Merge pull request #4633 from dotty-staging/fix-case-class-decompilation

Fix case class decompilation

Author: nicolasstucki

compiler/src/dotty/tools/dotc/tastyreflect/FlagSet.scala

@@ -48,7 +48,7 @@ class FlagSet(flags: Flags.FlagSet) extends scala.tasty.FlagSet {
     if (isInline) flags += "inline"
     if (isMacro) flags += "macro"
     if (isStatic) flags += "javaStatic"
-    if (isObject) flags += "module"
+    if (isObject) flags += "object"
     if (isTrait) flags += "trait"
     if (isLocal) flags += "local"
     if (isSynthetic) flags += "synthetic"

library/src/scala/tasty/util/ShowSourceCode.scala

@@ -112,8 +112,24 @@ class ShowSourceCode[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
           }
         }
 
+        def keepDefinition(d: Definition): Boolean = {
+          val flags = d.flags
+          def isCaseClassUnOverridableMethod: Boolean = {
+            // Currently the compiler does not allow overriding some of the methods generated for case classes
+            d.flags.isSynthetic &&
+            (d match {
+              case DefDef("apply" | "unapply", _, _, _, _) if d.owner.flags.isObject => true
+              case DefDef(n, _, _, _, _) if d.owner.flags.isCase =>
+                n == "copy" ||
+                n.matches("copy\\$default\\$[1-9][0-9]*") || // default parameters for the copy method
+                n.matches("_[1-9][0-9]*") // Getters from Product
+              case _ => false
+            })
+          }
+          !flags.isParam && !flags.isParamAccessor && !isCaseClassUnOverridableMethod
+        }
         val stats1 = stats.collect {
-          case stat@Definition() if !stat.flags.isParam && !stat.flags.isParamAccessor => stat
+          case stat@Definition() if keepDefinition(stat) => stat
           case stat@Import(_, _) => stat
           case stat@Term() => stat
         }
@@ -721,6 +737,10 @@ class ShowSourceCode[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
 
       case Type.ThisType(tp) =>
         printType(tp)
+        tp match {
+          case Type.SymRef(cdef @ ClassDef(_, _, _, _, _), _) if !cdef.flags.isObject => this += ".this"
+          case _ => this
+        }
 
       case _ =>
         throw new MatchError(tpe.show)

tests/pos/simpleCaseClass-1.decompiled

@@ -0,0 +1,19 @@
+/** Decompiled from out/posTestFromTasty/pos/simpleCaseClass-1/A.class */
+case class A() {
+  override def hashCode(): scala.Int = 1914112431
+  override def equals(x$0: scala.Any): scala.Boolean = this.eq(x$0.asInstanceOf[java.lang.Object]).||(x$0 match {
+    case x$0: A =>
+      true
+    case _ =>
+      false
+  })
+  override def toString(): java.lang.String = scala.runtime.ScalaRunTime._toString(this)
+  override def canEqual(that: scala.Any): scala.Boolean = that.isInstanceOf[A]
+  override def productArity: scala.Int = 0
+  override def productPrefix: java.lang.String = "A"
+  override def productElement(n: scala.Int): scala.Any = n match {
+    case _ =>
+      throw new java.lang.IndexOutOfBoundsException(n.toString())
+  }
+}
+object A extends scala.Function0[A]

tests/pos/simpleCaseClass-1.scala

@@ -0,0 +1 @@
+case class A()

tests/pos/simpleCaseClass-2.decompiled

@@ -0,0 +1,25 @@
+/** Decompiled from out/posTestFromTasty/pos/simpleCaseClass-2/A.class */
+case class A(x: scala.Int) {
+  override def hashCode(): scala.Int = {
+    var acc: scala.Int = 65
+    acc = scala.runtime.Statics.mix(acc, A.this.x)
+    scala.runtime.Statics.finalizeHash(acc, 1)
+  }
+  override def equals(x$0: scala.Any): scala.Boolean = this.eq(x$0.asInstanceOf[java.lang.Object]).||(x$0 match {
+    case x$0: A =>
+      this.x.==(x$0.x)
+    case _ =>
+      false
+  })
+  override def toString(): java.lang.String = scala.runtime.ScalaRunTime._toString(this)
+  override def canEqual(that: scala.Any): scala.Boolean = that.isInstanceOf[A]
+  override def productArity: scala.Int = 1
+  override def productPrefix: java.lang.String = "A"
+  override def productElement(n: scala.Int): scala.Any = n match {
+    case 0 =>
+      this._1
+    case _ =>
+      throw new java.lang.IndexOutOfBoundsException(n.toString())
+  }
+}
+object A extends scala.Function1[scala.Int, A]

tests/pos/simpleCaseClass-2.scala

@@ -0,0 +1 @@
+case class A(x: Int)

tests/pos/simpleCaseClass-3.decompiled

@@ -0,0 +1,25 @@
+/** Decompiled from out/posTestFromTasty/pos/simpleCaseClass-3/A.class */
+case class A[T](x: T) {
+  override def hashCode(): scala.Int = {
+    var acc: scala.Int = 65
+    acc = scala.runtime.Statics.mix(acc, scala.runtime.Statics.anyHash(A.this.x))
+    scala.runtime.Statics.finalizeHash(acc, 1)
+  }
+  override def equals(x$0: scala.Any): scala.Boolean = this.eq(x$0.asInstanceOf[java.lang.Object]).||(x$0 match {
+    case x$0: A[A.this.T] =>
+      this.x.==(x$0.x)
+    case _ =>
+      false
+  })
+  override def toString(): java.lang.String = scala.runtime.ScalaRunTime._toString(this)
+  override def canEqual(that: scala.Any): scala.Boolean = that.isInstanceOf[A[A.this.T]]
+  override def productArity: scala.Int = 1
+  override def productPrefix: java.lang.String = "A"
+  override def productElement(n: scala.Int): scala.Any = n match {
+    case 0 =>
+      this._1
+    case _ =>
+      throw new java.lang.IndexOutOfBoundsException(n.toString())
+  }
+}
+object A extends scala.AnyRef

tests/pos/simpleCaseClass-3.scala

@@ -0,0 +1 @@
+case class A[T](x: T)