13 files changed, 49 insertions, 15 deletions
diff --git a/src/mbgl/style/conversion/layer.cpp b/src/mbgl/style/conversion/layer.cpp
index 50401d1679..9690e0941e 100644
--- a/src/mbgl/style/conversion/layer.cpp
+++ b/src/mbgl/style/conversion/layer.cpp
@@ -10,9 +10,9 @@ namespace style {
 namespace conversion {
 
 namespace {
-bool setObjectMember(std::unique_ptr<Layer>& layer, const Convertible& value, const char* member, Error& error) {
+bool setObjectMember(LayerInitializer& layer, const Convertible& value, const char* member, Error& error) {
     if (auto memberValue = objectMember(value, member)) {
-        if (auto error_ = layer->setProperty(member, *memberValue)) {
+        if (auto error_ = layer.setProperty(member, *memberValue)) {
             error = *error_;
             return false;
         }
@@ -21,7 +21,7 @@ bool setObjectMember(std::unique_ptr<Layer>& layer, const Convertible& value, co
 }
 } // namespace
 
-optional<Error> setPaintProperties(Layer& layer, const Convertible& value) {
+optional<Error> setPaintProperties(LayerInitializer& layer, const Convertible& value) {
     auto paintValue = objectMember(value, "paint");
     if (!paintValue) {
         return nullopt;
@@ -62,14 +62,14 @@ optional<std::unique_ptr<Layer>> Converter<std::unique_ptr<Layer>>::operator()(c
         return nullopt;
     }
 
-    std::unique_ptr<Layer> layer = LayerManager::get()->createLayer(*type, *id, value, error);
+    auto layer = LayerManager::get()->createLayer(*type, *id, value, error);
     if (!layer) return nullopt;
-
-    if (!setObjectMember(layer, value, "minzoom", error)) return nullopt;
-    if (!setObjectMember(layer, value, "maxzoom", error)) return nullopt;
-    if (!setObjectMember(layer, value, "filter", error)) return nullopt;
-    if (layer->getTypeInfo()->source == LayerTypeInfo::Source::Required) {
-        if (!setObjectMember(layer, value, "source-layer", error)) return nullopt;
+    LayerInitializer initializer{std::move(layer)};
+    if (!setObjectMember(initializer, value, "minzoom", error)) return nullopt;
+    if (!setObjectMember(initializer, value, "maxzoom", error)) return nullopt;
+    if (!setObjectMember(initializer, value, "filter", error)) return nullopt;
+    if (initializer.getTypeInfo()->source == LayerTypeInfo::Source::Required) {
+        if (!setObjectMember(initializer, value, "source-layer", error)) return nullopt;
     }
 
     auto layoutValue = objectMember(value, "layout");
@@ -79,20 +79,20 @@ optional<std::unique_ptr<Layer>> Converter<std::unique_ptr<Layer>>::operator()(c
             return nullopt;
         }
         optional<Error> error_ = eachMember(
-            *layoutValue, [&](const std::string& k, const Convertible& v) { return layer->setProperty(k, v); });
+            *layoutValue, [&](const std::string& k, const Convertible& v) { return initializer.setProperty(k, v); });
         if (error_) {
             error = *error_;
             return nullopt;
         }
     }
 
-    optional<Error> error_ = setPaintProperties(*layer, value);
+    optional<Error> error_ = setPaintProperties(initializer, value);
     if (error_) {
         error = *error_;
         return nullopt;
     }
 
-    return layer;
+    return std::unique_ptr<Layer>(std::move(initializer));
 }
 
 } // namespace conversion
diff --git a/src/mbgl/style/layers/background_layer.cpp b/src/mbgl/style/layers/background_layer.cpp
index 336cd33599..10ef64c51a 100644
--- a/src/mbgl/style/layers/background_layer.cpp
+++ b/src/mbgl/style/layers/background_layer.cpp
@@ -47,6 +47,9 @@ const BackgroundLayer::Impl& BackgroundLayer::impl() const {
 }
 
 Mutable<BackgroundLayer::Impl> BackgroundLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/circle_layer.cpp b/src/mbgl/style/layers/circle_layer.cpp
index 8c81d8a23f..488dcb24b1 100644
--- a/src/mbgl/style/layers/circle_layer.cpp
+++ b/src/mbgl/style/layers/circle_layer.cpp
@@ -47,6 +47,9 @@ const CircleLayer::Impl& CircleLayer::impl() const {
 }
 
 Mutable<CircleLayer::Impl> CircleLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/fill_extrusion_layer.cpp b/src/mbgl/style/layers/fill_extrusion_layer.cpp
index 50afe80ea3..4be4c14087 100644
--- a/src/mbgl/style/layers/fill_extrusion_layer.cpp
+++ b/src/mbgl/style/layers/fill_extrusion_layer.cpp
@@ -47,6 +47,9 @@ const FillExtrusionLayer::Impl& FillExtrusionLayer::impl() const {
 }
 
