fix: IsInteger with number & { a: 1 }>

.changeset/sharp-walls-deliver.md

@@ -0,0 +1,5 @@
+---
+"type-plus": patch
+---
+
+Fix `IsInteger<number & { a: 1 }>` should returns `boolean`

packages/type-plus/src/numeric/is_integer.spec.ts

@@ -60,8 +60,14 @@ it('can disable union distribution', () => {
 	testType.equal<IsInteger<1 | string, { distributive: false }>, false>(true)
 })
 
-it('returns true for intersection type', () => {
-	testType.equal<IsInteger<number & { a: 1 }>, true>(true)
+it('returns true for intersection type with integer literals', () => {
+	testType.equal<IsInteger<1 & { a: 1 }>, true>(true)
+	testType.equal<IsInteger<-1 & { a: 1 }>, true>(true)
+	testType.equal<IsInteger<1n & { a: 1 }>, true>(true)
+})
+
+it('returns boolean when T is an intersection type with number', () => {
+	testType.equal<IsInteger<number & { a: 1 }>, boolean>(true)
 })
 
 it('works as filter', () => {

packages/type-plus/src/numeric/is_integer.ts

@@ -23,10 +23,11 @@ export type IsInteger<T, $O extends IsInteger.$Options = {}> = IsNumber<T, {
 	? R extends $Then ? (
 		number extends T
 		? $ResolveBranch<number, $O, [$Then]> | $ResolveBranch<T, $O, [$Else]>
-		: T extends number ? (
+		: T extends number & infer U ? (
 			`${T}` extends `${number}.${number}`
 			? $ResolveBranch<T, $O, [$Else]>
-			: $ResolveBranch<T, $O, [$Then]>
+			: [T, U] extends [U, T] ? $ResolveBranch<T, $O, [$Then]>
+			: $ResolveBranch<number, $O, [$Then]> | $ResolveBranch<T, $O, [$Else]>
 		)
 		: never
 	)