Fix enumeration type inference for inline members

Author: ezzatron

CHANGELOG.md

@@ -15,6 +15,11 @@ Versioning].
 - Added a `Declaration<T>` type that can be used to explicitly type
   declarations.
 
+### Fixed
+
+- Enumeration declarations can now infer the value type when the `members`
+  argument is passed as an object without needing to use `as const`.
+
 ## [v0.12.0] - 2024-11-08
 
 [v0.12.0]: https://github.com/ezzatron/austenite/releases/tag/v0.12.0

src/declaration/enumeration.ts

@@ -27,7 +27,7 @@ export type Options<T> = DeclarationOptions<T> &
   DeclarationConstraintOptions<T> &
   DeclarationExampleOptions<T>;
 
-export function enumeration<T, O extends Options<T>>(
+export function enumeration<const T, O extends Options<T>>(
   name: string,
   description: string,
   members: Members<T>,

test/suite/declaration/enumeration.spec-d.ts

@@ -82,6 +82,41 @@ describe("Enumeration declarations", () => {
     });
   });
 
+  describe('when declared with inline members that are not defined with "as const"', () => {
+    it("infers the declaration type from the members", () => {
+      const required = enumeration("AUSTENITE_ENUMERATION", "<description>", {
+        "<member-0>": {
+          value: 0,
+          description: "member 0",
+        },
+        "<member-1>": {
+          value: 1,
+          description: "member 1",
+        },
+      });
+      const optional = enumeration(
+        "AUSTENITE_ENUMERATION",
+        "<description>",
+        {
+          "<member-0>": {
+            value: 0,
+            description: "member 0",
+          },
+          "<member-1>": {
+            value: 1,
+            description: "member 1",
+          },
+        },
+        {
+          default: undefined,
+        },
+      );
+
+      expectTypeOf(required).toEqualTypeOf<Declaration<0 | 1>>();
+      expectTypeOf(optional).toEqualTypeOf<Declaration<0 | 1 | undefined>>();
+    });
+  });
+
   describe("when valid options are specified", () => {
     it("does not allow unknown options", () => {
       const declaration = enumeration(