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toErrorIfNull to return Result with non-null value. #86

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toErrorIfNull to return Result with non-null value. #86

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7 changes: 5 additions & 2 deletions kotlin-result/src/commonMain/kotlin/com/github/michaelbull/result/Map.kt
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Original file line number Diff line number Diff line change
Expand Up @@ -195,15 +195,18 @@ public inline fun <V, E> Result<V, E>.toErrorIf(predicate: (V) -> Boolean, trans
*
* @see [toErrorIf]
*/
public inline fun <V, E> Result<V, E>.toErrorIfNull(error: () -> E): Result<V, E> {
public inline fun <V, E> Result<V?, E>.toErrorIfNull(error: () -> E): Result<V, E> {
contract {
callsInPlace(error, InvocationKind.AT_MOST_ONCE)
}

return toErrorIf(
{ it == null },
{ error() }
)
).map {
@Suppress("UNCHECKED_CAST")
it as V
}
}

/**
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2 changes: 1 addition & 1 deletion kotlin-result/src/commonTest/kotlin/com/github/michaelbull/result/MapTest.kt
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Expand Up @@ -192,7 +192,7 @@ class MapTest {

@Test
fun returnsTransformedErrorIfNull() {
val result = Ok(null).toErrorIfNull { "a" }
val result: Result<Nothing, String> = Ok(null).toErrorIfNull { "a" }
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This would not have compiled before because the return type of toErrorIfNull was Result<Nothing?, String> which should not be possible.


result as Err

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