| use super::{Parser, PathStyle, TokenType}; |
| |
| use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole}; |
| |
| use rustc_ast::ptr::P; |
| use rustc_ast::token::{self, Token, TokenKind}; |
| use rustc_ast::{self as ast, BareFnTy, FnRetTy, GenericParam, Lifetime, MutTy, Ty, TyKind}; |
| use rustc_ast::{GenericBound, GenericBounds, MacCall, Mutability}; |
| use rustc_ast::{PolyTraitRef, TraitBoundModifier, TraitObjectSyntax}; |
| use rustc_errors::{pluralize, struct_span_err, Applicability, PResult}; |
| use rustc_span::source_map::Span; |
| use rustc_span::symbol::{kw, sym}; |
| |
| /// Any `?` or `?const` modifiers that appear at the start of a bound. |
| struct BoundModifiers { |
| /// `?Trait`. |
| maybe: Option<Span>, |
| |
| /// `?const Trait`. |
| maybe_const: Option<Span>, |
| } |
| |
| impl BoundModifiers { |
| fn to_trait_bound_modifier(&self) -> TraitBoundModifier { |
| match (self.maybe, self.maybe_const) { |
| (None, None) => TraitBoundModifier::None, |
| (Some(_), None) => TraitBoundModifier::Maybe, |
| (None, Some(_)) => TraitBoundModifier::MaybeConst, |
| (Some(_), Some(_)) => TraitBoundModifier::MaybeConstMaybe, |
| } |
| } |
| } |
| |
| #[derive(Copy, Clone, PartialEq)] |
| pub(super) enum AllowPlus { |
| Yes, |
| No, |
| } |
| |
| #[derive(PartialEq)] |
| pub(super) enum RecoverQPath { |
| Yes, |
| No, |
| } |
| |
| /// Signals whether parsing a type should recover `->`. |
| /// |
| /// More specifically, when parsing a function like: |
| /// ```rust |
| /// fn foo() => u8 { 0 } |
| /// fn bar(): u8 { 0 } |
| /// ``` |
| /// The compiler will try to recover interpreting `foo() => u8` as `foo() -> u8` when calling |
| /// `parse_ty` with anything except `RecoverReturnSign::No`, and it will try to recover `bar(): u8` |
| /// as `bar() -> u8` when passing `RecoverReturnSign::Yes` to `parse_ty` |
| #[derive(Copy, Clone, PartialEq)] |
| pub(super) enum RecoverReturnSign { |
| Yes, |
| OnlyFatArrow, |
| No, |
| } |
| |
| impl RecoverReturnSign { |
| /// [RecoverReturnSign::Yes] allows for recovering `fn foo() => u8` and `fn foo(): u8`, |
| /// [RecoverReturnSign::OnlyFatArrow] allows for recovering only `fn foo() => u8` (recovering |
| /// colons can cause problems when parsing where clauses), and |
| /// [RecoverReturnSign::No] doesn't allow for any recovery of the return type arrow |
| fn can_recover(self, token: &TokenKind) -> bool { |
| match self { |
| Self::Yes => matches!(token, token::FatArrow | token::Colon), |
| Self::OnlyFatArrow => matches!(token, token::FatArrow), |
| Self::No => false, |
| } |
| } |
| } |
| |
| // Is `...` (`CVarArgs`) legal at this level of type parsing? |
| #[derive(PartialEq)] |
| enum AllowCVariadic { |
| Yes, |
| No, |
| } |
| |
| /// 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) -> bool { |
| t == &token::ModSep || t == &token::Lt || t == &token::BinOp(token::Shl) |
| } |
| |
| impl<'a> Parser<'a> { |
| /// Parses a type. |
| pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> { |
| self.parse_ty_common( |
| AllowPlus::Yes, |
| AllowCVariadic::No, |
| RecoverQPath::Yes, |
| RecoverReturnSign::Yes, |
| ) |
| } |
| |
| /// Parse a type suitable for a function or function pointer parameter. |
| /// The difference from `parse_ty` is that this version allows `...` |
| /// (`CVarArgs`) at the top level of the type. |
| pub(super) fn parse_ty_for_param(&mut self) -> PResult<'a, P<Ty>> { |
| self.parse_ty_common( |
| AllowPlus::Yes, |
| AllowCVariadic::Yes, |
| RecoverQPath::Yes, |
| RecoverReturnSign::Yes, |
| ) |
| } |
| |
| /// Parses a type in restricted contexts where `+` is not permitted. |
