bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

Refactor parsing of generic arguments/parameters and where clauses

Browse source
This commit is contained in:
Vadim Petrochenkov 2017-01-17 21:18:29 +03:00
parent fe597dc9a9
commit b795abeb1d
22 changed files with 341 additions and 468 deletions
Download patch file Download diff file Expand all files Collapse all files

679
src/libsyntax/parse/parser.rs
View file

@ -22,7 +22,7 @@ use ast::{Expr, ExprKind, RangeLimits};
use ast::{Field, FnDecl};
use ast::{ForeignItem, ForeignItemKind, FunctionRetTy};
use ast::{Ident, ImplItem, Item, ItemKind};
use ast::{Lit, LitKind, UintTy};
use ast::{Lifetime, LifetimeDef, Lit, LitKind, UintTy};
use ast::Local;
use ast::MacStmtStyle;
use ast::Mac_;
@ -638,13 +638,7 @@ impl<'a> Parser<'a> {
let lo = span.lo + BytePos(1);
Ok(self.bump_with(token::Eq, lo, span.hi))
}
_ => {
let gt_str = Parser::token_to_string(&token::Gt);
let this_token_str = self.this_token_to_string();
Err(self.fatal(&format!("expected `{}`, found `{}`",
gt_str,
this_token_str)))
}
_ => self.unexpected()
}
}
@ -971,20 +965,11 @@ impl<'a> Parser<'a> {
Parses whatever can come after a `for` keyword in a type.
The `for` hasn't been consumed.
Deprecated:
- for <'lt> |S| -> T
Eventually:
- for <'lt> [unsafe] [extern "ABI"] fn (S) -> T
- for <'lt> path::foo(a, b)
- for <'lt> path::foo(a, b) + Trait + 'a
*/
// parse <'lt>
let lo = self.span.lo;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
// examine next token to decide to do
@ -993,9 +978,9 @@ impl<'a> Parser<'a> {
} else {
let hi = self.span.hi;
let trait_ref = self.parse_trait_ref()?;
let poly_trait_ref = ast::PolyTraitRef { bound_lifetimes: lifetime_defs,
trait_ref: trait_ref,
span: mk_sp(lo, hi)};
let poly_trait_ref = PolyTraitRef { bound_lifetimes: lifetime_defs,
trait_ref: trait_ref,
span: mk_sp(lo, hi)};
let other_bounds = if self.eat(&token::BinOp(token::Plus)) {
self.parse_ty_param_bounds()?
} else {
@ -1010,18 +995,9 @@ impl<'a> Parser<'a> {
}
pub fn parse_impl_trait_type(&mut self) -> PResult<'a, TyKind> {
/*
Parses whatever can come after a `impl` keyword in a type.
The `impl` has already been consumed.
*/
let bounds = self.parse_ty_param_bounds()?;
if !bounds.iter().any(|b| if let TraitTyParamBound(..) = *b { true } else { false }) {
self.span_err(self.prev_span, "at least one trait must be specified");
}
Ok(ast::TyKind::ImplTrait(bounds))
// Parses whatever can come after a `impl` keyword in a type.
// The `impl` has already been consumed.
Ok(ast::TyKind::ImplTrait(self.parse_ty_param_bounds()?))
