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-rw-r--r--docs/dev/style.md61
1 files changed, 60 insertions, 1 deletions
diff --git a/docs/dev/style.md b/docs/dev/style.md
index 44f0956c2..bb99c4855 100644
--- a/docs/dev/style.md
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@@ -181,6 +181,30 @@ fn frobnicate(walrus: Option<Walrus>) {
181} 181}
182``` 182```
183 183
184# Early Returns
185
186Do use early returns
187
188```rust
189// Good
190fn foo() -> Option<Bar> {
191 if !condition() {
192 return None;
193 }
194
195 Some(...)
196}
197
198// Not as good
199fn foo() -> Option<Bar> {
200 if condition() {
201 Some(...)
202 } else {
203 None
204 }
205}
206```
207
184# Getters & Setters 208# Getters & Setters
185 209
186If a field can have any value without breaking invariants, make the field public. 210If a field can have any value without breaking invariants, make the field public.
@@ -189,7 +213,7 @@ Never provide setters.
189 213
190Getters should return borrowed data: 214Getters should return borrowed data:
191 215
192``` 216```rust
193struct Person { 217struct Person {
194 // Invariant: never empty 218 // Invariant: never empty
195 first_name: String, 219 first_name: String,
@@ -231,6 +255,41 @@ if words.len() != 2 {
231} 255}
232``` 256```
233 257
258# Avoid Monomorphization
259
260Rust uses monomorphization to compile generic code, meaning that for each instantiation of a generic functions with concrete types, the function is compiled afresh, *per crate*.
261This allows for exceptionally good performance, but leads to increased compile times.
262Runtime performance obeys 80%/20% rule -- only a small fraction of code is hot.
263Compile time **does not** obey this rule -- all code has to be compiled.
264For this reason, avoid making a lot of code type parametric, *especially* on the boundaries between crates.
265
266```rust
267// Good
268fn frbonicate(f: impl FnMut()) {
269 frobnicate_impl(&mut f)
270}
271fn frobnicate_impl(f: &mut dyn FnMut()) {
272 // lots of code
273}
274
275// Not as good
276fn frbonicate(f: impl FnMut()) {
277 // lots of code
278}
279```
280
281Avoid `AsRef` polymorphism, it pays back only for widely used libraries:
282
283```rust
284// Good
285fn frbonicate(f: &Path) {
286}
287
288// Not as good
289fn frbonicate(f: impl AsRef<Path>) {
290}
291```
292
234# Documentation 293# Documentation
235 294
236For `.md` and `.adoc` files, prefer a sentence-per-line format, don't wrap lines. 295For `.md` and `.adoc` files, prefer a sentence-per-line format, don't wrap lines.