From a88da4461328d779fc46ce7a0a2540b9a58a3bff Mon Sep 17 00:00:00 2001 From: odersky Date: Tue, 28 May 2024 16:37:58 +0200 Subject: [PATCH] Fix isEffectivelySingleton As usual, OrTypes need to be excluded. a.type | b.type is not effectively a singleton. It seems to be an easy trap to fall into. Follow-up to #20474 [Cherry-picked d04005c048b4633b5897c4a79972ca20352f3e36] --- compiler/src/dotty/tools/dotc/core/Types.scala | 3 +-- tests/neg/i20474.scala | 13 +++++++++++++ 2 files changed, 14 insertions(+), 2 deletions(-) create mode 100644 tests/neg/i20474.scala diff --git a/compiler/src/dotty/tools/dotc/core/Types.scala b/compiler/src/dotty/tools/dotc/core/Types.scala index 66cd71754365..89c43ca1b236 100644 --- a/compiler/src/dotty/tools/dotc/core/Types.scala +++ b/compiler/src/dotty/tools/dotc/core/Types.scala @@ -327,13 +327,12 @@ object Types extends TypeUtils { def isSingleton(using Context): Boolean = dealias.isInstanceOf[SingletonType] /** Is this type a (possibly aliased) singleton type or a type proxy - * or Or/And type known to be a singleton type? + * or an AndType where one operand is effectively a singleton? */ def isEffectivelySingleton(using Context): Boolean = dealias match case tp: SingletonType => true case tp: TypeProxy => tp.superType.isEffectivelySingleton case AndType(tpL, tpR) => tpL.isEffectivelySingleton || tpR.isEffectivelySingleton - case OrType(tpL, tpR) => tpL.isEffectivelySingleton && tpR.isEffectivelySingleton case _ => false /** Is this type of kind `AnyKind`? */ diff --git a/tests/neg/i20474.scala b/tests/neg/i20474.scala new file mode 100644 index 000000000000..4623ec11dbf3 --- /dev/null +++ b/tests/neg/i20474.scala @@ -0,0 +1,13 @@ +class A +class B extends A + +def f(a: A, c: A) = + val b1: a.type = a + val b2: a.type & B = a.asInstanceOf[a.type & B] + val b3: c.type & A = c + val b4: a.type | c.type = c + + val d1: b1.type = a + val d2: b2.type = a // ok + val d3: b3.type = a // error + val d4: b4.type = a // error \ No newline at end of file