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Make case class hashCode take class into account #2159

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Merged
merged 4 commits into from
Apr 3, 2017
Merged

Make case class hashCode take class into account #2159

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f801c83
Make case class hashCode take class into account
odersky Mar 30, 2017
6aba35f
Optimize hashCode computation
odersky Mar 31, 2017
aa2522c
Use full name of case classes for hashing
odersky Mar 31, 2017
710e700
Merge branch 'master' into fix-hashcode
felixmulder Apr 1, 2017
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4 changes: 2 additions & 2 deletions compiler/src/dotty/tools/dotc/transform/SyntheticMethods.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -149,15 +149,15 @@ class SyntheticMethods(thisTransformer: DenotTransformer) {
* gets the hashCode method:
*
* def hashCode: Int = {
* <synthetic> var acc: Int = 0xcafebabe;
* <synthetic> var acc: Int = productPrefix.hashCode()
* 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, This(clazz).select(defn.Product_productPrefix).select(defn.Any_hashCode).ensureApplied)
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Given that this code generates also productPrefix itself, why not inline constant ownName here instead?

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Also, given that hashcodes on strings are fixed by the spec, we can actually compute the runtime value and inline it: Literal(ownName.toString.hashcode).

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@DarkDimius Neat! I'll change it.

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)))
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