fix ai NPE when selecting a unit where to spawn frost pylon

The NPE is caused by any piled permanent with which TilesInRange is
called.

5 files changed, 16 insertions, 15 deletions

diff --git a/go/game/ai.go b/go/game/ai.go
index 9b48c2f5..9f1ef488 100644
--- a/go/game/ai.go
+++ b/go/game/ai.go
@@ -121,7 +121,7 @@ func (m *Map) generateMapGraphFor(u *Unit) *dijkstra.Graph {
 }
 
 func findPathTo(graph *dijkstra.Graph, u *Unit, pos Position) (dijkstra.BestPath, error) {
-	srcId, err := graph.GetMapping(u.TileOrContainingPermTile().Position.String())
+	srcId, err := graph.GetMapping(TileOrContainingPermTile(u).Position.String())
 	if err != nil {
 		log.Fatalf("No mapping %s in Graph: %s", u.Tile().Position.String(), err)
 	}
diff --git a/go/game/cardImplementations.go b/go/game/cardImplementations.go
index 32208f09..da348fe1 100644
--- a/go/game/cardImplementations.go
+++ b/go/game/cardImplementations.go
@@ -176,7 +176,8 @@ type fishTrapImpl struct {
 	aoe areaEffect
 }
 
-func (*fishTrapImpl) stateBasedActions(s *State, p Permanent) {}
+func (*fishTrapImpl) additionalSpawnsFor(Permanent, CardType) []*Tile { return nil }
+func (*fishTrapImpl) stateBasedActions(*State, Permanent)             {}
 
 func (i *fishTrapImpl) onEntering(t *Tile) {
 	s := t.Permanent.Controller().gameState
diff --git a/go/game/permanent.go b/go/game/permanent.go
index ecc4459a..f211179b 100644
--- a/go/game/permanent.go
+++ b/go/game/permanent.go
@@ -206,3 +206,12 @@ func leaveTile(p Permanent) {
 		p.SetTile(nil)
 	}
 }
+
+func TileOrContainingPermTile(p Permanent) *Tile {
+	tile := p.Tile()
+	if tile == nil {
+		tile = p.ContainingPerm().Tile()
+	}
+
+	return tile
+}
diff --git a/go/game/range.go b/go/game/range.go
index bb60b54c..5f9d8e80 100644
--- a/go/game/range.go
+++ b/go/game/range.go
@@ -76,5 +76,5 @@ func TilesInRangeFromOrigin(m *Map, origin Position, r int) []*Tile {
 }
 
 func TilesInRange(m *Map, p Permanent, r int) []*Tile {
-	return TilesInRangeFromOrigin(m, p.Tile().Position, r)
+	return TilesInRangeFromOrigin(m, TileOrContainingPermTile(p).Position, r)
 }
diff --git a/go/game/unit.go b/go/game/unit.go
index adb608ab..c6c1839a 100644
--- a/go/game/unit.go
+++ b/go/game/unit.go
@@ -63,11 +63,11 @@ func NewUnit(card *Card, tile *Tile, owner *Player) *Unit {
 }
 
 func (u *Unit) Fmt() string {
-	return fmt.Sprintf("%s@%v", u.Card().Name, u.TileOrContainingPermTile())
+	return fmt.Sprintf("%s@%v", u.Card().Name, TileOrContainingPermTile(u))
 }
 
 func (u *Unit) FmtWController() string {
-	return fmt.Sprintf("%s's %s@%v", u.Controller().Name, u.Card().Name, u.TileOrContainingPermTile())
+	return fmt.Sprintf("%s's %s@%v", u.Controller().Name, u.Card().Name, TileOrContainingPermTile(u))
 }
 
 func NewUnitFromPath(cardPath string, tile *Tile, owner *Player) *Unit {
@@ -107,20 +107,11 @@ func (u *Unit) move(s *State, tile *Tile) {
 	}
 }
 
-func (u *Unit) TileOrContainingPermTile() *Tile {
-	tile := u.tile
-	if tile == nil {
-		tile = u.containingPerm.Tile()
-	}
-
-	return tile
-}
-
 func (u *Unit) MoveRangeTiles(m *Map) []*Tile {
 	tiles := []*Tile{}
 	// TODO: build graph only containing possible tile in movement range
 	graph := m.generateMapGraphFor(u)
-	origin := u.TileOrContainingPermTile().Position
+	origin := TileOrContainingPermTile(u).Position
 	for _, pos := range PositionsInRange(origin, u.Movement.Range, false) {
 		tile := m.TileAt(pos)
 		if tile == nil || !u.IsAvailableTile(tile) {