Avoid spurious procedure syntax migration warning

Author: odersky

src/dotty/tools/dotc/parsing/Parsers.scala

@@ -1736,7 +1736,7 @@ object Parsers {
         in.nextToken()
         val vparamss = paramClauses(nme.CONSTRUCTOR)
         val rhs = {
-          if (!scala2ProcedureSyntax || in.token != LBRACE) accept(EQUALS)
+          if (!(in.token == LBRACE && scala2ProcedureSyntax)) accept(EQUALS)
           atPos(in.offset) { constrExpr() }
         }
         makeConstructor(Nil, vparamss, rhs).withMods(mods)

tests/pos-special/variances-constr.scala

@@ -19,3 +19,9 @@ object Test {
   }
 }
 
+class CC[+A] {
+  class Inner {
+    def this(a: A) = this()
+  }
+}
+