[Issue 11276] Possibly spurious (did you forget a [] ?) error message

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=11276



--- Comment #2 from Kenji Hara <k.hara.pg at gmail.com> 2013-10-16 01:34:41 PDT ---
(In reply to comment #0)
> This could be a problem in DMD and one related but different in Phobos.
> 
> This used to work:
> 
> import std.algorithm: reduce;
> struct Foo { int x, y; }
> void main() {
>     Foo[] data = [{10, 20}, {30, 40}];
>     reduce!((a, b) => a[] += [b.x, b.y][])([0, 0], data);
> }
> 
> 
> Now it gives (dmd 2.064beta1):
> 
> test.d(5): Error: invalid array operation a[] += [b.x, b.y] (did you forget a
> [] ?)
> ...\dmd2\src\phobos\std\algorithm.d(763): Error: template instance
> test.main.__lambda1!(int[], Foo) error instantiating
> test.d(5):        instantiated from here: reduce!(int[], Foo[])
> test.d(5): Error: template instance test.main.reduce!((a, b) => a[] += [b.x,
> b.y][]).reduce!(int[], Foo[]) error instantiating

This is a duplicate issue of bug 10684. I'll increased importance of the issue.

(In reply to comment #0)
> Expanding the lambda doesn't fully solve the problem (now compiling with
> "-wi"):
> 
> import std.algorithm: reduce;
> struct Foo { int x, y; }
> void main() {
>     Foo[] data = [{10, 20}, {30, 40}];
>     reduce!((a, b) { int[2] c = [b.x, b.y];
>                      a[] += c[];
>                      return c;})([0, 0], data);
> }
> 
> Gives:
> 
> ...\dmd2\src\phobos\std\algorithm.d(763): Warning: explicit slice assignment
> result = (__lambda1(result, front(_param_1)))[] is better than result =
> __lambda1(result, front(_param_1))

This is a regression caused by implementing issue 7444.

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