| /// |
| /// Example 1: `&'a TYPE` |
| /// `+` is prohibited to maintain operator priority (P(+) < P(&)). |
| /// Example 2: `value1 as TYPE + value2` |
| /// `+` is prohibited to avoid interactions with expression grammar. |
| pub(super) fn parse_ty_no_plus(&mut self) -> PResult<'a, P<Ty>> { |
| self.parse_ty_common( |
| AllowPlus::No, |
| AllowCVariadic::No, |
| RecoverQPath::Yes, |
| RecoverReturnSign::Yes, |
| ) |
| } |
| |
| /// Parse a type without recovering `:` as `->` to avoid breaking code such as `where fn() : for<'a>` |
| pub(super) fn parse_ty_for_where_clause(&mut self) -> PResult<'a, P<Ty>> { |
| self.parse_ty_common( |
| AllowPlus::Yes, |
| AllowCVariadic::Yes, |
| RecoverQPath::Yes, |
| RecoverReturnSign::OnlyFatArrow, |
| ) |
| } |
| |
| /// Parses an optional return type `[ -> TY ]` in a function declaration. |
| pub(super) fn parse_ret_ty( |
| &mut self, |
| allow_plus: AllowPlus, |
| recover_qpath: RecoverQPath, |
| recover_return_sign: RecoverReturnSign, |
| ) -> PResult<'a, FnRetTy> { |
| Ok(if self.eat(&token::RArrow) { |
| // FIXME(Centril): Can we unconditionally `allow_plus`? |
| let ty = self.parse_ty_common( |
| allow_plus, |
| AllowCVariadic::No, |
| recover_qpath, |
| recover_return_sign, |
| )?; |
| FnRetTy::Ty(ty) |
| } else if recover_return_sign.can_recover(&self.token.kind) { |
| // Don't `eat` to prevent `=>` from being added as an expected token which isn't |
| // actually expected and could only confuse users |
| self.bump(); |
| self.struct_span_err(self.prev_token.span, "return types are denoted using `->`") |
| .span_suggestion_short( |
| self.prev_token.span, |
| "use `->` instead", |
| "->".to_string(), |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| let ty = self.parse_ty_common( |
| allow_plus, |
| AllowCVariadic::No, |
| recover_qpath, |
| recover_return_sign, |
| )?; |
| FnRetTy::Ty(ty) |
| } else { |
| FnRetTy::Default(self.token.span.shrink_to_lo()) |
| }) |
| } |
| |
| fn parse_ty_common( |
| &mut self, |
| allow_plus: AllowPlus, |
| allow_c_variadic: AllowCVariadic, |
| recover_qpath: RecoverQPath, |
| recover_return_sign: RecoverReturnSign, |
| ) -> PResult<'a, P<Ty>> { |
| let allow_qpath_recovery = recover_qpath == RecoverQPath::Yes; |
| maybe_recover_from_interpolated_ty_qpath!(self, allow_qpath_recovery); |
| maybe_whole!(self, NtTy, |x| x); |
| |
| let lo = self.token.span; |
| let mut impl_dyn_multi = false; |
| let kind = if self.check(&token::OpenDelim(token::Paren)) { |
| self.parse_ty_tuple_or_parens(lo, allow_plus)? |
| } else if self.eat(&token::Not) { |
| // Never type `!` |
| TyKind::Never |
| } else if self.eat(&token::BinOp(token::Star)) { |
| self.parse_ty_ptr()? |
| } else if self.eat(&token::OpenDelim(token::Bracket)) { |
| self.parse_array_or_slice_ty()? |
| } else if self.check(&token::BinOp(token::And)) || self.check(&token::AndAnd) { |
| // Reference |
| self.expect_and()?; |
| self.parse_borrowed_pointee()? |
| } else if self.eat_keyword_noexpect(kw::Typeof) { |
| self.parse_typeof_ty()? |
| } else if self.eat_keyword(kw::Underscore) { |
| // A type to be inferred `_` |
| TyKind::Infer |
| } else if self.check_fn_front_matter(false) { |
| // Function pointer type |
| self.parse_ty_bare_fn(lo, Vec::new(), recover_return_sign)? |
| } else if self.check_keyword(kw::For) { |
| // Function pointer type or bound list (trait object type) starting with a poly-trait. |
| // `for<'lt> [unsafe] [extern "ABI"] fn (&'lt S) -> T` |
| // `for<'lt> Trait1<'lt> + Trait2 + 'a` |
| let lifetime_defs = self.parse_late_bound_lifetime_defs()?; |
| if self.check_fn_front_matter(false) { |
