Update a comment in PatternTypeConstrainer

dotty-staging · Oct 18, 2022 · f2ede4c · f2ede4c
1 parent 5ed89ad
commit f2ede4c
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/compiler/src/dotty/tools/dotc/core/PatternTypeConstrainer.scala b/compiler/src/dotty/tools/dotc/core/PatternTypeConstrainer.scala
@@ -255,7 +255,8 @@ trait PatternTypeConstrainer { self: TypeComparer =>
             tyconS.typeParams.lazyZip(argsS).lazyZip(argsP).forall { (param, argS, argP) =>
               val variance = param.paramVarianceSign
               if variance == 0 || assumeInvariantRefinement ||
-                // heal the type if it's a (pattern-bound) type variable, provided we didn't upcast the pattern type:
+                // As a special case, when pattern and scrutinee types have the same type constructor,
+                // we infer better bounds for pattern-bound abstract types.
                 argP.typeSymbol.isPatternBound && patternTp.classSymbol == scrutineeTp.classSymbol
               then
                 val TypeBounds(loS, hiS) = argS.bounds