Welcome to Scala 2.13.15 (OpenJDK 64-Bit Server VM, Java 21.0.4).
Type in expressions for evaluation. Or try :help.

scala> class A {
     |   def this(x: Int) { this() }
     | }
         def this(x: Int) { this() }
                         ^
On line 2: warning: procedure syntax is deprecated for constructors: add `=`, as in method definition [quickfixable]

Welcome to Scala 3.3.4 (21.0.4, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
                                                                                                                                             
scala> class A {
     |   def this(x: Int) { this() }
-- [E040] Syntax Error: --------------------------------------------------------
2 |  def this(x: Int) { this() }
  |                   ^
  |                   '=' expected, but '{' found