| self.parse_ty_bare_fn(lo, lifetime_defs, recover_return_sign)? |
| } else { |
| let path = self.parse_path(PathStyle::Type)?; |
| let parse_plus = allow_plus == AllowPlus::Yes && self.check_plus(); |
| self.parse_remaining_bounds_path(lifetime_defs, path, lo, parse_plus)? |
| } |
| } else if self.eat_keyword(kw::Impl) { |
| self.parse_impl_ty(&mut impl_dyn_multi)? |
| } else if self.token.is_keyword(kw::Union) |
| && self.look_ahead(1, |t| t == &token::OpenDelim(token::Brace)) |
| { |
| self.bump(); |
| let (fields, recovered) = self.parse_record_struct_body("union")?; |
| let span = lo.to(self.prev_token.span); |
| self.sess.gated_spans.gate(sym::unnamed_fields, span); |
| TyKind::AnonymousUnion(fields, recovered) |
| } else if self.eat_keyword(kw::Struct) { |
| let (fields, recovered) = self.parse_record_struct_body("struct")?; |
| let span = lo.to(self.prev_token.span); |
| self.sess.gated_spans.gate(sym::unnamed_fields, span); |
| TyKind::AnonymousStruct(fields, recovered) |
| } else if self.is_explicit_dyn_type() { |
| self.parse_dyn_ty(&mut impl_dyn_multi)? |
| } else if self.eat_lt() { |
| // Qualified path |
| let (qself, path) = self.parse_qpath(PathStyle::Type)?; |
| TyKind::Path(Some(qself), path) |
| } else if self.check_path() { |
| self.parse_path_start_ty(lo, allow_plus)? |
| } else if self.can_begin_bound() { |
| self.parse_bare_trait_object(lo, allow_plus)? |
| } else if self.eat(&token::DotDotDot) { |
| if allow_c_variadic == AllowCVariadic::Yes { |
| TyKind::CVarArgs |
| } else { |
| // FIXME(Centril): Should we just allow `...` syntactically |
| // anywhere in a type and use semantic restrictions instead? |
| self.error_illegal_c_varadic_ty(lo); |
| TyKind::Err |
| } |
| } else { |
| let msg = format!("expected type, found {}", super::token_descr(&self.token)); |
| let mut err = self.struct_span_err(self.token.span, &msg); |
| err.span_label(self.token.span, "expected type"); |
| self.maybe_annotate_with_ascription(&mut err, true); |
| return Err(err); |
| }; |
| |
| let span = lo.to(self.prev_token.span); |
| let ty = self.mk_ty(span, kind); |
| |
| // Try to recover from use of `+` with incorrect priority. |
| self.maybe_report_ambiguous_plus(allow_plus, impl_dyn_multi, &ty); |
| self.maybe_recover_from_bad_type_plus(allow_plus, &ty)?; |
| self.maybe_recover_from_bad_qpath(ty, allow_qpath_recovery) |
| } |
| |
| /// Parses either: |
| /// - `(TYPE)`, a parenthesized type. |
| /// - `(TYPE,)`, a tuple with a single field of type TYPE. |
| fn parse_ty_tuple_or_parens(&mut self, lo: Span, allow_plus: AllowPlus) -> PResult<'a, TyKind> { |
| let mut trailing_plus = false; |
| let (ts, trailing) = self.parse_paren_comma_seq(|p| { |
| let ty = p.parse_ty()?; |
| trailing_plus = p.prev_token.kind == TokenKind::BinOp(token::Plus); |
| Ok(ty) |
| })?; |
| |
| if ts.len() == 1 && !trailing { |
| let ty = ts.into_iter().next().unwrap().into_inner(); |
| let maybe_bounds = allow_plus == AllowPlus::Yes && self.token.is_like_plus(); |
| match ty.kind { |
| // `(TY_BOUND_NOPAREN) + BOUND + ...`. |
| TyKind::Path(None, path) if maybe_bounds => { |
| self.parse_remaining_bounds_path(Vec::new(), path, lo, true) |
| } |
| TyKind::TraitObject(bounds, TraitObjectSyntax::None) |
| if maybe_bounds && bounds.len() == 1 && !trailing_plus => |
| { |
| self.parse_remaining_bounds(bounds, true) |
| } |
| // `(TYPE)` |
| _ => Ok(TyKind::Paren(P(ty))), |
| } |
| } else { |
| Ok(TyKind::Tup(ts)) |
| } |
| } |
| |
| fn parse_bare_trait_object(&mut self, lo: Span, allow_plus: AllowPlus) -> PResult<'a, TyKind> { |
| let lt_no_plus = self.check_lifetime() && !self.look_ahead(1, |t| t.is_like_plus()); |
