In `@src/core/types.ts`:
- Around line 114-125: Remove the duplicated type definitions (EffectCallback,
DependencyList, Reducer, MutableRefObject) from core/types and instead re-export
them from the canonical source where they are defined; locate the duplicate
declarations for EffectCallback, DependencyList, Reducer<State, Action>, and
MutableRefObject<T> in core/types and replace them with export-only statements
that re-export the same symbols from the hooks types module so there is a single
source of truth.
- Around line 94-95: The import "import type { PortalElement } from
\"../portals/types\";" is placed after runtime constants; move this type-only
import up into the existing import block at the top of the file alongside the
other imports (around the current imports near line 5) and remove the
duplicate/old import at its current location so linters and style rules are
satisfied.

In `@src/fiber/types.ts`:
- Around line 504-512: The isHostFiber type guard is incorrect because it
includes WorkTag.HostRoot but narrows stateNode to Element | Text
(HostRoot.stateNode is a FiberRoot), so either remove HostRoot from
isHostFiber's truthy tags or split into two guards: keep isHostFiber for
HostRoot if you want to detect root fibers (with its proper FiberRoot stateNode)
and add a new isDOMFiber (or similar) that returns fiber is Fiber & { stateNode:
Element | Text } and only checks WorkTag.HostComponent and WorkTag.HostText;
update callsites to use the appropriate guard (isDOMFiber when you need DOM
operations and isHostFiber when you need root detection).
- Around line 109-134: Replace the repeated "(... as number)" casts by adding a
small helper that builds a combined Flags value and delegates to createFlags;
implement a combineFlags(...flags: Flags): Flags that reduces flags with bitwise
OR (casting each flag to number inside the reducer) and passes the result into
createFlags, then update uses like PlacementAndUpdate, Deletion, MutationMask,
LayoutMask, PassiveMask to call combineFlags(Placement, Update, ...) instead of
calling createFlags with many explicit casts, keeping createFlags and the
original flag names (Placement, Update, ChildDeletion, ContentReset, Ref,
Hydrating, Visibility, Callback, Passive) as the references.
- Around line 254-261: The JSDoc for the stateNode field mentions "For class
components: the instance" but the stateNode union type on the Fiber interface
does not include a class instance type; update the declaration to prevent this
becoming a stale comment by either adding a clear TODO comment referencing
ClassComponent/WorkTag and stateNode (e.g., "TODO: add class component instance
type when implementing ClassComponent") or add a placeholder union member for
the class instance type (a named placeholder type) so the comment and the
stateNode type stay consistent; make the change near the stateNode declaration
and reference ClassComponent and WorkTag in the note.
- Around line 165-171: The Effect.type currently uses a plain number for the tag
field which loses type safety; change the tag property to use the const-backed
HookEffectTag union instead (e.g. define a type alias like `type
HookEffectTagType = typeof HookEffectTag[keyof typeof HookEffectTag]` and update
`export type Effect = { tag: HookEffectTagType; ... }`) so only valid
HookEffectTag values can be assigned; update the tag declaration in the Effect
type and add the small alias near the HookEffectTag definition if not already
present.
- Line 94: The file defines both a value constant named Update (export const
Update = createFlags(...)) and a generic type Update<S>, which is confusing;
rename the flag constant (e.g., to UpdateFlag or UpdateEffect) and update all
uses of that constant (including any combined flag masks and exports) to the new
name; ensure the createFlags(...) call and its export remain intact and update
any imports/refs elsewhere to the new symbol while leaving the generic type
Update<S> unchanged.
- Around line 487-495: The forward-declared MiniReactContext in fiber/types.ts
does not match the real context shape in context/types.ts (real has _contextId,
Provider: FunctionalComponent<...>, no Consumer, T = unknown), so replace the
lie with a single canonical type: import the actual context type from
context/types.ts (use a type-only import like "import type { Context } from
'context/types'") or move the canonical interface into a shared module and have
both files import it; ensure the symbol names match (update MiniReactContext to
the real interface shape including _contextId and Provider's FunctionalComponent
signature and remove Consumer) so the types are identical and the circular
dependency is handled via type-only imports or a new shared type file.

In `@src/core/types.ts`:
- Around line 110-111: The import for StateOrEffectHook is located after runtime
constants; move the import type declaration for StateOrEffectHook to the top of
the file together with the other imports so all imports are grouped, and delete
the stray import statement that currently sits mid-file (the duplicate import of
StateOrEffectHook).

In `@src/fiber/types.ts`:
- Around line 532-536: The type guard isPortal currently only narrows fiber.tag
but not fiber.stateNode; update its return type to narrow stateNode to
PortalStateNode so callers can access portal-specific fields (e.g.,
stateNode.containerInfo) without casting. Specifically, change the predicate
signature from "fiber is Fiber & { tag: typeof WorkTag.HostPortal }" to include
"& { tag: typeof WorkTag.HostPortal; stateNode: PortalStateNode }" and ensure
any imports or references to PortalStateNode are used so TypeScript recognizes
the narrowed type in the isPortal function.
- Around line 146-147: Remove the redundant type alias HookEffectTagType and
replace all uses of HookEffectTagType with the original HookEffectTag type
(e.g., update the reference on the line that currently uses HookEffectTagType to
use HookEffectTag instead); specifically delete the declaration "export type
HookEffectTagType = HookEffectTag" and update any downstream references to the
alias (such as the usage on the line referenced in the review) to reference
HookEffectTag directly so the code uses the single canonical type name.

In `@src/fiber/types.ts`:
- Around line 449-476: StateNodeFor currently lacks a branch for HostPortal so
StateNodeFor<typeof WorkTag.HostPortal> resolves to null; update the conditional
type in StateNodeFor to include a branch mapping T extends typeof
WorkTag.HostPortal to PortalStateNode (ensure PortalStateNode type is
imported/available) so the HostPortal fibers get the correct stateNode type.