How to Resolve the 'Invalid Recursive Type' Error in Go Structs?

Invalid Recursive Type in a Struct in Go

Problem Statement

In Go, defining a struct with a recursive type can result in an "invalid recursive type" error. This error occurs when a struct contains a field of the same type as the struct itself.

For instance, the following struct definition is invalid:

type Environment struct {
    parent Environment
    symbol string
    value  RCFAEValue
}

Cause

The error occurs because the compiler cannot determine the size of the struct. A pointer's size is known, but the size of a struct that contains itself is unknown.

Solution

To resolve this issue, you need to make the parent field a pointer:

type Environment struct {
    parent *Environment // note that this is now a pointer
    symbol string
    value  RCFAEValue
}

This ensures that the size of the Environment struct is known and allows the compiler to proceed with compilation.

Creating the Environment

After updating the struct definition, you can create an Environment struct as follows:

Environment{&fun_Val.ds, fun_Val.param, exp.arg_exp.interp(env)}

By using the & operator, you are obtaining the address of the fun_Val.ds variable and assigning it to the parent field, which is type *Environment.

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