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| author | Adriaan Moors <adriaan.moors@epfl.ch> | 2010-08-20 14:48:12 +0000 |
|---|---|---|
| committer | Adriaan Moors <adriaan.moors@epfl.ch> | 2010-08-20 14:48:12 +0000 |
| commit | e11cac6ecc3c8791be3a37fc3b9f6837c9d46d23 (patch) | |
| tree | dfa0ddc52703125288c6d7a85c4dc7befdb1508c /src/library | |
| parent | d4645f93728ee8cb40a17c23f92a272e27052889 (diff) | |
| download | scala-e11cac6ecc3c8791be3a37fc3b9f6837c9d46d23.tar.gz scala-e11cac6ecc3c8791be3a37fc3b9f6837c9d46d23.tar.bz2 scala-e11cac6ecc3c8791be3a37fc3b9f6837c9d46d23.zip | |
closes 2462. better implicit error messages.
@implicitNotFound(msg="Custom error message that may refer to type parameters ${T} and ${U}")
trait Constraint[T, U]
whenever an implicit argument of type Constraint[A, B] cannot be found,
the custom error message will be used, where the type arguments are
interpolated in the obvious way
note: if the msg in the annotation references non-existing type params,
a warning is emitted
the patch also cleans up annotation argument retrieval (moved it to
AnnotationInfo from Symbol)
review by odersky
Diffstat (limited to 'src/library')
| -rw-r--r-- | src/library/scala/annotation/implicitNotFound.scala | 18 | ||||
| -rw-r--r-- | src/library/scala/collection/generic/CanBuildFrom.scala | 3 |
2 files changed, 20 insertions, 1 deletions
diff --git a/src/library/scala/annotation/implicitNotFound.scala b/src/library/scala/annotation/implicitNotFound.scala new file mode 100644 index 0000000000..5d9b29c5f8 --- /dev/null +++ b/src/library/scala/annotation/implicitNotFound.scala @@ -0,0 +1,18 @@ +/* __ *\ +** ________ ___ / / ___ Scala API ** +** / __/ __// _ | / / / _ | (c) 2002-2010, LAMP/EPFL ** +** __\ \/ /__/ __ |/ /__/ __ | http://scala-lang.org/ ** +** /____/\___/_/ |_/____/_/ | | ** +** |/ ** +\* */ + +package scala.annotation + +/** + * An annotation that specifies the error message that is emitted when the compiler + * cannot find an implicit value of the annotated type. + * + * @author Adriaan Moors + * @since 2.8.1 + */ +final class implicitNotFound(msg: String) extends StaticAnnotation {}
\ No newline at end of file diff --git a/src/library/scala/collection/generic/CanBuildFrom.scala b/src/library/scala/collection/generic/CanBuildFrom.scala index 79e352690e..4c923dca44 100644 --- a/src/library/scala/collection/generic/CanBuildFrom.scala +++ b/src/library/scala/collection/generic/CanBuildFrom.scala @@ -11,7 +11,7 @@ package scala.collection package generic import mutable.Builder - +import scala.annotation.implicitNotFound /** A base trait for builder factories. * @@ -25,6 +25,7 @@ import mutable.Builder * @author Adriaan Moors * @since 2.8 */ +@implicitNotFound(msg = "Cannot construct a collection of type ${To} with elements of type ${Elem} based on a collection of type ${To}.") trait CanBuildFrom[-From, -Elem, +To] { /** Creates a new builder on request of a collection. |