Revert: Better error diagnostics for "not an extractor" errors.

No longer needed because we are going to allow dependent method types
in extractors, and the unary requirement is kind of obvious.

1 files changed, 2 insertions, 17 deletions

diff --git a/src/dotty/tools/dotc/typer/Applications.scala b/src/dotty/tools/dotc/typer/Applications.scala
index 13616ea6c..37a9f0ba0 100644
--- a/src/dotty/tools/dotc/typer/Applications.scala
+++ b/src/dotty/tools/dotc/typer/Applications.scala
@@ -659,23 +659,8 @@ trait Applications extends Compatibility { self: Typer =>
   def typedUnApply(tree: untpd.Apply, selType: Type)(implicit ctx: Context): Tree = track("typedUnApply") {
     val Apply(qual, args) = tree
 
-    def notAnExtractor(unapplyFn: Tree) = {
-      val methodStr = unapplyFn.symbol.name match {
-        case nme.unapply => "unapply"
-        case nme.unapplySeq => "unapplySeq"
-        case _ => "unapply or unapplySeq"
-      }
-      val because = unapplyFn.tpe.widen match {
-        case mt: MethodType =>
-          i"its $methodStr method of type $mt" + (
-            if (mt.isDependent) i" has a dependent type"
-            else if (mt.paramTypes.length != 1) i" does not take a single parameter"
-            else " is not eligible (this could be an internal compiler error)")
-        case _ =>
-          "it lacks a unapply or unapplySeq method"
-      }
-      errorTree(unapplyFn, s"${qual.show} cannot be used as an extractor in a pattern $because")
-    }
+    def notAnExtractor(tree: Tree) =
+      errorTree(tree, s"${qual.show} cannot be used as an extractor in a pattern because it lacks an unapply or unapplySeq method")
 
     /** If this is a term ref tree, try to typecheck with its type name.
      *  If this refers to a type alias, follow the alias, and if