bjoernager/rust
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let_chains: Refactor parse_{if,while}_expr a bit.

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This commit is contained in:
Mazdak Farrokhzad 2019-06-17 22:03:23 +02:00
parent 5ae5086cc5
commit 7465eb44f0
1 changed files with 12 additions and 9 deletions
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21
src/libsyntax/parse/parser.rs
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@ -3157,8 +3157,7 @@ impl<'a> Parser<'a> {
/// Parses an `if` expression (`if` token already eaten). /// Parses an `if` expression (`if` token already eaten).
fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { fn parse_if_expr(&mut self, attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
let lo = self.prev_span; let lo = self.prev_span;
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?; let cond = self.parse_cond_expr()?;
self.ungate_prev_let_expr(&cond);
// Verify that the parsed `if` condition makes sense as a condition. If it is a block, then // Verify that the parsed `if` condition makes sense as a condition. If it is a block, then
// verify that the last statement is either an implicit return (no `;`) or an explicit // verify that the last statement is either an implicit return (no `;`) or an explicit
@ -3188,12 +3187,17 @@ impl<'a> Parser<'a> {
Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs)) Ok(self.mk_expr(lo.to(hi), ExprKind::If(cond, thn, els), attrs))
} }
/// Remove the last feature gating of a `let` expression that must the one provided. /// Parse the condition of a `if`- or `while`-expression
fn ungate_prev_let_expr(&mut self, expr: &Expr) { fn parse_cond_expr(&mut self) -> PResult<'a, P<Expr>> {
if let ExprKind::Let(..) = expr.node { let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?;
if let ExprKind::Let(..) = cond.node {
// Remove the last feature gating of a `let` expression since it's stable.
let last = self.sess.let_chains_spans.borrow_mut().pop(); let last = self.sess.let_chains_spans.borrow_mut().pop();
debug_assert_eq!(expr.span, last.unwrap()); debug_assert_eq!(cond.span, last.unwrap());
} }
Ok(cond)
} }
/// Parses a `let $pats = $expr` pseudo-expression. /// Parses a `let $pats = $expr` pseudo-expression.
@ -3295,12 +3299,11 @@ impl<'a> Parser<'a> {
fn parse_while_expr(&mut self, opt_label: Option<Label>, fn parse_while_expr(&mut self, opt_label: Option<Label>,
span_lo: Span, span_lo: Span,
mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> { mut attrs: ThinVec<Attribute>) -> PResult<'a, P<Expr>> {
let cond = self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL, None)?; let cond = self.parse_cond_expr()?;
self.ungate_prev_let_expr(&cond);
let (iattrs, body) = self.parse_inner_attrs_and_block()?; let (iattrs, body) = self.parse_inner_attrs_and_block()?;
attrs.extend(iattrs); attrs.extend(iattrs);
let span = span_lo.to(body.span); let span = span_lo.to(body.span);
return Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs)); Ok(self.mk_expr(span, ExprKind::While(cond, body, opt_label), attrs))
} }
// parse `loop {...}`, `loop` token already eaten // parse `loop {...}`, `loop` token already eaten