C++: Add an interface for exprs that can contribute to range analysis

cpp/ql/src/semmle/code/cpp/models/interfaces/RangeAnalysisExpr.qll

@@ -0,0 +1,16 @@
+/**
+ * Provides a class for modeling `Expr`s with a restricted range.
+ */
+import cpp
+
+/**
+ * An expression for which a range can be deduced.
+ */
+abstract class RangeAnalysisExpr extends Expr {
+  /** Gets the lower bound of the expression. */
+  abstract float getLowerBounds();
+  /** Gets the upper bound of the expression. */
+  abstract float getUpperBounds();
+  /** Holds if this expression depends on the definition `srcDef` for StackVariable `srcVar`. */
+  predicate dependsOnDef(RangeSsaDefinition srcDef, StackVariable srcVar) { none() }
+}