Is this a bug? println!() can print argv[1] but now a value that may be it.

[Julian Fondren]

The following code works as is:

    #include "share/atspre_staload.hats"

    

    implement main0(argc, argv) =

      let

        val who = (if argc > 1 then argv[1] else "world")

      in

        if argc > 1 then

          println!("Hello, ", argv[1], "!");

        print_string("Hello, ");

        print_string(who);

        print_string("!");

        print_newline();

      end

And is used like this:

    $ patscc -O2 -flto -D_GNU_SOURCE -DATS_MEMALLOC_LIBC main3.dats -o main3 -latslib

    $ ./main3

    Hello, world!

    $ ./main3 bob

    Hello, bob!

    Hello, bob!

If however the `argv[1]` in `println!` is changed to `who`,

    #include "share/atspre_staload.hats"

    

    implement main0(argc, argv) =

      let

        val who = (if argc > 1 then argv[1] else "world")

      in

        if argc > 1 then

          println!("Hello, ", who, "!");

        print_string("Hello, ");

        print_string(who);

        print_string("!");

        print_newline();

      end

then it fails to compile:

    main3.dats: 161(line=8, offs=7) -- 190(line=8, offs=36): error(3): the symbol [print] cannot be resolved due to too many matches:

    D2ITMcst(print_option) of 0

    D2ITMcst(print_list_vt) of 0

[Hongwei Xi]

You need:

val who = (if argc > 1 then ... else ...): string

Otherwise, the compiler only knows that string is a subtype of the type

assigned to 'who', which is not enough to support overloading of 'print'.

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[Julian Fondren]

That works, but this is very surprising because I tried what I thought was completely equivalent, and it does not work:

// fails with same error

val who: string = (if argc > 1 then ... else ...)

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[gmhwxi]

>>val who: string = (if argc > 1 then ... else ...)

The pattern 'who: string' means that whatever matches
it should have a type X <= string.

This is something that I hope to be able to properly address in ATS3.