Merge pull request #3068 from laytan/json-unmarshal-union

encoding/json: try to unmarshal into union variants

core/encoding/json/unmarshal.odin

@@ -204,8 +204,9 @@ unmarshal_value :: proc(p: ^Parser, v: any) -> (err: Unmarshal_Error) {
 
 	v := v
 	ti := reflect.type_info_base(type_info_of(v.id))
+	if u, ok := ti.variant.(reflect.Type_Info_Union); ok && token.kind != .Null {
 		// NOTE: If it's a union with only one variant, then treat it as that variant
-	if u, ok := ti.variant.(reflect.Type_Info_Union); ok && len(u.variants) == 1 && token.kind != .Null {
+		if len(u.variants) == 1 {
 			variant := u.variants[0]
 			v.id = variant.id
 			ti = reflect.type_info_base(variant)
@@ -213,6 +214,22 @@ unmarshal_value :: proc(p: ^Parser, v: any) -> (err: Unmarshal_Error) {
 				tag := any{rawptr(uintptr(v.data) + u.tag_offset), u.tag_type.id}
 				assign_int(tag, 1)
 			}
+		} else if v.id != Value {
+			for variant, i in u.variants {
+				variant_any := any{v.data, variant.id}
+				variant_p := p^
+				if err = unmarshal_value(&variant_p, variant_any); err == nil {
+					p^ = variant_p
+
+					raw_tag := i
+					if !u.no_nil { raw_tag += 1 }
+					tag := any{rawptr(uintptr(v.data) + u.tag_offset), u.tag_type.id}
+					assign_int(tag, raw_tag)
+					return
+				}
+			}
+			return UNSUPPORTED_TYPE
+		}
 	}
 
 	switch &dst in v {