refactor: stronger theme props

src/_mixins/use-theme.ts

@@ -17,7 +17,11 @@ export interface Theme<T = {}, R = any> {
   self?: (vars: ThemeCommonVars) => T
 }
 
-export type ExtractThemeVars<T> = T extends Theme<infer U, unknown> ? U : {}
+export type ExtractThemeVars<T> = T extends Theme<infer U, unknown>
+  ? unknown extends U
+    ? {}
+    : U
+  : {}
 
 export type ExtractPeerOverrides<T> = T extends Theme<unknown, infer V>
   ? {
@@ -27,6 +31,12 @@ export type ExtractPeerOverrides<T> = T extends Theme<unknown, infer V>
   }
   : T
 
+export type ExtractMergedPeerOverrides<T> = T extends Theme<unknown, infer V>
+  ? {
+    [k in keyof V]?: ExtractThemeVars<V[k]>
+  }
+  : T
+
 export type ExtractThemeOverrides<T> = Partial<ExtractThemeVars<T>> &
 ExtractPeerOverrides<T> & { common?: ThemeCommonVars }
 
@@ -45,7 +55,7 @@ export type MergedTheme<T> = T extends Theme<infer V, infer W>
     common: ThemeCommonVars
     self: V
     peers: W
-    overrides: any
+    overrides: ExtractMergedPeerOverrides<T>
   }
   : T
 
@@ -114,7 +124,7 @@ function useTheme<T, R> (
       common: mergedCommon,
       self: mergedSelf,
       peers: merge({}, defaultTheme.peers, peers, injectedPeers),
-      overrides: merge(peersOverrides, injectedPeersOverrides)
+      overrides: merge({}, peersOverrides, injectedPeersOverrides)
     }
   })
   return mergedThemeRef

src/tree/styles/light.ts

@@ -2,7 +2,7 @@ import { changeColor } from 'seemly'
 import { checkboxLight } from '../../checkbox/styles'
 import { commonLight } from '../../_styles/new-common'
 import type { ThemeCommonVars } from '../../_styles/new-common'
-import { Theme } from '../../_mixins/use-theme'
+import { createTheme } from '../../_mixins/use-theme'
 
 const self = (vars: ThemeCommonVars) => {
   const {
@@ -30,14 +30,14 @@ const self = (vars: ThemeCommonVars) => {
 
 export type TreeThemeVars = ReturnType<typeof self>
 
-const treeLight: Theme<TreeThemeVars> = {
+const treeLight = createTheme({
   name: 'Tree',
   common: commonLight,
   peers: {
     Checkbox: checkboxLight
   },
   self
-}
+})
 
 export default treeLight
 export type TreeTheme = typeof treeLight