fix: do not force slots to be self-closed (#435)

Related to sveltejs/kit#12102

Author: jrmajor

src/print/index.ts

@@ -215,10 +215,10 @@ export function print(path: FastPath, options: ParserOptions, print: PrintFn): D
                 ((((node.type === 'Element' && !options.svelteStrictMode) ||
                     node.type === 'Head' ||
                     node.type === 'InlineComponent' ||
+                    node.type === 'Slot' ||
                     node.type === 'SlotTemplate' ||
                     node.type === 'Title') &&
                     didSelfClose) ||
-                    node.type === 'Slot' ||
                     node.type === 'Window' ||
                     selfClosingTags.indexOf(node.name) !== -1 ||
                     isDoctypeTag);

test/printer/samples/self-closing-tags-lenient.html

@@ -0,0 +1,2 @@
+<slot />
+<slot></slot>

test/printer/samples/self-closing-tags.html

@@ -6,6 +6,10 @@
 
 <MyComponent />
 
+<!-- TODO: self-closing slot shouldn't be allowed in the next major version -->
+<slot />
+<slot></slot>
+
 <img />
 
 <input />