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xuwei-k/Scala-2-12

Last active October 5, 2023 05:29
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scala xml pattern match
Raw
Scala-2-12
Welcome to Scala 2.12.18 (OpenJDK 64-Bit Server VM, Java 11.0.20).
Type in expressions for evaluation. Or try :help.
scala> val <a>{ b }</a> = <a></a>
scala.MatchError: <a></a> (of class scala.xml.Elem)
... 55 elided
scala> val <a>{ _ }</a> = <a>c</a>
scala> val <a>{ _* }</a> = <a>c</a>
Raw
Scala-2-13
Welcome to Scala 2.13.12 (OpenJDK 64-Bit Server VM, Java 11.0.20).
Type in expressions for evaluation. Or try :help.
scala> val <a>{ b }</a> = <a></a>
scala.MatchError: <a></a> (of class scala.xml.Elem)
... 59 elided
scala> val <a>{ _ }</a> = <a>c</a>
scala> val <a>{ _* }</a> = <a>c</a>
Raw
Scala-3
Welcome to Scala 3.3.1 (11.0.20, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
scala> val <a>{ b }</a> = <a></a>
1 warning found
-- Warning: --------------------------------------------------------------------
1 |val <a>{ b }</a> = <a></a>
| ^^^^^^^^^^^^^^^^^^^^^
|pattern binding uses refutable extractor `_root_.scala.xml.Elem`
|
|If this usage is intentional, this can be communicated by adding `: @unchecked` after the expression,
|which may result in a MatchError at runtime.
scala.MatchError: <a></a> (of class scala.xml.Elem)
... 66 elided
scala> val <a>{ _ }</a> = <a>c</a>
1 warning found
-- Warning: --------------------------------------------------------------------
1 |val <a>{ _ }</a> = <a>c</a>
| ^^^^^^^^^^^^^^^^^^^^^^
|pattern binding uses refutable extractor `_root_.scala.xml.Elem`
|
|If this usage is intentional, this can be communicated by adding `: @unchecked` after the expression,
|which may result in a MatchError at runtime.
scala> val <a>{ _* }</a> = <a>c</a>
-- [E032] Syntax Error: --------------------------------------------------------
1 |val <a>{ _* }</a> = <a>c</a>
| ^
| pattern expected
|
| longer explanation available when compiling with `-explain`
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