Fix #7812: Harden ensureStableSingleton

odersky · odersky · commit f017de8b05e9 · 2019-12-22T18:53:31.000+01:00
diff --git a/compiler/src/dotty/tools/dotc/core/TypeComparer.scala b/compiler/src/dotty/tools/dotc/core/TypeComparer.scala
@@ -1494,6 +1494,7 @@ class TypeComparer(initctx: Context) extends ConstraintHandling[AbsentContext] w
     case tp: SingletonType if tp.isStable => tp
     case tp: ValueType => SkolemType(tp)
     case tp: TypeProxy => ensureStableSingleton(tp.underlying)
+    case tp => assert(ctx.reporter.errorsReported); SkolemType(tp)
   }
 
   /** Skip refinements in `tp2` which match corresponding refinements in `tp1`.
diff --git a/tests/neg/i7812.scala b/tests/neg/i7812.scala
@@ -0,0 +1,3 @@
+def f(): Any = ???
+var f: (UndefinedA & UndefinedB) { val x: Int } = ??? // error // error
+val a = f // error

Original file line number	Diff line number	Diff line change
`@@ -1494,6 +1494,7 @@ class TypeComparer(initctx: Context) extends ConstraintHandling[AbsentContext] w`
`1494`	`1494`	`case tp: SingletonType if tp.isStable => tp`
`1495`	`1495`	`case tp: ValueType => SkolemType(tp)`
`1496`	`1496`	`case tp: TypeProxy => ensureStableSingleton(tp.underlying)`
	`1497`	`+ case tp => assert(ctx.reporter.errorsReported); SkolemType(tp)`
`1497`	`1498`	`}`
`1498`	`1499`
`1499`	`1500`	/** Skip refinements in `tp2` which match corresponding refinements in `tp1`.
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+def f(): Any = ???`
	`2`	`+var f: (UndefinedA & UndefinedB) { val x: Int } = ??? // error // error`
	`3`	`+val a = f // error`