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HIR const-checking

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This commit is contained in:
Dylan MacKenzie 2020-05-21 12:47:09 -07:00
parent 4c2383810b
commit 696084c764
1 changed files with 11 additions and 36 deletions
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47
src/librustc_passes/check_const.rs
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@ -23,7 +23,6 @@
enum NonConstExpr {
Loop(hir::LoopSource),
Match(hir::MatchSource),
OrPattern,
}
impl NonConstExpr {
@ -31,7 +30,6 @@ fn name(self) -> String {
match self {
Self::Loop(src) => format!("`{}`", src.name()),
Self::Match(src) => format!("`{}`", src.name()),
Self::OrPattern => "or-pattern".to_string(),
}
}
@ -40,22 +38,19 @@ fn required_feature_gates(self) -> Option<&'static [Symbol]> {
use hir::MatchSource::*;
let gates: &[_] = match self {
Self::Match(Normal)
| Self::Match(IfDesugar { .. })
| Self::Match(IfLetDesugar { .. })
| Self::OrPattern => &[sym::const_if_match],
Self::Loop(Loop) => &[sym::const_loop],
Self::Loop(While)
| Self::Loop(WhileLet)
| Self::Match(WhileDesugar | WhileLetDesugar) => {
&[sym::const_loop, sym::const_if_match]
}
// A `for` loop's desugaring contains a call to `IntoIterator::into_iter`,
// so they are not yet allowed with `#![feature(const_loop)]`.
_ => return None,
// Likewise, `?` desugars to a call to `Try::into_result`.
Self::Loop(ForLoop) | Self::Match(ForLoopDesugar | TryDesugar | AwaitDesugar) => {
return None;
}
Self::Loop(Loop | While | WhileLet) | Self::Match(WhileDesugar | WhileLetDesugar) => {
&[sym::const_loop]
}
// All other matches are allowed.
Self::Match(Normal | IfDesugar { .. } | IfLetDesugar { .. }) => &[],
};
Some(gates)
@ -114,17 +109,6 @@ fn const_check_violated(&self, expr: NonConstExpr, span: Span) {
match missing_gates.as_slice() {
&[] => struct_span_err!(self.tcx.sess, span, E0744, "{}", msg).emit(),
// If the user enabled `#![feature(const_loop)]` but not `#![feature(const_if_match)]`,
// explain why their `while` loop is being rejected.
&[gate @ sym::const_if_match] if required_gates.contains(&sym::const_loop) => {
feature_err(&self.tcx.sess.parse_sess, gate, span, &msg)
.note(
"`#![feature(const_loop)]` alone is not sufficient, \
since this loop expression contains an implicit conditional",
)
.emit();
}
&[missing_primary, ref missing_secondary @ ..] => {
let mut err = feature_err(&self.tcx.sess.parse_sess, missing_primary, span, &msg);
@ -175,15 +159,6 @@ fn visit_body(&mut self, body: &'tcx hir::Body<'tcx>) {
self.recurse_into(kind, |this| intravisit::walk_body(this, body));
}
fn visit_pat(&mut self, p: &'tcx hir::Pat<'tcx>) {
if self.const_kind.is_some() {
if let hir::PatKind::Or { .. } = p.kind {
self.const_check_violated(NonConstExpr::OrPattern, p.span);
}
}
intravisit::walk_pat(self, p)
}
fn visit_expr(&mut self, e: &'tcx hir::Expr<'tcx>) {
match &e.kind {
// Skip the following checks if we are not currently in a const context.