Improve warning for wildcard matching non-nullable types (scala#21577) #21623
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Adds a more detailed warning message when a wildcard case is unreachable on an non-nullable type to suggest adding a nullable type annotation. Fixes scala#21577
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Sep 21, 2024
| @@ -215,6 +215,7 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe | |||
| case TailrecNestedCallID //errorNumber: 199 | |||
| case FinalLocalDefID // errorNumber: 200 | |||
| case NonNamedArgumentInJavaAnnotationID // errorNumber: 201 | |||
| case MatchCaseNonNullableWildcardWarningID // errorNumber: 202 | |||
| @@ -928,7 +928,11 @@ object SpaceEngine { | |||
| && isSubspace(covered, prev) | |||
| then { | |||
| val nullOnly = isNullable && i == len - 1 && isWildcardArg(pat) | |||
| val msg = if nullOnly then MatchCaseOnlyNullWarning() else MatchCaseUnreachable() | |||
| val wildcardNotNullable = i == len - 1 && isWildcardArg(pat) | |||
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I don't think this will work. It will catch other cases which are not related to null. You may want to modify isNullable, since a flexible type is considered "nullable" in terms of values.
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Adds a more detailed warning message when a wildcard case is unreachable on an non-nullable type to suggest adding a nullable type annotation.
Fixes #21577
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