From eed5135e5ffdec1d15136af1f2310bdd453d77e4 Mon Sep 17 00:00:00 2001
From: gcanti <giulio.canti@gmail.com>
Date: Mon, 11 Nov 2019 09:00:45 +0100
Subject: [PATCH] `fromNullable` now uses `NonNullable` in its return type,
 fixes #1004

---
 CHANGELOG.md              |  5 +++++
 docs/modules/Either.ts.md |  2 +-
 docs/modules/Option.ts.md |  2 +-
 dtslint/ts3.5/index.ts    | 25 +++++++++++++++++++++++++
 package.json              |  2 +-
 src/Either.ts             |  4 ++--
 src/Option.ts             |  4 ++--
 7 files changed, 37 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b5433c684..2c3f9b719 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,11 @@
 **Note**: Gaps between patch versions are faulty/broken releases. **Note**: A feature tagged as Experimental is in a
 high state of flux, you're at risk of it changing without notice.
 
+# 2.1.2
+
+- **Bug Fix**
+  - `fromNullable` now uses `NonNullable` in its return type, fixes #1004 (@gcanti)
+
 # 2.1.1
 
 - **Bug Fix**
diff --git a/docs/modules/Either.ts.md b/docs/modules/Either.ts.md
index af1b9512e..e85800f15 100644
--- a/docs/modules/Either.ts.md
+++ b/docs/modules/Either.ts.md
@@ -246,7 +246,7 @@ the provided default as a `Left`
 **Signature**
 
 ```ts
-export function fromNullable<E>(e: E): <A>(a: A | null | undefined) => Either<E, A> { ... }
+export function fromNullable<E>(e: E): <A>(a: A) => Either<E, NonNullable<A>> { ... }
 ```
 
 **Example**
diff --git a/docs/modules/Option.ts.md b/docs/modules/Option.ts.md
index 8b8665359..0a788d398 100644
--- a/docs/modules/Option.ts.md
+++ b/docs/modules/Option.ts.md
@@ -275,7 +275,7 @@ returns the value wrapped in a `Some`
 **Signature**
 
 ```ts
-export function fromNullable<A>(a: A | null | undefined): Option<A> { ... }
+export function fromNullable<A>(a: A): Option<NonNullable<A>> { ... }
 ```
 
 **Example**
diff --git a/dtslint/ts3.5/index.ts b/dtslint/ts3.5/index.ts
index 27dd3dd54..2f15288d3 100644
--- a/dtslint/ts3.5/index.ts
+++ b/dtslint/ts3.5/index.ts
@@ -167,6 +167,31 @@ type C = A | B
 // $ExpectError
 O.getRefinement<C, A>(c => (c.type === 'B' ? O.some(c) : O.none))
 
+// fromNullable
+
+declare const fromNullableTest1: number | null | undefined
+O.fromNullable(fromNullableTest1) // $ExpectType Option<number>
+
+interface fromNullableTest2 {
+  foo: number | undefined
+}
+declare const fromNullableTest3: <Key extends keyof fromNullableTest2>(key: Key) => fromNullableTest2[Key]
+// $ExpectType Option<number>
+Fu.flow(
+  fromNullableTest3,
+  O.fromNullable
+)('foo')
+
+//
+// Either
+//
+
+// $ExpectType Either<string, number>
+Fu.flow(
+  fromNullableTest3,
+  E.fromNullable('error')
+)('foo')
+
 //
 // HKT
 //
diff --git a/package.json b/package.json
index 1de80d394..68e8fab47 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "fp-ts",
-  "version": "2.1.1",
+  "version": "2.1.2",
   "description": "Functional programming in TypeScript",
   "files": [
     "lib",
diff --git a/src/Either.ts b/src/Either.ts
index b5bf62a02..869147aff 100644
--- a/src/Either.ts
+++ b/src/Either.ts
@@ -118,8 +118,8 @@ export function right<E = never, A = never>(a: A): Either<E, A> {
  *
  * @since 2.0.0
  */
-export function fromNullable<E>(e: E): <A>(a: A | null | undefined) => Either<E, A> {
-  return a => (a == null ? left(e) : right(a))
+export function fromNullable<E>(e: E): <A>(a: A) => Either<E, NonNullable<A>> {
+  return <A>(a: A) => (a == null ? left(e) : right(a as NonNullable<A>))
 }
 
 /**
diff --git a/src/Option.ts b/src/Option.ts
index e3a710aec..de8791194 100644
--- a/src/Option.ts
+++ b/src/Option.ts
@@ -160,8 +160,8 @@ export function fold<A, B>(onNone: () => B, onSome: (a: A) => B): (ma: Option<A>
  *
  * @since 2.0.0
  */
-export function fromNullable<A>(a: A | null | undefined): Option<A> {
-  return a == null ? none : some(a)
+export function fromNullable<A>(a: A): Option<NonNullable<A>> {
+  return a == null ? none : some(a as NonNullable<A>)
 }
 
 /**