On Monday, 8 July 2013 at 20:46:35 UTC, H. S. Teoh wrote:
On Mon, Jul 08, 2013 at 09:47:46PM +0200, Peter Alexander wrote:
On Monday, 8 July 2013 at 18:10:45 UTC, H. S. Teoh wrote:
>On Sun, Jul 07, 2013 at 02:06:46PM +0200, Peter Alexander
>wrote:
>>It's a tough situation and I think the only way this could
>>even
>>reasonably be resolved is through some sophisticated IDE
>>integration. There is no way to display this kind of error
>>report in
>>a blob of command line text.
>
>I don't see how an IDE could do better than the compiler.
>Combinatorial explosion is a nasty problem, and if an IDE
>could solve
>it, so could the compiler. Sure, the IDE could give you a nice
>scrollable GUI widget to look through all the various reasons
>of the
>instantiation failure, but fundamentally speaking, that's not
>much
>different from running grep through 50 pages of compiler
>output. You
>still haven't solved the root problem, which is to narrow
>down the
>exponential set of possible problem causes to a manageable,
>human-comprehensible number.
I thinking of more of an interactive diagnostic: you choose
which
overload you intended to instantiate and then get a list of
reasons
why that failed to compile. Repeat recursively for any
sub-calls.
The problem is, this presumes knowledge of Phobos internals,
which most
D users probably would have no clue about. How is one supposed
to know
which of the 25 overloads should be used in this particular
case anyway?
For all one knows, it may be a Phobos bug or something.
Whereas a message like "cannot instantiate S in
std.blah.internal.func"
where S is the user-defined struct, would be a good indication
as to
what might be wrong without needing to understand how Phobos
works.
Maybe the compiler could just spew out every possible error
for every
instantiation, and expect the user to grep, but that's not
going to be
a pleasant experience.
The compiler could join all the constraints and then simplify it
to create the error message. (eg by creating a Binary Decision
Diagram (BDD))
eg given constraints:
if ( A && B && C )
if ( (A && D) || ( A && E && F) )
if ( E && G )
Suppose A is true but the conditions fail. The compiler could
then write that no templates match because ( B || D || E ) is
false.
