- Documented rationale of current solution
- Polished documentation

Fix rust-lang#71798.

I believe that this is a copy/paste error; this example was using f32,
but it's the docs for f64.

…pnkfelix

forbid `dyn Trait` in patterns

Do not allow `&dyn Trait` as a generic const parameters.
This also changes dyn trait in pattern from ICE to error.

closes rust-lang#63322
closes rust-lang#70972

r? @eddyb

…wesleywiser

Added MIR constant propagation of Scalars into function call arguments

Now for the function call arguments!

Caveats:
1. It's only being enabled at `mir-opt-2` or higher, because currently codegen gives performance regressions with this optimization.
2. Only propagates Scalars. Tuples and references (references are `Indirect`, right??) are not being propagated into as of this PR.
3. Maybe more tests would be nice?
4. I need (shamefully) to ask @wesleywiser to write in his words (or explain to me, and then I can write it down) why we want to ignore propagation into `ScalarPairs` and `Indirect` arguments.

r? @wesleywiser

doc: misc rustdoc things

Do not try to find binop method on RHS `TyErr`

Fix rust-lang#71798.

…ark-Simulacrum

Use f64 in f64 examples

I believe that this is a copy/paste error; this example was using f32,
but it's the docs for f64.