 Mutable<FillExtrusionLayer::Impl> FillExtrusionLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/fill_layer.cpp b/src/mbgl/style/layers/fill_layer.cpp
index 83049a33f0..aa7801e2b5 100644
--- a/src/mbgl/style/layers/fill_layer.cpp
+++ b/src/mbgl/style/layers/fill_layer.cpp
@@ -47,6 +47,9 @@ const FillLayer::Impl& FillLayer::impl() const {
 }
 
 Mutable<FillLayer::Impl> FillLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/heatmap_layer.cpp b/src/mbgl/style/layers/heatmap_layer.cpp
index 4f86519b31..8afba25171 100644
--- a/src/mbgl/style/layers/heatmap_layer.cpp
+++ b/src/mbgl/style/layers/heatmap_layer.cpp
@@ -47,6 +47,9 @@ const HeatmapLayer::Impl& HeatmapLayer::impl() const {
 }
 
 Mutable<HeatmapLayer::Impl> HeatmapLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/hillshade_layer.cpp b/src/mbgl/style/layers/hillshade_layer.cpp
index b5fef6e628..b6ae821d26 100644
--- a/src/mbgl/style/layers/hillshade_layer.cpp
+++ b/src/mbgl/style/layers/hillshade_layer.cpp
@@ -47,6 +47,9 @@ const HillshadeLayer::Impl& HillshadeLayer::impl() const {
 }
 
 Mutable<HillshadeLayer::Impl> HillshadeLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/layer.cpp.ejs b/src/mbgl/style/layers/layer.cpp.ejs
index 903d713755..b707bc198e 100644
--- a/src/mbgl/style/layers/layer.cpp.ejs
+++ b/src/mbgl/style/layers/layer.cpp.ejs
@@ -124,6 +124,9 @@ const <%- camelize(type) %>Layer::Impl& <%- camelize(type) %>Layer::impl() const
 }
 
 Mutable<<%- camelize(type) %>Layer::Impl> <%- camelize(type) %>Layer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/line_layer.cpp b/src/mbgl/style/layers/line_layer.cpp
index f5b5df9af7..1522f8ff2b 100644
--- a/src/mbgl/style/layers/line_layer.cpp
+++ b/src/mbgl/style/layers/line_layer.cpp
@@ -47,6 +47,9 @@ const LineLayer::Impl& LineLayer::impl() const {
 }
 
 Mutable<LineLayer::Impl> LineLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/location_indicator_layer.cpp b/src/mbgl/style/layers/location_indicator_layer.cpp
index b02e044c96..fe28399384 100644
--- a/src/mbgl/style/layers/location_indicator_layer.cpp
+++ b/src/mbgl/style/layers/location_indicator_layer.cpp
@@ -47,6 +47,9 @@ const LocationIndicatorLayer::Impl& LocationIndicatorLayer::impl() const {
 }
 
 Mutable<LocationIndicatorLayer::Impl> LocationIndicatorLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/raster_layer.cpp b/src/mbgl/style/layers/raster_layer.cpp
index 6db4feb65e..63240e816c 100644
--- a/src/mbgl/style/layers/raster_layer.cpp
+++ b/src/mbgl/style/layers/raster_layer.cpp
@@ -47,6 +47,9 @@ const RasterLayer::Impl& RasterLayer::impl() const {
 }
 
 Mutable<RasterLayer::Impl> RasterLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/layers/symbol_layer.cpp b/src/mbgl/style/layers/symbol_layer.cpp
index b9f0b70209..b768827b9e 100644
--- a/src/mbgl/style/layers/symbol_layer.cpp
+++ b/src/mbgl/style/layers/symbol_layer.cpp
@@ -47,6 +47,9 @@ const SymbolLayer::Impl& SymbolLayer::impl() const {
 }
 
 Mutable<SymbolLayer::Impl> SymbolLayer::mutableImpl() const {
+    if (initializing) {
+        return constImmutableCast<Impl, Layer::Impl>(baseImpl);
+    }
     return makeMutable<Impl>(impl());
 }
 
diff --git a/src/mbgl/style/parser.cpp b/src/mbgl/style/parser.cpp
index 9d9b80276a..b8ad4088d3 100644
--- a/src/mbgl/style/parser.cpp
+++ b/src/mbgl/style/parser.cpp
@@ -253,8 +253,9 @@ void Parser::parseLayer(const std::string& id, const JSValue& value, std::unique
             return;
         }
 
-        layer = reference->cloneRef(id);
-        conversion::setPaintProperties(*layer, conversion::Convertible(&value));
+        LayerInitializer layerInitializer{reference->cloneRef(id)};
+        conversion::setPaintProperties(layerInitializer, conversion::Convertible(&value));
+        layer = std::unique_ptr<Layer>(std::move(layerInitializer));
     } else {
         conversion::Error error;
         optional<std::unique_ptr<Layer>> converted = conversion::convert<std::unique_ptr<Layer>>(value, error);