}
pub fn parse_ty_path(&mut self) -> PResult<'a, TyKind> {
@ -1029,7 +1005,7 @@ impl<'a> Parser<'a> {
}
/// parse a TyKind::BareFn type:
pub fn parse_ty_bare_fn(&mut self, lifetime_defs: Vec<ast::LifetimeDef>)
pub fn parse_ty_bare_fn(&mut self, lifetime_defs: Vec<LifetimeDef>)
-> PResult<'a, TyKind> {
/*
@ -1201,13 +1177,6 @@ impl<'a> Parser<'a> {
})
}
/// Parse a possibly mutable type
pub fn parse_mt(&mut self) -> PResult<'a, MutTy> {
let mutbl = self.parse_mutability()?;
let t = self.parse_ty_no_plus()?;
Ok(MutTy { ty: t, mutbl: mutbl })
}
/// Parse optional return type [ -> TY ] in function decl
pub fn parse_ret_ty(&mut self) -> PResult<'a, FunctionRetTy> {
if self.eat(&token::RArrow) {
@ -1259,8 +1228,8 @@ impl<'a> Parser<'a> {
pprust::ty_to_string(&lhs));
err.span_label(lhs.span, &format!("expected a path"));
let hi = bounds.iter().map(|x| match *x {
ast::TraitTyParamBound(ref tr, _) => tr.span.hi,
ast::RegionTyParamBound(ref r) => r.span.hi,
TraitTyParamBound(ref tr, _) => tr.span.hi,
RegionTyParamBound(ref r) => r.span.hi,
}).max_by_key(|x| x.to_usize());
let full_span = hi.map(|hi| Span {
lo: lhs.span.lo,
@ -1308,9 +1277,7 @@ impl<'a> Parser<'a> {
let lo = self.span.lo;
let t = if self.check(&token::OpenDelim(token::Paren)) {
self.bump();
let t = if self.eat(&token::OpenDelim(token::Paren)) {
// (t) is a parenthesized ty
// (t,) is the type of a tuple with only one field,
// of type t
@ -1318,9 +1285,8 @@ impl<'a> Parser<'a> {
let mut last_comma = false;
while self.token != token::CloseDelim(token::Paren) {
ts.push(self.parse_ty()?);
if self.check(&token::Comma) {
if self.eat(&token::Comma) {
last_comma = true;
self.bump();
} else {
last_comma = false;
break;
@ -1335,13 +1301,11 @@ impl<'a> Parser<'a> {
}
} else if self.eat(&token::Not) {
TyKind::Never
} else if self.check(&token::BinOp(token::Star)) {
} else if self.eat(&token::BinOp(token::Star)) {
// STAR POINTER (bare pointer?)
self.bump();
TyKind::Ptr(self.parse_ptr()?)
} else if self.check(&token::OpenDelim(token::Bracket)) {
} else if self.eat(&token::OpenDelim(token::Bracket)) {
// VECTOR
self.expect(&token::OpenDelim(token::Bracket))?;
let t = self.parse_ty()?;
// Parse the `; e` in `[ i32; e ]`
@ -1353,13 +1317,15 @@ impl<'a> Parser<'a> {
self.expect(&token::CloseDelim(token::Bracket))?;
t
} else if self.check(&token::BinOp(token::And)) ||
self.token == token::AndAnd {
self.check(&token::AndAnd) {
// BORROWED POINTER
self.expect_and()?;
self.parse_borrowed_pointee()?
} else if self.check_keyword(keywords::For) {
// FIXME plus priority
self.parse_for_in_type()?
} else if self.eat_keyword(keywords::Impl) {
// FIXME plus priority
self.parse_impl_trait_type()?
} else if self.token_is_bare_fn_keyword() {
// BARE FUNCTION
@ -1372,10 +1338,7 @@ impl<'a> Parser<'a> {
self.expect(&token::CloseDelim(token::Paren))?;
TyKind::Typeof(e)
} else if self.eat_lt() {
let (qself, path) =
self.parse_qualified_path(PathStyle::Type)?;
let (qself, path) = self.parse_qualified_path(PathStyle::Type)?;
TyKind::Path(Some(qself), path)
} else if self.token.is_path_start() {
let path = self.parse_path(PathStyle::Type)?;
@ -1405,10 +1368,10 @@ impl<'a> Parser<'a> {
pub fn parse_borrowed_pointee(&mut self) -> PResult<'a, TyKind> {
// look for `&'lt` or `&'foo ` and interpret `foo` as the region name:
let opt_lifetime = self.parse_opt_lifetime()?;
let mt = self.parse_mt()?;
return Ok(TyKind::Rptr(opt_lifetime, mt));
let opt_lifetime = self.eat_lifetime();
let mutbl = self.parse_mutability()?;
let ty = self.parse_ty_no_plus()?;
return Ok(TyKind::Rptr(opt_lifetime, MutTy { ty: ty, mutbl: mutbl }));
}
pub fn parse_ptr(&mut self) -> PResult<'a, MutTy> {
@ -1504,8 +1467,7 @@ impl<'a> Parser<'a> {
}
pub fn maybe_parse_fixed_length_of_vec(&mut self) -> PResult<'a, Option<P<ast::Expr>>> {
if self.check(&token::Semi) {
self.bump();
if self.eat(&token::Semi) {
Ok(Some(self.parse_expr()?))
