diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/library/scala/reflect/base/Trees.scala | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/src/library/scala/reflect/base/Trees.scala b/src/library/scala/reflect/base/Trees.scala index 74928a0cc6..78174f354c 100644 --- a/src/library/scala/reflect/base/Trees.scala +++ b/src/library/scala/reflect/base/Trees.scala @@ -605,10 +605,30 @@ trait Trees { self: Universe => def unapply(bind: Bind): Option[(Name, Tree)] } - /** Noone knows what this is. - * It is not idempotent w.r.t typechecking. - * Can we, please, remove it? + /** Used to represent `unapply` methods in pattern matching. * Introduced by typer, eliminated by patmat/explicitouter. + * + * For example: + * {{{ + * 2 match { case Foo(x) => x } + * }}} + * + * Is represented as: + * {{{ + * Match( + * Literal(Constant(2)), + * List( + * CaseDef( + * UnApply( + * // a dummy node that carries the type of unapplication to patmat + * // the <unapply-selector> here doesn't have an underlying symbol + * // it only has a type assigned, therefore after `resetAllAttrs` this tree is no longer typeable + * Apply(Select(Ident(Foo), newTermName("unapply")), List(Ident(newTermName("<unapply-selector>")))), + * // arguments of the unapply => nothing synthetic here + * List(Bind(newTermName("x"), Ident(nme.WILDCARD)))), + * EmptyTree, + * Ident(newTermName("x"))))) + * }}} */ type UnApply >: Null <: TermTree |