| use super::{Parser, PResult, PathStyle, PrevTokenKind, TokenType}; |
| |
| use crate::{maybe_whole, maybe_recover_from_interpolated_ty_qpath}; |
| use crate::ptr::P; |
| use crate::ast::{self, Ty, TyKind, MutTy, BareFnTy, FunctionRetTy, GenericParam, Lifetime, Ident}; |
| use crate::ast::{TraitBoundModifier, TraitObjectSyntax, GenericBound, GenericBounds, PolyTraitRef}; |
| use crate::ast::{Mutability, AnonConst, FnDecl, Mac_}; |
| use crate::parse::token::{self, Token}; |
| use crate::source_map::{respan, Span}; |
| use crate::symbol::{kw}; |
| |
| use rustc_target::spec::abi::Abi; |
| |
| use errors::{Applicability}; |
| |
| /// 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(true, true, false) |
| } |
| |
| /// 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(false, true, false) |
| } |
| |
| /// Parses an optional return type `[ -> TY ]` in a function declaration. |
| pub(super) fn parse_ret_ty(&mut self, allow_plus: bool) -> PResult<'a, FunctionRetTy> { |
| if self.eat(&token::RArrow) { |
| Ok(FunctionRetTy::Ty(self.parse_ty_common(allow_plus, true, false)?)) |
| } else { |
| Ok(FunctionRetTy::Default(self.token.span.shrink_to_lo())) |
| } |
| } |
| |
| pub(super) fn parse_ty_common(&mut self, allow_plus: bool, allow_qpath_recovery: bool, |
| allow_c_variadic: bool) -> PResult<'a, P<Ty>> { |
| 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 node = if self.eat(&token::OpenDelim(token::Paren)) { |
| // `(TYPE)` is a parenthesized type. |
| // `(TYPE,)` is a tuple with a single field of type TYPE. |
| let mut ts = vec![]; |
| let mut last_comma = false; |
| while self.token != token::CloseDelim(token::Paren) { |
| ts.push(self.parse_ty()?); |
| if self.eat(&token::Comma) { |
| last_comma = true; |
| } else { |
| last_comma = false; |
| break; |
| } |
| } |
| let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus; |
| self.expect(&token::CloseDelim(token::Paren))?; |
| |
| if ts.len() == 1 && !last_comma { |
| let ty = ts.into_iter().nth(0).unwrap().into_inner(); |
| let maybe_bounds = allow_plus && self.token.is_like_plus(); |
| match ty.node { |
| // `(TY_BOUND_NOPAREN) + BOUND + ...`. |
| TyKind::Path(None, ref path) if maybe_bounds => { |
| self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)? |
| } |
| TyKind::TraitObject(ref bounds, TraitObjectSyntax::None) |
| if maybe_bounds && bounds.len() == 1 && !trailing_plus => { |
| let path = match bounds[0] { |
| GenericBound::Trait(ref pt, ..) => pt.trait_ref.path.clone(), |
| GenericBound::Outlives(..) => self.bug("unexpected lifetime bound"), |
| }; |
| self.parse_remaining_bounds(Vec::new(), path, lo, true)? |
| } |
| // `(TYPE)` |
| _ => TyKind::Paren(P(ty)) |
| } |
| } else { |
| TyKind::Tup(ts) |
| } |
| } else if self.eat(&token::Not) { |
| // Never type `!` |
| TyKind::Never |
| } else if self.eat(&token::BinOp(token::Star)) { |
| // Raw pointer |
| TyKind::Ptr(self.parse_ptr()?) |
| } else if self.eat(&token::OpenDelim(token::Bracket)) { |
| // Array or slice |
| let t = self.parse_ty()?; |
| // Parse optional `; EXPR` in `[TYPE; EXPR]` |
| let t = match self.maybe_parse_fixed_length_of_vec()? { |
| None => TyKind::Slice(t), |
| Some(length) => TyKind::Array(t, AnonConst { |
| id: ast::DUMMY_NODE_ID, |
| value: length, |
| }), |
| }; |
| self.expect(&token::CloseDelim(token::Bracket))?; |
| t |
| } 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) { |
| // `typeof(EXPR)` |
| // In order to not be ambiguous, the type must be surrounded by parens. |
| self.expect(&token::OpenDelim(token::Paren))?; |
| let e = AnonConst { |
| id: ast::DUMMY_NODE_ID, |
| value: self.parse_expr()?, |
| }; |
| self.expect(&token::CloseDelim(token::Paren))?; |
| TyKind::Typeof(e) |
| } else if self.eat_keyword(kw::Underscore) { |
| // A type to be inferred `_` |
| TyKind::Infer |
| } else if self.token_is_bare_fn_keyword() { |
| // Function pointer type |
| self.parse_ty_bare_fn(Vec::new())? |
| } 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 lo = self.token.span; |
| let lifetime_defs = self.parse_late_bound_lifetime_defs()?; |
| if self.token_is_bare_fn_keyword() { |
| self.parse_ty_bare_fn(lifetime_defs)? |
| } else { |
| let path = self.parse_path(PathStyle::Type)?; |
| let parse_plus = allow_plus && self.check_plus(); |
| self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)? |