| let bounds = self.parse_generic_bounds_common(allow_plus, None)?; |
| if lt_no_plus { |
| self.struct_span_err(lo, "lifetime in trait object type must be followed by `+`").emit() |
| } |
| Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None)) |
| } |
| |
| fn parse_remaining_bounds_path( |
| &mut self, |
| generic_params: Vec<GenericParam>, |
| path: ast::Path, |
| lo: Span, |
| parse_plus: bool, |
| ) -> PResult<'a, TyKind> { |
| let poly_trait_ref = PolyTraitRef::new(generic_params, path, lo.to(self.prev_token.span)); |
| let bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)]; |
| self.parse_remaining_bounds(bounds, parse_plus) |
| } |
| |
| /// Parse the remainder of a bare trait object type given an already parsed list. |
| fn parse_remaining_bounds( |
| &mut self, |
| mut bounds: GenericBounds, |
| plus: bool, |
| ) -> PResult<'a, TyKind> { |
| if plus { |
| self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded |
| bounds.append(&mut self.parse_generic_bounds(Some(self.prev_token.span))?); |
| } |
| Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None)) |
| } |
| |
| /// Parses a raw pointer type: `*[const | mut] $type`. |
| fn parse_ty_ptr(&mut self) -> PResult<'a, TyKind> { |
| let mutbl = self.parse_const_or_mut().unwrap_or_else(|| { |
| let span = self.prev_token.span; |
| let msg = "expected mut or const in raw pointer type"; |
| self.struct_span_err(span, msg) |
| .span_label(span, msg) |
| .help("use `*mut T` or `*const T` as appropriate") |
| .emit(); |
| Mutability::Not |
| }); |
| let ty = self.parse_ty_no_plus()?; |
| Ok(TyKind::Ptr(MutTy { ty, mutbl })) |
| } |
| |
| /// Parses an array (`[TYPE; EXPR]`) or slice (`[TYPE]`) type. |
| /// The opening `[` bracket is already eaten. |
| fn parse_array_or_slice_ty(&mut self) -> PResult<'a, TyKind> { |
| let elt_ty = match self.parse_ty() { |
| Ok(ty) => ty, |
| Err(mut err) |
| if self.look_ahead(1, |t| t.kind == token::CloseDelim(token::Bracket)) |
| | self.look_ahead(1, |t| t.kind == token::Semi) => |
| { |
| // Recover from `[LIT; EXPR]` and `[LIT]` |
| self.bump(); |
| err.emit(); |
| self.mk_ty(self.prev_token.span, TyKind::Err) |
| } |
| Err(err) => return Err(err), |
| }; |
| |
| let ty = if self.eat(&token::Semi) { |
| let mut length = self.parse_anon_const_expr()?; |
| if let Err(e) = self.expect(&token::CloseDelim(token::Bracket)) { |
| // Try to recover from `X<Y, ...>` when `X::<Y, ...>` works |
| self.check_mistyped_turbofish_with_multiple_type_params(e, &mut length.value)?; |
| self.expect(&token::CloseDelim(token::Bracket))?; |
| } |
| TyKind::Array(elt_ty, length) |
| } else { |
| self.expect(&token::CloseDelim(token::Bracket))?; |
| TyKind::Slice(elt_ty) |
| }; |
| |
| Ok(ty) |
| } |
| |
| fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> { |
| let and_span = self.prev_token.span; |
| let mut opt_lifetime = |
| if self.check_lifetime() { Some(self.expect_lifetime()) } else { None }; |
| let mut mutbl = self.parse_mutability(); |
| if self.token.is_lifetime() && mutbl == Mutability::Mut && opt_lifetime.is_none() { |
| // A lifetime is invalid here: it would be part of a bare trait bound, which requires |
| // it to be followed by a plus, but we disallow plus in the pointee type. |
| // So we can handle this case as an error here, and suggest `'a mut`. |
| // If there *is* a plus next though, handling the error later provides better suggestions |
| // (like adding parentheses) |
| if !self.look_ahead(1, |t| t.is_like_plus()) { |
| let lifetime_span = self.token.span; |
| let span = and_span.to(lifetime_span); |
| |
