Unreachable code suppresses warnings

[ranma42]

println!("{}", false && ((1u8 - 5u8) == 42));

results in "warning: attempted to sub with overflow", but

println!("{}", if false { ((1u8 - 5u8) == 42) } else { false });

compiles with no warning at all.

I would expect both expressions to warn, either because of the overflow or because of dead code (or both).

[0xmohit]

The second example produces warning with 1.12.0 -- https://is.gd/Pz7wkc.