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author | Paul Phillips <paulp@improving.org> | 2012-08-09 14:10:22 -0700 |
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committer | Paul Phillips <paulp@improving.org> | 2012-08-09 14:32:51 -0700 |
commit | eb2375cc5327293c708226e78f80a97cc780a12f (patch) | |
tree | 61a10ec88c12546ccf44dbe653fec42a8429d203 /test | |
parent | c0d5f0aaddc7bc309f84afd5d4f4b5c136c65816 (diff) | |
download | scala-eb2375cc5327293c708226e78f80a97cc780a12f.tar.gz scala-eb2375cc5327293c708226e78f80a97cc780a12f.tar.bz2 scala-eb2375cc5327293c708226e78f80a97cc780a12f.zip |
Warn when Any or AnyVal is inferred.
For the very small price of annotating types as Any/AnyVal in those
cases where we wish to use them, we can obtain useful warnings.
I made trunk clean against this warning and found several bugs
or at least suboptimalities in the process.
I put the warning behind -Xlint for the moment, but I think this
belongs on by default, even for this alone:
scala> List(1, 2, 3) contains "a"
<console>:8: warning: a type was inferred to be `Any`; this may indicate a programming error.
List(1, 2, 3) contains "a"
^
res0: Boolean = false
Or this punishment meted out by SI-4042:
scala> 1l to 5l contains 5
<console>:8: warning: a type was inferred to be `AnyVal`; this may indicate a programming error.
1l to 5l contains 5
^
res0: Boolean = false
A different situation where this arises, which I have seen variations
of many times:
scala> class A[T](default: T) {
def get(x: => Option[T]) = x getOrElse Some(default)
}
<console>:7: warning: a type was inferred to be `Any`; this may indicate a programming error.
class A[T](default: T) { def get(x: => Option[T]) = x getOrElse Some(default) }
^
// Oops, this was what I meant
scala> class A[T](default: T) {
def get(x: => Option[T]) = x getOrElse default
}
defined class A
Harder to avoid spurious warnings when "Object" is inferred.
Diffstat (limited to 'test')
-rw-r--r-- | test/files/neg/warn-inferred-any.check | 10 | ||||
-rw-r--r-- | test/files/neg/warn-inferred-any.flags | 1 | ||||
-rw-r--r-- | test/files/neg/warn-inferred-any.scala | 19 |
3 files changed, 30 insertions, 0 deletions
diff --git a/test/files/neg/warn-inferred-any.check b/test/files/neg/warn-inferred-any.check new file mode 100644 index 0000000000..8c18616b6f --- /dev/null +++ b/test/files/neg/warn-inferred-any.check @@ -0,0 +1,10 @@ +warn-inferred-any.scala:8: error: a type was inferred to be `Any`; this may indicate a programming error. + { List(1, 2, 3) contains "a" } // only this warns + ^ +warn-inferred-any.scala:16: error: a type was inferred to be `AnyVal`; this may indicate a programming error. + { 1l to 5l contains 5 } + ^ +warn-inferred-any.scala:17: error: a type was inferred to be `AnyVal`; this may indicate a programming error. + { 1l to 5l contains 5d } + ^ +three errors found diff --git a/test/files/neg/warn-inferred-any.flags b/test/files/neg/warn-inferred-any.flags new file mode 100644 index 0000000000..a3127d392a --- /dev/null +++ b/test/files/neg/warn-inferred-any.flags @@ -0,0 +1 @@ +-Xfatal-warnings -Ywarn-infer-any diff --git a/test/files/neg/warn-inferred-any.scala b/test/files/neg/warn-inferred-any.scala new file mode 100644 index 0000000000..b853e6e5a8 --- /dev/null +++ b/test/files/neg/warn-inferred-any.scala @@ -0,0 +1,19 @@ +trait Foo[-A <: AnyRef, +B <: AnyRef] { + def run[U](x: A)(action: B => U): Boolean = ??? + + { run(_: A)(_: B => String) } +} + +trait Xs[+A] { + { List(1, 2, 3) contains "a" } // only this warns + { List(1, 2, 3) contains 1 } + { identity(List(1, 2, 3) contains 1) } + { List("a") foreach println } +} + +trait Ys[+A] { + { 1 to 5 contains 5l } + { 1l to 5l contains 5 } + { 1l to 5l contains 5d } + { 1l to 5l contains 5l } +} |