| let mut err = self.struct_span_err(span, "lifetime must precede `mut`"); |
| if let Ok(lifetime_src) = self.span_to_snippet(lifetime_span) { |
| err.span_suggestion( |
| span, |
| "place the lifetime before `mut`", |
| format!("&{} mut", lifetime_src), |
| Applicability::MaybeIncorrect, |
| ); |
| } |
| err.emit(); |
| |
| opt_lifetime = Some(self.expect_lifetime()); |
| } |
| } else if self.token.is_keyword(kw::Dyn) |
| && mutbl == Mutability::Not |
| && self.look_ahead(1, |t| t.is_keyword(kw::Mut)) |
| { |
| // We have `&dyn mut ...`, which is invalid and should be `&mut dyn ...`. |
| let span = and_span.to(self.look_ahead(1, |t| t.span)); |
| let mut err = self.struct_span_err(span, "`mut` must precede `dyn`"); |
| err.span_suggestion( |
| span, |
| "place `mut` before `dyn`", |
| "&mut dyn".to_string(), |
| Applicability::MachineApplicable, |
| ); |
| err.emit(); |
| |
| // Recovery |
| mutbl = Mutability::Mut; |
| let (dyn_tok, dyn_tok_sp) = (self.token.clone(), self.token_spacing); |
| self.bump(); |
| self.bump_with((dyn_tok, dyn_tok_sp)); |
| } |
| let ty = self.parse_ty_no_plus()?; |
| Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl })) |
| } |
| |
| // Parses the `typeof(EXPR)`. |
| // To avoid ambiguity, the type is surrounded by parenthesis. |
| fn parse_typeof_ty(&mut self) -> PResult<'a, TyKind> { |
| self.expect(&token::OpenDelim(token::Paren))?; |
| let expr = self.parse_anon_const_expr()?; |
| self.expect(&token::CloseDelim(token::Paren))?; |
| Ok(TyKind::Typeof(expr)) |
| } |
| |
| /// Parses a function pointer type (`TyKind::BareFn`). |
| /// ``` |
| /// [unsafe] [extern "ABI"] fn (S) -> T |
| /// ^~~~~^ ^~~~^ ^~^ ^ |
| /// | | | | |
| /// | | | Return type |
| /// Function Style ABI Parameter types |
| /// ``` |
| /// We actually parse `FnHeader FnDecl`, but we error on `const` and `async` qualifiers. |
| fn parse_ty_bare_fn( |
| &mut self, |
| lo: Span, |
| params: Vec<GenericParam>, |
| recover_return_sign: RecoverReturnSign, |
| ) -> PResult<'a, TyKind> { |
| let ast::FnHeader { ext, unsafety, constness, asyncness } = self.parse_fn_front_matter()?; |
| let decl = self.parse_fn_decl(|_| false, AllowPlus::No, recover_return_sign)?; |
| let whole_span = lo.to(self.prev_token.span); |
| if let ast::Const::Yes(span) = constness { |
| self.error_fn_ptr_bad_qualifier(whole_span, span, "const"); |
| } |
| if let ast::Async::Yes { span, .. } = asyncness { |
| self.error_fn_ptr_bad_qualifier(whole_span, span, "async"); |
| } |
| Ok(TyKind::BareFn(P(BareFnTy { ext, unsafety, generic_params: params, decl }))) |
| } |
| |
| /// Emit an error for the given bad function pointer qualifier. |
| fn error_fn_ptr_bad_qualifier(&self, span: Span, qual_span: Span, qual: &str) { |
| self.struct_span_err(span, &format!("an `fn` pointer type cannot be `{}`", qual)) |
| .span_label(qual_span, format!("`{}` because of this", qual)) |
| .span_suggestion_short( |
| qual_span, |
| &format!("remove the `{}` qualifier", qual), |
| String::new(), |
| Applicability::MaybeIncorrect, |
| ) |
| .emit(); |
| } |
| |
| /// Parses an `impl B0 + ... + Bn` type. |
| fn parse_impl_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> { |
| // Always parse bounds greedily for better error recovery. |
| let bounds = self.parse_generic_bounds(None)?; |
| *impl_dyn_multi = bounds.len() > 1 || self.prev_token.kind == TokenKind::BinOp(token::Plus); |
| Ok(TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds)) |
| } |
| |
| /// Is a `dyn B0 + ... + Bn` type allowed here? |
| fn is_explicit_dyn_type(&mut self) -> bool { |
| self.check_keyword(kw::Dyn) |
