Teach provablyDisjoint to fold compile-time constants

dwijnand · Jun 20, 2023 · 7c861cb · 7c861cb
1 parent 55898df
commit 7c861cb
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diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -2845,6 +2845,10 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
             else
               invariantDisjoint(arg1, arg2, tparam)
         }
+      case (tp1: AppliedType, tp2) if tp1.tryCompiletimeConstantFold.exists =>
+        provablyDisjoint(tp1.tryCompiletimeConstantFold, tp2)
+      case (tp1, tp2: AppliedType) if tp2.tryCompiletimeConstantFold.exists =>
+        provablyDisjoint(tp1, tp2.tryCompiletimeConstantFold)
       case (tp1: HKLambda, tp2: HKLambda) =>
         provablyDisjoint(tp1.resType, tp2.resType)
       case (_: HKLambda, _) =>

diff --git a/tests/pos/i16596.scala b/tests/pos/i16596.scala
@@ -0,0 +1,7 @@
+import scala.compiletime.ops.int, int.-
+
+type Count[N, T] <: Tuple = (N, T) match
+  case (0, T) => EmptyTuple
+  case (N, T) => T *: Count[N - 1, T]
+
+val a: Count[3, Int] = (1, 2, 3)