8 files changed, 46 insertions, 5 deletions
diff --git a/src/3rdparty/squirrel/include/squirrel.h b/src/3rdparty/squirrel/include/squirrel.h
index 806454721..63fb96e39 100644
--- a/src/3rdparty/squirrel/include/squirrel.h
+++ b/src/3rdparty/squirrel/include/squirrel.h
@@ -311,6 +311,7 @@ SQUIRREL_API void sq_setprintfunc(HSQUIRRELVM v, SQPRINTFUNCTION printfunc);
 SQUIRREL_API SQPRINTFUNCTION sq_getprintfunc(HSQUIRRELVM v);
 SQUIRREL_API SQRESULT sq_suspendvm(HSQUIRRELVM v);
 SQUIRREL_API bool sq_resumecatch(HSQUIRRELVM v, int suspend = -1);
+SQUIRREL_API bool sq_resumeerror(HSQUIRRELVM v);
 SQUIRREL_API SQRESULT sq_wakeupvm(HSQUIRRELVM v,SQBool resumedret,SQBool retval,SQBool raiseerror,SQBool throwerror);
 SQUIRREL_API SQInteger sq_getvmstate(HSQUIRRELVM v);
 
diff --git a/src/3rdparty/squirrel/squirrel/sqapi.cpp b/src/3rdparty/squirrel/squirrel/sqapi.cpp
index 1e8b456f6..2d53d71bb 100644
--- a/src/3rdparty/squirrel/squirrel/sqapi.cpp
+++ b/src/3rdparty/squirrel/squirrel/sqapi.cpp
@@ -1012,6 +1012,14 @@ bool sq_resumecatch(HSQUIRRELVM v, int suspend)
 	return v->Execute(_null_, v->_top, -1, -1, ret, SQTrue, SQVM::ET_RESUME_OPENTTD);
 }
 
+bool sq_resumeerror(HSQUIRRELVM v)
+{
+	SQObjectPtr ret;
+	v->_can_suspend = true;
+	v->_ops_till_suspend = 1;
+	return v->Execute(_null_, v->_top, -1, -1, ret, SQTrue, SQVM::ET_RESUME_THROW_VM);
+}
+
 void sq_setreleasehook(HSQUIRRELVM v,SQInteger idx,SQRELEASEHOOK hook)
 {
 	if(sq_gettop(v) >= 1){
diff --git a/src/ai/ai_instance.cpp b/src/ai/ai_instance.cpp
index 6d3397a70..a5ef5135b 100644
--- a/src/ai/ai_instance.cpp
+++ b/src/ai/ai_instance.cpp
@@ -352,6 +352,10 @@ void AIInstance::GameLoop()
 		} catch (AI_VMSuspend e) {
 			this->suspend  = e.GetSuspendTime();
 			this->callback = e.GetSuspendCallback();
+		} catch (AI_FatalError e) {
+			this->engine->ThrowError(e.GetErrorMessage());
+			this->engine->ResumeError();
+			this->Died();
 		}
 
 		this->is_started = true;
@@ -368,6 +372,10 @@ void AIInstance::GameLoop()
 	} catch (AI_VMSuspend e) {
 		this->suspend  = e.GetSuspendTime();
 		this->callback = e.GetSuspendCallback();
+	} catch (AI_FatalError e) {
+		this->engine->ThrowError(e.GetErrorMessage());
+		this->engine->ResumeError();
+		this->Died();
 	}
 }
 
diff --git a/src/ai/ai_instance.hpp b/src/ai/ai_instance.hpp
index f260d46d4..c93bf0472 100644
--- a/src/ai/ai_instance.hpp
+++ b/src/ai/ai_instance.hpp
@@ -18,7 +18,7 @@ public:
 	AI_VMSuspend(int time, AISuspendCallbackProc *callback) :
 		time(time),
 		callback(callback)
-		{}
+	{}
 
 	int GetSuspendTime() { return time; }
 	AISuspendCallbackProc *GetSuspendCallback() { return callback; }
@@ -28,6 +28,21 @@ private:
 	AISuspendCallbackProc *callback;
 };
 
+/**
+ * A throw-class that is given when the AI made a fatal error.
+ */
+class AI_FatalError {
+public:
+	AI_FatalError(const char *msg) :
+		msg(msg)
+	{}
+
+	const char *GetErrorMessage() { return msg; }
+
+private:
+	const char *msg;
+};
+
 class AIInstance {
 public:
 	friend class AIObject;
diff --git a/src/ai/api/ai_controller.cpp b/src/ai/api/ai_controller.cpp
index 24510b7e7..7553f5944 100644
--- a/src/ai/api/ai_controller.cpp
+++ b/src/ai/api/ai_controller.cpp
@@ -24,8 +24,7 @@
 /* static */ void AIController::Sleep(int ticks)
 {
 	if (!AIObject::GetAllowDoCommand()) {
-		AILog::Error("You are not allowed to call Sleep in your constructor, Save(), Load(), and any valuator.\n");
-		return;
+		throw AI_FatalError("You are not allowed to call Sleep in your constructor, Save(), Load(), and any valuator.");
 	}
 
 	if (ticks <= 0) {
diff --git a/src/ai/api/ai_object.cpp b/src/ai/api/ai_object.cpp
index bb17e58f8..825c76c30 100644
--- a/src/ai/api/ai_object.cpp
+++ b/src/ai/api/ai_object.cpp
@@ -191,8 +191,7 @@ int AIObject::GetCallbackVariable(int index)
 bool AIObject::DoCommand(TileIndex tile, uint32 p1, uint32 p2, uint cmd, const char *text, AISuspendCallbackProc *callback)
 {
 	if (AIObject::GetAllowDoCommand() == false) {
-		AILog::Error("You are not allowed to execute any DoCommand (even indirect) in your constructor, Save(), Load(), and any valuator.\n");
-		return false;
+		throw AI_FatalError("You are not allowed to execute any DoCommand (even indirect) in your constructor, Save(), Load(), and any valuator.");
 	}
 
 	CommandCost res;
diff --git a/src/script/squirrel.cpp b/src/script/squirrel.cpp
index 31dcf6aea..1dd407589 100644
--- a/src/script/squirrel.cpp
+++ b/src/script/squirrel.cpp
@@ -187,6 +187,12 @@ bool Squirrel::Resume(int suspend)
 	return this->vm->_suspended != 0;
 }
 
+void Squirrel::ResumeError()
+{
+	assert(!this->crashed);
+	sq_resumeerror(this->vm);
+}
+
 void Squirrel::CollectGarbage()
 {
 	sq_collectgarbage(this->vm);
diff --git a/src/script/squirrel.hpp b/src/script/squirrel.hpp
index 612c6ce2e..97dd7988d 100644
--- a/src/script/squirrel.hpp
+++ b/src/script/squirrel.hpp
@@ -107,6 +107,11 @@ public:
 	bool Resume(int suspend = -1);
 
 	/**
+	 * Resume the VM with an error so it prints a stack trace.
+	 */
+	void ResumeError();
+
+	/**
 	 * Tell the VM to do a garbage collection run.
 	 */
 	void CollectGarbage();