diff options
| -rw-r--r-- | src/compiler/scala/tools/nsc/typechecker/Infer.scala | 22 | ||||
| -rw-r--r-- | test/files/pos/bug2486.scala | 3 |
2 files changed, 20 insertions, 5 deletions
diff --git a/src/compiler/scala/tools/nsc/typechecker/Infer.scala b/src/compiler/scala/tools/nsc/typechecker/Infer.scala index 6c3b6af081..4a9399bf99 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Infer.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Infer.scala @@ -1419,11 +1419,23 @@ trait Infer { val ptvars = ptparams map freshVar val pt1 = pt.instantiateTypeParams(ptparams, ptvars) if (!(isPopulated(tp, pt1) && isInstantiatable(tvars ::: ptvars))) { - //println(tpparams) - //println(tvars map instBounds) - //println(ptvars map instBounds) - error(pos, "pattern type is incompatible with expected type"+foundReqMsg(pattp, pt)) - return pattp + // In ticket #2486 we have this example of code which would fail + // here without a change: + // + // class A[T] + // class B extends A[Int] + // class C[T] extends A[T] { def f(t: A[T]) = t match { case x: B => () } } + // + // This reports error: pattern type is incompatible with expected type; + // found : B + // required: A[T] + // + // I am not sure what is the ideal fix, but for the moment I am intercepting + // it at the last minute and applying a looser check before failing. + if (!isPlausiblyCompatible(pattp, pt)) { + error(pos, "pattern type is incompatible with expected type"+foundReqMsg(pattp, pt)) + return pattp + } } ptvars foreach instantiateTypeVar } diff --git a/test/files/pos/bug2486.scala b/test/files/pos/bug2486.scala new file mode 100644 index 0000000000..69fe4c127e --- /dev/null +++ b/test/files/pos/bug2486.scala @@ -0,0 +1,3 @@ +class A[T] +class B extends A[Int] +class C[T] extends A[T] { def f(t: A[T]) = t match { case x: B => () } } |