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implement std.traits.isInstanceOf for non-types #4739

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andralex merged 1 commit into from
Aug 30, 2016
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implement std.traits.isInstanceOf for non-types #4739

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25 changes: 24 additions & 1 deletion std/traits.d
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Original file line number Diff line number Diff line change
Expand Up @@ -5620,6 +5620,13 @@ enum bool isMutable(T) = !is(T == const) && !is(T == immutable) && !is(T == inou
* Returns true if T is an instance of the template S.
*/
enum bool isInstanceOf(alias S, T) = is(T == S!Args, Args...);
/// ditto
template isInstanceOf(alias S, alias T)
{
enum impl(alias T : S!Args, Args...) = true;
enum impl(alias T) = false;
enum isInstanceOf = impl!T;
}
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@aG0aep6G aG0aep6G Aug 18, 2016

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I would have written this as

enum bool isInstanceOf(alias S, alias T : S!Args, Args...) = true;
enum bool isInstanceOf(alias S, alias T) = false;

But: https://issues.dlang.org/show_bug.cgi?id=16403

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@andralex andralex Aug 30, 2016

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noice


///
@safe unittest
Expand All @@ -5628,12 +5635,28 @@ enum bool isInstanceOf(alias S, T) = is(T == S!Args, Args...);
static struct Bar(T...) { }
static struct Doo(T) { }
static struct ABC(int x) { }
static void fun(T)() { }
template templ(T) { }

static assert(isInstanceOf!(Foo, Foo!int));
static assert(!isInstanceOf!(Foo, Bar!int));
static assert(!isInstanceOf!(Foo, int));
static assert(isInstanceOf!(Doo, Doo!int));
static assert(isInstanceOf!(ABC, ABC!1));
static assert(!__traits(compiles, isInstanceOf!(Foo, Foo)));
static assert(!isInstanceOf!(Foo, Foo));
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@aG0aep6G aG0aep6G Aug 18, 2016

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This might need some attention. I don't see a reason why isInstanceOf!(Foo, Foo) should fail compilation, but since this was specifically stated here, maybe there is a reason.

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@lodo1995 lodo1995 Aug 18, 2016

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I guess it's because the original implementation did not handle things different from types as second parameter, and Foo is not a type, so it wouldn't compile.

static assert(isInstanceOf!(fun, fun!int));
static assert(isInstanceOf!(templ, templ!int));
}

@safe unittest
{
static void fun1(T)() { }
static void fun2(T)() { }
template templ1(T) { }
template templ2(T) { }

static assert(!isInstanceOf!(fun1, fun2!int));
static assert(!isInstanceOf!(templ1, templ2!int));
}

/**
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