} else {
Ok(None)
@ -1727,7 +1689,8 @@ impl<'a> Parser<'a> {
// Parse types, optionally.
let parameters = if self.eat_lt() {
let (lifetimes, types, bindings) = self.parse_generic_values_after_lt()?;
let (lifetimes, types, bindings) = self.parse_generic_args()?;
self.expect_gt()?;
ast::AngleBracketedParameterData {
lifetimes: lifetimes,
types: types,
@ -1785,7 +1748,8 @@ impl<'a> Parser<'a> {
// Check for a type segment.
if self.eat_lt() {
// Consumed `a::b::<`, go look for types
let (lifetimes, types, bindings) = self.parse_generic_values_after_lt()?;
let (lifetimes, types, bindings) = self.parse_generic_args()?;
self.expect_gt()?;
segments.push(ast::PathSegment {
identifier: identifier,
parameters: ast::AngleBracketedParameterData {
@ -1827,121 +1791,18 @@ impl<'a> Parser<'a> {
}
}
/// parses 0 or 1 lifetime
pub fn parse_opt_lifetime(&mut self) -> PResult<'a, Option<ast::Lifetime>> {
/// Parse single lifetime 'a or nothing.
pub fn eat_lifetime(&mut self) -> Option<Lifetime> {
match self.token {
token::Lifetime(..) => {
Ok(Some(self.parse_lifetime()?))
}
_ => {
Ok(None)
}
}
}
/// Parses a single lifetime
/// Matches lifetime = LIFETIME
pub fn parse_lifetime(&mut self) -> PResult<'a, ast::Lifetime> {
match self.token {
token::Lifetime(i) => {
let span = self.span;
token::Lifetime(ident) => {
self.bump();
return Ok(ast::Lifetime {
Some(Lifetime {
id: ast::DUMMY_NODE_ID,
span: span,
name: i.name
});
span: self.prev_span,
name: ident.name
})
}
_ => {
return Err(self.fatal("expected a lifetime name"));
}
}
}
/// Parses `lifetime_defs = [ lifetime_defs { ',' lifetime_defs } ]` where `lifetime_def =
/// lifetime [':' lifetimes]`
///
/// If `followed_by_ty_params` is None, then we are in a context
/// where only lifetime parameters are allowed, and thus we should
/// error if we encounter attributes after the bound lifetimes.
///
/// If `followed_by_ty_params` is Some(r), then there may be type
/// parameter bindings after the lifetimes, so we should pass
/// along the parsed attributes to be attached to the first such
/// type parmeter.
pub fn parse_lifetime_defs(&mut self,
followed_by_ty_params: Option<&mut Vec<ast::Attribute>>)
-> PResult<'a, Vec<ast::LifetimeDef>>
{
let mut res = Vec::new();
loop {
let attrs = self.parse_outer_attributes()?;
match self.token {
token::Lifetime(_) => {
let lifetime = self.parse_lifetime()?;
let bounds =
if self.eat(&token::Colon) {
self.parse_lifetimes(token::BinOp(token::Plus))?
} else {
Vec::new()
};
res.push(ast::LifetimeDef { attrs: attrs.into(),
lifetime: lifetime,
bounds: bounds });
}
_ => {
if let Some(recv) = followed_by_ty_params {
assert!(recv.is_empty());
*recv = attrs;
debug!("parse_lifetime_defs ret {:?}", res);
return Ok(res);
} else if !attrs.is_empty() {
let msg = "trailing attribute after lifetime parameters";
return Err(self.fatal(msg));
}
}
}
match self.token {
token::Comma => { self.bump();}
token::Gt => { return Ok(res); }
token::BinOp(token::Shr) => { return Ok(res); }
_ => {
let this_token_str = self.this_token_to_string();
let msg = format!("expected `,` or `>` after lifetime \
name, found `{}`",
this_token_str);
return Err(self.fatal(&msg[..]));
}
}
}
}
/// matches lifetimes = ( lifetime ) | ( lifetime , lifetimes ) actually, it matches the empty
/// one too, but putting that in there messes up the grammar....
