this.getAChild() and
+    child.getExprType() instanceof BoolType
+  }
+
   /**
    * Holds if the result of this `TranslatedExpr` is a glvalue.
    */

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedInitialization.qll

@@ -143,6 +143,11 @@ abstract class TranslatedInitialization extends TranslatedElement, TTranslatedIn
 
   TranslatedInitialization() { this = TTranslatedInitialization(expr) }
 
+  final override predicate expectsBooleanChild(TranslatedExpr child) {
+    child = this.getAChild() and
+    child.getExprType() instanceof BoolType
+  }
+
   final override string toString() { result = "init: " + expr.toString() }
 
   final override Declaration getFunction() {

cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/internal/TranslatedStmt.qll

@@ -320,6 +320,11 @@ abstract class TranslatedStmt extends TranslatedElement, TTranslatedStmt {
   final override Locatable getAst() { result = stmt }
 
   final override Function getFunction() { result = stmt.getEnclosingFunction() }
+
+  final override predicate expectsBooleanChild(TranslatedExpr child) {
+    child = this.getAChild() and
+    child.getExprType() instanceof BoolType
+  }
 }
 
 class TranslatedEmptyStmt extends TranslatedStmt {