Fix #2234: Dealias before type erasing

compiler/src/dotty/tools/dotc/core/TypeErasure.scala

@@ -377,6 +377,8 @@ class TypeErasure(isJava: Boolean, semiEraseVCs: Boolean, isConstructor: Boolean
       defn.FunctionType(0)
     case AndType(tp1, tp2) =>
       erasedGlb(this(tp1), this(tp2), isJava)
+    case tp: HKApply =>
+      apply(tp.superType)
     case OrType(tp1, tp2) =>
       ctx.typeComparer.orType(this(tp1), this(tp2), erased = true)
     case tp: MethodType =>
@@ -508,6 +510,8 @@ class TypeErasure(isJava: Boolean, semiEraseVCs: Boolean, isConstructor: Boolean
           normalizeClass(sym.asClass).fullName.asTypeName
       case defn.ArrayOf(elem) =>
         sigName(this(tp))
+      case tp: HKApply =>
+        sigName(tp.superType)
       case JavaArrayType(elem) =>
         sigName(elem) ++ "[]"
       case tp: TermRef =>

tests/pos/i2234.scala

@@ -0,0 +1,13 @@
+object Test {
+  type Dummy[A] = A
+
+  def a(d: Dummy[String]) = ()
+  def a(d: Dummy[Int]) = ()
+
+  implicit def dummy[A]: Dummy[A] = null.asInstanceOf[A]
+  def m(x: List[String])(implicit d: Dummy[String]) = "string"
+  def m(x: List[Int])(implicit d: Dummy[Int]) = "int"
+
+  m(List(1, 2, 3))
+  m(List("a"))
+}