Source: ast.go in package github.com/aws/aws-sdk-go/internal/ini

package ini

ASTKind represents different states in the parse table and the type of AST that is being constructed

type ASTKind int

ASTKind* is used in the parse table to transition between the different states

const (
	ASTKindNone = ASTKind(iota)
	ASTKindStart
	ASTKindExpr
	ASTKindEqualExpr
	ASTKindStatement
	ASTKindSkipStatement
	ASTKindExprStatement
	ASTKindSectionStatement
	ASTKindNestedSectionStatement
	ASTKindCompletedNestedSectionStatement
	ASTKindCommentStatement
	ASTKindCompletedSectionStatement
)

func (k ASTKind) String() string {
	switch k {
	case ASTKindNone:
		return "none"
	case ASTKindStart:
		return "start"
	case ASTKindExpr:
		return "expr"
	case ASTKindStatement:
		return "stmt"
	case ASTKindSectionStatement:
		return "section_stmt"
	case ASTKindExprStatement:
		return "expr_stmt"
	case ASTKindCommentStatement:
		return "comment"
	case ASTKindNestedSectionStatement:
		return "nested_section_stmt"
	case ASTKindCompletedSectionStatement:
		return "completed_stmt"
	case ASTKindSkipStatement:
		return "skip"
	default:
		return ""
	}
}

AST interface allows us to determine what kind of node we are on and casting may not need to be necessary. The root is always the first node in Children

type AST struct {
	Kind      ASTKind
	Root      Token
	RootToken bool
	Children  []AST
}

func newAST(kind ASTKind, root AST, children ...AST) AST {
	return AST{
		Kind:     kind,
		Children: append([]AST{root}, children...),
	}
}

func newASTWithRootToken(kind ASTKind, root Token, children ...AST) AST {
	return AST{
		Kind:      kind,
		Root:      root,
		RootToken: true,
		Children:  children,
	}
}

AppendChild will append to the list of children an AST has.

func (a *AST) AppendChild(child AST) {
	a.Children = append(a.Children, child)
}

GetRoot will return the root AST which can be the first entry in the children list or a token.

func (a *AST) GetRoot() AST {
	if a.RootToken {
		return *a
	}

	if len(a.Children) == 0 {
		return AST{}
	}

	return a.Children[0]
}

GetChildren will return the current AST's list of children

func (a *AST) GetChildren() []AST {
	if len(a.Children) == 0 {
		return []AST{}
	}

	if a.RootToken {
		return a.Children
	}

	return a.Children[1:]
}

SetChildren will set and override all children of the AST.

func (a *AST) SetChildren(children []AST) {
	if a.RootToken {
		a.Children = children
	} else {
		a.Children = append(a.Children[:1], children...)
	}
}

Start is used to indicate the starting state of the parse table.