For case specification is change I will paste it here:

'''

If a StructInitializer is supplied, the fields are initialized by the StructMemberInitializer syntax. StructMemberInitializers with the Identifier : NonVoidInitializer syntax may be appear in any order, where Identifier is the field identifier. StructMemberInitializers with the NonVoidInitializer syntax appear in the lexical order of the fields in the StructDeclaration. 

'''

And StructMemberInitializer is defined as:

'''

StructMemberInitializer:
    NonVoidInitializer
    Identifier : NonVoidInitializer

'''

And NonVoidInitializer is defined as:

'''

NonVoidInitializer:
    ExpInitializer
    ArrayInitializer
    StructInitializer

'''

And as you can see there is ArrayInitializer

And there is definition of Array literals here

and in section 2. there is this text:

'''

By default, an array literal is typed as a dynamic array, but the element count is known at compile time. So all array literals can be implicitly converted to static array types.

'''