From 6e20e35ab7e0980d3fea418b913643343f210387 Mon Sep 17 00:00:00 2001
From: Albert Meltzer <7529386+kitbellew@users.noreply.github.com>
Date: Sat, 27 Apr 2024 00:48:44 +0300
Subject: [PATCH] BestFirstSearch: switch to Long as State key

State column is unlikely to exceed 24 bits (or 16+ mln bytes), but even
in cases when it might, a given token (that is, at a given State depth)
cannot conceivably be formatted at two different column values which are
a multiple of 2^24 bytes apart.

Hence, let's form state key by keeping indentation (just like before)
at 8 bits, limiting column to 24 bits and combining with depth in the
remaining 32 bits (and this combining is what ensures no hash conflict).
---
 .../org/scalafmt/internal/BestFirstSearch.scala    | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/BestFirstSearch.scala b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/BestFirstSearch.scala
index 4ba29df290..c144665ebb 100644
--- a/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/BestFirstSearch.scala
+++ b/scalafmt-core/shared/src/main/scala/org/scalafmt/internal/BestFirstSearch.scala
@@ -49,8 +49,6 @@ private class BestFirstSearch private (
   val visits = new Array[Int](tokens.length)
   var keepSlowStates = !pruneSlowStates
 
-  type StateHash = Long
-
   /** Returns true if it's OK to skip over state.
     */
   def shouldEnterState(curr: State): Boolean = keepSlowStates ||
@@ -70,10 +68,7 @@ private class BestFirstSearch private (
       }
     } else None
 
-  def stateColumnKey(state: State): StateHash = state.column << 8 |
-    state.indentation
-
-  val memo = mutable.Map.empty[(Int, StateHash), State]
+  private val memo = mutable.Map.empty[Long, State]
 
   def shortestPathMemo(
       start: State,
@@ -81,10 +76,9 @@ private class BestFirstSearch private (
       depth: Int,
       maxCost: Int,
   ): Option[State] = {
-    val key = (start.depth, stateColumnKey(start))
-    val cachedState = memo.get(key)
-    if (cachedState.nonEmpty) cachedState
-    else {
+    val key = (start.indentation & 0xffL) | (start.column & 0xffffffL) << 8 |
+      (start.depth & 0xffffffffL) << 32
+    memo.get(key).orElse {
       // Only update state if it reached stop.
       val nextState = shortestPath(start, stop, depth, maxCost)
       if (null == nextState) None