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Bounds parsing refactoring #37511

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9d179e6
Fix where clauses parsing
matklad Oct 19, 2016
8909e1b
Don't allow empty type parameter bounds
matklad Nov 1, 2016
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2 changes: 1 addition & 1 deletion src/librustc_borrowck/borrowck/mir/dataflow/graphviz.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -88,7 +88,7 @@ pub trait MirWithFlowState<'tcx> {
}

impl<'a, 'tcx: 'a, BD> MirWithFlowState<'tcx> for MirBorrowckCtxtPreDataflow<'a, 'tcx, BD>
where 'a, 'tcx: 'a, BD: BitDenotation<Ctxt=MoveDataParamEnv<'tcx>>
where 'tcx: 'a, BD: BitDenotation<Ctxt=MoveDataParamEnv<'tcx>>
{
type BD = BD;
fn node_id(&self) -> NodeId { self.node_id }
Expand Down
119 changes: 61 additions & 58 deletions src/libsyntax/parse/parser.rs
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Expand Up @@ -1091,14 +1091,12 @@ impl<'a> Parser<'a> {
let poly_trait_ref = ast::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(BoundParsingMode::Bare)?
} else {
P::new()
};

let other_bounds = self.parse_opt_ty_param_bounds(&token::BinOp(token::Plus),
BoundParsingMode::Bare)?;
let all_bounds =
Some(TraitTyParamBound(poly_trait_ref, TraitBoundModifier::None)).into_iter()
.chain(other_bounds.into_vec())
.chain(other_bounds.unwrap_or_else(P::new).into_vec())
.collect();
Ok(ast::TyKind::PolyTraitRef(all_bounds))
}
Expand Down Expand Up @@ -1319,24 +1317,15 @@ impl<'a> Parser<'a> {
let lo = self.span.lo;
let lhs = self.parse_ty()?;

if !self.eat(&token::BinOp(token::Plus)) {
return Ok(lhs);
}

let bounds = self.parse_ty_param_bounds(BoundParsingMode::Bare)?;

// In type grammar, `+` is treated like a binary operator,
// and hence both L and R side are required.
if bounds.is_empty() {
let prev_span = self.prev_span;
self.span_err(prev_span,
"at least one type parameter bound \
must be specified");
match self.parse_opt_ty_param_bounds(&token::BinOp(token::Plus),
BoundParsingMode::Bare)? {
None => Ok(lhs),
Some(bounds) => {
let sp = mk_sp(lo, self.prev_span.hi);
let sum = ast::TyKind::ObjectSum(lhs, bounds);
Ok(P(Ty {id: ast::DUMMY_NODE_ID, node: sum, span: sp}))
}
}

let sp = mk_sp(lo, self.prev_span.hi);
let sum = ast::TyKind::ObjectSum(lhs, bounds);
Ok(P(Ty {id: ast::DUMMY_NODE_ID, node: sum, span: sp}))
}

/// Parse a type.
Expand Down Expand Up @@ -4186,11 +4175,25 @@ impl<'a> Parser<'a> {
mode: BoundParsingMode)
-> PResult<'a, TyParamBounds>
{
if !self.eat(&token::Colon) {
Ok(P::new())
} else {
self.parse_ty_param_bounds(mode)
Ok(self.parse_opt_ty_param_bounds(&token::Colon, mode)?.unwrap_or_else(P::new))
}

fn parse_opt_ty_param_bounds(&mut self,
intoducing_token: &token::Token,
mode: BoundParsingMode)
-> PResult<'a, Option<TyParamBounds>> {
if !self.eat(intoducing_token) {
return Ok(None);
}

let bounds = self.parse_ty_param_bounds(mode)?;
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I'd rather remove plain parse_ty_param_bounds and leave only the opt version, but unfortunately this wont work for parse_impl_trait_type, because it used a keyword (impl) as an introducing_token, and you can't eat a keyword token. Or can you?

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@jseyfried jseyfried Nov 11, 2016 •
edited
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Or can you?

parser.eat(&token::Ident(keywords::Impl.ident())) should work.


if bounds.is_empty() {
self.span_err(self.prev_span,
"at least one type parameter bound must be specified");
}

Ok(Some(bounds))
}

// matches bounds = ( boundseq )?
Expand Down Expand Up @@ -4440,14 +4443,20 @@ impl<'a> Parser<'a> {
let bounded_lifetime =
self.parse_lifetime()?;

self.eat(&token::Colon);
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);

if bounds.is_empty() {
self.span_err(span,
"each predicate in a `where` clause must have \
at least one bound in it");
}

where_clause.predicates.push(ast::WherePredicate::RegionPredicate(
ast::WhereRegionPredicate {
span: span,
Expand All @@ -4472,46 +4481,40 @@ impl<'a> Parser<'a> {

let bounded_ty = self.parse_ty()?;

if self.eat(&token::Colon) {
let bounds = self.parse_ty_param_bounds(BoundParsingMode::Bare)?;
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");
}
if let Some(bounds) = self.parse_opt_ty_param_bounds(&token::Colon,
BoundParsingMode::Bare)? {
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If you refactor this to

let opt_bounds = self.parse_opt_ty_param_bounds(&token::Colon, BoundParsingMode::Bare)?;
if let Some(bounds) = opt_bounds {

then you can continue using else if below.


where_clause.predicates.push(ast::WherePredicate::BoundPredicate(
ast::WhereBoundPredicate {
span: span,
span: mk_sp(lo, self.prev_span.hi),
bound_lifetimes: bound_lifetimes,
bounded_ty: bounded_ty,
bounds: bounds,
}));

parsed_something = true;
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For some reason I can't use else if here: #37510 :(

} else if self.eat(&token::Eq) {
// let ty = try!(self.parse_ty());
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");
if self.eat(&token::Eq) {
// let ty = try!(self.parse_ty());
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");
}
}
}
};
Expand Down
22 changes: 22 additions & 0 deletions src/test/parse-fail/empty-type-parameter-bounds.rs
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@@ -0,0 +1,22 @@
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// compile-flags: -Z parse-only -Z continue-parse-after-error

trait T {}

type S = for<'a> T+;
//~^ ERROR at least one type parameter bound must be specified

fn foo<T:>(x: T) -> T { x }
//~^ ERROR at least one type parameter bound must be specified

fn main() {
}
12 changes: 9 additions & 3 deletions src/test/parse-fail/where-clauses-no-bounds-or-predicates.rs
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@@ -1,4 +1,4 @@
// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
Expand All @@ -8,17 +8,23 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// compile-flags: -Z parse-only
// compile-flags: -Z parse-only -Z continue-parse-after-error

fn equal1<T>(_: &T, _: &T) -> bool where {
//~^ ERROR a `where` clause must have at least one predicate in it
true
}

fn equal2<T>(_: &T, _: &T) -> bool where T: {
//~^ ERROR each predicate in a `where` clause must have at least one bound
//~^ ERROR at least one type parameter bound must be specified
true
}

fn foo2<'a>() where 'a: {}
//~^ ERROR each predicate in a `where` clause must have at least one bound

fn foo1<'a>() where 'a {}
//~^ ERROR expected `:`, found `{`

fn main() {
}