From 0aaeebd8042facb4e5d1a1e915f484c7c0c0dc82 Mon Sep 17 00:00:00 2001
From: R4vager <tvschonleber@gmail.com>
Date: Wed, 15 Apr 2026 14:00:31 -0400
Subject: [PATCH] renderer-three, ui: drop 'as unknown as' double-casts by
 widening callee signatures

Two callsites were forced into 'as unknown as X' shapes because the target
function took a narrower parameter than needed:

- packages/renderer-three/src/three-scene-basics.ts:207 passed
  value as unknown as Record<string, unknown> to the private helper
  isPlainGeometraThreeSceneBasicsOptionsRecord, because the outer type guard
  had already narrowed value to PlainGeometraThreeViewSizingState and TS
  refused the single-step cast to Record.

- packages/ui/src/theme.ts:244 laundered peekTheme() and the partial through
  Record<string, unknown> in both directions just to satisfy deepMerge's
  Record-typed signature, then re-asserted the result as Theme.

Widens isPlainGeometraThreeSceneBasicsOptionsRecord to take 'unknown' and
handle the null/object narrowing internally (one contained cast inside the
guard). Both public wrappers now call it with no casts and their behavior
is unchanged. Also collapses the redundant null/object precheck in
isPlainGeometraThreeSceneBasicsOptions now that the helper owns it.

Makes deepMerge generic over '<T extends object>' so mergeTheme collapses to
'deepMerge(peekTheme(), partial)' with zero casts at the callsite. The
internal Record casts inside deepMerge are standard 'I know this shape
better than the compiler' implementation details, and stay contained to
the helper body.

Full workspace build + fast vitest suite (2360 tests) pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 .../renderer-three/src/three-scene-basics.ts  |  9 +++++----
 packages/ui/src/theme.ts                      | 19 +++++++++----------
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/packages/renderer-three/src/three-scene-basics.ts b/packages/renderer-three/src/three-scene-basics.ts
index ab594acc..19fab3e7 100644
--- a/packages/renderer-three/src/three-scene-basics.ts
+++ b/packages/renderer-three/src/three-scene-basics.ts
@@ -168,7 +168,9 @@ function isPlainCameraPosition(value: unknown): value is THREE.Vector3Tuple {
   )
 }
 
-function isPlainGeometraThreeSceneBasicsOptionsRecord(o: Record<string, unknown>): boolean {
+function isPlainGeometraThreeSceneBasicsOptionsRecord(value: unknown): boolean {
+  if (value === null || typeof value !== 'object') return false
+  const o = value as Record<string, unknown>
   if (typeof o.threeBackgroundHex !== 'number' || !Number.isFinite(o.threeBackgroundHex)) {
     return false
   }
@@ -192,8 +194,7 @@ function isPlainGeometraThreeSceneBasicsOptionsRecord(o: Record<string, unknown>
 export function isPlainGeometraThreeSceneBasicsOptions(
   value: unknown,
 ): value is PlainGeometraThreeSceneBasicsOptions {
-  if (value === null || typeof value !== 'object') return false
-  return isPlainGeometraThreeSceneBasicsOptionsRecord(value as Record<string, unknown>)
+  return isPlainGeometraThreeSceneBasicsOptionsRecord(value)
 }
 
 /**
@@ -204,7 +205,7 @@ export function isPlainGeometraThreeSceneBasicsOptions(
  */
 export function isPlainGeometraThreeHostSnapshot(value: unknown): value is PlainGeometraThreeHostSnapshot {
   if (!isPlainGeometraThreeViewSizingState(value)) return false
-  return isPlainGeometraThreeSceneBasicsOptionsRecord(value as unknown as Record<string, unknown>)
+  return isPlainGeometraThreeSceneBasicsOptionsRecord(value)
 }
 
 /**
diff --git a/packages/ui/src/theme.ts b/packages/ui/src/theme.ts
index c61a2210..f566d54f 100644
--- a/packages/ui/src/theme.ts
+++ b/packages/ui/src/theme.ts
@@ -223,25 +223,24 @@ export type DeepPartial<T> = {
   [K in keyof T]?: T[K] extends object ? DeepPartial<T[K]> : T[K]
 }
 
-function deepMerge(base: Record<string, unknown>, partial: Record<string, unknown>): Record<string, unknown> {
-  const result = { ...base }
-  for (const key of Object.keys(partial)) {
-    const val = partial[key]
+function deepMerge<T extends object>(base: T, partial: DeepPartial<T>): T {
+  const result = { ...base } as Record<string, unknown>
+  const src = partial as Record<string, unknown>
+  for (const key of Object.keys(src)) {
+    const val = src[key]
     if (val !== undefined && typeof val === 'object' && val !== null && !Array.isArray(val)) {
-      result[key] = deepMerge(
-        (base[key] ?? {}) as Record<string, unknown>,
-        val as Record<string, unknown>,
-      )
+      const existing = (result[key] ?? {}) as object
+      result[key] = deepMerge(existing, val as DeepPartial<object>)
     } else if (val !== undefined) {
       result[key] = val
     }
   }
-  return result
+  return result as T
 }
 
 /** Deep-merge a partial override onto the current theme. Returns a new `Theme`. */
 export function mergeTheme(partial: DeepPartial<Theme>): Theme {
-  return deepMerge(peekTheme() as unknown as Record<string, unknown>, partial as unknown as Record<string, unknown>) as unknown as Theme
+  return deepMerge(peekTheme(), partial)
 }
 
 // ---------------------------------------------------------------------------