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Add way to express no-values with check-cfg

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Urgau 2024-01-13 12:18:51 +01:00
parent 284cb714d2
commit 41b69aae91
10 changed files with 89 additions and 32 deletions
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25
src/doc/unstable-book/src/compiler-flags/check-cfg.md
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@ -44,15 +44,20 @@ To enable checking of values, but to provide an *none*/empty set of expected val
```bash
rustc --check-cfg 'cfg(name)'
rustc --check-cfg 'cfg(name, values())'
rustc --check-cfg 'cfg(name, values(none()))'
```
To enable checking of name but not values (i.e. unknown expected values), use this form:
To enable checking of name but not values, use one of these forms:
```bash
rustc --check-cfg 'cfg(name, values(any()))'
```
- No expected values (_will lint on every value_):
```bash
rustc --check-cfg 'cfg(name, values())'
```
- Unknown expected values (_will never lint_):
```bash
rustc --check-cfg 'cfg(name, values(any()))'
```
To avoid repeating the same set of values, use this form:
@ -114,18 +119,14 @@ as argument to `--check-cfg`.
This table describe the equivalence of a `--cfg` argument to a `--check-cfg` argument.
| `--cfg` | `--check-cfg` |
|-----------------------------|----------------------------------------------------------|
|-------------------------------|------------------------------------------------------------|
| *nothing* | *nothing* or `--check-cfg=cfg()` (to enable the checking) |
| `--cfg foo` | `--check-cfg=cfg(foo), --check-cfg=cfg(foo, values())` or `--check-cfg=cfg(foo, values(none()))` |
| `--cfg foo` | `--check-cfg=cfg(foo)` or `--check-cfg=cfg(foo, values(none()))` |
| `--cfg foo=""` | `--check-cfg=cfg(foo, values(""))` |
| `--cfg foo="bar"` | `--check-cfg=cfg(foo, values("bar"))` |
| `--cfg foo="1" --cfg foo="2"` | `--check-cfg=cfg(foo, values("1", "2"))` |
| `--cfg foo="1" --cfg bar="2"` | `--check-cfg=cfg(foo, values("1")) --check-cfg=cfg(bar, values("2"))` |
| `--cfg foo --cfg foo="bar"` | `--check-cfg=cfg(foo) --check-cfg=cfg(foo, values("bar"))` |
NOTE: There is (currently) no way to express that a condition name is expected but no (!= none)
values are expected. Passing an empty `values()` means *(none)* in the sense of `#[cfg(foo)]`
with no value. Users are expected to NOT pass a `--check-cfg` with that condition name.
| `--cfg foo --cfg foo="bar"` | `--check-cfg=cfg(foo, values(none(), "bar"))` |
### Example: Cargo-like `feature` example