Reapply sveltejs#3128 changes to new interfaces.

Author: campbeln

src/compiler/compile/render_dom/index.ts

@@ -453,7 +453,12 @@ export default function dom(
 							@insert(options.target, this, options.anchor);
 						}
 
+						this.$$.slotted = {};
 						${(props.length > 0 || uses_props) && b`
+						for (const key in options.props.$$slots) {
+							this.$$.slotted[key] = options.props.$$slots[key][0]();
+							this.$$.slotted[key].c();
+						}
 						if (options.props) {
 							this.$set(options.props);
 							@flush();

src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts

@@ -401,7 +401,12 @@ export default class InlineComponentWrapper extends Wrapper {
 			}
 
 			block.chunks.mount.push(b`
-				if (${name}) {
+				if (component.compile_options.customElement) {
+					block.chunks.mount.push(
+						@insert(${parent_node || '#target'}, ${name}, ${parent_node ? 'null' : 'anchor'});
+					)
+				}
+				else if (${name}) {
 					@mount_component(${name}, ${parent_node || '#target'}, ${parent_node ? 'null' : 'anchor'});
 				}
 			`);

src/runtime/internal/Component.ts

@@ -174,7 +174,8 @@ if (typeof HTMLElement === 'function') {
 			// @ts-ignore todo: improve typings
 			for (const key in this.$$.slotted) {
 				// @ts-ignore todo: improve typings
-				this.appendChild(this.$$.slotted[key]);
+				//this.appendChild(this.$$.slotted[key]);
+				this.$$.slotted[key].m(this, null);
 			}
 		}
 
@@ -183,6 +184,11 @@ if (typeof HTMLElement === 'function') {
 		}
 
 		$destroy() {
+			// @ts-ignore todo: improve typings
+			for (const key in this.$$.slotted) {
+				// @ts-ignore todo: improve typings
+				this.$$.slotted[key].d();
+			}
 			destroy_component(this, 1);
 			this.$destroy = noop;
 		}