Why does a where clause confuse lifetime analysis?

[vitalyd]

Here's a previous discussion on compiler "forgetting" about other impls:

Lend me your google-fu on the issue tracker

Today, I have run into an error most magical. It turns out that if you write f64: Mul<C> as a trait bound on a function, then rustc forgets that f64s can be multiplied with f64s. use ::std::ops::Mul; fn foo<C>(max: C) -> <f64 as Mul<C>>::Output where f64: Mul<C>, { 1.0f64 * 3.0f64 * max } fn main() { } Compiling wtfbounds v0.1.0 (file:///home/lampam/cpp/throwaway/wtfbounds) error[E0308]: mismatched types --> src/main.rs:6:14 | 6 | 1.0f64 * 3.0f64 * max | ^^^^^^ …