Go: cast slice of primitive to a slice of its alias

Question

I'm trying to do something along these lines:

package main                                                                                                                                                                                                                                   

import (          
    "fmt"         
)                 

type StringWrap string

func main() {     
    s := []string{"a","b","c"}
    sw := []StringWrap(s) //ERROR: cannot convert s (type []string) to type []StringWrap
    fmt.Println(sw)
}

Am I doing something wrong? Or is this simply a limitation in go?

peterSO · Accepted Answer · 2013-07-13T03:16:26.030

The Go Programming Language Specification

Types

A type determines the set of values and operations specific to values of that type. A type may be specified by a (possibly qualified) type name or a type literal, which composes a new type from previously declared types.
Type      = TypeName | TypeLit | "(" Type ")" .
TypeName  = identifier | QualifiedIdent .
TypeLit   = ArrayType | StructType | PointerType | FunctionType |
            InterfaceType | SliceType | MapType | ChannelType .
Named instances of the boolean, numeric, and string types are predeclared. Composite types—array, struct, pointer, function, interface, slice, map, and channel types—may be constructed using type literals.

Each type T has an underlying type: If T is a predeclared type or a type literal, the corresponding underlying type is T itself. Otherwise, T's underlying type is the underlying type of the type to which T refers in its type declaration.
   type T1 string
   type T2 T1
   type T3 []T1
   type T4 T3
The underlying type of string, T1, and T2 is string. The underlying type of []T1, T3, and T4 is []T1.

Conversions

Conversions are expressions of the form T(x) where T is a type and x is an expression that can be converted to type T.

A non-constant value x can be converted to type T in the case: x's type and T have identical underlying types.

For example,

package main

import "fmt"

type StringSliceWrap []string

func main() {
    s := []string{"a", "b", "c"}
    ssw := StringSliceWrap(s)
    fmt.Println(ssw)
}

Output:

[a b c]

Go: cast slice of primitive to a slice of its alias

1 Answers1