From 8af698edf949a09ed844e7e3b50ab698b98e712c Mon Sep 17 00:00:00 2001
From: Brian Ingles <brianingles@deephaven.io>
Date: Mon, 3 Jul 2023 11:45:37 -0500
Subject: [PATCH 1/3] feat: "Extends" TypeScript util type

#1393
---
 packages/utils/src/TypeUtils.ts | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/packages/utils/src/TypeUtils.ts b/packages/utils/src/TypeUtils.ts
index 143e6ba456..1b1eb0a0f8 100644
--- a/packages/utils/src/TypeUtils.ts
+++ b/packages/utils/src/TypeUtils.ts
@@ -1,3 +1,18 @@
+/**
+ * Util type to create a "subtype" of T. Useful for creating subsets of union
+ * types.
+ *
+ * e.g.
+ * declare type Direction = 'north' | 'south' | 'east' | 'west'
+ *
+ * // This works
+ * type Down = Subset<Direction, 'south'> // 'south'
+ *
+ * // Compiler will complain
+ * type NotDirection = Subset<Direction, 'blah'>
+ */
+export type Extends<T, U extends T> = U;
+
 /**
  * Util type to extract the value from an object.
  *

From ebe55fa62cede72f81959b41e2871aab0e4c252e Mon Sep 17 00:00:00 2001
From: Brian Ingles <brianingles@deephaven.io>
Date: Mon, 3 Jul 2023 12:32:24 -0500
Subject: [PATCH 2/3] Fixed comment block

#1393
---
 packages/utils/src/TypeUtils.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/utils/src/TypeUtils.ts b/packages/utils/src/TypeUtils.ts
index 1b1eb0a0f8..c543ee72db 100644
--- a/packages/utils/src/TypeUtils.ts
+++ b/packages/utils/src/TypeUtils.ts
@@ -6,10 +6,10 @@
  * declare type Direction = 'north' | 'south' | 'east' | 'west'
  *
  * // This works
- * type Down = Subset<Direction, 'south'> // 'south'
+ * type Down = Extends<Direction, 'south'> // 'south'
  *
  * // Compiler will complain
- * type NotDirection = Subset<Direction, 'blah'>
+ * type NotDirection = Extends<Direction, 'blah'>
  */
 export type Extends<T, U extends T> = U;
 

From 39b203e924428c675d646858f7c3467823413d35 Mon Sep 17 00:00:00 2001
From: Brian Ingles <brianingles@deephaven.io>
Date: Mon, 3 Jul 2023 12:44:34 -0500
Subject: [PATCH 3/3] Constraining type a bit more

#1393
---
 packages/utils/src/TypeUtils.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/utils/src/TypeUtils.ts b/packages/utils/src/TypeUtils.ts
index c543ee72db..fbcef13871 100644
--- a/packages/utils/src/TypeUtils.ts
+++ b/packages/utils/src/TypeUtils.ts
@@ -11,7 +11,7 @@
  * // Compiler will complain
  * type NotDirection = Extends<Direction, 'blah'>
  */
-export type Extends<T, U extends T> = U;
+export type Extends<T, U extends T> = U extends T ? U : never;
 
 /**
  * Util type to extract the value from an object.