| } |
| } else if self.eat_keyword(kw::Impl) { |
| // 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 == PrevTokenKind::Plus; |
| TyKind::ImplTrait(ast::DUMMY_NODE_ID, bounds) |
| } else if self.check_keyword(kw::Dyn) && |
| (self.token.span.rust_2018() || |
| 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_generic_bounds(None)?; |
| impl_dyn_multi = bounds.len() > 1 || self.prev_token_kind == PrevTokenKind::Plus; |
| TyKind::TraitObject(bounds, TraitObjectSyntax::Dyn) |
| } else if self.check(&token::Question) || |
| self.check_lifetime() && self.look_ahead(1, |t| t.is_like_plus()) { |
| // Bound list (trait object type) |
| TyKind::TraitObject(self.parse_generic_bounds_common(allow_plus, None)?, |
| TraitObjectSyntax::None) |
| } else if self.eat_lt() { |
| // Qualified path |
| let (qself, path) = self.parse_qpath(PathStyle::Type)?; |
| TyKind::Path(Some(qself), path) |
| } else if self.token.is_path_start() { |
| // Simple path |
| let path = self.parse_path(PathStyle::Type)?; |
| if self.eat(&token::Not) { |
| // Macro invocation in type position |
| let (delim, tts) = self.expect_delimited_token_tree()?; |
| let node = Mac_ { |
| path, |
| tts, |
| delim, |
| prior_type_ascription: self.last_type_ascription, |
| }; |
| TyKind::Mac(respan(lo.to(self.prev_span), node)) |
| } else { |
| // Just a type path or bound list (trait object type) starting with a trait. |
| // `Type` |
| // `Trait1 + Trait2 + 'a` |
| if allow_plus && self.check_plus() { |
| self.parse_remaining_bounds(Vec::new(), path, lo, true)? |
| } else { |
| TyKind::Path(None, path) |
| } |
| } |
| } else if self.check(&token::DotDotDot) { |
| if allow_c_variadic { |
| self.eat(&token::DotDotDot); |
| TyKind::CVarArgs |
| } else { |
| return Err(self.fatal( |
| "only foreign functions are allowed to be C-variadic" |
| )); |
| } |
| } else { |
| let msg = format!("expected type, found {}", self.this_token_descr()); |
| let mut err = self.fatal(&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_span); |
| let ty = P(Ty { node, span, id: ast::DUMMY_NODE_ID }); |
| |
| // 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) |
| } |
| |
| fn parse_remaining_bounds(&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_span)); |
| let mut bounds = vec![GenericBound::Trait(poly_trait_ref, TraitBoundModifier::None)]; |
| if parse_plus { |
| self.eat_plus(); // `+`, or `+=` gets split and `+` is discarded |
| bounds.append(&mut self.parse_generic_bounds(Some(self.prev_span))?); |
| } |
| Ok(TyKind::TraitObject(bounds, TraitObjectSyntax::None)) |
| } |
| |
| fn parse_ptr(&mut self) -> PResult<'a, MutTy> { |
| let mutbl = if self.eat_keyword(kw::Mut) { |
| Mutability::Mutable |
| } else if self.eat_keyword(kw::Const) { |
| Mutability::Immutable |
| } else { |
| let span = self.prev_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::Immutable |
| }; |
| let t = self.parse_ty_no_plus()?; |
| Ok(MutTy { ty: t, mutbl }) |
| } |
| |
| fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> { |
| if self.eat(&token::Semi) { |
| Ok(Some(self.parse_expr()?)) |
| } else { |
| Ok(None) |
| } |
| } |
| |
| fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> { |
| let opt_lifetime = if self.check_lifetime() { Some(self.expect_lifetime()) } else { None }; |
| let mutbl = self.parse_mutability(); |
| let ty = self.parse_ty_no_plus()?; |
| return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty, mutbl })); |
| } |
| |
| /// Is the current token one of the keywords that signals a bare function type? |
| fn token_is_bare_fn_keyword(&mut self) -> bool { |
| self.check_keyword(kw::Fn) || |
| self.check_keyword(kw::Unsafe) || |
| self.check_keyword(kw::Extern) |
| } |
| |
| /// Parses a `TyKind::BareFn` type. |
| fn parse_ty_bare_fn(&mut self, generic_params: Vec<GenericParam>) -> PResult<'a, TyKind> { |
| /* |
| |
| [unsafe] [extern "ABI"] fn (S) -> T |
| ^~~~^ ^~~~^ ^~^ ^ |
| | | | | |
| | | | Return type |
| | | Argument types |
| | | |
| | ABI |
| Function Style |
| */ |
| |
| let unsafety = self.parse_unsafety(); |
| let abi = if self.eat_keyword(kw::Extern) { |
| self.parse_opt_abi()?.unwrap_or(Abi::C) |
| } else { |
| Abi::Rust |
| }; |
| |
| self.expect_keyword(kw::Fn)?; |
| let (inputs, c_variadic) = self.parse_fn_args(false, true)?; |