///
/// Parses zero or more comma separated lifetimes. Expects each lifetime to be followed by
/// either a comma or `>`. Used when parsing type parameter lists, where we expect something
/// like `<'a, 'b, T>`.
pub fn parse_lifetimes(&mut self, sep: token::Token) -> PResult<'a, Vec<ast::Lifetime>> {
let mut res = Vec::new();
loop {
match self.token {
token::Lifetime(_) => {
res.push(self.parse_lifetime()?);
}
_ => {
return Ok(res);
}
}
if self.token != sep {
return Ok(res);
}
self.bump();
_ => None
}
}
@ -2458,7 +2319,9 @@ impl<'a> Parser<'a> {
-> PResult<'a, P<Expr>> {
let (_, tys, bindings) = if self.eat(&token::ModSep) {
self.expect_lt()?;
self.parse_generic_values_after_lt()?
let args = self.parse_generic_args()?;
self.expect_gt()?;
args
} else {
(Vec::new(), Vec::new(), Vec::new())
};
@ -4075,69 +3938,76 @@ impl<'a> Parser<'a> {
}).emit();
}
// Parses a sequence of bounds if a `:` is found,
// otherwise returns empty list.
fn parse_colon_then_ty_param_bounds(&mut self) -> PResult<'a, TyParamBounds>
{
if !self.eat(&token::Colon) {
Ok(Vec::new())
} else {
self.parse_ty_param_bounds()
}
}
// matches bounds = ( boundseq )?
// where boundseq = ( polybound + boundseq ) | polybound
// and polybound = ( 'for' '<' 'region '>' )? bound
// and bound = 'region | trait_ref
// Parse bounds of a type parameter `BOUND + BOUND + BOUND` without trailing `+`.
// BOUND = TY_BOUND | LT_BOUND
// LT_BOUND = LIFETIME (e.g. `'a`)
// TY_BOUND = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g. `?for<'a: 'b> m::Trait<'a>`)
fn parse_ty_param_bounds(&mut self) -> PResult<'a, TyParamBounds>
{
let mut result = vec![];
let mut bounds = Vec::new();
loop {
let question_span = self.span;
let ate_question = self.eat(&token::Question);
match self.token {
token::Lifetime(lifetime) => {
if ate_question {
self.span_err(question_span,
"`?` may only modify trait bounds, not lifetime bounds");
}
result.push(RegionTyParamBound(ast::Lifetime {
id: ast::DUMMY_NODE_ID,
span: self.span,
name: lifetime.name
}));
self.bump();
let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
if let Some(lifetime) = self.eat_lifetime() {
if let Some(question_span) = question {
self.span_err(question_span,
"`?` may only modify trait bounds, not lifetime bounds");
}
_ if self.token.is_path_start() || self.token.is_keyword(keywords::For) => {
let poly_trait_ref = self.parse_poly_trait_ref()?;
let modifier = if ate_question {
TraitBoundModifier::Maybe
} else {
TraitBoundModifier::None
};
result.push(TraitTyParamBound(poly_trait_ref, modifier))
}
_ => break,
bounds.push(RegionTyParamBound(lifetime));
} else if self.token.is_keyword(keywords::For) || self.token.is_path_start() {
let poly_trait_ref = self.parse_poly_trait_ref()?;
let modifier = if question.is_some() {
TraitBoundModifier::Maybe
} else {
TraitBoundModifier::None
};
bounds.push(TraitTyParamBound(poly_trait_ref, modifier));
} else {
break
}
if !self.eat(&token::BinOp(token::Plus)) {
break;
// Trailing plus is not allowed for now and we have to detect it.
let is_bound_start = |token: &token::Token| {
token == &token::Question || token.is_lifetime() ||
token.is_keyword(keywords::For) || token.is_path_start()
};
if self.check(&token::BinOp(token::Plus)) && self.look_ahead(1, is_bound_start) {
self.bump();
} else {
break
}
}
return Ok(result);
return Ok(bounds);
}
// Parse bounds of a type parameter `BOUND + BOUND + BOUND` without trailing `+`.
