Fix #12594: Give descriptive error when company takeover fails due to vehicle limit (#12676)

src/company_cmd.cpp

@@ -668,12 +668,12 @@ void InitializeCompanies()
 }
 
 /**
- * May company \a cbig buy company \a csmall?
+ * Can company \a cbig buy company \a csmall without exceeding vehicle limits?
  * @param cbig   Company buying \a csmall.
  * @param csmall Company getting bought.
  * @return Return \c true if it is allowed.
  */
-bool MayCompanyTakeOver(CompanyID cbig, CompanyID csmall)
+bool CheckTakeoverVehicleLimit(CompanyID cbig, CompanyID csmall)
 {
 	const Company *c1 = Company::Get(cbig);
 	const Company *c2 = Company::Get(csmall);
@@ -725,7 +725,7 @@ static void HandleBankruptcyTakeover(Company *c)
 		if (c2->bankrupt_asked == 0 && // Don't ask companies going bankrupt themselves
 				!HasBit(c->bankrupt_asked, c2->index) &&
 				best_performance < c2->old_economy[1].performance_history &&
-				MayCompanyTakeOver(c2->index, c->index)) {
+				CheckTakeoverVehicleLimit(c2->index, c->index)) {
 			best_performance = c2->old_economy[1].performance_history;
 			best = c2;
 		}

src/company_func.h

@@ -15,7 +15,7 @@
 #include "gfx_type.h"
 #include "vehicle_type.h"
 
-bool MayCompanyTakeOver(CompanyID cbig, CompanyID small);
+bool CheckTakeoverVehicleLimit(CompanyID cbig, CompanyID small);
 void ChangeOwnershipOfCompanyItems(Owner old_owner, Owner new_owner);
 static const int OWNED_BY_OWNER_IN_PARAMETERS_OFFSET = 2; ///< The index in the parameters for the owner information.
 void SetDParamsForOwnedBy(Owner owner, TileIndex tile);

src/economy.cpp

@@ -2066,8 +2066,8 @@ CommandCost CmdBuyCompany(DoCommandFlag flags, CompanyID target_company, bool ho
 	/* Do not allow companies to take over themselves */
 	if (target_company == _current_company) return CMD_ERROR;
 
-	/* Disable taking over when not allowed. */
+	/* Do not allow takeover if the resulting company would have too many vehicles. */
-	if (!MayCompanyTakeOver(_current_company, target_company)) return CMD_ERROR;
+	if (!CheckTakeoverVehicleLimit(_current_company, target_company)) return_cmd_error(STR_ERROR_TOO_MANY_VEHICLES_IN_GAME);
 
 	/* Get the cost here as the company is deleted in DoAcquireCompany.
 	 * For bankruptcy this amount is calculated when the offer was made;