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November 09, 2011
immutable & alias this
I find typedef useful still. While trying to create a poor's man typedef using a struct with alis this, I have found this problem:



struct Typedef(T) {
   T data;
   alias data this;
}

alias int[] TA1;
typedef int[] TA2;
alias Typedef!(int[]) TA3;

immutable TA1 a1;
immutable TA2 a2;
TA3 a3a;
immutable TA3 a3b;

static this() {
   a1 = [1, 2, 3];  // OK
   a2 = [1, 2, 3];  // OK
   a3a = [1, 2, 3]; // OK
   a3b = [1, 2, 3]; // line 16, error
}
void main() {}



DMD 2.057beta gives:

test.d(16): Error: cannot implicitly convert expression ([1,2,3]) of type int[] to immutable(Typedef!(int[]))

What do you think?

Bye,
bearophile
November 09, 2011
Re: immutable & alias this
> test.d(16): Error: cannot implicitly convert expression ([1,2,3]) of  
> type int[] to immutable(Typedef!(int[]))

OT: this shows another possible problem.
See http://clang.llvm.org/diagnostics.html, section "Typedef Preservation  
and Selective Unwrapping"
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