TypeChecker::check_box_free_inputs never happens

[glandium]

I have, in my patch queue, a change that removes TypeChecker::check_box_free_inputs because I changed the MIR emitted for box_free such that the normal TypeChecker::check_call_inputs should work for it. I wanted to check whether that's true, but couldn't find any case where it's called. I went as far as reverting all my changes, and making check_box_free_inputs eprintln a message, and never saw one. Not while compiling the compiler itself, and not while compiling the testcase from #50041 (which does create a basic block with a termination call to box_free, contrary to most cases where the MIR only contains a drop ; and I tried adding #[feature(nll)] to that testcase in case that matters, to no avail)

Actually, full disclosure: I did see two calls... when compiling liballoc, which contains explicit calls to the function. (

rust/src/liballoc/arc.rs

Line 581 in 99d4886

box_free(bptr);

rust/src/liballoc/rc.rs

Line 696 in 99d4886

box_free(bptr);

). And for those, check_call_inputs is clearly enough, since type checking actually happens before MIR.

Cc: @nikomatsakis

[Mark-Simulacrum]

dfa6111 was merged and removed check_box_free_inputs so I'm closing this.