Fix and add neg tests with custom args

Author: nicolasstucki

compiler/test/dotty/tools/dotc/CompilationTests.scala

@@ -154,6 +154,7 @@ class CompilationTests extends ParallelTesting {
       compileDir("tests/neg-custom-args/adhoc-extension", defaultOptions.and("-strict", "-feature", "-Xfatal-warnings")),
       compileFile("tests/neg/i7575.scala", defaultOptions.and("-language:_")),
       compileFile("tests/neg-custom-args/kind-projector.scala", defaultOptions.and("-Ykind-projector")),
+      compileFile("tests/neg-custom-args/typeclass-derivation2.scala", defaultOptions.and("-Yerased-terms")),
     ).checkExpectedErrors()
   }
 

tests/neg-custom-args/typeclass-derivation2.scala

@@ -214,7 +214,6 @@ object Show {
   import TypeLevel._
 
   inline def tryShow[T](x: T): String = summonInline[Show[T]].show(x)
-  }
 
   inline def showElems[Elems <: Tuple](elems: Mirror, n: Int): List[String] =
     inline erasedValue[Elems] match {