go/types: generic type parameter cannot be inferred from calling function's return type #50398
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Full example code: // You can edit this code!
// Click here and start typing.
package main
import "fmt"
type Optional[V any] struct {
Value V
Set bool
}
func NewSetOptional[V any](val V) Optional[V] {
return Optional[V]{
Value: val,
Set: true,
}
}
func NewUnsetOptional[V any]() Optional[V] {
return Optional[V]{
Set: false,
}
}
func ReturnsOptionalInteger() Optional[int] {
// THIS IS FINE:
return NewSetOptional(3)
}
func ReturnsUnsetOptionalInteger() Optional[int] {
// DOES NOT COMPILE:
// should be able to infer V from function return type
return NewUnsetOptional()
// Workaround:
// return NewUnsetOptional[int]()
}
func main() {
fmt.Println("%v", ReturnsOptionalInteger())
fmt.Println("%v", ReturnsUnsetOptionalInteger())
}
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andrewortman
changed the title
andrewortman
changed the title
|
Duplicate of #49297 |
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What version of Go are you using (
go version)?Does this issue reproduce with the latest release?
With the current beta1 release
What operating system and processor architecture are you using (
go env)?go envOutputWhat did you do?
Reproduction: https://go.dev/play/p/GYUfSmIuzx4?v=gotip
What did you expect to see?
In the sandbox code, the function
ReturnsUnsetOptionalIntegershould have compiled because the generic parameter V could be inferred from it's explicit return type Optional[int]What did you see instead?
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