| let ret_ty = self.parse_ret_ty(false)?; |
| let decl = P(FnDecl { |
| inputs, |
| output: ret_ty, |
| c_variadic, |
| }); |
| Ok(TyKind::BareFn(P(BareFnTy { |
| abi, |
| unsafety, |
| generic_params, |
| decl, |
| }))) |
| } |
| |
| crate fn parse_generic_bounds(&mut self, |
| colon_span: Option<Span>) -> PResult<'a, GenericBounds> { |
| self.parse_generic_bounds_common(true, colon_span) |
| } |
| |
| /// Parses bounds of a type parameter `BOUND + BOUND + ...`, possibly with trailing `+`. |
| /// |
| /// ``` |
| /// BOUND = TY_BOUND | LT_BOUND |
| /// LT_BOUND = LIFETIME (e.g., `'a`) |
| /// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN) |
| /// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g., `?for<'a: 'b> m::Trait<'a>`) |
| /// ``` |
| fn parse_generic_bounds_common(&mut self, |
| allow_plus: bool, |
| colon_span: Option<Span>) -> PResult<'a, GenericBounds> { |
| let mut bounds = Vec::new(); |
| let mut negative_bounds = Vec::new(); |
| let mut last_plus_span = None; |
| let mut was_negative = false; |
| loop { |
| // This needs to be synchronized with `TokenKind::can_begin_bound`. |
| let is_bound_start = 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)); |
| if is_bound_start { |
| 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 question = if self.eat(&token::Question) { Some(self.prev_span) } else { None }; |
| if self.token.is_lifetime() { |
| if let Some(question_span) = question { |
| self.span_err(question_span, |
| "`?` may only modify trait bounds, not lifetime bounds"); |
| } |
| bounds.push(GenericBound::Outlives(self.expect_lifetime())); |
| if has_parens { |
| let inner_span = inner_lo.to(self.prev_span); |
| self.expect(&token::CloseDelim(token::Paren))?; |
| let mut err = self.struct_span_err( |
| lo.to(self.prev_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_span), |
| "remove the parentheses", |
| snippet.to_owned(), |
| Applicability::MachineApplicable |
| ); |
| } |
| err.emit(); |
| } |
| } else { |
| let lifetime_defs = self.parse_late_bound_lifetime_defs()?; |
| let path = self.parse_path(PathStyle::Type)?; |
| if has_parens { |
| self.expect(&token::CloseDelim(token::Paren))?; |
| } |
| let poly_span = lo.to(self.prev_span); |
| if is_negative { |
| was_negative = true; |
| if let Some(sp) = last_plus_span.or(colon_span) { |
| negative_bounds.push(sp.to(poly_span)); |
| } |
| } else { |
| let poly_trait = PolyTraitRef::new(lifetime_defs, path, poly_span); |
| let modifier = if question.is_some() { |
| TraitBoundModifier::Maybe |
| } else { |
| TraitBoundModifier::None |
| }; |
| bounds.push(GenericBound::Trait(poly_trait, modifier)); |
| } |
| } |
| } else { |
| break |
| } |
| |
| if !allow_plus || !self.eat_plus() { |
| break |
| } else { |
| last_plus_span = Some(self.prev_span); |
| } |
| } |
| |
| if !negative_bounds.is_empty() || was_negative { |
| let plural = negative_bounds.len() > 1; |
| let last_span = negative_bounds.last().map(|sp| *sp); |
| let mut err = self.struct_span_err( |
| negative_bounds, |
| "negative trait bounds are not supported", |
| ); |
| if let Some(sp) = last_span { |
| err.span_label(sp, "negative trait bounds are not supported"); |
| } |
| if let Some(bound_list) = colon_span { |
| let bound_list = bound_list.to(self.prev_span); |
| let mut new_bound_list = String::new(); |
| if !bounds.is_empty() { |
| let mut snippets = bounds.iter().map(|bound| bound.span()) |
| .map(|span| self.span_to_snippet(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.span_suggestion_hidden( |
| bound_list, |
| &format!("remove the trait bound{}", if plural { "s" } else { "" }), |
| new_bound_list, |
| Applicability::MachineApplicable, |
| ); |
| } |
| err.emit(); |
| } |
| |
| return Ok(bounds); |
| } |
| |
| 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()) |
| } |
| } |
| |
| crate fn check_lifetime(&mut self) -> bool { |
| self.expected_tokens.push(TokenType::Lifetime); |
| self.token.is_lifetime() |
| } |
| |
| /// Parses a single lifetime `'a` or panics. |
| crate fn expect_lifetime(&mut self) -> Lifetime { |
| if let Some(ident) = self.token.lifetime() { |
| let span = self.token.span; |
| self.bump(); |
| Lifetime { ident: Ident::new(ident.name, span), id: ast::DUMMY_NODE_ID } |
| } else { |
| self.span_bug(self.token.span, "not a lifetime") |
| } |
| } |
| } |