| && (!self.token.uninterpolated_span().rust_2015() |
| || self.look_ahead(1, |t| { |
| t.can_begin_bound() && !can_continue_type_after_non_fn_ident(t) |
| })) |
| } |
| |
| /// Parses a `dyn B0 + ... + Bn` type. |
| /// |
| /// Note that this does *not* parse bare trait objects. |
| fn parse_dyn_ty(&mut self, impl_dyn_multi: &mut bool) -> PResult<'a, TyKind> { |
| self.bump(); // `dyn` |
| // Always parse bounds greedily for better error recovery. |
| let bounds = self.parse_generic_bounds(None)?; |
| *impl_dyn_multi = bounds.len() > 1 || self.prev_token.kind == TokenKind::BinOp(token::Plus); |
| Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn)) |
| } |
| |
| /// Parses a type starting with a path. |
| /// |
| /// This can be: |
| /// 1. a type macro, `mac!(...)`, |
| /// 2. a bare trait object, `B0 + ... + Bn`, |
| /// 3. or a path, `path::to::MyType`. |
| fn parse_path_start_ty(&mut self, lo: Span, allow_plus: AllowPlus) -> PResult<'a, TyKind> { |
| // Simple path |
| let path = self.parse_path(PathStyle::Type)?; |
| if self.eat(&token::Not) { |
| // Macro invocation in type position |
| Ok(TyKind::MacCall(MacCall { |
| path, |
| args: self.parse_mac_args()?, |
| prior_type_ascription: self.last_type_ascription, |
| })) |
| } else if allow_plus == AllowPlus::Yes && self.check_plus() { |
| // `Trait1 + Trait2 + 'a` |
| self.parse_remaining_bounds_path(Vec::new(), path, lo, true) |
| } else { |
| // Just a type path. |
| Ok(TyKind::Path(None, path)) |
| } |
| } |
| |
| fn error_illegal_c_varadic_ty(&self, lo: Span) { |
| struct_span_err!( |
| self.sess.span_diagnostic, |
| lo.to(self.prev_token.span), |
| E0743, |
| "C-variadic type `...` may not be nested inside another type", |
| ) |
| .emit(); |
| } |
| |
| pub(super) fn parse_generic_bounds( |
| &mut self, |
| colon_span: Option<Span>, |
| ) -> PResult<'a, GenericBounds> { |
| self.parse_generic_bounds_common(AllowPlus::Yes, colon_span) |
| } |
| |
| /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`. |
| /// |
| /// See `parse_generic_bound` for the `BOUND` grammar. |
| fn parse_generic_bounds_common( |
| &mut self, |
| allow_plus: AllowPlus, |
| colon_span: Option<Span>, |
| ) -> PResult<'a, GenericBounds> { |
| let mut bounds = Vec::new(); |
| let mut negative_bounds = Vec::new(); |
| |
| while self.can_begin_bound() || self.token.is_keyword(kw::Dyn) { |
| if self.token.is_keyword(kw::Dyn) { |
| // Account for `&dyn Trait + dyn Other`. |
| self.struct_span_err(self.token.span, "invalid `dyn` keyword") |
| .help("`dyn` is only needed at the start of a trait `+`-separated list") |
| .span_suggestion( |
| self.token.span, |
| "remove this keyword", |
| String::new(), |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| self.bump(); |
| } |
| match self.parse_generic_bound()? { |
| Ok(bound) => bounds.push(bound), |
| Err(neg_sp) => negative_bounds.push(neg_sp), |
| } |
| if allow_plus == AllowPlus::No || !self.eat_plus() { |
| break; |
| } |
| } |
| |
| if !negative_bounds.is_empty() { |
| self.error_negative_bounds(colon_span, &bounds, negative_bounds); |
| } |
| |
| Ok(bounds) |
| } |
| |
| /// Can the current token begin a bound? |
| fn can_begin_bound(&mut self) -> bool { |
| // This needs to be synchronized with `TokenKind::can_begin_bound`. |
| self.check_path() |
| || self.check_lifetime() |
| || self.check(&token::Not) // Used for error reporting only. |
| || self.check(&token::Question) |
| || self.check_keyword(kw::For) |
| || self.check(&token::OpenDelim(token::Paren)) |
| } |
| |
| fn error_negative_bounds( |
| &self, |
| colon_span: Option<Span>, |
| bounds: &[GenericBound], |
| negative_bounds: Vec<Span>, |
