Issue 12653 - Implement the getFunctionAttributes trait. #3501

ghost · 2014-04-26T13:32:37Z

https://issues.dlang.org/show_bug.cgi?id=12653

The current std.traits.functionAttributes implementation is very complicated due to reliance on demangling to figure out the attributes of a function. Additionally it doesn't support const/immutable/inout/shared.

Although support for these could be added in the library it's IMO time to move this whole functionality into the compiler as a trait. It's simpler this way and will speed up compilation.

The same could be done later for ParameterStorageClassTuple which uses demangling as well.

ghost · 2014-04-26T13:34:09Z

The test-case is largely based on the existing std.traits.functionAttributes unittest block. If there are missed cases please let me know!

WalterBright · 2014-04-26T20:25:54Z

src/traits.c

@@ -604,6 +604,65 @@ Expression *semanticTraits(TraitsExp *e, Scope *sc)
        TupleExp *tup = new TupleExp(e->loc, udad ? udad->getAttributes() : new Expressions());
        return tup->semantic(sc);
    }
+    else if (e->ident == Id::getFunctionAttributes)


Could really use some documentation comments here. Note that there'll need to be a corresponding spec PR explaining this as well, the two should be fairly similar.

Note that there'll need to be a corresponding spec PR explaining this as well, the two should be fairly similar.

Yes, and since we already have getAttributes I'll make sure to document the difference between the two.

ghost · 2014-04-26T20:54:56Z

Updated everything except this block:

if (tf->isref) mods->push(new StringExp(Loc(), "ref"));
if (tf->isproperty) mods->push(new StringExp(Loc(), "@property"));
if (tf->isnothrow) mods->push(new StringExp(Loc(), "nothrow"));
if (tf->isnogc) mods->push(new StringExp(Loc(), "@nogc"));
if (tf->purity) mods->push(new StringExp(Loc(), "pure"));

I don't know where else the code uses tuples or arrays of these, otherwise I could refactor it to a common function. Well I guess I could do that preemptively anyway?

WalterBright · 2014-04-26T21:19:24Z

src/hdrgen.c

+        case TRUSTdefault:
+            break;
+
+        default: assert(0);  // unhandled trust


ghost · 2014-04-26T22:10:01Z

Update: I've implemented a generic foreachAttributes in TypeFunction which takes a callback. Maybe we could do the same with type modifiers (MODconst, etc.).

Let me know what you think @WalterBright.

ghost · 2014-04-26T22:33:35Z

Documentation/spec pull made: dlang/dlang.org#566

ghost · 2014-04-26T22:52:00Z

Just noticed this doesn't work with function templates:

void main()
{
    int sum(T1, T2)(T1 t1, T2 t2) { return t1 + t2; }
    pragma(msg, __traits(getFunctionAttributes, sum));  // fail
}

Should it work?

WalterBright · 2014-04-26T23:52:29Z

Should it work?

No. It's not a function until it is instantiated. In fact, the attributes cannot be determined until it is instantiated, because attributes are inferred on function templates.

WalterBright · 2014-04-27T00:00:21Z

src/hdrgen.c

-            trustToBuffer(buf, t->trust);
-        }
+
+        t->foreachAttributes(&buf, preAppendStrings);


I think this is a nice improvement. Great! It can go a little further. We can sort of create lambda functions in C++ using a little trick - local structs with member functions. This trick is done elsewhere in dmd, such as ParamUnique and ParamExact in func.c.

I'll have a look and fix it up.

ghost · 2014-04-27T10:42:06Z

Implemented attributesApply and modifiersApply. I didn't add a this parameter like in overloadAppy since it wasn't really needed here.

Issue 12653 - Implement the getFunctionAttributes trait.

ghost · 2014-04-27T21:15:12Z

@WalterBright: I seem to have forgotten to support typeof(func), IOW:

struct S2
{
    int pure_const() const pure { return 0; }
}

static assert(__traits(getFunctionAttributes, typeof(S2.pure_const)) == tuple!("const", "pure"));

I can add a fixup for this. However I've noticed that const/immutable/inout/shared are not visible when using typeof, even though things like purity are visible. So the results will be different. I'm not sure whether this is a new bug?

