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Rollup merge of #48481 - Manishearth:dyn-paren, r=petrochenkov

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Allow parentheses in `dyn (Trait)`

r? @eddyb @nikomatsakis
This commit is contained in:
Manish Goregaokar 2018-02-24 15:52:16 -08:00 • committed by GitHub
commit 7e6829938c
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3 changed files with 11 additions and 10 deletions
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14
src/libsyntax/parse/parser.rs
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@ -405,11 +405,14 @@ impl TokenType {
}
}
// Returns true if `IDENT t` can start a type - `IDENT::a::b`, `IDENT<u8, u8>`,
// `IDENT<<u8 as Trait>::AssocTy>`, `IDENT(u8, u8) -> u8`.
fn can_continue_type_after_ident(t: &token::Token) -> bool {
/// Returns true if `IDENT t` can start a type - `IDENT::a::b`, `IDENT<u8, u8>`,
/// `IDENT<<u8 as Trait>::AssocTy>`.
///
/// Types can also be of the form `IDENT(u8, u8) -> u8`, however this assumes
/// that IDENT is not the ident of a fn trait
fn can_continue_type_after_non_fn_ident(t: &token::Token) -> bool {
t == &token::ModSep || t == &token::Lt ||
t == &token::BinOp(token::Shl) || t == &token::OpenDelim(token::Paren)
t == &token::BinOp(token::Shl)
}
/// Information about the path to a module.
@ -1619,7 +1622,8 @@ impl<'a> Parser<'a> {
impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus;
TyKind::ImplTrait(bounds)
} else if self.check_keyword(keywords::Dyn) &&
self.look_ahead(1, |t| t.can_begin_bound() && !can_continue_type_after_ident(t)) {
self.look_ahead(1, |t| t.can_begin_bound() &&
!can_continue_type_after_non_fn_ident(t)) {
self.bump(); // `dyn`
// Always parse bounds greedily for better error recovery.
let bounds = self.parse_ty_param_bounds()?;