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32 lines
1.1 KiB
Go
32 lines
1.1 KiB
Go
// Package nodefault provides newtypes around builtin Go types
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// so that if the newtype is used as a field in a struct and that field
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// is zero-initialized (https://golang.org/ref/spec#The_zero_value),
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// accessing the field will cause a null pointer deref panic.
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// Or in other terms: It soft-enforces that the caller sets the field
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// explicitly when constructing the struct.
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//
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// Example:
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//
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// type Config struct {
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// // This field must be set to a non-nil value,
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// // forcing the caller to make their mind up
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// // about this field.
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// CriticalSetting *nodefault.Bool
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// }
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//
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// An function that takes such a Config should _not_ check for nil-ness:
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// and instead unconditionally dereference:
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//
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// func f(c Config) {
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// if (c.CriticalSetting) { }
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// }
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//
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// If the caller of f forgot to specify the .CriticalSetting
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// field, the Go runtime will issue a nil-pointer deref panic
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// and it'll be clear that the caller did not read the docs of Config.
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//
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// f(Config{}) // crashes
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//
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// f Config{ CriticalSetting: &nodefault.Bool{B: false}} // doesn't crash
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package nodefault
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