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let_chains: Move feature gating to pre-expansion.

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This commit is contained in:
Mazdak Farrokhzad 2019-06-17 05:41:21 +02:00
parent d551880267
commit eb4f54a58d
3 changed files with 28 additions and 28 deletions
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36
src/libsyntax/feature_gate.rs
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@ -1940,27 +1940,6 @@ impl<'a> PostExpansionVisitor<'a> {
Err(mut err) => err.emit(),
}
}
/// Recurse into all places where a `let` expression would be feature gated
/// and emit gate post errors for those.
fn find_and_gate_lets(&mut self, e: &'a ast::Expr) {
match &e.node {
ast::ExprKind::Paren(e) => {
self.find_and_gate_lets(e);
}
ast::ExprKind::Binary(op, lhs, rhs) if op.node == ast::BinOpKind::And => {
self.find_and_gate_lets(lhs);
self.find_and_gate_lets(rhs);
}
ast::ExprKind::Let(..) => {
gate_feature_post!(
&self, let_chains, e.span,
"`let` expressions in this position are experimental"
);
}
_ => {}
}
}
}
impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
@ -2158,10 +2137,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
fn visit_expr(&mut self, e: &'a ast::Expr) {
match e.node {
ast::ExprKind::If(ref e, ..) | ast::ExprKind::While(ref e, ..) => match e.node {
ast::ExprKind::Let(..) => {} // Stable!,
_ => self.find_and_gate_lets(e),
}
ast::ExprKind::Box(_) => {
gate_feature_post!(&self, box_syntax, e.span, EXPLAIN_BOX_SYNTAX);
}
@ -2546,6 +2521,17 @@ pub fn check_crate(krate: &ast::Crate,
"attributes on function parameters are unstable"
));
sess
.let_chains_spans
.borrow()
.iter()
.for_each(|span| gate_feature!(
&ctx,
let_chains,
*span,
"`let` expressions in this position are experimental"
));
let visitor = &mut PostExpansionVisitor {
context: &ctx,
builtin_attributes: &*BUILTIN_ATTRIBUTE_MAP,