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Fix Issue 19226 - std.typecons.Nullable(T, T nullValue) doesn't fully handle non-self-equal nullValue #6693

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May 9, 2019
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Fix Issue 19226 - std.typecons.Nullable(T, T nullValue) doesn't fully handle non-self-equal nullValue #6693

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29 changes: 28 additions & 1 deletion std/typecons.d
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Original file line number Diff line number Diff line change
Expand Up @@ -3542,7 +3542,7 @@ Returns:
}
//Need to use 'is' if T is a float type
//because NaN != NaN
else static if (isFloatingPoint!T)
else static if (__traits(isFloating, T) || __traits(compiles, { static assert(!(nullValue == nullValue)); }))
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Q: Why is there the seemingly-extraneous __traits(isFloating, T)?
A: So this patch doesn't change the behavior of Nullable!(double, -0.0).

{
return _value is nullValue;
}
Expand All @@ -3563,6 +3563,14 @@ Returns:
assert(!ni.isNull);
}

@system unittest
{
assert(typeof(this).init.isNull, typeof(this).stringof ~
".isNull does not work correctly because " ~ T.stringof ~
" has an == operator that is non-reflexive and could not be" ~
" determined before runtime to be non-reflexive!");
}

// https://issues.dlang.org/show_bug.cgi?id=11135
// disable test until https://issues.dlang.org/show_bug.cgi?id=15316 gets fixed
version (none) @system unittest
Expand Down Expand Up @@ -3737,6 +3745,25 @@ if (is (typeof(nullValue) == T))
assert(a.isNull);
}

@nogc nothrow pure @safe unittest
{
// issue 19226 - fully handle non-self-equal nullValue
static struct Fraction
{
int denominator;
bool isNaN() const
{
return denominator == 0;
}
bool opEquals(const Fraction rhs) const
{
return !isNaN && denominator == rhs.denominator;
}
}
alias N = Nullable!(Fraction, Fraction.init);
assert(N.init.isNull);
}

@safe unittest
{
static int f(scope const Nullable!(int, int.min) x) {
Expand Down