Merge pull request tobymao#10128 from andrewzwicky/8053

[18EU] Properly restrict stock exchange to match rules

lib/engine/game/g_18_eu/step/final_exchange.rb

@@ -98,7 +98,12 @@ def can_discard?(minor)
           def can_gain?(_entity, bundle, exchange: false)
             return false unless exchange
 
-            bundle.corporation.ipoed
+            return false unless bundle.corporation.ipoed
+
+            # must take treasury shares if they exist.
+            return false if (bundle.owner == @game.share_pool) && bundle.corporation.num_ipo_shares.positive?
+
+            true
           end
 
           def buy_shares(entity, shares, exchange: nil, swap: nil, allow_president_change: true, borrow_from: nil)

lib/engine/game/g_18_eu/step/minor_exchange.rb

@@ -18,7 +18,7 @@ def exchange?(corporation)
         end
 
         def merge_minor!(minor, corporation, source)
-          maybe_remove_token(minor, corporation)
+          maybe_remove_token(minor, corporation, source)
 
           if source == corporation
             transfer_treasury(minor, corporation)
@@ -32,10 +32,15 @@ def merge_minor!(minor, corporation, source)
           minor.close! unless @round.pending_acquisition
         end
 
-        def maybe_remove_token(minor, corporation)
+        def maybe_remove_token(minor, corporation, source)
           return unless corporation
           return minor.tokens.first.remove! if corporation.placed_tokens.empty?
 
+          # if this merge share is coming from somewhere other than a corporation
+          # i.e. the share pool, don't make a pending acquisition, because
+          # a share pool exchange does not allow for token replacement.
+          return if source != corporation
+
           @round.pending_acquisition = { minor: minor, corporation: corporation }
         end