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digitalmars.D.bugs - [Issue 3934] New: Some untidy attributes

reply d-bugmail puremagic.com writes:
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           Summary: Some untidy attributes
           Product: D
           Version: 2.041
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid, rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc


--- Comment #0 from bearophile_hugs eml.cc 2010-03-11 14:08:26 PST ---
This D2 program compiles and runs with no errors or warnings:


static foo1() {}
final foo2() {}
ref foo3() {}
enum void foo4() {}
nothrow foo5() {}
pure foo6() {}
static int x1 = 10;
static x2 = 10;
void main() {}


Notes:
- foo1, x1, x2: I don't know what a static global void function/variable is in
D2, so 'static' can be disallowed for global functions/variables.
- foo2, foo3, foo4: they look like bugs.
- Are most of those attributes supposed to not need the "void"? I think
requiring for example "pure void" is a little better than allowing just "pure".


The following lines don't compile, is this correct? 

int static x3 = 10;
int enum x4 = 1;
int const x5 = 2;


I like the strictness of the Java compiler, it makes sure your attributes are
all correct and meaningful, this helps avoid possible bugs. And I'm sure it
helps newbies learn the language in less time too (because when you don't know
the rules yet, it's very useful if they don't change).

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--- Comment #1 from bearophile_hugs eml.cc 2010-04-14 07:35:46 PDT ---
A person in the IRC channel suggests that this too can be bad (this program
compiles and runs with dmd 2.043):

extern struct foo;
void main() {}

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Stewart Gordon <smjg iname.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |smjg iname.com


--- Comment #2 from Stewart Gordon <smjg iname.com> 2010-05-30 14:21:25 PDT ---
This seems to be partly a duplicate of issue 3118.

Without a clear spec on the matter, it's hard to decide which of these it's a
bug that the compiler accepts, but certainly foo3 and foo4 AISI.

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--- Comment #3 from bearophile_hugs eml.cc 2010-06-15 17:10:04 PDT ---
This too is wrong (this compiles with dmd v2.047):


struct Foo {
    static invariant() {}
}
void main() {}

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--- Comment #4 from bearophile_hugs eml.cc 2010-06-30 13:14:48 PDT ---
One from Leopold Walkling, this compiles:

auto void main() {}

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--- Comment #5 from Stewart Gordon <smjg iname.com> 2010-06-30 16:33:29 PDT ---
I certainly call that a bug.

Partly a consequence of auto being an attribute rather than a placeholder for a
type, though this seems to be partly for backward compatibility with the old
meaning of auto.  Either way, it's an inapplicable attribute and one that ought
not to be accepted.

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--- Comment #6 from bearophile_hugs eml.cc 2010-07-25 07:01:22 PDT ---
Two more related cases:

This looks correct:

auto main() {
    return 0;
}

But dmd 2.047 prints:
test.d(1): Error: function D main must return int or void

----------------

The error message shows that foo() is not pure:
test.d(5): Error: pure function 'bar' cannot call impure function 'foo'


auto pure foo() {
    return 1;
}
pure void bar() {
    foo();
}
void main() {}


So it seems 'pure' is ignored if 'auto' is present.

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--- Comment #7 from bearophile_hugs eml.cc 2010-08-17 06:07:58 PDT ---
From Simen kjaeraas:

__gshared struct foo {
    int n;
}

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--- Comment #8 from bearophile_hugs eml.cc 2010-08-19 06:14:56 PDT ---
From bernardh on IRC, this program compiles:

auto scope shared import std.stdio;
void main() {}

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--- Comment #9 from bearophile_hugs eml.cc 2010-08-19 09:11:44 PDT ---
This D2 program compiles and runs with DMD 2.048 with no errors, but I think
the compiler has to flag this usage of the 'private final' attributes as
incorrect:


import std.c.stdio: puts;
class Base {
     private final ~this() { puts("Base.~this"); }
}
class Derived : Base {
    private final ~this() { puts("Derived.~this"); }
}
void main() {
    new Derived();
}

