From 3b98173d25efe4c8fb01ca41dfcd004b11ad6420 Mon Sep 17 00:00:00 2001
From: Ronen Amiel <ronen.amiel@gmail.com>
Date: Sat, 4 Oct 2025 23:36:01 +0300
Subject: [PATCH] initial implementation

---
 .../eslint-plugin/src/rules/unbound-method.ts | 10 ++
 .../tests/rules/unbound-method.test.ts        | 96 ++++++++++++++++++-
 2 files changed, 104 insertions(+), 2 deletions(-)

diff --git a/packages/eslint-plugin/src/rules/unbound-method.ts b/packages/eslint-plugin/src/rules/unbound-method.ts
index 49f8dbe23802..0582056c2518 100644
--- a/packages/eslint-plugin/src/rules/unbound-method.ts
+++ b/packages/eslint-plugin/src/rules/unbound-method.ts
@@ -328,6 +328,15 @@ function checkIfMethod(
       }
       return checkMethod(assignee as ts.FunctionExpression, ignoreStatic);
     }
+    case ts.SyntaxKind.PropertySignature: {
+      const type = (valueDeclaration as ts.PropertySignature).type;
+      if (type?.kind !== ts.SyntaxKind.FunctionType) {
+        return {
+          dangerous: false,
+        };
+      }
+      return checkMethod(type as ts.FunctionTypeNode, ignoreStatic);
+    }
     case ts.SyntaxKind.MethodDeclaration:
     case ts.SyntaxKind.MethodSignature: {
       return checkMethod(
@@ -343,6 +352,7 @@ function checkIfMethod(
 function checkMethod(
   valueDeclaration:
     | ts.FunctionExpression
+    | ts.FunctionTypeNode
     | ts.MethodDeclaration
     | ts.MethodSignature,
   ignoreStatic: boolean,
diff --git a/packages/eslint-plugin/tests/rules/unbound-method.test.ts b/packages/eslint-plugin/tests/rules/unbound-method.test.ts
index aeca1a171d50..b15c55282a86 100644
--- a/packages/eslint-plugin/tests/rules/unbound-method.test.ts
+++ b/packages/eslint-plugin/tests/rules/unbound-method.test.ts
@@ -463,7 +463,11 @@ class Foo {
 type foo = new ({ unbound }: Foo) => void;
     `,
     'const { unbound } = { unbound: () => {} };',
-    'function foo({ unbound }: { unbound: () => void } = { unbound: () => {} }) {}',
+    `
+function foo(
+  { unbound }: { unbound: (this: void) => void } = { unbound: () => {} },
+) {}
+    `,
     // https://github.com/typescript-eslint/typescript-eslint/issues/1866
     `
 class BaseClass {
@@ -480,6 +484,30 @@ class OtherClass extends BaseClass {
 const oc = new OtherClass();
 oc.superLogThis();
     `,
+    `
+interface Foo {
+  bound: (this: void) => number;
+}
+
+declare const foo: Foo;
+foo.bound;
+    `,
+    `
+interface Foo {
+  bound: (this: void) => number;
+}
+
+declare const foo: Foo;
+const { bound } = foo;
+    `,
+    `
+type Foo = {
+  bound: (this: void) => number;
+};
+
+declare const foo: Foo;
+const { bound } = foo;
+    `,
   ],
   invalid: [
     {
@@ -965,7 +993,7 @@ function foo({ unbound }: { unbound: () => string } | Foo) {}
       errors: [
         {
           line: 5,
-          messageId: 'unbound',
+          messageId: 'unboundWithoutThisAnnotation',
         },
       ],
     },
@@ -1252,5 +1280,69 @@ const f = objectLiteral.f;
         },
       ],
     },
+    {
+      code: `
+interface Foo {
+  bound: () => number;
+}
+
+declare const foo: Foo;
+foo.bound;
+      `,
+      errors: [
+        {
+          line: 7,
+          messageId: 'unboundWithoutThisAnnotation',
+        },
+      ],
+    },
+    {
+      code: `
+interface Foo {
+  bound: () => number;
+}
+
+declare const foo: Foo;
+const { bound } = foo;
+      `,
+      errors: [
+        {
+          line: 7,
+          messageId: 'unboundWithoutThisAnnotation',
+        },
+      ],
+    },
+    {
+      code: `
+interface Foo {
+  bound: (this: Foo) => number;
+}
+
+declare const foo: Foo;
+foo.bound;
+      `,
+      errors: [
+        {
+          line: 7,
+          messageId: 'unbound',
+        },
+      ],
+    },
+    {
+      code: `
+type Foo = {
+  bound: () => number;
+};
+
+declare const foo: Foo;
+foo.bound;
+      `,
+      errors: [
+        {
+          line: 7,
+          messageId: 'unboundWithoutThisAnnotation',
+        },
+      ],
+    },
   ],
 });