From dfaaada8b6cf09fde47810c9dff79b8165b07ca0 Mon Sep 17 00:00:00 2001
From: richiethomas
Date: Fri, 13 Oct 2017 19:33:45 -0400
Subject: Memoize recursive dependency checks; reduces calls to
 'f.recursive_dependencies' by an order of magnitude

---
 Library/Homebrew/cmd/uses.rb | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Library/Homebrew/cmd/uses.rb b/Library/Homebrew/cmd/uses.rb
index 0b09e1bf1..5b6319cdc 100644
--- a/Library/Homebrew/cmd/uses.rb
+++ b/Library/Homebrew/cmd/uses.rb
@@ -54,11 +54,14 @@ module Homebrew
     end
     ignores << "recommended?" if ARGV.include? "--skip-recommended"
 
+    memo = {}
     uses = formulae.select do |f|
       used_formulae.all? do |ff|
         begin
           if recursive
             deps = f.recursive_dependencies do |dependent, dep|
+              memo_key = [dependent, dep].to_s
+              next if memo[memo_key]
               if dep.recommended?
                 Dependency.prune if ignores.include?("recommended?") || dependent.build.without?(dep)
               elsif dep.optional?
@@ -72,6 +75,7 @@ module Homebrew
               if dep.is_a?(TapDependency) && !dep.tap.installed?
                 Dependency.keep_but_prune_recursive_deps
               end
+              memo[memo_key] = true
             end
 
             dep_formulae = deps.flat_map do |dep|
-- 
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