Why Can\'t I Directly Convert a `[]string` to `[]interface{}` in Go?

Why Conversion from []string to []interface{} Fails in Go

In Go, attempting to convert a slice of strings ([]string) to a slice of interfaces ([]interface{}) triggers a compilation error. This comes as a surprise to some developers, given the following observations:

• Both []string and []interface{} are slices.
• Each element of []string is a string, which is a valid type for []interface{}.

Therefore, it seems reasonable to expect the conversion to succeed automatically. However, this is not the case due to the different memory layouts of the two slice types.

Memory Layouts

A []string slice consists of an array containing the individual strings. In contrast, a []interface{} slice holds both type information and pointers to the actual interface values. Since an interface{} variable can hold values of different types, the associated type information is crucial for retrieving those values correctly.

Conversion Complexity

Converting from a []string to a []interface{} requires copying both the strings and their type information into a new memory location. This process is both time-consuming and susceptible to errors.

Clarity and Reasoning

Automatic conversion in this scenario would introduce potential ambiguity into code. For instance, if a function f(s) accepts a []string argument, modifying the strings within s would have no impact on the slice passed to f. However, if f instead takes a []interface{} argument, modifications within s would be reflected in the passed slice.

To maintain clarity and avoid unexpected behavior, Go prohibits automatic conversion between slices of different base types. Developers must explicitly handle these conversions if desired, ensuring that the memory layouts and type information are maintained appropriately.

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