Slots and snippets

Svelte uses the word “slot” for two things, and libwasm uses Slot for a third. A content <slot> is a hole in a layout or component that the parent fills. A {#snippet} is a named fragment instantiated at {@render}. mixin Slot!"click" is an EventEmitter. The first two belong on this page. The third belongs on events. The names collide in English and they do not collide in D; the printed file is what tells them apart.

A content <slot> prints as mixin Slot!("name") plus fallback children. The fallback is what you see in the admin layout when nothing is projected — admin fallback in the example. Named <slot name="aside"> is a named Slot (ComboOr.svelte). <slot let:item> prints string item; // let:item on the slot or element. A parent that writes <Panel>hello</Panel> is the slot site. Layouts use <slot> so KitRoutes can remount the page inside the wrapper. A layout that inlined the page instead of slotting it would force the page to be a field of the layout type, and nested routes would become a compile-time tree of every possible child.

{#snippet} stores a body. {@render greet(who)} instantiates it. Multi-param {#snippet pair(a, b)} plus {@render pair(who, extra)} assigns each parameter and then walks (ComboSem.svelte). A snippet site on <svelte:component> is ComboNext.svelte. The failed snippet on <svelte:boundary> is await / boundary; it is a snippet that happens to be the failed branch, not a fourth kind of slot.