// BOUND = LT_BOUND (e.g. `'a`)
fn parse_lt_param_bounds(&mut self) -> Vec<Lifetime> {
let mut lifetimes = Vec::new();
while let Some(lifetime) = self.eat_lifetime() {
lifetimes.push(lifetime);
if self.check(&token::BinOp(token::Plus)) && self.look_ahead(1, |t| t.is_lifetime()) {
self.bump();
} else {
break
}
}
lifetimes
}
/// Matches typaram = IDENT (`?` unbound)? optbounds ( EQ ty )?
fn parse_ty_param(&mut self, preceding_attrs: Vec<ast::Attribute>) -> PResult<'a, TyParam> {
fn parse_ty_param(&mut self, preceding_attrs: Vec<Attribute>) -> PResult<'a, TyParam> {
let span = self.span;
let ident = self.parse_ident()?;
let bounds = self.parse_colon_then_ty_param_bounds()?;
// Parse optional colon and param bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_ty_param_bounds()?
} else {
Vec::new()
};
let default = if self.check(&token::Eq) {
self.bump();
let default = if self.eat(&token::Eq) {
Some(self.parse_ty()?)
} else {
None
@ -4153,6 +4023,51 @@ impl<'a> Parser<'a> {
})
}
/// Parses (possibly empty) list of lifetime and type parameters, possibly including
/// trailing comma and erroneous trailing attributes.
pub fn parse_generic_params(&mut self) -> PResult<'a, (Vec<LifetimeDef>, Vec<TyParam>)> {
let mut lifetime_defs = Vec::new();
let mut ty_params = Vec::new();
let mut seen_ty_param = false;
loop {
let attrs = self.parse_outer_attributes()?;
if let Some(lifetime) = self.eat_lifetime() {
// Parse lifetime parameter.
let bounds = if self.eat(&token::Colon) {
self.parse_lt_param_bounds()
} else {
Vec::new()
};
lifetime_defs.push(LifetimeDef {
attrs: attrs.into(),
lifetime: lifetime,
bounds: bounds,
});
if seen_ty_param {
self.span_err(self.prev_span,
"lifetime parameters must be declared prior to type parameters");
}
} else if self.token.is_ident() {
// Parse type parameter.
ty_params.push(self.parse_ty_param(attrs)?);
seen_ty_param = true;
} else {
// Check for trailing attributes and stop parsing.
if !attrs.is_empty() {
let param_kind = if seen_ty_param { "type" } else { "lifetime" };
self.span_err(attrs[0].span,
&format!("trailing attribute after {} parameters", param_kind));
}
break
}
if !self.eat(&token::Comma) {
break
}
}
Ok((lifetime_defs, ty_params))
}
/// Parse a set of optional generic type parameter declarations. Where
/// clauses are not parsed here, and must be added later via
/// `parse_where_clause()`.
@ -4162,45 +4077,11 @@ impl<'a> Parser<'a> {
/// where typaramseq = ( typaram ) | ( typaram , typaramseq )
pub fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
maybe_whole!(self, NtGenerics, |x| x);
let span_lo = self.span.lo;
if self.eat(&token::Lt) {
// Upon encountering attribute in generics list, we do not
// know if it is attached to lifetime or to type param.
//
// Solution: 1. eagerly parse attributes in tandem with
// lifetime defs, 2. store last set of parsed (and unused)
// attributes in `attrs`, and 3. pass in those attributes
// when parsing formal type param after lifetime defs.
let mut attrs = vec![];
let lifetime_defs = self.parse_lifetime_defs(Some(&mut attrs))?;
let mut seen_default = false;
let mut post_lifetime_attrs = Some(attrs);
let ty_params = self.parse_seq_to_gt(Some(token::Comma), |p| {
p.forbid_lifetime()?;
// Move out of `post_lifetime_attrs` if present. O/w
// not first type param: parse attributes anew.
