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author | Jason Zaugg <jzaugg@gmail.com> | 2013-10-07 15:06:22 +0200 |
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committer | Jason Zaugg <jzaugg@gmail.com> | 2013-10-07 23:45:31 +0200 |
commit | 8ed7099f7db6a1060a490a594c958ca9a8b41487 (patch) | |
tree | 0ab90bf897c9d323a59465983f771ae931194f31 /test/files/run | |
parent | 90a312669b37d6e3e3f08685953ded24759e6102 (diff) | |
download | scala-8ed7099f7db6a1060a490a594c958ca9a8b41487.tar.gz scala-8ed7099f7db6a1060a490a594c958ca9a8b41487.tar.bz2 scala-8ed7099f7db6a1060a490a594c958ca9a8b41487.zip |
SI-7899 Don't infer by-name types during, e.g. eta-expansion
Given:
def id[A](a: A): A = a
def foo(f: (=> Int) => Int) = ()
foo(id)
We eta-expanded `id` and inferred `A` to be `=> Int` to satisfy the
expected type set forth by the formal parameter `f`.
We really shouldn't go about inferring types that we can't *write*.
Our attempt to do so led promptly into a `ClassCastException` in the
enclosed test.
This commit:
- drops by-name-ness during `inferExprInstance`
- tests that this results in a type error for the reported bug
(neg/t7899)
- tests that a method with a by-name parameter can still be
eta expanded to match function with a corresponding by-name
parameter (run/t7899)
- discovers the same latent CCE in pos/t7584
- now that would be a type error
- so we compensate by using placeholder functions rather than
eta-expansion.
- and move that that test to `run` for good measure.
Diffstat (limited to 'test/files/run')
-rw-r--r-- | test/files/run/t7584b.scala | 14 | ||||
-rw-r--r-- | test/files/run/t7899.scala | 5 |
2 files changed, 19 insertions, 0 deletions
diff --git a/test/files/run/t7584b.scala b/test/files/run/t7584b.scala new file mode 100644 index 0000000000..fd560f0418 --- /dev/null +++ b/test/files/run/t7584b.scala @@ -0,0 +1,14 @@ +object Test extends App { + def fold[A, B](f: (A, => B) => B) = (b: B) => f(null.asInstanceOf[A], b) + def f[A, B](x: A, y: B): B = y + def bip[A, B] = fold[A, B]((x, y) => f(x, y)) + def bop[A, B] = fold[A, B](f(_, _)) + + // these work: + fold[Int, Int]((x, y) => f(x, y))(0) + fold[Int, Int](f(_, _))(0) + + // Used to throw a ClassCastException. Since the fix for SI-7899, these issue type errors. + // fold[Int, Int](f _)(0) + // fold[Int, Int](f)(0) +} diff --git a/test/files/run/t7899.scala b/test/files/run/t7899.scala new file mode 100644 index 0000000000..5879d4b9fe --- /dev/null +++ b/test/files/run/t7899.scala @@ -0,0 +1,5 @@ +object Test extends App { + def id[A](a: => A): A = null.asInstanceOf[A] + def foo(f: (=> Int) => Int) = () => f(???) + foo(id)() // should be allowed and not throw ??? +} |