Manually annotated types on assignments don't show up in generated code

[ameliatastic]

When adding a type annotation on an assignment, the annotation is only used for the Seahorse type checker.

-- This Seahorse code:
n = 1
m: u64 = 2
-- Turns into roughly this Rust code:
let mut n = 1;
let mut m = 2;

This leads to unintuitive bugs popping up when you try to use a type annotation to solve a compilation error:

-- This Seahorse code:
n = 10**2
-- Turns into this Rust code, which fails to compile because .pow() is not defined on arbitrary integers:
let mut n = 10.pow(2);

-- Intuitively, you might try to fix the code in one of these two ways, but both will fail because the
-- generated code doesn't care about the type annotation:
n1: u64 = 10**2

b: u64 = 10
n2 = b**2

To prevent this issue, type annotations in Seahorse should lead to type annotations in the generated Rust code.

[kubanemil]

Is this problem still relevant?