Add support for sorting literal numeric unions

Resolves #2502

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Unreleased
 
+### Features
+
+-   Literal numeric unions will now be sorted during conversion, #2502.
+
 ### Bug Fixes
 
 -   Module readmes will now be included in JSON output, #2500.

src/lib/converter/types.ts

@@ -1045,9 +1045,10 @@ const unionConverter: TypeConverter<ts.UnionTypeNode, ts.UnionType> = {
         );
     },
     convertType(context, type) {
-        return new UnionType(
-            type.types.map((type) => convertType(context, type)),
-        );
+        const types = type.types.map((type) => convertType(context, type));
+        sortLiteralUnion(types);
+
+        return new UnionType(types);
     },
 };
 
@@ -1115,3 +1116,18 @@ function kindToModifier(
             return undefined;
     }
 }
+
+function sortLiteralUnion(types: SomeType[]) {
+    if (
+        types.some((t) => t.type !== "literal" || typeof t.value !== "number")
+    ) {
+        return;
+    }
+
+    types.sort((a, b) => {
+        const aLit = a as LiteralType;
+        const bLit = b as LiteralType;
+
+        return (aLit.value as number) - (bLit.value as number);
+    });
+}

src/test/converter2/issues/gh2502.ts

@@ -0,0 +1,7 @@
+// A future TS version might change this so that numbers are hardcoded
+// to show up in a specific order. As of TS 5.3.3, this makes the union display
+// as 3 | 1 | 2.
+type WeirdOrder = [1, 2, 3][number];
+//   ^?
+
+export const Test = null! as WeirdOrder;

src/test/issues.c2.test.ts

@@ -1389,6 +1389,12 @@ describe("Issue Tests", () => {
         convert();
     });
 
+    it("Sorts literal numeric unions when converting a type, #2502", () => {
+        const project = convert();
+        const refl = query(project, "Test");
+        equal(refl.type?.toString(), "1 | 2 | 3");
+    });
+
     it("Handles an infinitely recursive type, #2507", () => {
         const project = convert();
         const type = querySig(project, "fromPartial").typeParameters![0].type;