From 193b21ea3b8e98eceace500f2f9a80f25e2a58cf Mon Sep 17 00:00:00 2001
From: Gorbachev Egor <7gorbachevm@gmail.com>
Date: Thu, 17 Mar 2022 10:12:11 +0300
Subject: [PATCH 1/2] Replace 'any' with a generic in Set (Close #3337)

---
 .changeset/tall-seas-study.md                       |  5 +++++
 packages/mobx/__tests__/v5/base/typescript-tests.ts | 11 +++++++++++
 packages/mobx/src/types/observableset.ts            |  4 ++--
 3 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/tall-seas-study.md

diff --git a/.changeset/tall-seas-study.md b/.changeset/tall-seas-study.md
new file mode 100644
index 000000000..6e1fc6a99
--- /dev/null
+++ b/.changeset/tall-seas-study.md
@@ -0,0 +1,5 @@
+---
+"mobx": patch
+---
+
+Replace any with a generic in Set methods
diff --git a/packages/mobx/__tests__/v5/base/typescript-tests.ts b/packages/mobx/__tests__/v5/base/typescript-tests.ts
index 2ce5ef056..ddde0886c 100644
--- a/packages/mobx/__tests__/v5/base/typescript-tests.ts
+++ b/packages/mobx/__tests__/v5/base/typescript-tests.ts
@@ -2054,6 +2054,17 @@ test("type inference of the action callback", () => {
     }
 })
 
+test("TS - type inference of Set", () => {
+    const set = observable.set<number>()
+    set.add(1)
+    // @ts-expect-error
+    set.add("1")
+    // @ts-expect-error
+    set.has("1")
+    // @ts-expect-error
+    set.delete("1")
+})
+
 test("TS - type inference of observe & intercept functions", () => {
     const array = [1, 2]
     const object = { numberKey: 1, stringKey: "string" }
diff --git a/packages/mobx/src/types/observableset.ts b/packages/mobx/src/types/observableset.ts
index 062829acb..05171775a 100644
--- a/packages/mobx/src/types/observableset.ts
+++ b/packages/mobx/src/types/observableset.ts
@@ -159,7 +159,7 @@ export class ObservableSet<T = any> implements Set<T>, IInterceptable<ISetWillCh
         return this
     }
 
-    delete(value: any) {
+    delete(value: T) {
         if (hasInterceptors(this)) {
             const change = interceptChange<ISetWillChange<T>>(this, {
                 type: DELETE,
@@ -202,7 +202,7 @@ export class ObservableSet<T = any> implements Set<T>, IInterceptable<ISetWillCh
         return false
     }
 
-    has(value: any) {
+    has(value: T) {
         this.atom_.reportObserved()
         return this.data_.has(this.dehanceValue_(value))
     }

From 56a2e8026c240a8b6844fda44c090da92a11dbeb Mon Sep 17 00:00:00 2001
From: Gorbachev Egor <7gorbachevm@gmail.com>
Date: Thu, 17 Mar 2022 12:58:45 +0300
Subject: [PATCH 2/2] Test more methods

---
 .changeset/{tall-seas-study.md => fluffy-crabs-exercise.md} | 2 +-
 packages/mobx/__tests__/v5/base/typescript-tests.ts         | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)
 rename .changeset/{tall-seas-study.md => fluffy-crabs-exercise.md} (78%)

diff --git a/.changeset/tall-seas-study.md b/.changeset/fluffy-crabs-exercise.md
similarity index 78%
rename from .changeset/tall-seas-study.md
rename to .changeset/fluffy-crabs-exercise.md
index 6e1fc6a99..3b54d3ce7 100644
--- a/.changeset/tall-seas-study.md
+++ b/.changeset/fluffy-crabs-exercise.md
@@ -1,5 +1,5 @@
 ---
-"mobx": patch
+"mobx": minor
 ---
 
 Replace any with a generic in Set methods
diff --git a/packages/mobx/__tests__/v5/base/typescript-tests.ts b/packages/mobx/__tests__/v5/base/typescript-tests.ts
index ddde0886c..c65f66736 100644
--- a/packages/mobx/__tests__/v5/base/typescript-tests.ts
+++ b/packages/mobx/__tests__/v5/base/typescript-tests.ts
@@ -2057,6 +2057,8 @@ test("type inference of the action callback", () => {
 test("TS - type inference of Set", () => {
     const set = observable.set<number>()
     set.add(1)
+    set.has(1)
+    set.delete(1)
     // @ts-expect-error
     set.add("1")
     // @ts-expect-error