Bug 20167 – Issue warning when result discarded from strong pure function?

It would be nice to have a compile error (or warning maybe) when the user discards the result from a stong pure function. If the function receives args `const`, and has no side effects, then calling the function is completely redundant if the result is discarded. At best it's pointless and inefficient, but in practise it's almost certainly a bug that the user didn't notice.

(In reply to Manu from comment #0) > It would be nice to have a compile error (or warning maybe) when the user > discards the result from a stong pure function. ``` int f() nothrow pure { return 1; } void main() { f(); } ``` When compiling with -w: onlineapp.d(6): Warning: calling onlineapp.f without side effects discards return value of type int, prepend a cast(void) if intentional Is there anything lacking on the current warning or can this be closed?

Interesting. I did this same test, but I didn't have `nothrow`. Why wasn't `nothrow` inferred for this trivial function where the source is as plain as day to the compiler? We're meant to be all about attribute inference these days.

> Why wasn't `nothrow` inferred for this trivial function where the source is as plain as day to the compiler? FWIW the compiler does inference if the function is a template or the return type is auto: that is auto f() { return 1; } and int f()() { return 1; } will trigger a warning when compiled with -w

> I did this same test, but I didn't have `nothrow`. Why wasn't `nothrow` inferred for this trivial function where the source is as plain as day to the compiler? We have been discussing about this for a long time, but I don't know if attribute inference is going to be a thing for normal functions. That could be filed as a different issue. However, this bug report, as Dennis pointed out has nothing actionable.