diff options
Diffstat (limited to 'test')
-rw-r--r-- | test/files/neg/t8431.check | 27 | ||||
-rw-r--r-- | test/files/neg/t8431.scala | 63 |
2 files changed, 90 insertions, 0 deletions
diff --git a/test/files/neg/t8431.check b/test/files/neg/t8431.check new file mode 100644 index 0000000000..75351a8ae7 --- /dev/null +++ b/test/files/neg/t8431.check @@ -0,0 +1,27 @@ +t8431.scala:24: error: type mismatch; + found : CanBuildFrom[Invariant[Nothing]] + required: CanBuildFrom[Invariant[G]] + s.combined // fail + ^ +t8431.scala:24: error: value combined is not a member of Invariant[Nothing] + s.combined // fail + ^ +t8431.scala:35: error: type mismatch; + found : CanBuildFrom[Invariant[Nothing]] + required: CanBuildFrom[Invariant[G]] + s.combined // was okay! + ^ +t8431.scala:35: error: value combined is not a member of Invariant[Nothing] + s.combined // was okay! + ^ +t8431.scala:45: error: type mismatch; + found : CanBuildFrom[Invariant[Nothing]] + required: CanBuildFrom[Invariant[G]] + convert2(s).combined + ^ +t8431.scala:48: error: type mismatch; + found : CanBuildFrom[Invariant[Nothing]] + required: CanBuildFrom[Invariant[G]] + {val c1 = convert2(s); c1.combined} + ^ +6 errors found diff --git a/test/files/neg/t8431.scala b/test/files/neg/t8431.scala new file mode 100644 index 0000000000..29b852d0c0 --- /dev/null +++ b/test/files/neg/t8431.scala @@ -0,0 +1,63 @@ +trait Covariant[+A] +trait Invariant[A] extends Covariant[A @annotation.unchecked.uncheckedVariance] + +trait Combinable[G] { + def combined = 0 +} + +trait CanBuildFrom[+C] + +object C { + implicit def convert1[G, TRAVONCE[+e] <: Covariant[e]] + (xs: TRAVONCE[G]): Combinable[G] = ??? + + implicit def convert2[G, SET[e] <: Invariant[e]] + (xs: SET[_ <: G]) + (implicit cbf: CanBuildFrom[SET[G]]): Combinable[G] = ??? + + implicit def cbf[A]: CanBuildFrom[Invariant[A]] = ??? +} + +class Test1 { + import C.{cbf, convert1, convert2} + val s: Invariant[Nothing] = ??? + s.combined // fail +} + +class Test2 { + import C.{cbf, convert2, convert1} + + val s: Invariant[Nothing] = ??? + + // Non-uniformity with Test1 was due to order of typechecking implicit candidates: + // the last candidate typechecked was the only one that could contribute undetermined type parameters + // to the enclosing context, due to mutation of `Context#undetparam` in `doTypedApply`. + s.combined // was okay! +} + + +class TestExplicit { + import C.{cbf, convert2} + + val s: Invariant[Nothing] = ??? + + // Now the implicit Test fail uniformly as per this explicit conversion + convert2(s).combined + + // Breaking this expression down makes it work. + {val c1 = convert2(s); c1.combined} +} + +// These ones work before and after; infering G=Null doesn't need to contribute an undetermined type param. +class Test3 { + import C.{cbf, convert1, convert2} + val s: Invariant[Null] = ??? + s.combined // okay +} + +class Test4 { + import C.{cbf, convert2, convert1} + + val s: Invariant[Null] = ??? + s.combined // okay +} |