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Match if sub cases #23786

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Merged
hamzaremmal merged 16 commits into from
Aug 21, 2025
Merged

Match if sub cases #23786

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0a391cd
Add SubMatch Tree
EugeneFlesselle Aug 13, 2025
17ca7fc
Add scala.language.experimental.matchWithSubCases
EugeneFlesselle Aug 13, 2025
3922789
Add parsing of match sub cases
EugeneFlesselle Aug 13, 2025
4c28954
Add pickling of match sub cases
EugeneFlesselle Aug 13, 2025
5e46b01
Handle sub cases in PatternMatcher
EugeneFlesselle Aug 13, 2025
e26be67
Handle exhaustivity and reachability checking of matches with sub cases
EugeneFlesselle Aug 13, 2025
352317c
Handle inlining of matches with sub cases
EugeneFlesselle Aug 13, 2025
3e89455
Test match with sub sub cases and catch with sub cases
EugeneFlesselle Aug 14, 2025
3b86dc9
Handle partial functions with sub cases
EugeneFlesselle Aug 15, 2025
4da6103
Rename experimental feature to `subCases`
EugeneFlesselle Aug 15, 2025
f7e0512
Allow single sub case without new line
EugeneFlesselle Aug 15, 2025
367acdd
Replace sub match introducer keyword from `with` to `if`
EugeneFlesselle Aug 20, 2025
24bdb6e
Fix error case EmptyTree span
EugeneFlesselle Aug 20, 2025
e5a73b0
Use preexisting tag for pickling of match with sub cases
EugeneFlesselle Aug 21, 2025
466da83
Add reference doc
EugeneFlesselle Aug 21, 2025
c432c0f
Apply suggestions from code review
hamzaremmal Aug 21, 2025
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Rename experimental feature to subCases 
Avoids the issue with match completion with suggests importing the feature.
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@EugeneFlesselle
EugeneFlesselle committed Aug 15, 2025
commit 4da6103fe94961bf3792d169aa4e0a613454e92e
2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/config/Feature.scala
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Expand Up @@ -37,7 +37,7 @@ object Feature:
val modularity = experimental("modularity")
val quotedPatternsWithPolymorphicFunctions = experimental("quotedPatternsWithPolymorphicFunctions")
val packageObjectValues = experimental("packageObjectValues")
val matchWithSubCases = experimental("matchWithSubCases")
val subCases = experimental("subCases")

def experimentalAutoEnableFeatures(using Context): List[TermName] =
defn.languageExperimentalFeatures
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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/parsing/Parsers.scala
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Expand Up @@ -3108,7 +3108,7 @@ object Parsers {
(withinMatchPattern(pattern()), guard())
}
val body =
if in.token == WITH && in.featureEnabled(Feature.matchWithSubCases) then atSpan(in.skipToken()):
if in.token == WITH && in.featureEnabled(Feature.subCases) then atSpan(in.skipToken()):
subMatchClause(simpleExpr(Location.ElseWhere))
else atSpan(accept(ARROW)):
if exprOnly then
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6 changes: 3 additions & 3 deletions library/src/scala/language.scala
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Expand Up @@ -350,10 +350,10 @@ object language {
@compileTimeOnly("`packageObjectValues` can only be used at compile time in import statements")
object packageObjectValues

/** Experimental support for match expressions with sub-cases.
/** Experimental support for match expressions with sub cases.
*/
@compileTimeOnly("`matchWithSubCases` can only be used at compile time in import statements")
object matchWithSubCases
@compileTimeOnly("`subCases` can only be used at compile time in import statements")
object subCases

}

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6 changes: 3 additions & 3 deletions library/src/scala/runtime/stdLibPatches/language.scala
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Expand Up @@ -155,10 +155,10 @@ object language:
@compileTimeOnly("`packageObjectValues` can only be used at compile time in import statements")
object packageObjectValues

/** Experimental support for match expressions with sub-cases.
/** Experimental support for match expressions with sub cases.
*/
@compileTimeOnly("`matchWithSubCases` can only be used at compile time in import statements")
object matchWithSubCases
@compileTimeOnly("`subCases` can only be used at compile time in import statements")
object subCases
end experimental

/** The deprecated object contains features that are no longer officially suypported in Scala.
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2 changes: 1 addition & 1 deletion tests/pos/inline-sub-match.scala → tests/pos/inline-match-sub-cases.scala
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@@ -1,4 +1,4 @@
import scala.language.experimental.matchWithSubCases
import scala.language.experimental.subCases

object Test:

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2 changes: 1 addition & 1 deletion tests/pos/sub-sub-match.scala → tests/pos/match-sub-sub-cases.scala
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@@ -1,4 +1,4 @@
import scala.language.experimental.matchWithSubCases
import scala.language.experimental.subCases

object Test:
val x: Option[Option[Int]] = ???
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2 changes: 1 addition & 1 deletion tests/run/sub-catch.scala → tests/run/catch-sub-cases.scala
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@@ -1,4 +1,4 @@
import scala.language.experimental.matchWithSubCases
import scala.language.experimental.subCases

enum E extends Exception:
case A(x: Any)
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2 changes: 1 addition & 1 deletion tests/run/sub-cases.scala → tests/run/match-sub-cases.scala
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import scala.language.experimental.matchWithSubCases
import scala.language.experimental.subCases

enum E:
case A(e: E)
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2 changes: 1 addition & 1 deletion tests/run/pf-sub-cases.scala
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@@ -1,4 +1,4 @@
import scala.language.experimental.matchWithSubCases
import scala.language.experimental.subCases

val pf: PartialFunction[Option[Option[Int]], String] =
case Some(x2) with x2 match
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2 changes: 1 addition & 1 deletion tests/warn/sub-cases-exhaustivity.scala
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@@ -1,4 +1,4 @@
import scala.language.experimental.matchWithSubCases
import scala.language.experimental.subCases

enum E:
case A(e: E)
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