| ) { |
| let negative_bounds_len = negative_bounds.len(); |
| let last_span = *negative_bounds.last().expect("no negative bounds, but still error?"); |
| let mut err = self.struct_span_err(negative_bounds, "negative bounds are not supported"); |
| err.span_label(last_span, "negative bounds are not supported"); |
| if let Some(bound_list) = colon_span { |
| let bound_list = bound_list.to(self.prev_token.span); |
| let mut new_bound_list = String::new(); |
| if !bounds.is_empty() { |
| let mut snippets = bounds.iter().map(|bound| self.span_to_snippet(bound.span())); |
| while let Some(Ok(snippet)) = snippets.next() { |
| new_bound_list.push_str(" + "); |
| new_bound_list.push_str(&snippet); |
| } |
| new_bound_list = new_bound_list.replacen(" +", ":", 1); |
| } |
| err.tool_only_span_suggestion( |
| bound_list, |
| &format!("remove the bound{}", pluralize!(negative_bounds_len)), |
| new_bound_list, |
| Applicability::MachineApplicable, |
| ); |
| } |
| err.emit(); |
| } |
| |
| /// Parses a bound according to the grammar: |
| /// ``` |
| /// BOUND = TY_BOUND | LT_BOUND |
| /// ``` |
| fn parse_generic_bound(&mut self) -> PResult<'a, Result<GenericBound, Span>> { |
| let anchor_lo = self.prev_token.span; |
| let lo = self.token.span; |
| let has_parens = self.eat(&token::OpenDelim(token::Paren)); |
| let inner_lo = self.token.span; |
| let is_negative = self.eat(&token::Not); |
| |
| let modifiers = self.parse_ty_bound_modifiers(); |
| let bound = if self.token.is_lifetime() { |
| self.error_lt_bound_with_modifiers(modifiers); |
| self.parse_generic_lt_bound(lo, inner_lo, has_parens)? |
| } else { |
| self.parse_generic_ty_bound(lo, has_parens, modifiers)? |
| }; |
| |
| Ok(if is_negative { Err(anchor_lo.to(self.prev_token.span)) } else { Ok(bound) }) |
| } |
| |
| /// Parses a lifetime ("outlives") bound, e.g. `'a`, according to: |
| /// ``` |
| /// LT_BOUND = LIFETIME |
| /// ``` |
| fn parse_generic_lt_bound( |
| &mut self, |
| lo: Span, |
| inner_lo: Span, |
| has_parens: bool, |
| ) -> PResult<'a, GenericBound> { |
| let bound = GenericBound::Outlives(self.expect_lifetime()); |
| if has_parens { |
| // FIXME(Centril): Consider not erroring here and accepting `('lt)` instead, |
| // possibly introducing `GenericBound::Paren(P<GenericBound>)`? |
| self.recover_paren_lifetime(lo, inner_lo)?; |
| } |
| Ok(bound) |
| } |
| |
| /// Emits an error if any trait bound modifiers were present. |
| fn error_lt_bound_with_modifiers(&self, modifiers: BoundModifiers) { |
| if let Some(span) = modifiers.maybe_const { |
| self.struct_span_err( |
| span, |
| "`?const` may only modify trait bounds, not lifetime bounds", |
| ) |
| .emit(); |
| } |
| |
| if let Some(span) = modifiers.maybe { |
| self.struct_span_err(span, "`?` may only modify trait bounds, not lifetime bounds") |
| .emit(); |
| } |
| } |
| |
| /// Recover on `('lifetime)` with `(` already eaten. |
| fn recover_paren_lifetime(&mut self, lo: Span, inner_lo: Span) -> PResult<'a, ()> { |
| let inner_span = inner_lo.to(self.prev_token.span); |
| self.expect(&token::CloseDelim(token::Paren))?; |
| let mut err = self.struct_span_err( |
| lo.to(self.prev_token.span), |
| "parenthesized lifetime bounds are not supported", |
| ); |
| if let Ok(snippet) = self.span_to_snippet(inner_span) { |
| err.span_suggestion_short( |
| lo.to(self.prev_token.span), |
| "remove the parentheses", |
| snippet, |
| Applicability::MachineApplicable, |
| ); |
| } |
| err.emit(); |
| Ok(()) |
| } |
| |
| /// Parses the modifiers that may precede a trait in a bound, e.g. `?Trait` or `?const Trait`. |
| /// |
