Construct Composite Using Indexed Access Type (#420)

test/static/composite.ts

@@ -43,19 +43,24 @@ import { Type, Static } from '@sinclair/typebox'
     A: number
   }>()
 }
-// Overlapping All Optional
+// Overlapping All Optional (Deferred)
+// Note for: https://github.com/sinclairzx81/typebox/issues/419
+// Determining if a composite property is optional requires a deep check for all properties gathered during a indexed access
+// call. Currently, there isn't a trivial way to perform this check without running into possibly infinite instantiation issues.
+// The optional check is only specific to overlapping properties. Singular properties will continue to work as expected. The
+// rule is "if all composite properties for a key are optional, then the composite property is optional". Defer this test and
+// document as minor breaking change.
 {
-  const A = Type.Object({
-    A: Type.Optional(Type.Number()),
-  })
-  const B = Type.Object({
-    A: Type.Optional(Type.Number()),
-  })
-  const T = Type.Composite([A, B])
-
-  Expect(T).ToInfer<{
-    A: number | undefined
-  }>()
+  // const A = Type.Object({
+  //   A: Type.Optional(Type.Number()),
+  // })
+  // const B = Type.Object({
+  //   A: Type.Optional(Type.Number()),
+  // })
+  // const T = Type.Composite([A, B])
+  // Expect(T).ToInfer<{
+  //   A: number | undefined
+  // }>()
 }
 // Distinct Properties
 {