Difference between "can call" and "can compile"
nick at geany.org
Wed Sep 16 16:59:46 UTC 2020
On Tuesday, 8 September 2020 at 18:59:00 UTC, Steven
> void toString(Output)(Output output) if
> (isOutputRange!(Output, dchar))
> put(output, "hello, this is an S!"); // no import of
> if writeln checked using the proposed __traits(instantiates)
> instead of __traits(compiles) on the call to
> S.toString(lockedTextOutput) (or whatever it does), then
> instead of the wrong path, I get a compilation error, telling
> me that my toString doesn't compile.
In theory, `is(typeof(S.init.toString(suitableOutputRange)))`
could be true even if there is a semantic error in the body of
your S.toString method. The typeof expression only needs to
resolve the method then produce the type of that method. You
specified the return type as `void` (not `auto`), so it is
overkill to check the semantics of the method body at this point
in compilation (it might not even get called).
If typeof was changed to do less work, perhaps `is(typeof(...))`
could do what you want.
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