Only throw TypeErrors for match types with no cases if ctx.isTyper

scala · Mar 17, 2024 · be4065e · be4065e
1 parent ed5ddfe
commit be4065e
Showing 1 changed file with 8 additions and 2 deletions.
diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -3594,8 +3594,14 @@ class MatchReducer(initctx: Context) extends TypeComparer(initctx) {
             MatchTypeTrace.emptyScrutinee(scrut)
             NoType
       case Nil =>
-        val casesText = MatchTypeTrace.noMatchesText(scrut, cases)
-        throw MatchTypeReductionError(em"Match type reduction $casesText")
+        if ctx.isTyper then
+          val casesText = MatchTypeTrace.noMatchesText(scrut, cases)
+          throw MatchTypeReductionError(em"Match type reduction $casesText")
+        else
+          NoType
+          /* The match type is left unreduced if an error can not be reported
+           * See pos/constvalue-of-failed-match-type.scala for an example
+           */
 
     inFrozenConstraint(recur(cases))
   }