let attrs = match post_lifetime_attrs.as_mut() {
None => p.parse_outer_attributes()?,
Some(attrs) => mem::replace(attrs, vec![]),
};
post_lifetime_attrs = None;
let ty_param = p.parse_ty_param(attrs)?;
if ty_param.default.is_some() {
seen_default = true;
} else if seen_default {
let prev_span = p.prev_span;
p.span_err(prev_span,
"type parameters with a default must be trailing");
}
Ok(ty_param)
})?;
if let Some(attrs) = post_lifetime_attrs {
if !attrs.is_empty() {
self.span_err(attrs[0].span,
"trailing attribute after lifetime parameters");
}
}
let span_lo = self.span.lo;
if self.eat_lt() {
let (lifetime_defs, ty_params) = self.parse_generic_params()?;
self.expect_gt()?;
Ok(ast::Generics {
lifetimes: lifetime_defs,
ty_params: ty_params,
@ -4215,85 +4096,53 @@ impl<'a> Parser<'a> {
}
}
fn parse_generic_values_after_lt(&mut self) -> PResult<'a, (Vec<ast::Lifetime>,
Vec<P<Ty>>,
Vec<TypeBinding>)> {
let span_lo = self.span.lo;
let lifetimes = self.parse_lifetimes(token::Comma)?;
let missing_comma = !lifetimes.is_empty() &&
!self.token.is_like_gt() &&
self.prev_token_kind != PrevTokenKind::Comma;
if missing_comma {
let msg = format!("expected `,` or `>` after lifetime \
name, found `{}`",
self.this_token_to_string());
let mut err = self.diagnostic().struct_span_err(self.span, &msg);
let span_hi = self.span.hi;
let span_hi = match self.parse_ty_no_plus() {
Ok(..) => self.span.hi,
Err(ref mut err) => {
self.cancel(err);
span_hi
/// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
/// possibly including trailing comma.
fn parse_generic_args(&mut self) -> PResult<'a, (Vec<Lifetime>, Vec<P<Ty>>, Vec<TypeBinding>)> {
let mut lifetimes = Vec::new();
let mut types = Vec::new();
let mut bindings = Vec::new();
let mut seen_type = false;
let mut seen_binding = false;
loop {
let eq_is_next = self.look_ahead(1, |t| t == &token::Eq); // borrowck workaround
if let Some(lifetime) = self.eat_lifetime() {
// Parse lifetime argument.
lifetimes.push(lifetime);
if seen_type || seen_binding {
self.span_err(self.prev_span,
"lifetime parameters must be declared prior to type parameters");
}
};
let msg = format!("did you mean a single argument type &'a Type, \
or did you mean the comma-separated arguments \
'a, Type?");
err.span_note(mk_sp(span_lo, span_hi), &msg);
return Err(err);
}
// First parse types.
let (types, returned) = self.parse_seq_to_gt_or_return(
Some(token::Comma),
|p| {
p.forbid_lifetime()?;
if p.look_ahead(1, |t| t == &token::Eq) {
Ok(None)
} else {
Ok(Some(p.parse_ty()?))
}
}
)?;
// If we found the `>`, don't continue.
if !returned {
return Ok((lifetimes, types, Vec::new()));
}
// Then parse type bindings.
let bindings = self.parse_seq_to_gt(
Some(token::Comma),
|p| {
p.forbid_lifetime()?;
let lo = p.span.lo;
let ident = p.parse_ident()?;
p.expect(&token::Eq)?;
let ty = p.parse_ty_no_plus()?;
let hi = ty.span.hi;
let span = mk_sp(lo, hi);
return Ok(TypeBinding{id: ast::DUMMY_NODE_ID,
} else if self.token.is_ident() && eq_is_next {
// Parse associated type binding.
let lo = self.span.lo;
let ident = self.parse_ident()?;
self.bump();
let ty = self.parse_ty()?;
bindings.push(TypeBinding {
id: ast::DUMMY_NODE_ID,
ident: ident,
ty: ty,
span: span,
span: mk_sp(lo, self.prev_span.hi),
});
seen_binding = true;
} else if self.token.can_begin_type() {
// Parse type argument.
