LLVM assert with boolean negation in unreachable code

[bytwise]

In the latest master the following code

fn foo() -> bool { false }
fn main() {
    return;
    !foo();
}

produces

rustc: /build/rust-git/src/rust/src/llvm/include/llvm/Support/Casting.h:231: typename llvm::enable_if<llvm::is_same<Y, typename llvm::simplify_type<From>::SimpleType>, typename llvm::cast_retty<X, Y*>::ret_type>::type llvm::cast(Y*) [with X = llvm::SequentialType; Y = llvm::Type; typename llvm::enable_if<llvm::is_same<Y, typename llvm::simplify_type<From>::SimpleType>, typename llvm::cast_retty<X, Y*>::ret_type>::type = llvm::SequentialType*]: Assertion `isa<X>(Val) && "cast<Ty>() argument of incompatible type!"' failed.

The failure still happens if you replace foo() by any expression which returns bool. But as soon as you remove the ! it compiles just fine.

[huonw]

Possibly the same issue (at least, it gives the same assertion):

fn main() {
    let x = "foo";
    return;
    if x == "foo" {}
}

It doesn't happen if x is a primitive type like int or float.

This appears to be a crash in the depths of trans_to_datum... I'm having a look at it now, but I probably won't make much progress. Backtrace for the code in the issue:

#0  0x00007ffff37b11e5 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#1  0x00007ffff37b4398 in __GI_abort () at abort.c:90
#2  0x00007ffff37aa272 in __assert_fail_base (fmt=0x7ffff38e7900 "%s%s%s:%u: %s%sAssertion `%s' failed.\n%n", assertion=assertion@entry=0x7ffff4ee2d40 "isa<X>(Val) && \"cast<Ty>() argument of incompatible type!\"", file=file@entry=0x7ffff4ee2ce0 "/home/huon/rust/src/llvm/include/llvm/Support/Casting.h", line=line@entry=231, function=function@entry=0x7ffff54839a0 <_ZZN4llvm4castINS_14SequentialTypeENS_4TypeEEENS_9enable_ifINS_7is_sameIT0_NS_13simplify_typeIS5_E10SimpleTypeEEENS_10cast_rettyIT_PS5_E8ret_typeEE4typeESC_E19__PRETTY_FUNCTION__> "typename llvm::enable_if<llvm::is_same<Y, typename llvm::simplify_type<From>::SimpleType>, typename llvm::cast_retty<X, Y*>::ret_type>::type llvm::cast(Y*) [with X = llvm::SequentialType; Y = llvm::Ty"...) at assert.c:92
#3  0x00007ffff37aa322 in __GI___assert_fail (assertion=0x7ffff4ee2d40 "isa<X>(Val) && \"cast<Ty>() argument of incompatible type!\"", file=0x7ffff4ee2ce0 "/home/huon/rust/src/llvm/include/llvm/Support/Casting.h", line=231, function=0x7ffff54839a0 <_ZZN4llvm4castINS_14SequentialTypeENS_4TypeEEENS_9enable_ifINS_7is_sameIT0_NS_13simplify_typeIS5_E10SimpleTypeEEENS_10cast_rettyIT_PS5_E8ret_typeEE4typeESC_E19__PRETTY_FUNCTION__> "typename llvm::enable_if<llvm::is_same<Y, typename llvm::simplify_type<From>::SimpleType>, typename llvm::cast_retty<X, Y*>::ret_type>::type llvm::cast(Y*) [with X = llvm::SequentialType; Y = llvm::Ty"...) at assert.c:101
#4  0x00007ffff4daee84 in LLVMGetElementType () from /usr/local/bin/../lib/librustllvm.so
#5  0x00007ffff61046f5 in middle::trans::build::LoadRangeAssert::_55594db7263cd047::_0$x2e8$x2dpre () from /usr/local/bin/../lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so
#6  0x00007ffff6104516 in middle::trans::datum::__extensions__::meth_26894::to_value_llval::_7eff40c77bdb254::_0$x2e8$x2dpre () from /usr/local/bin/../lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so
#7  0x00007ffff61043ad in middle::trans::datum::__extensions__::meth_26891::to_value_datum::_7fae9ce1f4e115c3::_0$x2e8$x2dpre () from /usr/local/bin/../lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so
#8  0x00007ffff6105199 in middle::trans::datum::__extensions__::meth_26908::to_appropriate_datum::_7fae9ce1f4e115c3::_0$x2e8$x2dpre () from /usr/local/bin/../lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so
#9  0x00007ffff613c4c7 in middle::trans::expr::trans_to_datum_unadjusted::_4ecb3fec4142e0c1::_0$x2e8$x2dpre () from /usr/local/bin/../lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so
#10 0x00007ffff60dae2f in middle::trans::expr::trans_to_datum::_4ecb3fec4142e0c1::_0$x2e8$x2dpre () from /usr/local/bin/../lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so
#11 0x00007ffff614bd7b in middle::trans::expr::trans_unary_datum::_3071da634f922af2::_0$x2e8$x2dpre () from /usr/local/bin/../lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so
#12 0x00007ffff6143b0b in middle::trans::expr::trans_rvalue_datum_unadjusted::_4ecb3fec4142e0c1::_0$x2e8$x2dpre () from /usr/local/bin/../lib/librustc-d3cb8c2ccd84a7a7-0.8-pre.so