From 9c36201a3f0dcfe04e6b4d77939b8a94ca14e773 Mon Sep 17 00:00:00 2001
From: YeonJuan <yeonjuan93@naver.com>
Date: Mon, 24 Feb 2025 23:25:51 +0900
Subject: [PATCH 1/3] fix(eslint-plugin): [no-unnecessary-type-assertion]
 handle unknown

---
 .../rules/no-unnecessary-type-assertion.ts    | 10 +++++
 .../no-unnecessary-type-assertion.test.ts     | 44 +++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-type-assertion.ts b/packages/eslint-plugin/src/rules/no-unnecessary-type-assertion.ts
index 83c8afe9b78c..526e2449b999 100644
--- a/packages/eslint-plugin/src/rules/no-unnecessary-type-assertion.ts
+++ b/packages/eslint-plugin/src/rules/no-unnecessary-type-assertion.ts
@@ -349,6 +349,16 @@ export default createRule<Options, MessageIds>({
 
           const contextualType = getContextualType(checker, originalNode);
           if (contextualType) {
+            const typeIsUnknown = isTypeFlagSet(type, ts.TypeFlags.Unknown);
+            const contextualTypeIsUnknown = isTypeFlagSet(
+              contextualType,
+              ts.TypeFlags.Unknown,
+            );
+
+            if (typeIsUnknown && !contextualTypeIsUnknown) {
+              return;
+            }
+
             // in strict mode you can't assign null to undefined, so we have to make sure that
             // the two types share a nullable type
             const typeIncludesUndefined = isTypeFlagSet(
diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
index 1ef1a3dfb371..c711d9b14d38 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
@@ -416,6 +416,18 @@ enum T {
 const b = 1 as T.Value2;
       `,
     },
+    `
+const foo: unknown = {};
+const bar: object = foo!;
+const baz: {} = foo!;
+    `,
+    `
+function foo<T extends unknown>(bar: T) {
+  return {} as T;
+}
+const baz: unknown = {}
+foo(baz!);
+    `,
   ],
 
   invalid: [
@@ -1335,5 +1347,37 @@ declare const a: T.Value1;
 const b = a;
       `,
     },
+    {
+      code: `
+const foo: unknown = {};
+const bar: unknown = foo!;
+      `,
+      errors: [
+        {
+          messageId: 'contextuallyUnnecessary',
+        },
+      ],
+      output: `
+const foo: unknown = {};
+const bar: unknown = foo;
+      `,
+    },
+    {
+      code: `
+function foo(bar: unknown) {}
+const baz: unknown = {};
+foo(baz!);
+      `,
+      errors: [
+        {
+          messageId: 'contextuallyUnnecessary',
+        },
+      ],
+      output: `
+function foo(bar: unknown) {}
+const baz: unknown = {};
+foo(baz);
+      `,
+    },
   ],
 });

From 437b7f93b11cdbdbb6f1e4691c901d165af7129f Mon Sep 17 00:00:00 2001
From: YeonJuan <yeonjuan93@naver.com>
Date: Mon, 24 Feb 2025 23:33:34 +0900
Subject: [PATCH 2/3] fix format

---
 .../tests/rules/no-unnecessary-type-assertion.test.ts           | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
index c711d9b14d38..b9660ad79f73 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
@@ -425,7 +425,7 @@ const baz: {} = foo!;
 function foo<T extends unknown>(bar: T) {
   return {} as T;
 }
-const baz: unknown = {}
+const baz: unknown = {};
 foo(baz!);
     `,
   ],

From f6100800e53cfb53dda5a17dc62a09fa69cf147f Mon Sep 17 00:00:00 2001
From: YeonJuan <yeonjuan93@naver.com>
Date: Mon, 3 Mar 2025 20:48:14 +0900
Subject: [PATCH 3/3] apply reviews

---
 .../src/rules/no-unnecessary-type-assertion.ts        | 11 ++++-------
 .../tests/rules/no-unnecessary-type-assertion.test.ts |  9 +++++----
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/no-unnecessary-type-assertion.ts b/packages/eslint-plugin/src/rules/no-unnecessary-type-assertion.ts
index 526e2449b999..4e26d6e20aa2 100644
--- a/packages/eslint-plugin/src/rules/no-unnecessary-type-assertion.ts
+++ b/packages/eslint-plugin/src/rules/no-unnecessary-type-assertion.ts
@@ -349,13 +349,10 @@ export default createRule<Options, MessageIds>({
 
           const contextualType = getContextualType(checker, originalNode);
           if (contextualType) {
-            const typeIsUnknown = isTypeFlagSet(type, ts.TypeFlags.Unknown);
-            const contextualTypeIsUnknown = isTypeFlagSet(
-              contextualType,
-              ts.TypeFlags.Unknown,
-            );
-
-            if (typeIsUnknown && !contextualTypeIsUnknown) {
+            if (
+              isTypeFlagSet(type, ts.TypeFlags.Unknown) &&
+              !isTypeFlagSet(contextualType, ts.TypeFlags.Unknown)
+            ) {
               return;
             }
 
diff --git a/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts b/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
index b9660ad79f73..c28260e79b4a 100644
--- a/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unnecessary-type-assertion.test.ts
@@ -418,13 +418,14 @@ const b = 1 as T.Value2;
     },
     `
 const foo: unknown = {};
-const bar: object = foo!;
 const baz: {} = foo!;
     `,
     `
-function foo<T extends unknown>(bar: T) {
-  return {} as T;
-}
+const foo: unknown = {};
+const bar: object = foo!;
+    `,
+    `
+declare function foo<T extends unknown>(bar: T): T;
 const baz: unknown = {};
 foo(baz!);
     `,