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Parse closure binders

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This is first step in implementing RFC 3216.
- Parse `for<'a>` before closures in ast
  - Error in lowering
- Add `closure_lifetime_binder` feature
This commit is contained in:
Maybe Waffle 2022-06-02 20:15:05 +04:00
parent fbdb07f4e7
commit 40ae7b5b8e
24 changed files with 288 additions and 39 deletions
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50
compiler/rustc_parse/src/parser/expr.rs
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@ -15,10 +15,10 @@ use rustc_ast::util::classify;
use rustc_ast::util::literal::LitError;
use rustc_ast::util::parser::{prec_let_scrutinee_needs_par, AssocOp, Fixity};
use rustc_ast::visit::Visitor;
use rustc_ast::StmtKind;
use rustc_ast::{self as ast, AttrStyle, AttrVec, CaptureBy, ExprField, Lit, UnOp, DUMMY_NODE_ID};
use rustc_ast::{AnonConst, BinOp, BinOpKind, FnDecl, FnRetTy, MacCall, Param, Ty, TyKind};
use rustc_ast::{Arm, Async, BlockCheckMode, Expr, ExprKind, Label, Movability, RangeLimits};
use rustc_ast::{ClosureBinder, StmtKind};
use rustc_ast_pretty::pprust;
use rustc_data_structures::thin_vec::ThinVec;
use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, PResult};
@ -1343,11 +1343,7 @@ impl<'a> Parser<'a> {
self.parse_if_expr(attrs)
} else if self.check_keyword(kw::For) {
if self.choose_generics_over_qpath(1) {
// NOTE(Centril, eddyb): DO NOT REMOVE! Beyond providing parser recovery,
// this is an insurance policy in case we allow qpaths in (tuple-)struct patterns.
// When `for <Foo as Bar>::Proj in $expr $block` is wanted,
// you can disambiguate in favor of a pattern with `(...)`.
self.recover_quantified_closure_expr(attrs)
self.parse_closure_expr(attrs)
} else {
assert!(self.eat_keyword(kw::For));
self.parse_for_expr(None, self.prev_token.span, attrs)
@ -2094,30 +2090,22 @@ impl<'a> Parser<'a> {
Ok(self.mk_expr(blk.span, ExprKind::Block(blk, None), AttrVec::new()))
}
/// Recover on an explicitly quantified closure expression, e.g., `for<'a> |x: &'a u8| *x + 1`.
fn recover_quantified_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
let lo = self.token.span;
let _ = self.parse_late_bound_lifetime_defs()?;
let span_for = lo.to(self.prev_token.span);
let closure = self.parse_closure_expr(attrs)?;
self.struct_span_err(span_for, "cannot introduce explicit parameters for a closure")
.span_label(closure.span, "the parameters are attached to this closure")
.span_suggestion(
span_for,
"remove the parameters",
"",
Applicability::MachineApplicable,
)
.emit();
Ok(self.mk_expr_err(lo.to(closure.span)))
}
/// Parses a closure expression (e.g., `move |args| expr`).
fn parse_closure_expr(&mut self, attrs: AttrVec) -> PResult<'a, P<Expr>> {
let lo = self.token.span;
let binder = if self.check_keyword(kw::For) {
let lo = self.token.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
let span = lo.to(self.prev_token.span);
self.sess.gated_spans.gate(sym::closure_lifetime_binder, span);
ClosureBinder::For { span, generic_params: P::from_vec(lifetime_defs) }
} else {
ClosureBinder::NotPresent
};
let movability =
if self.eat_keyword(kw::Static) { Movability::Static } else { Movability::Movable };
@ -2160,7 +2148,15 @@ impl<'a> Parser<'a> {
let closure = self.mk_expr(
lo.to(body.span),
ExprKind::Closure(capture_clause, asyncness, movability, decl, body, lo.to(decl_hi)),
ExprKind::Closure(
binder,
capture_clause,
asyncness,
movability,
decl,
body,
lo.to(decl_hi),
),
attrs,
);