RustIntermediate~4h

Rust: Types & Traits

Make the wrong program unwriteable

Most Rust is not about the borrow checker. It is about choosing the enum that cannot hold the bad value, carrying a failure as a value instead of throwing it, and naming the one ability a function actually needs — then reading code somebody else wrote and knowing what it does.

Start this project See the modules

Modules: 6
Drills: 10
Build steps: 5
Time: ~4h

Walk out able to

Read unfamiliar Rust and say what it produces — and choose between a generic parameter and a `dyn` without guessing which one the design needs.

What you work on

Enums that refuse bad states

Variants that differ, and a match that has to be total.

Option, Result and ?

Absence and failure carried as values, never thrown.

Generics and traits

One bound per ability — then generic or dyn, on purpose.

Pipelines, then the build

Adapters instead of loops, and a Rust program that runs.

The pitch

What you practise, and what you leave with

A Rust program that parses a log into an enum, checks it behind one trait, and reports through iterator pipelines.

You will practise

Enum shape, match arms, exhaustiveness
Option, Result, combinators and ?
Trait bounds, dyn, object safety
Iterator chains and the three iters

Afterwards you can

Pick the enum that refuses the bad value
Carry a failure out with ? and no panic
Name the bound a rejected line asked for
Choose a generic or a dyn, and say why

Modules

6 modules, 20 items

Lessons explain one idea. Drills repeat it until it sticks. Build steps make something that exists afterwards.

1
Make the states explicit
~40 min
Choose the type that refuses the bad value, then read any match over it.
- LessonGive the states one type17 min
- DrillChoose the definition that refuses it12 min
- DrillSay which arm runs11 min
2
Absence and failure are values
~39 min
Carry a missing or failed result through a program without unwrapping it.
- LessonCarry the failure instead of throwing it16 min
- DrillSay what the chain evaluates to12 min
- DrillFollow a failure out of a function11 min
3
One function, many types
~25 min
Write a generic function, bound it, and read the error when the bound is missing.
- LessonWrite it once, for every type13 min
- DrillName the bound the body needs12 min
4
Behaviour as a contract
~40 min
Name a behaviour, require it, and choose how the caller carries it.
- LessonName the behaviour, then require it16 min
- DrillPick the one the design needs13 min
- DrillSay whether it can be a trait object11 min
5
Pipelines instead of loops
~36 min
Predict what an adapter chain produces, and start it with the right one of three.
- LessonSay what you want, not how to loop14 min
- DrillSay what the pipeline produces13 min
- DrillStart the loop with the right one9 min
6
Build the reader
~50 min
Get the spellings under your fingers, then ship a Rust program that uses all five.
- DrillWrite the syntax from memory9 min
- Build stepModel the log as one enum5 min
- Build stepFill the type from the text7 min
- Build stepBreak it with one bad number4 min
- Build stepPut the checks behind one trait13 min
- Build stepFinish it with one pipeline12 min