Type checker fails to remove Null in some cases

import Toybox.Lang;

function a() as Number or Null {
    return 42;
}

function b() as Float or Null {
    return 24.0;
}

function odd(x as Boolean) as Numeric? {
    var v = x ? a() : b();
    if (v != null) {
        return v * 24;
    }
    return null;
}

ERROR: <device>: bug.mc:14: Attempting to perform operation 'mul' with invalid types 'Null' and '$.Toybox.Lang.Number'.

At the point of definition, v should be typed as Number or Float or Null - and regardless, it can't possibly be Null on line 14.

The error goes away if a() and b() both return the same type - even if the type is Number or Float or Null.

markw65

flocsy🤠 over 1 year ago in reply to flocsy🤠

sdk 4.1.7
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flocsy🤠 over 1 year ago in reply to ES

I don't understand how it works in line 9, because even this simple thing doesn't work:

var a = cond ? 1 : null;
foo(a != null ? a : -1);

function foo(n as Number) {}
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flocsy🤠 over 1 year ago

Why was this closed as "Compleeted" if it wasn't fixed / released yet? See: forums.garmin.com/.../1538021
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ES over 2 years ago

Likely a variation of the the same type checker topic:

Accessing an object's private variable explicitly ("self.Xyz") and implicitly ("Xyz") is interpreted differently be the compiler.

explicitly (line 9): no error
implicitly (line 13): Cannot find symbol ':length' on type 'Null'.

class Demo {
    private var Xyz as Toybox.Lang.String or Null;

    function initialize (x as Toybox.Lang.String or Null){
        Xyz = x;
    }

    function implicitly() as Toybox.Lang.Number {
        return (Xyz != null) ? Xyz.length() : -1;
    }

    function explicitly() as Toybox.Lang.Number {
        return (self.Xyz != null) ? self.Xyz.length() : -1;
    }
}