Edit: Nevermind.

ghost · 2014-04-27T21:24:54Z

Nevermind, that is not a bug. typeof() means you don't have a function declaration, so const/inout/etc are naturally missing.

MartinNowak · 2014-05-05T19:35:27Z

Nice, so we can replace the mangling based implementation of std.traits.functionAttributes now?

ghost · 2014-05-05T19:40:37Z

Nice, so we can replace the mangling based implementation of std.traits.functionAttributes now?

First this needs to be pulled, and then the Phobos pull to implement just that is here.

9rnsr · 2014-05-08T02:52:57Z

src/traits.c

+
+        // const/immutable/inout/shared is only valid for member functions
+        if (fd)
+            fd->type->modifiersApply(&pa, &PushAttributes::fp);


Why not print member function attributes (const, immutable, etc) when the argument is a type?

struct S { void foo() const {} } pragma(msg, __traits(getFunctionAttributes, S.foo )); // tuple("const") pragma(msg, typeof(S.foo)); // const void() pragma(msg, __traits(getFunctionAttributes, typeof(S.foo))); // tuple(), inconsistent

Note that, typeof(S.foo) == 'const void()' == 'const(void())' == 'void() const' internally.

Why not print member function attributes (const, immutable, etc) when the argument is a type?

I don't know how to get from a TypeFunction to a FuncDeclaration, which holds these attributes. I would actually appreciate some help here. If you can improve getFunctionAttributes further it would be awesome!

These attributes are in the mod field of TypeFunction. So if the TypeFunction comes from member function, you can access them without fd.

Oh, right! I will fixup, thanks.

9rnsr · 2014-05-08T03:42:09Z

test/runnable/traits.d

+        int pureF() pure { return 0; }
+    }
+
+    static assert(tupleLength!(__traits(getFunctionAttributes, S.noF)) == 0);


S.noF is a system function, so __traits(getFunctionAttributes) should list it?

Ah, I didn't notice this. So if trust is set to TRUSTdefault this implies system, I didn't actually check the enum even though it describes this:

enum TRUST { TRUSTdefault = 0, TRUSTsystem = 1, // @system (same as TRUSTdefault) TRUSTtrusted = 2, // @trusted TRUSTsafe = 3, // @safe };

Although I'm not sure why an explicit TRUSTdefault was even added.

I can fix this up, but I'm unsure about extracting const/immutable via typeof(func).

Made pull: #3533

yebblies · 2014-05-08T11:55:50Z

Although I'm not sure why an explicit TRUSTdefault was even added.

So you can tell the difference between 'trust not specified' and 'trust specified as system' when deciding to do inference.

WalterBright reviewed Apr 26, 2014
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src/hdrgen.c

case TRUSTdefault:

break;

default: assert(0); // unhandled trust

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yay!

ghost closed this Apr 26, 2014

ghost reopened this Apr 26, 2014

ghost mentioned this pull request Apr 26, 2014

Issue 12653 - Document the getFunctionAttributes trait. dlang/dlang.org#566

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WalterBright reviewed Apr 27, 2014
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ghost closed this Apr 27, 2014

ghost reopened this Apr 27, 2014

Fix Issue 12653 - Implement the getFunctionAttributes trait.

989b73f

WalterBright added a commit that referenced this pull request Apr 27, 2014

Merge pull request #3501 from AndrejMitrovic/Fix12653

b65f13e

Issue 12653 - Implement the getFunctionAttributes trait.

WalterBright merged commit b65f13e into dlang:master Apr 27, 2014

ghost mentioned this pull request Apr 27, 2014

Fixup funcAttributes. #3506

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9rnsr reviewed May 8, 2014
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ghost mentioned this pull request May 8, 2014

Fix Issue 12705 and Fixup Pull 3501 - Fix @system and missing attributes when typeof(func) is used #3533

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ghost mentioned this pull request May 12, 2014

Issue 12668 - std.traits.functionAttributes should use the new getFunctionAttributes trait. dlang/phobos#2131

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Issue 12653 - Implement the getFunctionAttributes trait. #3501

Issue 12653 - Implement the getFunctionAttributes trait. #3501

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yebblies commented May 8, 2014

Issue 12653 - Implement the getFunctionAttributes trait. #3501

Issue 12653 - Implement the getFunctionAttributes trait. #3501

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yebblies commented May 8, 2014