From 8a29753e0dc2bfab7c13922c99b2b6f1bdbf7029 Mon Sep 17 00:00:00 2001
From: Mattia Manzati <mattia.manzati@gmail.com>
Date: Tue, 16 Dec 2025 12:48:43 +0100
Subject: [PATCH] Add test for ensuring typeConstructor is attached

---
 .changeset/curly-mice-march.md                       |  5 +++++
 packages/effect/src/Schema.ts                        |  1 +
 .../effect/test/Schema/Schema/annotations.test.ts    | 12 ++++++++++++
 3 files changed, 18 insertions(+)
 create mode 100644 .changeset/curly-mice-march.md

diff --git a/.changeset/curly-mice-march.md b/.changeset/curly-mice-march.md
new file mode 100644
index 00000000000..91989343e24
--- /dev/null
+++ b/.changeset/curly-mice-march.md
@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Add test for ensuring typeConstructor is attached
diff --git a/packages/effect/src/Schema.ts b/packages/effect/src/Schema.ts
index 885e36ca166..db74f0387a6 100644
--- a/packages/effect/src/Schema.ts
+++ b/packages/effect/src/Schema.ts
@@ -231,6 +231,7 @@ interface AllAnnotations<A, TypeParameters extends ReadonlyArray<any>>
 {}
 
 const builtInAnnotations = {
+  typeConstructor: AST.TypeConstructorAnnotationId,
   schemaId: AST.SchemaIdAnnotationId,
   message: AST.MessageAnnotationId,
   missingMessage: AST.MissingMessageAnnotationId,
diff --git a/packages/effect/test/Schema/Schema/annotations.test.ts b/packages/effect/test/Schema/Schema/annotations.test.ts
index 3da762bcac3..e2ea1672a88 100644
--- a/packages/effect/test/Schema/Schema/annotations.test.ts
+++ b/packages/effect/test/Schema/Schema/annotations.test.ts
@@ -1,5 +1,6 @@
 import { describe, it } from "@effect/vitest"
 import { assertTrue, deepStrictEqual, strictEqual } from "@effect/vitest/utils"
+import * as Option from "effect/Option"
 import type * as ParseResult from "effect/ParseResult"
 import type * as Pretty from "effect/Pretty"
 import * as S from "effect/Schema"
@@ -81,6 +82,17 @@ describe(".annotations()", () => {
     })
   })
 
+  it("typeConstructor", () => {
+    const schema = S.Struct({ a: S.String }).annotations({ typeConstructor: { _tag: "MyTypeConstructor" } })
+    deepStrictEqual(schema.ast.annotations, {
+      [AST.TypeConstructorAnnotationId]: { _tag: "MyTypeConstructor" }
+    })
+    deepStrictEqual(
+      AST.getTypeConstructorAnnotation(schema.ast),
+      Option.some({ _tag: "MyTypeConstructor" })
+    )
+  })
+
   it("parseIssueTitle", async () => {
     const getOrderId = ({ actual }: ParseResult.ParseIssue) => {
       if (S.is(S.Struct({ id: S.Number }))(actual)) {