Stupid Go declaration tricks

This is a brief post highlighting a curious aspect of the declaration syntax in Go.

Most Go programmers know that the following of import declarations are equivalent

import "fmt"
import "math/big"

// same as
import (
        "fmt"
        "math/big"
)

The same applies to const declarations

const FORTYTWO = 42
const TRUE = 1

// same as
const (
        FORTYTWO = 42
        TRUE     = 1
)

But perhaps you didn’t know that the syntax is also valid for type declarations. For example, the following is valid syntax in Go.

type (
        B struct{ a, b int }
        C interface {
                Hello() error
        }
)

However because the func declaration has been extended to place methods on types, the following is not valid syntax

func (
        main() {
                fmt.Println("wowzers")
        }
)

Dave Cheney