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Auto merge of #56392 - petrochenkov:regensym, r=oli-obk

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Delay gensym creation for "underscore items" (`use foo as _`/`const _`) until name resolution

So they cannot be cloned by macros. See https://github.com/rust-lang/rust/pull/56303 for the discussion.

Mostly fix cross-crate use of underscore items by inverting the "gensyms are lost in metadata" bug as described in https://github.com/rust-lang/rust/pull/56303#issuecomment-442464695.
Fix unused import warnings for single-segment imports (first commit) and `use crate_name as _` imports (as specified in https://github.com/rust-lang/rust/pull/56303#issuecomment-442274118).
Prohibit accidentally implemented `static _: TYPE = EXPR;` (cc https://github.com/rust-lang/rust/pull/55983).
Add more tests for `use foo as _` imports.
This commit is contained in:
bors 2018-12-06 15:08:11 +00:00
commit 4bb5d35659
19 changed files with 212 additions and 70 deletions
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27
src/libsyntax/parse/parser.rs
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@ -2017,6 +2017,17 @@ impl<'a> Parser<'a> {
}
}
fn parse_ident_or_underscore(&mut self) -> PResult<'a, ast::Ident> {
match self.token {
token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
let span = self.span;
self.bump();
Ok(Ident::new(ident.name, span))
}
_ => self.parse_ident(),
}
}
/// Parses qualified path.
/// Assumes that the leading `<` has been parsed already.
///
@ -6434,13 +6445,7 @@ impl<'a> Parser<'a> {
}
fn parse_item_const(&mut self, m: Option<Mutability>) -> PResult<'a, ItemInfo> {
let id = match self.token {
token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
self.bump(); // `_`
ident.gensym()
},
_ => self.parse_ident()?,
};
let id = if m.is_none() { self.parse_ident_or_underscore() } else { self.parse_ident() }?;
self.expect(&token::Colon)?;
let ty = self.parse_ty()?;
self.expect(&token::Eq)?;
@ -7725,13 +7730,7 @@ impl<'a> Parser<'a> {
fn parse_rename(&mut self) -> PResult<'a, Option<Ident>> {
if self.eat_keyword(keywords::As) {
match self.token {
token::Ident(ident, false) if ident.name == keywords::Underscore.name() => {
self.bump(); // `_`
Ok(Some(ident.gensym()))
}
_ => self.parse_ident().map(Some),
}
self.parse_ident_or_underscore().map(Some)
} else {
Ok(None)
}