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34 changes: 34 additions & 0 deletions src/conditional-compilation.md
Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,7 @@ ConfigurationPredicate ->
| ConfigurationAll
| ConfigurationAny
| ConfigurationNot
| ConfigurationVersion
| `true`
| `false`

Expand All @@ -23,6 +24,15 @@ ConfigurationAny ->
ConfigurationNot ->
`not` `(` ConfigurationPredicate `)`

ConfigurationVersion ->
`version` `(` `"` ConfigurationVersionLiteral `"` `)`

ConfigurationVersionLiteral ->
ConfigurationVersionPart `.` ConfigurationVersionPart (`.` ConfigurationVersionPart)?

ConfigurationVersionPart ->
(DEC_DIGIT)+

ConfigurationPredicateList ->
ConfigurationPredicate (`,` ConfigurationPredicate)* `,`?
```
Expand Down Expand Up @@ -55,6 +65,11 @@ r[cfg.predicate.not]
r[cfg.predicate.literal]
* `true` or `false` literals, which are always true or false respectively.

r[cfg.predicate.version]
* `version()` with a version number inside. It is true if the language version
the compiler targets is higher or equal to the contained version number.
It is false otherwise.
Comment on lines +68 to +71
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This needs grammar, above, as for the other predicates.


r[cfg.option-spec]
_Configuration options_ are either names or key-value pairs, and are either set or unset.

Expand Down Expand Up @@ -299,6 +314,19 @@ r[cfg.proc_macro]
Set when the crate being compiled is being compiled with the `proc_macro`
[crate type].

r[cfg.version]
### `version()`

r[cfg.version.behavior]
The `version()` predicate evaluates to true if both:

* The version number contained inside follows the format and
* The version number contained inside is less than or equal to the version
of the language the compiler targets.

r[cfg.version.format]
In order for it to be considered of valid format, the version number has to follow either the `"a.b.c"` scheme or the `"a.b"` scheme. Semantically, assume `c` to be 0 if not present. Order wise, version numbers behave as if they were Rust tuples of type `(u16, u16, u16)`.

r[cfg.panic]
### `panic`

Expand Down Expand Up @@ -371,6 +399,12 @@ fn needs_not_foo() {
// ...
}

// This function is only included if the language version is at least 1.50.0
#[cfg(version("1.50.0"))]
fn needs_new_compiler() {
// ...
}

// This function is only included when the panic strategy is set to unwind
#[cfg(panic = "unwind")]
fn when_unwinding() {
Expand Down
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