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proc_macro: Update docs for Spacing

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Brings the docs more in line with reality
This commit is contained in:
Vadim Petrochenkov 2023-08-08 16:21:42 +08:00
parent 4e3ce0e782
commit 176a9392d1
1 changed files with 25 additions and 13 deletions
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38
library/proc_macro/src/lib.rs
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@ -916,21 +916,34 @@ impl !Send for Punct {}
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
impl !Sync for Punct {}
/// Describes whether a `Punct` is followed immediately by another `Punct` ([`Spacing::Joint`]) or
/// by a different token or whitespace ([`Spacing::Alone`]).
/// Indicates whether a `Punct` token can join with the following token
/// to form a multi-character operator.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub enum Spacing {
/// A `Punct` is not immediately followed by another `Punct`.
/// E.g. `+` is `Alone` in `+ =`, `+ident` and `+()`.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
Alone,
/// A `Punct` is immediately followed by another `Punct`.
/// E.g. `+` is `Joint` in `+=` and `++`.
/// A `Punct` token can join with the following token to form a multi-character operator.
///
/// Additionally, single quote `'` can join with identifiers to form lifetimes: `'ident`.
/// In token streams constructed using proc macro interfaces `Joint` punctuation tokens can be
/// followed by any other tokens. \
/// However, in token streams parsed from source code compiler will only set spacing to `Joint`
/// in the following cases:
/// - A `Punct` is immediately followed by another `Punct` without a whitespace. \
/// E.g. `+` is `Joint` in `+=` and `++`.
/// - A single quote `'` is immediately followed by an identifier without a whitespace. \
/// E.g. `'` is `Joint` in `'lifetime`.
///
/// This list may be extended in the future to enable more token combinations.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
Joint,
/// A `Punct` token cannot join with the following token to form a multi-character operator.
///
/// `Alone` punctuation tokens can be followed by any other tokens. \
/// In token streams parsed from source code compiler will set spacing to `Alone` in all cases
/// not covered by the conditions for `Joint` above. \
/// E.g. `+` is `Alone` in `+ =`, `+ident` and `+()`.
/// In particular, token not followed by anything will also be marked as `Alone`.
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
Alone,
}
impl Punct {
@ -962,10 +975,9 @@ pub fn as_char(&self) -> char {
self.0.ch as char
}
/// Returns the spacing of this punctuation character, indicating whether it's immediately
/// followed by another `Punct` in the token stream, so they can potentially be combined into
/// a multi-character operator (`Joint`), or it's followed by some other token or whitespace
/// (`Alone`) so the operator has certainly ended.
/// Returns the spacing of this punctuation character, indicating whether it can be potentially
/// combined into a multi-character operator with the following token (`Joint`), or the operator
/// has certainly ended (`Alone`).
#[stable(feature = "proc_macro_lib2", since = "1.29.0")]
pub fn spacing(&self) -> Spacing {
if self.0.joint { Spacing::Joint } else { Spacing::Alone }