Merge pull request #2159 from dotty-staging/fix-hashcode

Make case class hashCode take class into account

Author: DarkDimius

compiler/src/dotty/tools/dotc/transform/SyntheticMethods.scala

@@ -144,20 +144,21 @@ class SyntheticMethods(thisTransformer: DenotTransformer) {
 
     /** The class
      *
+     *   package p
      *    case class C(x: T, y: T)
      *
      *  gets the hashCode method:
      *
      *    def hashCode: Int = {
-     *      <synthetic> var acc: Int = 0xcafebabe;
+     *      <synthetic> var acc: Int = "p.C".hashCode // constant folded
      *      acc = Statics.mix(acc, x);
      *      acc = Statics.mix(acc, Statics.this.anyHash(y));
      *      Statics.finalizeHash(acc, 2)
      *    }
      */
     def caseHashCodeBody(implicit ctx: Context): Tree = {
       val acc = ctx.newSymbol(ctx.owner, "acc".toTermName, Mutable | Synthetic, defn.IntType, coord = ctx.owner.pos)
-      val accDef = ValDef(acc, Literal(Constant(0xcafebabe)))
+      val accDef = ValDef(acc, Literal(Constant(clazz.fullName.toString.hashCode)))
       val mixes = for (accessor <- accessors.toList) yield
         Assign(ref(acc), ref(defn.staticsMethod("mix")).appliedTo(ref(acc), hashImpl(accessor)))
       val finish = ref(defn.staticsMethod("finalizeHash")).appliedTo(ref(acc), Literal(Constant(accessors.size)))

tests/run/caseClassHash.check

@@ -1,9 +1,9 @@
 Foo(true,-1,-1,d,-5,-10,500.0,500.0,List(),5.0)
 Foo(true,-1,-1,d,-5,-10,500.0,500.0,List(),5)
-1383698062
-1383698062
+205963949
+205963949
 true
-## method 1: 1383698062
-## method 2: 1383698062
+## method 1: 205963949
+## method 2: 205963949
    Murmur 1: 1383698062
    Murmur 2: 1383698062