go/types.Typ is a slice-of-pointer-to-struct yet uses map syntax

[Will Faught]

The go/types.Typ decl:

var Typ = []*Basic{

        Invalid:       {Invalid, 0, "invalid type"},

        Bool:          {Bool, IsBoolean, "bool"},

        Int:           {Int, IsInteger, "int"},

        Int8:          {Int8, IsInteger, "int8"},

        ...

}

Typ is a slice of pointer to Basic—got it; Basic is a struct—got it; the {Bool, IsBoolean, "bool"} stuff is clearly a Basic or *Basic—got it; but where is the map syntax coming from? How does that work?

[Ian Lance Taylor]

That's not "map syntax", it's general composite literal syntax and is
permitted for all kinds of composite literals. For a slice, it means
that the element with index `Invalid` gets the value `{Invalid, 0,
"invalid type"}`, and so forth. For a slice composite literal the
keys (in this case, `Invalid`, `Bool`, etc.) must all be non-negative
integer constant expressions.

Ian

[howar...@gmail.com]

Invalid, Bool, Int, Int8 there are const integers, and they are specifying the entry's position in the slice, allowing gaps in the list to be implicitly defined.

See this example: https://play.golang.org/p/KVqO40R6mP

[Will Faught]

Ah, I forgot about that syntax. Thanks!

On Wed, Feb 15, 2017 at 11:31 AM <howar...@gmail.com> wrote:

Invalid, Bool, Int, Int8 there are const integers, and they are specifying the entry's position in the slice, allowing gaps in the list to be implicitly defined.

See this example: https://play.golang.org/p/KVqO40R6mP

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