[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492
Kenji Hara k.hara...@gmail.com changed:
What|Removed |Added
Status|NEW |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Kenji Hara k.hara...@gmail.com ---
(In reply to Denis Shelomovskij from comment #0)
---
auto f() { return new char[1]; }
immutable s = f(); // error, works with non-character arrays
---
Error: cannot implicitly convert expression (\xff) of type char[] to
immutable(char[])
The function returns char[]. In D type system, char[] to immutable(char[])
conversion is not allowed.
If you annotate the function f with pure attribute, f() will return an unique
array so compiler will allow the conversion.
Anyway, this is not CTFE problem. The code is trying to violate D type system,
and compiler reports the error correctly.
--
[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492 --- Comment #4 from Kenji Hara k.hara...@gmail.com --- (In reply to Denis Shelomovskij from comment #3) If function is executed during CTFE it's definitely effectively `pure` for given parameters so I don't understand your arguments. Again, CTFE is not relevant. The OP code just fails to pass semantic analysis. CTFE never runs on invalid code. Anyway works with non-character arrays comment isn't addressed. Event if this compiler error is an expected behaviour, the issue is in the fact other types don't produce the same error (try e.g. `int` and `Object` arrays). Is that diagnostic issue? Please file another report. Thanks! --
[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492 Denis Shelomovskij verylonglogin@gmail.com changed: What|Removed |Added Status|REOPENED|RESOLVED Resolution|--- |INVALID --- Comment #5 from Denis Shelomovskij verylonglogin@gmail.com --- (In reply to Kenji Hara from comment #4) (In reply to Denis Shelomovskij from comment #3) Anyway works with non-character arrays comment isn't addressed. Event if this compiler error is an expected behaviour, the issue is in the fact other types don't produce the same error (try e.g. `int` and `Object` arrays). Is that diagnostic issue? Please file another report. Thanks! Filed issue 14017. --
[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492
Denis Shelomovskij verylonglogin@gmail.com changed:
What|Removed |Added
Status|RESOLVED|REOPENED
Resolution|INVALID |---
--- Comment #3 from Denis Shelomovskij verylonglogin@gmail.com ---
(In reply to Kenji Hara from comment #2)
(In reply to Denis Shelomovskij from comment #0)
---
auto f() { return new char[1]; }
immutable s = f(); // error, works with non-character arrays
---
Error: cannot implicitly convert expression (\xff) of type char[] to
immutable(char[])
The function returns char[]. In D type system, char[] to immutable(char[])
conversion is not allowed.
If you annotate the function f with pure attribute, f() will return an
unique array so compiler will allow the conversion.
Anyway, this is not CTFE problem. The code is trying to violate D type
system, and compiler reports the error correctly.
If function is executed during CTFE it's definitely effectively `pure` for
given parameters so I don't understand your arguments.
Anyway works with non-character arrays comment isn't addressed. Event if this
compiler error is an expected behaviour, the issue is in the fact other types
don't produce the same error (try e.g. `int` and `Object` arrays).
--
[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492
--- Comment #8 from Denis Shelomovskij verylonglogin@gmail.com ---
(In reply to Kenji Hara from comment #7)
(In reply to Denis Shelomovskij from comment #5)
Filed issue 14017.
...
Anyway, at least it's an inconsistent compiler behavior. I reopen this.
Issue 14017 is about this inconsistent behavior.
Also we both changed our positions. I see no reasonable profit from
effectively `pure` CTFE-able functions and worst of all such feature will
introduce unpleasant inconsistency:
---
int[] f() { return new int[1]; }
void main()
{
// With effectively `pure` feature:
static immutable s = f(); // OK
immutable s = f(); // error
}
---
So I'm for marking this one as INVALID and for fixing Issue 14017.
