immutable bug?

[Steven Schveighoffer]

On Wed, 25 Jan 2012 10:46:57 -0500, Era Scarecrow <rtcvb32 at yahoo.com>  
wrote:

>  DMD 2.057 - Windows version
>
>  I'm in the middle of converting a medium sized project from C to D.  
> While I'm doing that I have several static data structures. Here's where  
> I find myself. Can't probably duplicate the error message without the  
> full sources.
>
>  Since immutable is transitive, this should not cause an error. But I am  
> getting this one, which repeats 4 times for all four Notepart entries:
>
> Error: cannot implicitly convert expression ("fQuality") of type string  
> to char[]
>
> //for reference on types
> const nLen = 4;
> enum ValueType {}
> struct Flags {}
>
> alias NotePart NP;
> alias ValueType VT;
>
> struct NotePart {
> 	ValueType type;	
> 	char[] id;
> 	Flags flags;
> 	int _size;
> }
>
> struct SubRecordParts {
> 	char name[nLen];
> 	char requ[nLen];
> 	int size;
> 	NotePart[] notes;
> 	int identifyBy = -1;
> }
>
> //immutable should (i think) implicitly change char[] to  
> immutable(char[])
> immutable SubRecordParts subParts[] = [
> 	{"AADT", "", 16, [
> 		NP(VT.ranged_32, "IApparatus"),
> 		NP(VT.float_32, "fQuality"),
> 		NP(VT.float_32, "fWeight"),
> 		NP(VT.i_32, "iuses")]}
> ];

Your issue is here, (I'm guessing).  If do this (after slimming down to a  
compilable sample):

alias immutable(NotePart) NP;

then it compiles.

Because the expression (guessing that you have NP aliased to NotePart)  
NP(...) is constructing a NotePart and not an *immutable* NotePart, it  
cannot resolve that part of the expression, even though the whole  
expression is treated as immutable after evaluation.

Maybe there's an enhancement lurking in here...

-Steve