Goの抽象構文木（AST）を手入力してHello, Worldを作る #golang ref: http://qiita.com/tenntenn/items/0cbc6f1f00dc579fcd8c

file0.go

package main

import "fmt"

func main() {
    fmt.Println("Hello, 世界")
}

file1.go

type File struct {
        Doc        *CommentGroup   // associated documentation; or nil
        Package    token.Pos       // position of "package" keyword
        Name       *Ident          // package name
        Decls      []Decl          // top-level declarations; or nil
        Scope      *Scope          // package scope (this file only)
        Imports    []*ImportSpec   // imports in this file
        Unresolved []*Ident        // unresolved identifiers in this file
        Comments   []*CommentGroup // list of all comments in the source file
}

file10.go

type ExprStmt struct {
        X Expr // expression
}

file11.go

type CallExpr struct {
        Fun      Expr      // function expression
        Lparen   token.Pos // position of "("
        Args     []Expr    // function arguments; or nil
        Ellipsis token.Pos // position of "...", if any
        Rparen   token.Pos // position of ")"
}

file12.go

type SelectorExpr struct {
        X   Expr   // expression
        Sel *Ident // field selector
}

file13.go

type CallExpr struct {
        Fun      Expr      // function expression
        Lparen   token.Pos // position of "("
        Args     []Expr    // function arguments; or nil
        Ellipsis token.Pos // position of "...", if any
        Rparen   token.Pos // position of ")"
}

file14.go

&ast.ExprStmt{
    X: &ast.CallExpr{
        Fun: &ast.SelectorExpr{
            X:   ast.NewIdent("fmt"),
            Sel: ast.NewIdent("Println"),
        },
        Args: []ast.Expr{
            &ast.BasicLit{
                Kind:  token.STRING,
                Value: strconv.Quote("Hello, 世界"),
            },
        },
    },
}

file15.go

format.Node(os.Stdout, token.NewFileSet(), f)

file16.go

package main

import (
    "go/ast"
    "go/format"
    "go/token"
    "os"
    "strconv"
)

func main() {
    f := &ast.File{
        Name: ast.NewIdent("main"),
        Decls: []ast.Decl{
            &ast.GenDecl{
                Tok: token.IMPORT,
                Specs: []ast.Spec{
                    &ast.ImportSpec{
                        Path: &ast.BasicLit{
                            Kind:  token.STRING,
                            Value: strconv.Quote("fmt"),
                        },
                    },
                },
            },
            &ast.FuncDecl{
                Name: ast.NewIdent("main"),
                Type: &ast.FuncType{},
                Body: &ast.BlockStmt{
                    List: []ast.Stmt{
                        &ast.ExprStmt{
                            X: &ast.CallExpr{
                                Fun: &ast.SelectorExpr{
                                    X:   ast.NewIdent("fmt"),
                                    Sel: ast.NewIdent("Println"),
                                },
                                Args: []ast.Expr{
                                    &ast.BasicLit{
                                        Kind:  token.STRING,
                                        Value: strconv.Quote("Hello, 世界"),
                                    },
                                },
                            },
                        },
                    },
                },
            },
        },
    }

    format.Node(os.Stdout, token.NewFileSet(), f)
}

file2.go

type GenDecl struct {
        Doc    *CommentGroup // associated documentation; or nil
        TokPos token.Pos     // position of Tok
        Tok    token.Token   // IMPORT, CONST, TYPE, VAR
        Lparen token.Pos     // position of '(', if any
        Specs  []Spec
        Rparen token.Pos // position of ')', if any
}

file3.go

&ast.GenDecl{
    Tok: token.IMPORT,
    Specs: []ast.Spec{
        &ast.ImportSpec{
            // TODO: フィールドを埋める
        },
    },
}

file4.go

type ImportSpec struct {
        Doc     *CommentGroup // associated documentation; or nil
        Name    *Ident        // local package name (including "."); or nil
        Path    *BasicLit     // import path
        Comment *CommentGroup // line comments; or nil
        EndPos  token.Pos     // end of spec (overrides Path.Pos if nonzero)
}

file5.go

&ast.ImportSpec{
    Path: &ast.BasicLit{
        Kind:  token.STRING,
        Value: strconv.Quote("fmt"),
    },
}

file6.go

type FuncDecl struct {
        Doc  *CommentGroup // associated documentation; or nil
        Recv *FieldList    // receiver (methods); or nil (functions)
        Name *Ident        // function/method name
        Type *FuncType     // function signature: parameters, results, and position of "func" keyword
        Body *BlockStmt    // function body; or nil (forward declaration)
}

file7.go

type FuncType struct {
        Func    token.Pos  // position of "func" keyword (token.NoPos if there is no "func")
        Params  *FieldList // (incoming) parameters; non-nil
        Results *FieldList // (outgoing) results; or nil
}

file8.go

&ast.FuncDecl{
    Name: ast.NewIdent("main"),
    Type: &ast.FuncType{},
    Body: /* TODO: 本体を設定する */,
}

file9.go

type BlockStmt struct {
        Lbrace token.Pos // position of "{"
        List   []Stmt
        Rbrace token.Pos // position of "}"
}

出力結果

package main

import "fmt"

func main() {
    fmt.Println("Hello, 世界")
}