--
[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492 --- Comment #9 from Steven Schveighoffer schvei...@yahoo.com --- (In reply to Denis Shelomovskij from comment #8) So I'm for marking this one as INVALID and for fixing Issue 14017. I disagree completely. CTFE is a special case, and should be treated specially. There are many cases where a function can be used as CTFE in some cases, and some cases it cannot. One of those requirements is that it is effectively pure. Given that CTFE functions MUST provide all source, they should be able to be inferred pure, with all the benefits that entails. I think the issue here is not the function, but what you can do with the return value. In your example, both calls return a mutable int[]. It's just that the compiler can prove due to CTFE that it is unique and has free reign to convert to any constancy required. --
[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492 Denis Shelomovskij verylonglogin@gmail.com changed: What|Removed |Added Status|REOPENED|RESOLVED Resolution|--- |INVALID --- Comment #10 from Denis Shelomovskij verylonglogin@gmail.com --- (In reply to Steven Schveighoffer from comment #9) (In reply to Denis Shelomovskij from comment #8) So I'm for marking this one as INVALID and for fixing Issue 14017. I disagree completely. CTFE is a special case, and should be treated specially. There are many cases where a function can be used as CTFE in some cases, and some cases it cannot. One of those requirements is that it is effectively pure. Given that CTFE functions MUST provide all source, they should be able to be inferred pure, with all the benefits that entails. I think the issue here is not the function, but what you can do with the return value. In your example, both calls return a mutable int[]. It's just that the compiler can prove due to CTFE that it is unique and has free reign to convert to any constancy required. Nobody argues the function IS effectively `pure` in CTFE contexts. The problem is in introduction of a new language type system rule. Anyway this issue is INVALID and for such enhancement I opened Issue 14018. --
[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492 Steven Schveighoffer schvei...@yahoo.com changed: What|Removed |Added CC||schvei...@yahoo.com --- Comment #6 from Steven Schveighoffer schvei...@yahoo.com --- can't the compiler imply pure on f? --
[Issue 7492] [CTFE] Error at assign to immutable character array
https://issues.dlang.org/show_bug.cgi?id=7492
Kenji Hara k.hara...@gmail.com changed:
What|Removed |Added
Status|RESOLVED|REOPENED
See Also||https://issues.dlang.org/sh
||ow_bug.cgi?id=14017
Resolution|INVALID |---
--- Comment #7 from Kenji Hara k.hara...@gmail.com ---
(In reply to Denis Shelomovskij from comment #5)
Filed issue 14017.
By looking the code in 14017, I recognized the real issue at last...
Full code to illustrate issue.
int[] f() { return new int[](1); }
char[] g() { return new char[](1); }
immutable( int[]) a = f(); // [A] accepted
immutable(char[]) s = g(); // [B] rejected
If we just only consider type system, both conversions:
int[] to immutable( int[])
char[] to immutable(char[])
are not possible.
But if we also consider CTFE, we can regard that the function calls will be
replaced with the literals that returned by CTFE:
immutable( int[]) a = [0];
immutable(char[]) s = ['\xff'];
and literals can be convertible to the variable type.
---
By looking dmd internals, current semantic process is nearly the latter
replacement model. And maybe the [B] case is happened by the issue in the
interpreter code for scrubbing CTFE return value.
But, at the same time the case [A] looks like a kind of type system breaking.
Anyway, at least it's an inconsistent compiler behavior. I reopen this.
--
[Issue 7492] [CTFE] Error at assign to immutable character array
http://d.puremagic.com/issues/show_bug.cgi?id=7492 Don clugd...@yahoo.com.au changed: What|Removed |Added CC||clugd...@yahoo.com.au --- Comment #1 from Don clugd...@yahoo.com.au 2012-02-23 02:06:22 PST --- I'm not sure about this. The int[] case may be an accepts-invalid bug. If you move the declaration of 's' into the inside of a function, you get the same error message, even though CTFE is not involved. And when you do that, if it's an int[] instead of char[], you get the same error. In any case the error is not generated by CTFE. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email --- You are receiving this mail because: ---
