About: https://github.com/lampepfl/dotty/issues/6996

console.txt

$ Compiled from "StringLiteralType.scala"
public final class StringLiteralType$ implements scala.Serializable {
  public static final StringLiteralType$ MODULE$;

  public static {};
    Code:
       0: new           #2                  // class StringLiteralType$
       3: invokespecial #14                 // Method "<init>":()V
       6: return

  public void isAType(java.lang.String);
    Code:
       0: aload_1
       1: astore_2
       2: ldc           #29                 // String a
       4: aload_2
       5: invokevirtual #33                 // Method java/lang/Object.equals:(Ljava/lang/Object;)Z
       8: ifeq          22
      11: getstatic     #38                 // Field scala/Predef$.MODULE$:Lscala/Predef$;
      14: ldc           #40                 // String This is `a` type
      16: invokevirtual #44                 // Method scala/Predef$.println:(Ljava/lang/Object;)V
      19: goto          33
      22: getstatic     #38                 // Field scala/Predef$.MODULE$:Lscala/Predef$;
      25: ldc           #46                 // String not `a`
      27: invokevirtual #44                 // Method scala/Predef$.println:(Ljava/lang/Object;)V
      30: goto          33
      33: return

  public void a1();
    Code:
       0: aload_0
       1: ldc           #29                 // String a
       3: invokevirtual #53                 // Method isAType:(Ljava/lang/String;)V
       6: return

  public void a2();
    Code:
       0: aload_0
       1: new           #50                 // class java/lang/String
       4: dup
       5: ldc           #29                 // String a
       7: invokespecial #56                 // Method java/lang/String."<init>":(Ljava/lang/String;)V
      10: invokevirtual #53                 // Method isAType:(Ljava/lang/String;)V
      13: return

  public boolean a3();
    Code:
       0: new           #50                 // class java/lang/String
       3: dup
       4: ldc           #29                 // String a
       6: invokespecial #56                 // Method java/lang/String."<init>":(Ljava/lang/String;)V
       9: ldc           #29                 // String a
      11: if_acmpne     18
      14: iconst_1
      15: goto          19
      18: iconst_0
      19: ireturn

  public void main(java.lang.String[]);
    Code:
       0: getstatic     #38                 // Field scala/Predef$.MODULE$:Lscala/Predef$;
       3: aload_0
       4: invokevirtual #62                 // Method a1:()V
       7: getstatic     #68                 // Field scala/runtime/BoxedUnit.UNIT:Lscala/runtime/BoxedUnit;
      10: invokevirtual #44                 // Method scala/Predef$.println:(Ljava/lang/Object;)V
      13: getstatic     #38                 // Field scala/Predef$.MODULE$:Lscala/Predef$;
      16: aload_0
      17: invokevirtual #70                 // Method a2:()V
      20: getstatic     #68                 // Field scala/runtime/BoxedUnit.UNIT:Lscala/runtime/BoxedUnit;
      23: invokevirtual #44                 // Method scala/Predef$.println:(Ljava/lang/Object;)V
      26: getstatic     #38                 // Field scala/Predef$.MODULE$:Lscala/Predef$;
      29: aload_0
      30: invokevirtual #72                 // Method a3:()Z
      33: invokestatic  #78                 // Method scala/runtime/BoxesRunTime.boxToBoolean:(Z)Ljava/lang/Boolean;
      36: invokevirtual #44                 // Method scala/Predef$.println:(Ljava/lang/Object;)V
      39: return
}

StringLiteralType.scala

object StringLiteralType {
  def isAType(arg: String): Unit = arg match {    
    case _ : "a" => println("This is `a` type")
    case _ => println("not `a`")
  }

  def a1 = isAType("a")
  def a2 = isAType(new String("a"))
  def a3 = new String("a").isInstanceOf["a"]


  def main(args: Array[String]): Unit = {
    println(a1)
    println(a2)
    println(a3)
  }
}