Bad error message when having a single handler that's supposed to match everything #81
Description
Example:
int someFun(T)(T v)
{
static assert(!is(T == int));
return 3;
}
SumType!(int, string, This[]) v;
v.match!(all => someFun(all));use-case is that I have a generic (de)serialization function that's supposed to work on every type of my sumtype, but it doesn't for one. The current error message says something like:
/usr/include/dlang/dmd/std/sumtype.d(1998,13): Error: static assert: "`handlers[0]` of type `template` never matches"
/usr/include/dlang/dmd/std/sumtype.d(1590,52): instantiated from here: `matchImpl!(SumType!(typeof(null), string, bool, long, double, This[], This[string]))`
source/workspaced/backend.d(132,15): instantiated from here: `match!(SumType!(typeof(null), string, bool, long, double, This[], This[string]))`
source/workspaced/backend.d(149,22): instantiated from here: `deepCopy!(SumType!(typeof(null), string, bool, long, double, This[], This[string]))`
source/workspaced/backend.d(136,40): instantiated from here: `deepCopy!(SumType!(typeof(null), string, bool, long, double, This[], This[string])[string])`
source/workspaced/backend.d(113,30): instantiated from here: `deepCopy!(Section)`
which is hard to debug.
I propose to add a special case for single-pattern match invocations, where it will just shove it into my custom handler without testing if it's plausible and just let compiler errors break it.