types.push(self.parse_ty()?);
if seen_binding {
self.span_err(types[types.len() - 1].span,
"type parameters must be declared prior to associated type bindings");
}
seen_type = true;
} else {
break
}
)?;
Ok((lifetimes, types, bindings))
}
fn forbid_lifetime(&mut self) -> PResult<'a, ()> {
if self.token.is_lifetime() {
let span = self.span;
return Err(self.diagnostic().struct_span_err(span, "lifetime parameters must be \
declared prior to type parameters"))
if !self.eat(&token::Comma) {
break
}
}
Ok(())
Ok((lifetimes, types, bindings))
}
/// Parses an optional `where` clause and places it in `generics`.
@ -4301,7 +4150,7 @@ impl<'a> Parser<'a> {
/// ```ignore
/// where T : Trait<U, V> + 'b, 'a : 'b
/// ```
pub fn parse_where_clause(&mut self) -> PResult<'a, ast::WhereClause> {
pub fn parse_where_clause(&mut self) -> PResult<'a, WhereClause> {
maybe_whole!(self, NtWhereClause, |x| x);
let mut where_clause = WhereClause {
@ -4313,7 +4162,7 @@ impl<'a> Parser<'a> {
return Ok(where_clause);
}
// This is a temporary hack.
// This is a temporary future proofing.
//
// 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
@ -4330,106 +4179,64 @@ impl<'a> Parser<'a> {
}
}
let mut parsed_something = false;
loop {
let lo = self.span.lo;
match self.token {
token::OpenDelim(token::Brace) => {
break
}
if let Some(lifetime) = self.eat_lifetime() {
// Bounds starting with a colon are mandatory, but possibly empty.
self.expect(&token::Colon)?;
let bounds = self.parse_lt_param_bounds();
where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
ast::WhereRegionPredicate {
span: mk_sp(lo, self.prev_span.hi),
lifetime: lifetime,
bounds: bounds,
}
));
} else if self.token.can_begin_type() {
// Parse optional `for<'a, 'b>`.
// This `for` is parsed greedily and applies to the whole predicate,
// the bounded type can have its own `for` applying only to it.
// Example 1: for<'a> Trait1<'a>: Trait2<'a /*ok*/>
// Example 2: (for<'a> Trait1<'a>): Trait2<'a /*not ok*/>
// Example 3: for<'a> for<'b> Trait1<'a, 'b>: Trait2<'a /*ok*/, 'b /*not ok*/>
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
token::Lifetime(..) => {
let bounded_lifetime =
self.parse_lifetime()?;
self.expect(&token::Colon)?;
let bounds =
self.parse_lifetimes(token::BinOp(token::Plus))?;
let hi = self.prev_span.hi;
let span = mk_sp(lo, hi);
where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
ast::WhereRegionPredicate {
span: span,
lifetime: bounded_lifetime,
bounds: bounds
// Parse type with mandatory colon and (possibly empty) bounds,
// or with mandatory equality sign and the second type.
let ty = self.parse_ty()?;
if self.eat(&token::Colon) {
let bounds = self.parse_ty_param_bounds()?;
where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
ast::WhereBoundPredicate {
span: mk_sp(lo, self.prev_span.hi),
bound_lifetimes: lifetime_defs,
bounded_ty: ty,
bounds: bounds,
}
));
parsed_something = true;
}
_ => {
let bound_lifetimes = if self.eat_keyword(keywords::For) {
// Higher ranked constraint.
self.expect(&token::Lt)?;
let lifetime_defs = self.parse_lifetime_defs(None)?;
self.expect_gt()?;
lifetime_defs
} else {
vec![]
};
let bounded_ty = self.parse_ty_no_plus()?;
if self.eat(&token::Colon) {
let bounds = self.parse_ty_param_bounds()?;
let hi = self.prev_span.hi;
let span = mk_sp(lo, hi);
if bounds.is_empty() {
self.span_err(span,
"each predicate in a `where` clause must have \
at least one bound in it");
// FIXME: Decide what should be used here, `=` or `==`.
