Add test cases

Author: Sporarum

tests/pos/i14451.scala

@@ -2,6 +2,26 @@
 class Foo
 
 extension (dfVal: Foo)
-  def prevErr[T](step: Int): Foo = ???
-  def prevErr[T]: Foo = ???
-val err = (new Foo).prevErr
+  def f0(step: Int): Foo = ???
+  def f0: Foo = ???
+val v0 = (new Foo).f0
+
+extension (dfVal: Foo)
+  def f1[T](step: Int): Foo = ???
+  def f1: Foo = ???
+val v1 = (new Foo).f1
+
+extension (dfVal: Foo)
+  def f2[T](step: Int): Foo = ???
+  def f2[T]: Foo = ???
+val v2 = (new Foo).f2
+
+extension [A](dfVal: Foo)
+  def f3[T](step: Int): Foo = ???
+  def f3: Foo = ???
+val v3 = (new Foo).f3
+
+extension [A](dfVal: Foo)
+  def f4[T](step: Int): Foo = ???
+  def f4[T]: Foo = ???
+val v4 = (new Foo).f4