From 620642857d3238867f0defb62b31f59e0c8ed2df Mon Sep 17 00:00:00 2001
From: Tomasz Pluskiewicz <tpluscode@users.noreply.github.com>
Date: Fri, 11 Apr 2025 11:33:00 +0200
Subject: [PATCH] feat: equals type guards

---
 .changeset/wicked-keys-behave.md |  5 +++++
 data-model.d.ts                  | 14 +++++++-------
 2 files changed, 12 insertions(+), 7 deletions(-)
 create mode 100644 .changeset/wicked-keys-behave.md

diff --git a/.changeset/wicked-keys-behave.md b/.changeset/wicked-keys-behave.md
new file mode 100644
index 0000000..2f5923f
--- /dev/null
+++ b/.changeset/wicked-keys-behave.md
@@ -0,0 +1,5 @@
+---
+"@rdfjs/types": minor
+---
+
+Added [`this`-based type guards](https://www.typescriptlang.org/docs/handbook/2/classes.html#this-based-type-guards) to `Term#equals` methods
diff --git a/data-model.d.ts b/data-model.d.ts
index 3ecb7d6..999f2cf 100644
--- a/data-model.d.ts
+++ b/data-model.d.ts
@@ -29,7 +29,7 @@ export interface NamedNode<Iri extends string = string> {
      * @param other The term to compare with.
      * @return True if and only if other has termType "NamedNode" and the same `value`.
      */
-    equals(other: Term | null | undefined): boolean;
+    equals<T extends Term = Term>(other: T | null | undefined): this is T;
 }
 
 /**
@@ -52,7 +52,7 @@ export interface BlankNode {
      * @param other The term to compare with.
      * @return True if and only if other has termType "BlankNode" and the same `value`.
      */
-    equals(other: Term | null | undefined): boolean;
+    equals<T extends Term = Term>(other: T | null | undefined): this is T;
 }
 
 /**
@@ -87,7 +87,7 @@ export interface Literal {
      * @return True if and only if other has termType "Literal"
      *                   and the same `value`, `language`, `direction`, and `datatype`.
      */
-    equals(other: Term | null | undefined): boolean;
+    equals<T extends Term = Term>(other: T | null | undefined): this is T;
 }
 
 /**
@@ -107,7 +107,7 @@ export interface Variable {
      * @param other The term to compare with.
      * @return True if and only if other has termType "Variable" and the same `value`.
      */
-    equals(other: Term | null | undefined): boolean;
+    equals<T extends Term = Term>(other: T | null | undefined): this is T;
 }
 
 /**
@@ -128,7 +128,7 @@ export interface DefaultGraph {
      * @param other The term to compare with.
      * @return True if and only if other has termType "DefaultGraph".
      */
-    equals(other: Term | null | undefined): boolean;
+    equals<T extends Term = Term>(other: T | null | undefined): this is T;
 }
 
 /**
@@ -202,7 +202,7 @@ export interface BaseQuad {
      * @param other The term to compare with.
      * @return True if and only if the argument is a) of the same type b) has all components equal.
      */
-    equals(other: Term | null | undefined): boolean;
+    equals<T extends Term = Term>(other: T | null | undefined): this is T;
 }
 
 /**
@@ -234,7 +234,7 @@ export interface Quad extends BaseQuad {
      * @param other The term to compare with.
      * @return True if and only if the argument is a) of the same type b) has all components equal.
      */
-    equals(other: Term | null | undefined): boolean;
+    equals<T extends Term = Term>(other: T | null | undefined): this is T;
 }
 
 /**