Move common expression classes to simple parsing setup

src/Parser/Parsing/Simple/Expression/ISimpleExpression.h

@@ -0,0 +1,20 @@
+#pragma once
+
+class SimpleExpressionValue;
+class ISimpleExpression
+{
+protected:
+    ISimpleExpression() = default;
+public:
+    virtual ~ISimpleExpression() = default;
+    ISimpleExpression(const ISimpleExpression& other) = default;
+    ISimpleExpression(ISimpleExpression&& other) noexcept = default;
+    ISimpleExpression& operator=(const ISimpleExpression& other) = default;
+    ISimpleExpression& operator=(ISimpleExpression&& other) noexcept = default;
+
+    virtual bool IsStatic() = 0;
+    virtual SimpleExpressionValue Evaluate() = 0;
+};
+
+// Include SimpleExpressionValue after definition to avoid "base class not defined"
+#include "SimpleExpressionValue.h"