} else if self.eat(&token::Eq) || self.eat(&token::EqEq) {
let rhs_ty = self.parse_ty()?;
where_clause.predicates.push(ast::WherePredicate::EqPredicate(
ast::WhereEqPredicate {
span: mk_sp(lo, self.prev_span.hi),
lhs_ty: ty,
rhs_ty: rhs_ty,
id: ast::DUMMY_NODE_ID,
}
where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
ast::WhereBoundPredicate {
span: span,
bound_lifetimes: bound_lifetimes,
bounded_ty: bounded_ty,
bounds: bounds,
}));
parsed_something = true;
} else if self.eat(&token::Eq) {
// let ty = try!(self.parse_ty_no_plus());
let hi = self.prev_span.hi;
let span = mk_sp(lo, hi);
// where_clause.predicates.push(
// ast::WherePredicate::EqPredicate(ast::WhereEqPredicate {
// id: ast::DUMMY_NODE_ID,
// span: span,
// path: panic!("NYI"), //bounded_ty,
// ty: ty,
// }));
// parsed_something = true;
// // FIXME(#18433)
self.span_err(span,
"equality constraints are not yet supported \
in where clauses (#20041)");
} else {
let prev_span = self.prev_span;
self.span_err(prev_span,
"unexpected token in `where` clause");
}
));
} else {
return self.unexpected();
}
};
} else {
break
}
if !self.eat(&token::Comma) {
break
}
}
if !parsed_something {
let prev_span = self.prev_span;
self.span_err(prev_span,
"a `where` clause must have at least one predicate \
in it");
}
Ok(where_clause)
}
@ -4528,13 +4335,13 @@ impl<'a> Parser<'a> {
} else if self.look_ahead(1, |t| t.is_lifetime()) &&
isolated_self(self, 2) {
self.bump();
let lt = self.parse_lifetime()?;
let lt = self.eat_lifetime().expect("not a lifetime");
(SelfKind::Region(Some(lt), Mutability::Immutable), expect_ident(self))
} else if self.look_ahead(1, |t| t.is_lifetime()) &&
self.look_ahead(2, |t| t.is_keyword(keywords::Mut)) &&
isolated_self(self, 3) {
self.bump();
let lt = self.parse_lifetime()?;
let lt = self.eat_lifetime().expect("not a lifetime");
self.bump();
(SelfKind::Region(Some(lt), Mutability::Mutable), expect_ident(self))
} else {
@ -4836,8 +4643,12 @@ impl<'a> Parser<'a> {
let ident = self.parse_ident()?;
let mut tps = self.parse_generics()?;
// Parse supertrait bounds.
let bounds = self.parse_colon_then_ty_param_bounds()?;
// Parse optional colon and supertrait bounds.
let bounds = if self.eat(&token::Colon) {
self.parse_ty_param_bounds()?
} else {
Vec::new()
};
tps.where_clause = self.parse_where_clause()?;
@ -4928,17 +4739,21 @@ impl<'a> Parser<'a> {
/// Parse a::B<String,i32>
fn parse_trait_ref(&mut self) -> PResult<'a, TraitRef> {
Ok(ast::TraitRef {
Ok(TraitRef {
path: self.parse_path(PathStyle::Type)?,
ref_id: ast::DUMMY_NODE_ID,
})
}
fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<ast::LifetimeDef>> {
fn parse_late_bound_lifetime_defs(&mut self) -> PResult<'a, Vec<LifetimeDef>> {
if self.eat_keyword(keywords::For) {
self.expect(&token::Lt)?;
let lifetime_defs = self.parse_lifetime_defs(None)?;
self.expect_lt()?;
let (lifetime_defs, ty_params) = self.parse_generic_params()?;
self.expect_gt()?;
if !ty_params.is_empty() {
self.span_err(ty_params[0].span,
"only lifetime parameters can be used in this context");
}
Ok(lifetime_defs)
} else {
Ok(Vec::new())
@ -4950,7 +4765,7 @@ impl<'a> Parser<'a> {
let lo = self.span.lo;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
Ok(ast::PolyTraitRef {
Ok(PolyTraitRef {
bound_lifetimes: lifetime_defs,
trait_ref: self.parse_trait_ref()?,
span: mk_sp(lo, self.prev_span.hi),