fix(menubar,menu,tieredmenu,megamenu,contextmenu,panelmenu,breadcrumb,steps,tabmenu,splitbutton,dock,speeddial): enable generic type inference for model and slots

[YevheniiKotyrlo]

Defect Fixes

Fixes #8494
Fixes #4175

All menu-family components use MenuItem for their model prop and all slot scoped data. Developers who extend MenuItem with custom properties get no type safety — custom properties resolve to any via the [key: string]: any index signature instead of their declared types.

Same root cause as #8442 — DefineComponent's no-arg constructor prevents generic inference. Same fix pattern as #8444 (DataTable/DatePicker).

Related: #7426, #6041

Reproducer: StackBlitz — bun run type-check (0 errors, typo undetected) → bun run patch && bun run type-check (TS2339 catches it)

Problem

interface MyMenuItem extends MenuItem {
  route?: string;
  badge?: number;
}

const items: MyMenuItem[] = [
  { label: 'Home', route: '/home', badge: 5 }
];

<Menubar :model="items">
  <template #item="{ item }">
    {{ item.route }}
    <!-- No error — `item.route` is `any` (from index signature), typo ships to production -->
  </template>
</Menubar>

After this fix, TypeScript infers T = MyMenuItem from the :model binding and flows it to all slots:

<Menubar :model="items">
  <template #item="{ item }">
    {{ item.route }}
    <!-- item.route is `string | undefined` — proper type from MyMenuItem -->
  </template>
</Menubar>

Changes

For each component (Menubar, Menu, TieredMenu, MegaMenu, ContextMenu, PanelMenu, Breadcrumb, Steps, TabMenu, SplitButton, Dock, SpeedDial):

• [Component]Props<T extends MenuItem = MenuItem> — model: T[]
• [Component]Slots<T extends MenuItem = MenuItem> — all item-bearing slot parameters become T
• Generic constructor: new <T extends MenuItem = MenuItem>(props: [Component]Props<T>) with $slots: [Component]Slots<T>
• T defaults to MenuItem (not any) — menu components have a well-defined base type, and the [key: string]: any index signature on MenuItem is preserved for undeclared properties

Special cases:

• Breadcrumb: home?: T prop also becomes generic
• PanelMenu: headericon slot also receives item: T
• SplitButton: uses menuitemicon slot name instead of itemicon
• Menu, TieredMenu, ContextMenu: Methods interfaces preserved (toggle, show, hide)
• Dock: icon (deprecated) and itemicon slots also receive item: T
• SpeedDial: itemicon slot also receives item: T

What gets typed

Slot	Before	After
#item item	MenuItem	T
#itemicon / #menuitemicon item	MenuItem	T
#submenuicon item (where present)	MenuItem	T
#start / #end (Menubar)	no change	no change
PanelMenu #headericon item	MenuItem	T
Breadcrumb home prop	MenuItem	T

Scope / Impact

• No breaking changes — backward compatible, T defaults to MenuItem
• No runtime changes — types only (.d.ts files)
• 12 components: Menubar, Menu, TieredMenu, MegaMenu, ContextMenu, PanelMenu, Breadcrumb, Steps, TabMenu, SplitButton, Dock, SpeedDial

Verification

Gate	Result
pnpm run format:check	PASS
pnpm run lint	PASS
pnpm run test:unit	Pre-existing failures only, 0 new
pnpm run build:packages	Pre-existing Windows build issue (NODE_ENV= syntax), 0 new

Series

This is part of a series bringing generic type inference to all PrimeVue data components:

PR	Components	Status
#8444	DataTable, DatePicker	Open
#8484	Select, MultiSelect, Listbox	Open
#8485	Column (phantom of prop)	Open
#8489	AutoComplete, CascadeSelect, DataView	Open
#8490	Carousel, Galleria, Timeline	Open
#8491	OrderList, PickList	Open
#8493	VirtualScroller, SelectButton, InputChips	Open
#8495	Menubar, Menu, TieredMenu, MegaMenu, ContextMenu, PanelMenu, Breadcrumb, Steps, TabMenu, SplitButton, Dock, SpeedDial	This PR

After this series, every PrimeVue component with a collection prop will infer T from the binding and flow it to slots — giving developers full IDE autocomplete and compile-time type safety in templates.