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reflect: StructOf allows creation of impossible types #23063

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dsnet opened this issue Dec 8, 2017 · 2 comments
Closed

reflect: StructOf allows creation of impossible types #23063

dsnet opened this issue Dec 8, 2017 · 2 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.11

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@dsnet
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dsnet commented Dec 8, 2017

The validation logic in reflect.StructOf needs some work.

Can embed an anonymous type

t := reflect.TypeOf(struct{ Nobody string }{})
sf := reflect.StructField{Name: "Billy", Type: t, Anonymous: true}
t2 := reflect.StructOf([]reflect.StructField{sf})
t2.Field(0) // StructField{Name: "Billy", Type: t, Anonymous: true}

This is invalid because the Go language forbids embedding an anonymous type.

Can rename an embedded type

type Batman struct{ Banananananana string }
t := reflect.TypeOf(Batman{})
sf := reflect.StructField{Name: "Superman", Type: t, Anonymous: true}
t2 := reflect.StructOf([]reflect.StructField{sf})
t2.Field(0) // StructField{Name: "Superman", Type: t, Anonymous: true}

When a type is embedded, the field takes on the name of the type. However, I was able to rename the field to Superman, when it should have been Batman.
@dsnet dsnet added the NeedsFix The path to resolution is known, but the work has not been done. label Dec 8, 2017
@dsnet dsnet added this to the Go1.11 milestone Dec 8, 2017
@jimmyfrasche
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Renaming is to support type aliases.

@dsnet
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dsnet commented Dec 8, 2017

Renaming is to support type aliases.

Ah, you are correct. Type aliases actually make both cases possible.

@dsnet dsnet closed this as completed Dec 8, 2017
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.11
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