Question

我试图在Go中进行一些元编程，我试图使用go/ast包。

这是创建AST的片段：

// Create an AST
fooFn := &ast.FuncDecl{
    Name: &ast.Ident{Name: "foofn"},
    Body: &ast.BlockStmt{
        List: []ast.Stmt{&ast.ExprStmt{
            X: &ast.CallExpr{
                Fun: &ast.Ident{Name: "println"},
                Args: []ast.Expr{
                    &ast.BasicLit{Kind: token.INT, Value: "42"},
                },
            },
        }},
    },
}

f := &ast.File{
    Name:  &ast.Ident{Name: "foopackage"},
    Decls: []ast.Decl{fooFn},
    Scope: &ast.Scope{
        Objects: map[string]*ast.Object{
            "Foo": &ast.Object{
                Kind: ast.Fun,
                Name: "Foo",
                Decl: fooFn,
            },
        },
    },
}

请参阅此处http://play.golang.org/p/zTJdnqVx__的完整代码，该代码应生成此输出：

panic: runtime error: invalid memory address or nil pointer dereference
[signal 0xb code=0xffffffff addr=0x0 pc=0x773ae]

goroutine 16 [running]:
runtime.panic(0x18b5a0, 0x24c8af)
    /tmp/sandbox/go/src/pkg/runtime/panic.c:279 +0x120
go/ast.(*FuncType).Pos(0x0, 0x1c827eb4, 0xfefd02b8, 0x10422360)
    /tmp/sandbox/go/src/pkg/go/ast/ast.go:446 +0x2e
go/ast.(*FuncDecl).Pos(0x10422360, 0x10422360, 0x47, 0xfeee1cb0)
    /tmp/sandbox/go/src/pkg/go/ast/ast.go:933 +0x40
go/printer.(*printer).declList(0x10402840, 0x1040e108, 0x1, 0x1)
    /tmp/sandbox/go/src/pkg/go/printer/nodes.go:1587 +0x180
go/printer.(*printer).file(0x10402840, 0x10442080)
    /tmp/sandbox/go/src/pkg/go/printer/nodes.go:1597 +0x1e0
go/printer.(*printer).printNode(0x10402840, 0x184ba0, 0x10442080, 0x104223c0, 0x0, 0x0)
    /tmp/sandbox/go/src/pkg/go/printer/printer.go:1087 +0xa40
go/printer.(*Config).fprint(0xfeee1e90, 0xfefd02d8, 0x10426180, 0x104181b0, 0x184ba0, 0x10442080, 0x104223c0, 0xfefd02d8, 0x0, 0x0)
    /tmp/sandbox/go/src/pkg/go/printer/printer.go:1226 +0xc0
go/printer.(*Config).Fprint(0xfeee1e90, 0xfefd02d8, 0x10426180, 0x104181b0, 0x184ba0, 0x10442080, 0x0, 0x0)
    /tmp/sandbox/go/src/pkg/go/printer/printer.go:1284 +0xa0
main.main()
    /tmpfs/gosandbox-eb231fa6_4e4e43ec_79a6f993_ce4170ce_07ee185b/prog.go:46 +0x8c0

修改：这是设置FuncDelc.Type并删除Scope的工作版本（因为我只在源代码缓冲区之后）：

http://play.golang.org/p/B0Xp61rSce

Answer 1

您可能需要向ast.FuncType提供ast.FuncDecl。该错误似乎是在您的（无）IsValid()的{{1}}属性上调用Func的结果。

使用go / ast包

http://play.golang.org/p/B0Xp61rSce

1 个答案: