reflection.sc

using import enum

@@ memo
inline member-typeof (T member)
    let result =
        static-if ((T < Struct) or (T < CStruct))
            field-count := (countof T)
            let result =
                va-lfold none
                    inline (_ignore value computed-result)
                        let _key = (keyof value)
                        static-if (_key == member)
                            unqualified value
                        else
                            computed-result
                    elementsof T

        elseif (T < Enum)
            # TODO: this
            # Unknown
        else
            # need branch to compile correctly; it doesn't matter that this compiles
            # straight to an error because we want this inline to only have compile-time statements.
            if true
                hide-traceback;
                error@ ('anchor `T) "while querying type information" "not an aggregate type."
            # Unknown

    static-if (none? result)
        if true
            hide-traceback;
            error (.. "field " (tostring member) " not found in type " (tostring T) ".")
    result

fn run-tests ()
    using import struct
    using import testing
    struct A
        A : i32
        B : i32
        C : u64
    test (constant? (member-typeof A 'A))
    test ((member-typeof A 'B) == i32)
    test-error
        member-typeof A 'doesnt-exist

    enum B plain
        A
        B
        C
    test-error
        member-typeof B 'A

static-if main-module?
    run-tests;

locals;