Fix issue with IsNumeric when input is whitespace (#539)

source/internal.d.ts

@@ -1,5 +1,6 @@
 import type {Primitive} from './primitive';
 import type {Simplify} from './simplify';
+import type {Trim} from './trim';
 
 /**
 Infer the length of the given array `<T>`.
@@ -47,6 +48,34 @@ export type WordSeparators = '-' | '_' | ' ';
 
 export type StringDigit = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9';
 
+export type Whitespace =
+	| '\u{9}' // '\t'
+	| '\u{A}' // '\n'
+	| '\u{B}' // '\v'
+	| '\u{C}' // '\f'
+	| '\u{D}' // '\r'
+	| '\u{20}' // ' '
+	| '\u{85}'
+	| '\u{A0}'
+	| '\u{1680}'
+	| '\u{2000}'
+	| '\u{2001}'
+	| '\u{2002}'
+	| '\u{2003}'
+	| '\u{2004}'
+	| '\u{2005}'
+	| '\u{2006}'
+	| '\u{2007}'
+	| '\u{2008}'
+	| '\u{2009}'
+	| '\u{200A}'
+	| '\u{2028}'
+	| '\u{2029}'
+	| '\u{202F}'
+	| '\u{205F}'
+	| '\u{3000}'
+	| '\u{FEFF}';
+
 /**
 Matches any unknown record.
 */
@@ -109,10 +138,25 @@ Returns a boolean for whether the string is uppercased.
 */
 export type IsUpperCase<T extends string> = T extends Uppercase<T> ? true : false;
 
+/**
+Returns a boolean for whether a string is whitespace.
+*/
+export type IsWhitespace<T extends string> = T extends Whitespace
+	? true
+	: T extends `${Whitespace}${infer Rest}`
+		? IsWhitespace<Rest>
+		: false;
+
 /**
 Returns a boolean for whether the string is numeric.
+
+This type is a workaround for [Microsoft/TypeScript#46109](https://github.com/microsoft/TypeScript/issues/46109#issuecomment-930307987).
 */
-export type IsNumeric<T extends string> = T extends `${number}` ? true : false;
+export type IsNumeric<T extends string> = T extends `${number}`
+	? Trim<T> extends T
+		? true
+		: false
+	: false;
 
 /**
 Returns a boolean for whether the the type is `any`.

source/trim.d.ts

@@ -1,12 +1,14 @@
+import type {Whitespace} from './internal';
+
 /**
 Remove spaces from the left side.
 */
-type TrimLeft<V extends string> = V extends ` ${infer R}` ? TrimLeft<R> : V;
+type TrimLeft<V extends string> = V extends `${Whitespace}${infer R}` ? TrimLeft<R> : V;
 
 /**
 Remove spaces from the right side.
 */
-type TrimRight<V extends string> = V extends `${infer R} ` ? TrimRight<R> : V;
+type TrimRight<V extends string> = V extends `${infer R}${Whitespace}` ? TrimRight<R> : V;
 
 /**
 Remove leading and trailing spaces from a string.

test-d/internal.ts

@@ -0,0 +1,29 @@
+import {expectType} from 'tsd';
+import type {IsWhitespace, IsNumeric} from '../source/internal';
+
+expectType<IsWhitespace<''>>(false);
+expectType<IsWhitespace<' '>>(true);
+expectType<IsWhitespace<'\n'>>(true);
+expectType<IsWhitespace<'\u{9}'>>(true);
+expectType<IsWhitespace<'a'>>(false);
+expectType<IsWhitespace<'a '>>(false);
+expectType<IsWhitespace<'   '>>(true);
+expectType<IsWhitespace<' \t '>>(true);
+
+expectType<IsNumeric<''>>(false);
+expectType<IsNumeric<'0'>>(true);
+expectType<IsNumeric<'1'>>(true);
+expectType<IsNumeric<'-1'>>(true);
+expectType<IsNumeric<'123'>>(true);
+expectType<IsNumeric<'1e2'>>(true);
+expectType<IsNumeric<'1.23'>>(true);
+expectType<IsNumeric<'123.456'>>(true);
+expectType<IsNumeric<'1.23e4'>>(true);
+expectType<IsNumeric<'1.23e-4'>>(true);
+expectType<IsNumeric<' '>>(false);
+expectType<IsNumeric<'\n'>>(false);
+expectType<IsNumeric<'\u{9}'>>(false);
+expectType<IsNumeric<' 1.2'>>(false);
+expectType<IsNumeric<'1 2'>>(false);
+expectType<IsNumeric<'1_200'>>(false);
+expectType<IsNumeric<' 1 '>>(false);

test-d/trim.ts

@@ -8,3 +8,5 @@ expectType<'bar'>(trim('bar '));
 expectType<'baz'>(trim(' baz '));
 expectType<'waldo'>(trim('  waldo  '));
 expectType<'fr ed'>(trim(' fr ed '));
+expectType<'foo'>(trim(' foo\n'));
+expectType<'foo'>(trim(' foo\n\t '));