diff options
Diffstat (limited to 'compiler/rustc_parse/src/parser/path.rs')
| -rw-r--r-- | compiler/rustc_parse/src/parser/path.rs | 117 |
1 files changed, 91 insertions, 26 deletions
diff --git a/compiler/rustc_parse/src/parser/path.rs b/compiler/rustc_parse/src/parser/path.rs index 79e73749038..17e5bcf7605 100644 --- a/compiler/rustc_parse/src/parser/path.rs +++ b/compiler/rustc_parse/src/parser/path.rs @@ -3,10 +3,9 @@ use super::{Parser, TokenType}; use crate::maybe_whole; use rustc_ast::ptr::P; use rustc_ast::token::{self, Token}; -use rustc_ast::{ - self as ast, AngleBracketedArg, AngleBracketedArgs, GenericArg, ParenthesizedArgs, -}; +use rustc_ast::{self as ast, AngleBracketedArg, AngleBracketedArgs, ParenthesizedArgs}; use rustc_ast::{AnonConst, AssocTyConstraint, AssocTyConstraintKind, BlockCheckMode}; +use rustc_ast::{GenericArg, GenericArgs}; use rustc_ast::{Path, PathSegment, QSelf}; use rustc_errors::{pluralize, Applicability, PResult}; use rustc_span::source_map::{BytePos, Span}; @@ -414,32 +413,40 @@ impl<'a> Parser<'a> { /// Parses a single argument in the angle arguments `<...>` of a path segment. fn parse_angle_arg(&mut self) -> PResult<'a, Option<AngleBracketedArg>> { - if self.check_ident() && self.look_ahead(1, |t| matches!(t.kind, token::Eq | token::Colon)) - { - // Parse associated type constraint. - let lo = self.token.span; - let ident = self.parse_ident()?; - let kind = if self.eat(&token::Eq) { - let ty = self.parse_assoc_equality_term(ident, self.prev_token.span)?; - AssocTyConstraintKind::Equality { ty } - } else if self.eat(&token::Colon) { - let bounds = self.parse_generic_bounds(Some(self.prev_token.span))?; - AssocTyConstraintKind::Bound { bounds } - } else { - unreachable!(); - }; + let lo = self.token.span; + let arg = self.parse_generic_arg()?; + match arg { + Some(arg) => { + if self.check(&token::Colon) | self.check(&token::Eq) { + let (ident, gen_args) = self.get_ident_from_generic_arg(arg, lo)?; + let kind = if self.eat(&token::Colon) { + // Parse associated type constraint bound. + + let bounds = self.parse_generic_bounds(Some(self.prev_token.span))?; + AssocTyConstraintKind::Bound { bounds } + } else if self.eat(&token::Eq) { + // Parse associated type equality constraint + + let ty = self.parse_assoc_equality_term(ident, self.prev_token.span)?; + AssocTyConstraintKind::Equality { ty } + } else { + unreachable!(); + }; - let span = lo.to(self.prev_token.span); + let span = lo.to(self.prev_token.span); - // Gate associated type bounds, e.g., `Iterator<Item: Ord>`. - if let AssocTyConstraintKind::Bound { .. } = kind { - self.sess.gated_spans.gate(sym::associated_type_bounds, span); + // Gate associated type bounds, e.g., `Iterator<Item: Ord>`. + if let AssocTyConstraintKind::Bound { .. } = kind { + self.sess.gated_spans.gate(sym::associated_type_bounds, span); + } + let constraint = + AssocTyConstraint { id: ast::DUMMY_NODE_ID, ident, gen_args, kind, span }; + Ok(Some(AngleBracketedArg::Constraint(constraint))) + } else { + Ok(Some(AngleBracketedArg::Arg(arg))) + } } - - let constraint = AssocTyConstraint { id: ast::DUMMY_NODE_ID, ident, kind, span }; - Ok(Some(AngleBracketedArg::Constraint(constraint))) - } else { - Ok(self.parse_generic_arg()?.map(AngleBracketedArg::Arg)) + _ => Ok(None), } } @@ -489,6 +496,7 @@ impl<'a> Parser<'a> { /// - An expression surrounded in `{}`. /// - A literal. /// - A numeric literal prefixed by `-`. + /// - A single-segment path. pub(super) fn expr_is_valid_const_arg(&self, expr: &P<rustc_ast::Expr>) -> bool { match &expr.kind { ast::ExprKind::Block(_, _) | ast::ExprKind::Lit(_) => true, @@ -496,6 +504,13 @@ impl<'a> Parser<'a> { ast::ExprKind::Lit(_) => true, _ => false, }, + // We can only resolve single-segment paths at the moment, because multi-segment paths + // require type-checking: see `visit_generic_arg` in `src/librustc_resolve/late.rs`. + ast::ExprKind::Path(None, path) + if path.segments.len() == 1 && path.segments[0].args.is_none() => + { + true + } _ => false, } } @@ -534,4 +549,54 @@ impl<'a> Parser<'a> { }; Ok(Some(arg)) } + + fn get_ident_from_generic_arg( + &self, + gen_arg: GenericArg, + lo: Span, + ) -> PResult<'a, (Ident, Option<GenericArgs>)> { + let gen_arg_span = gen_arg.span(); + match gen_arg { + GenericArg::Type(t) => match t.into_inner().kind { + ast::TyKind::Path(qself, mut path) => { + if let Some(qself) = qself { + let mut err = self.struct_span_err( + gen_arg_span, + "qualified paths cannot be used in associated type constraints", + ); + err.span_label( + qself.path_span, + "not allowed in associated type constraints", + ); + return Err(err); + } + if path.segments.len() == 1 { + let path_seg = path.segments.remove(0); + let ident = path_seg.ident; + let gen_args = path_seg.args.map(|args| args.into_inner()); + return Ok((ident, gen_args)); + } + let err = self.struct_span_err( + path.span, + "paths with multiple segments cannot be used in associated type constraints", + ); + return Err(err); + } + _ => { + let span = lo.to(self.prev_token.span); + let err = self.struct_span_err( + span, + "only path types can be used in associated type constraints", + ); + return Err(err); + } + }, + _ => { + let span = lo.to(self.prev_token.span); + let err = self + .struct_span_err(span, "only types can be used in associated type constraints"); + return Err(err); + } + } + } } |