| /// If no modifiers are present, this does not consume any tokens. |
| /// |
| /// ``` |
| /// TY_BOUND_MODIFIERS = "?" ["const" ["?"]] |
| /// ``` |
| fn parse_ty_bound_modifiers(&mut self) -> BoundModifiers { |
| if !self.eat(&token::Question) { |
| return BoundModifiers { maybe: None, maybe_const: None }; |
| } |
| |
| // `? ...` |
| let first_question = self.prev_token.span; |
| if !self.eat_keyword(kw::Const) { |
| return BoundModifiers { maybe: Some(first_question), maybe_const: None }; |
| } |
| |
| // `?const ...` |
| let maybe_const = first_question.to(self.prev_token.span); |
| self.sess.gated_spans.gate(sym::const_trait_bound_opt_out, maybe_const); |
| if !self.eat(&token::Question) { |
| return BoundModifiers { maybe: None, maybe_const: Some(maybe_const) }; |
| } |
| |
| // `?const ? ...` |
| let second_question = self.prev_token.span; |
| BoundModifiers { maybe: Some(second_question), maybe_const: Some(maybe_const) } |
| } |
| |
| /// Parses a type bound according to: |
| /// ``` |
| /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN) |
| /// TY_BOUND_NOPAREN = [TY_BOUND_MODIFIERS] [for<LT_PARAM_DEFS>] SIMPLE_PATH |
| /// ``` |
| /// |
| /// For example, this grammar accepts `?const ?for<'a: 'b> m::Trait<'a>`. |
| fn parse_generic_ty_bound( |
| &mut self, |
| lo: Span, |
| has_parens: bool, |
| modifiers: BoundModifiers, |
| ) -> PResult<'a, GenericBound> { |
| let lifetime_defs = self.parse_late_bound_lifetime_defs()?; |
| let path = self.parse_path(PathStyle::Type)?; |
| if has_parens { |
| if self.token.is_like_plus() { |
| // Someone has written something like `&dyn (Trait + Other)`. The correct code |
| // would be `&(dyn Trait + Other)`, but we don't have access to the appropriate |
| // span to suggest that. When written as `&dyn Trait + Other`, an appropriate |
| // suggestion is given. |
| let bounds = vec![]; |
| self.parse_remaining_bounds(bounds, true)?; |
| self.expect(&token::CloseDelim(token::Paren))?; |
| let sp = vec![lo, self.prev_token.span]; |
| let sugg: Vec<_> = sp.iter().map(|sp| (*sp, String::new())).collect(); |
| self.struct_span_err(sp, "incorrect braces around trait bounds") |
| .multipart_suggestion( |
| "remove the parentheses", |
| sugg, |
| Applicability::MachineApplicable, |
| ) |
| .emit(); |
| } else { |
| self.expect(&token::CloseDelim(token::Paren))?; |
| } |
| } |
| |
| let modifier = modifiers.to_trait_bound_modifier(); |
| let poly_trait = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_token.span)); |
| Ok(GenericBound::Trait(poly_trait, modifier)) |
| } |
| |
| /// Optionally parses `for<$generic_params>`. |
| pub(super) fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<GenericParam>> { |
| if self.eat_keyword(kw::For) { |
| self.expect_lt()?; |
| let params = self.parse_generic_params()?; |
| self.expect_gt()?; |
| // We rely on AST validation to rule out invalid cases: There must not be type |
| // parameters, and the lifetime parameters must not have bounds. |
| Ok(params) |
| } else { |
| Ok(Vec::new()) |
| } |
| } |
| |
| pub(super) fn check_lifetime(&mut self) -> bool { |
| self.expected_tokens.push(TokenType::Lifetime); |
| self.token.is_lifetime() |
| } |
| |
| /// Parses a single lifetime `'a` or panics. |
| pub(super) fn expect_lifetime(&mut self) -> Lifetime { |
| if let Some(ident) = self.token.lifetime() { |
| self.bump(); |
| Lifetime { ident, id: ast::DUMMY_NODE_ID } |
| } else { |
| self.span_bug(self.token.span, "not a lifetime") |
| } |
| } |
| |
| pub(super) fn mk_ty(&self, span: Span, kind: TyKind) -> P<Ty> { |
| P(Ty { kind, span, id: ast::DUMMY_NODE_ID, tokens: None }) |
| } |
| } |
