Add neg test

Author: odersky

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

@@ -141,7 +141,8 @@ class CompilationTests extends ParallelTesting {
       compileFile("tests/neg-custom-args/infix.scala", defaultOptions.and("-strict", "-deprecation", "-Xfatal-warnings")),
       compileFile("tests/neg-custom-args/missing-alpha.scala", defaultOptions.and("-strict", "-deprecation", "-Xfatal-warnings")),
       compileFile("tests/neg-custom-args/wildcards.scala", defaultOptions.and("-strict", "-deprecation", "-Xfatal-warnings")),
-      compileFile("tests/neg-custom-args/indentRight.scala", defaultOptions.and("-noindent", "-Xfatal-warnings"))
+      compileFile("tests/neg-custom-args/indentRight.scala", defaultOptions.and("-noindent", "-Xfatal-warnings")),
+      compileFile("tests/neg-custom-args/extmethods-tparams.scala", defaultOptions.and("-deprecation", "-Xfatal-warnings"))
     ).checkExpectedErrors()
   }
 

tests/neg-custom-args/extmethods-tparams.scala

@@ -0,0 +1,2 @@
+def (self: T) foo[T] = ??? // error
+def [T1](self: T1) bar[T2] = ??? // error