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--- Comment #10 from bearophile_hugs eml.cc 2010-09-21 13:28:24 PDT ---
Structs can't be subclassed, so protected struct fields seem a bug. This
compiles with dmd 2.049:


struct Foo {
    protected int x;
}
void main() {}

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--- Comment #11 from bearophile_hugs eml.cc 2010-09-26 10:40:03 PDT ---
This compiles with no errors with dmd 2.049, but I'd like a compile-time error
similar to "manifest constants are always static":


void foo() {
    static enum x = 10;
}
void main() {}

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--- Comment #12 from bearophile_hugs eml.cc 2010-11-05 11:17:28 PDT ---
See the closed bug 5171 for code that may be disallowed statically:


class A {
     disable override equals_t opEquals(Object other) {
        return false;
    }
}

void main() {
    auto a = new A();
    auto b = new A();

    if(a == b)
        assert(0);
}

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--- Comment #13 from bearophile_hugs eml.cc 2010-11-08 03:24:30 PST ---
This is C# code:

class Foo {}
public class Test : Foo {
    public static void Main() {}
}


The C# compiler gives this error:
prog.cs(2,14): error CS0060: Inconsistent accessibility: base class `Foo' is
less accessible than class `Test'


While the D 2.050 compiler gives no errors with this code:

private class Foo {}
public class Bar : Foo {}
void main() {}

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--- Comment #14 from bearophile_hugs eml.cc 2010-11-08 04:19:31 PST ---
This bug is now fixed:

auto pure foo() {
    return 1;
}
pure void bar() {
    foo();
}
void main() {}


DMD 2.050 gives the error:

test.d(5): Error: pure function 'bar' cannot call impure function 'foo'

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--- Comment #15 from bearophile_hugs eml.cc 2010-11-08 04:38:03 PST ---
(In reply to comment #14)

 This bug is now fixed:



Ignore comment #14, the bug is not fixed, sorry.

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--- Comment #16 from bearophile_hugs eml.cc 2011-01-23 07:18:39 PST ---
This shows something strange, dmd 2.051:

const struct Foo1 { int* p; }
struct Foo2 { int* p; }
void bar1(Foo1 f1) {}
void bar2(Foo2 f2) {}
void main() {
    const f1 = Foo1();
    bar1(f1); // no error
    const f2 = Foo2();
    bar2(f2); // error
}

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--- Comment #17 from bearophile_hugs eml.cc 2011-01-23 09:26:37 PST ---
(In reply to comment #16)

 This shows something strange, dmd 2.051:



According to Mafi that code is correct:
http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.learn&article_id=24058


 I think it's absolutely correct. Look: Foo3 is declared as const
 struct meaning all it's members are const. We are passing a struct
 like that to bar3:
  const Foo3 { const int* p}
 which is implicitely converted to:
  Foo3 { const int* p } //not ref !!
 Because it's not ref you can't manipulate the original struct anyways
 and the pointer is still const. As long as you don't cast you cannot
 change what the pointer points to so this implicit conversion is
 correct IMO.
 It's like const(T[]) => const(T)[] .



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--- Comment #18 from bearophile_hugs eml.cc 2011-01-23 16:18:58 PST ---
Another variant of the code, found by Dan Olson, this compiles and runs with no
errors with DMD 2.051:

struct Foo { int x; }
void bar(ref Foo f) { f.x = 1; }
void main() {
    const f = Foo();
    bar(f);
}

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--- Comment #19 from bearophile_hugs eml.cc 2011-03-19 06:47:16 PDT ---
It seems "emum" implies "static":


enum X = 10;
void main() {
    enum int X = 20;
    static int foo() {
        return X; // No errors
    }
    assert(foo() == 20); // No errors
}


Yet this compiles:

void main() {
    enum static int x = 1;
}


While this:

void main() {
    static static int x = 1;
}

Produces the error:
test.d(2): redundant storage class 'static'

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