diff options
Diffstat (limited to 'compiler/rustc_parse/src/parser/generics.rs')
| -rw-r--r-- | compiler/rustc_parse/src/parser/generics.rs | 118 |
1 files changed, 108 insertions, 10 deletions
diff --git a/compiler/rustc_parse/src/parser/generics.rs b/compiler/rustc_parse/src/parser/generics.rs index fa75670b2..8ba811715 100644 --- a/compiler/rustc_parse/src/parser/generics.rs +++ b/compiler/rustc_parse/src/parser/generics.rs @@ -1,11 +1,20 @@ +use crate::errors::{WhereClauseBeforeTupleStructBody, WhereClauseBeforeTupleStructBodySugg}; + use super::{ForceCollect, Parser, TrailingToken}; +use ast::token::Delimiter; use rustc_ast::token; use rustc_ast::{ self as ast, AttrVec, GenericBounds, GenericParam, GenericParamKind, TyKind, WhereClause, }; use rustc_errors::{Applicability, PResult}; -use rustc_span::symbol::kw; +use rustc_span::symbol::{kw, Ident}; +use rustc_span::Span; + +enum PredicateOrStructBody { + Predicate(ast::WherePredicate), + StructBody(Vec<ast::FieldDef>), +} impl<'a> Parser<'a> { /// Parses bounds of a lifetime parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`. @@ -240,23 +249,39 @@ impl<'a> Parser<'a> { }) } - /// Parses an optional where-clause and places it in `generics`. + /// Parses an optional where-clause. /// /// ```ignore (only-for-syntax-highlight) /// where T : Trait<U, V> + 'b, 'a : 'b /// ``` pub(super) fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> { + self.parse_where_clause_common(None).map(|(clause, _)| clause) + } + + pub(super) fn parse_struct_where_clause( + &mut self, + struct_name: Ident, + body_insertion_point: Span, + ) -> PResult<'a, (WhereClause, Option<Vec<ast::FieldDef>>)> { + self.parse_where_clause_common(Some((struct_name, body_insertion_point))) + } + + fn parse_where_clause_common( + &mut self, + struct_: Option<(Ident, Span)>, + ) -> PResult<'a, (WhereClause, Option<Vec<ast::FieldDef>>)> { let mut where_clause = WhereClause { has_where_token: false, predicates: Vec::new(), span: self.prev_token.span.shrink_to_hi(), }; + let mut tuple_struct_body = None; if !self.eat_keyword(kw::Where) { - return Ok(where_clause); + return Ok((where_clause, None)); } where_clause.has_where_token = true; - let lo = self.prev_token.span; + let where_lo = self.prev_token.span; // We are considering adding generics to the `where` keyword as an alternative higher-rank // parameter syntax (as in `where<'a>` or `where<T>`. To avoid that being a breaking @@ -272,7 +297,8 @@ impl<'a> Parser<'a> { } loop { - let lo = self.token.span; + let where_sp = where_lo.to(self.prev_token.span); + let pred_lo = self.token.span; if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) { let lifetime = self.expect_lifetime(); // Bounds starting with a colon are mandatory, but possibly empty. @@ -280,13 +306,21 @@ impl<'a> Parser<'a> { let bounds = self.parse_lt_param_bounds(); where_clause.predicates.push(ast::WherePredicate::RegionPredicate( ast::WhereRegionPredicate { - span: lo.to(self.prev_token.span), + span: pred_lo.to(self.prev_token.span), lifetime, bounds, }, )); } else if self.check_type() { - where_clause.predicates.push(self.parse_ty_where_predicate()?); + match self.parse_ty_where_predicate_or_recover_tuple_struct_body( + struct_, pred_lo, where_sp, + )? { + PredicateOrStructBody::Predicate(pred) => where_clause.predicates.push(pred), + PredicateOrStructBody::StructBody(body) => { + tuple_struct_body = Some(body); + break; + } + } } else { break; } @@ -297,7 +331,7 @@ impl<'a> Parser<'a> { if self.eat_keyword_noexpect(kw::Where) { let msg = "cannot define duplicate `where` clauses on an item"; let mut err = self.struct_span_err(self.token.span, msg); - err.span_label(lo, "previous `where` clause starts here"); + err.span_label(pred_lo, "previous `where` clause starts here"); err.span_suggestion_verbose( prev_token.shrink_to_hi().to(self.prev_token.span), "consider joining the two `where` clauses into one", @@ -310,8 +344,72 @@ impl<'a> Parser<'a> { } } - where_clause.span = lo.to(self.prev_token.span); - Ok(where_clause) + where_clause.span = where_lo.to(self.prev_token.span); + Ok((where_clause, tuple_struct_body)) + } + + fn parse_ty_where_predicate_or_recover_tuple_struct_body( + &mut self, + struct_: Option<(Ident, Span)>, + pred_lo: Span, + where_sp: Span, + ) -> PResult<'a, PredicateOrStructBody> { + let mut snapshot = None; + + if let Some(struct_) = struct_ + && self.may_recover() + && self.token.kind == token::OpenDelim(Delimiter::Parenthesis) + { + snapshot = Some((struct_, self.create_snapshot_for_diagnostic())); + }; + + match self.parse_ty_where_predicate() { + Ok(pred) => Ok(PredicateOrStructBody::Predicate(pred)), + Err(type_err) => { + let Some(((struct_name, body_insertion_point), mut snapshot)) = snapshot else { + return Err(type_err); + }; + + // Check if we might have encountered an out of place tuple struct body. + match snapshot.parse_tuple_struct_body() { + // Since we don't know the exact reason why we failed to parse the + // predicate (we might have stumbled upon something bogus like `(T): ?`), + // employ a simple heuristic to weed out some pathological cases: + // Look for a semicolon (strong indicator) or anything that might mark + // the end of the item (weak indicator) following the body. + Ok(body) + if matches!(snapshot.token.kind, token::Semi | token::Eof) + || snapshot.token.can_begin_item() => + { + type_err.cancel(); + + let body_sp = pred_lo.to(snapshot.prev_token.span); + let map = self.sess.source_map(); + + self.sess.emit_err(WhereClauseBeforeTupleStructBody { + span: where_sp, + name: struct_name.span, + body: body_sp, + sugg: map.span_to_snippet(body_sp).ok().map(|body| { + WhereClauseBeforeTupleStructBodySugg { + left: body_insertion_point.shrink_to_hi(), + snippet: body, + right: map.end_point(where_sp).to(body_sp), + } + }), + }); + + self.restore_snapshot(snapshot); + Ok(PredicateOrStructBody::StructBody(body)) + } + Ok(_) => Err(type_err), + Err(body_err) => { + body_err.cancel(); + Err(type_err) + } + } + } + } } fn parse_ty_where_predicate(&mut self) -> PResult<'a, ast::WherePredicate> { |