use middle::subst;
use middle::ty;
use std::fmt;
+use std::mem::replace;
use syntax::ast;
use syntax::codemap::Span;
use syntax::parse::token::special_idents;
// I'm sorry.
trait_ref_hack: bool,
+
+ // List of labels in the function/method currently under analysis.
+ labels_in_fn: Vec<(ast::Ident, Span)>,
}
enum ScopeChain<'a> {
scope: &ROOT_SCOPE,
def_map: def_map,
trait_ref_hack: false,
+ labels_in_fn: vec![],
}, krate);
sess.abort_if_errors();
named_region_map
impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> {
fn visit_item(&mut self, item: &ast::Item) {
+ // Items save/restore the set of labels. This way innner items
+ // can freely reuse names, be they loop labels or lifetimes.
+ let saved = replace(&mut self.labels_in_fn, vec![]);
+
// Items always introduce a new root scope
self.with(RootScope, |_, this| {
match item.node {
}
}
});
+
+ // Done traversing the item; restore saved set of labels.
+ replace(&mut self.labels_in_fn, saved);
}
fn visit_fn(&mut self, fk: visit::FnKind<'v>, fd: &'v ast::FnDecl,
match fk {
visit::FkItemFn(_, generics, _, _, _) => {
self.visit_early_late(subst::FnSpace, generics, |this| {
- visit::walk_fn(this, fk, fd, b, s)
+ this.walk_fn(fk, fd, b, s)
})
}
visit::FkMethod(_, sig, _) => {
self.visit_early_late(subst::FnSpace, &sig.generics, |this| {
- visit::walk_fn(this, fk, fd, b, s)
+ this.walk_fn(fk, fd, b, s)
})
}
visit::FkFnBlock(..) => {
- visit::walk_fn(self, fk, fd, b, s)
+ self.walk_fn(fk, fd, b, s)
}
}
}
}
fn visit_trait_item(&mut self, trait_item: &ast::TraitItem) {
+ // We reset the labels on every trait item, so that different
+ // methods in an impl can reuse label names.
+ let saved = replace(&mut self.labels_in_fn, vec![]);
+
if let ast::MethodTraitItem(ref sig, None) = trait_item.node {
self.visit_early_late(
subst::FnSpace, &sig.generics,
} else {
visit::walk_trait_item(self, trait_item);
}
+
+ replace(&mut self.labels_in_fn, saved);
}
fn visit_block(&mut self, b: &ast::Block) {
}
}
+#[derive(Copy, Clone, PartialEq)]
+enum ShadowKind { Label, Lifetime }
+struct Original { kind: ShadowKind, span: Span }
+struct Shadower { kind: ShadowKind, span: Span }
+
+fn original_label(span: Span) -> Original {
+ Original { kind: ShadowKind::Label, span: span }
+}
+fn shadower_label(span: Span) -> Shadower {
+ Shadower { kind: ShadowKind::Label, span: span }
+}
+fn original_lifetime(l: &ast::Lifetime) -> Original {
+ Original { kind: ShadowKind::Lifetime, span: l.span }
+}
+fn shadower_lifetime(l: &ast::Lifetime) -> Shadower {
+ Shadower { kind: ShadowKind::Lifetime, span: l.span }
+}
+
+impl ShadowKind {
+ fn desc(&self) -> &'static str {
+ match *self {
+ ShadowKind::Label => "label",
+ ShadowKind::Lifetime => "lifetime",
+ }
+ }
+}
+
+fn signal_shadowing_problem(
+ sess: &Session, name: ast::Name, orig: Original, shadower: Shadower) {
+ if let (ShadowKind::Lifetime, ShadowKind::Lifetime) = (orig.kind, shadower.kind) {
+ // lifetime/lifetime shadowing is an error
+ sess.span_err(shadower.span,
+ &format!("{} name `{}` shadows a \
+ {} name that is already in scope",
+ shadower.kind.desc(), name, orig.kind.desc()));
+ } else {
+ // shadowing involving a label is only a warning, due to issues with
+ // labels and lifetimes not being macro-hygienic.
+ sess.span_warn(shadower.span,
+ &format!("{} name `{}` shadows a \
+ {} name that is already in scope",
+ shadower.kind.desc(), name, orig.kind.desc()));
+ }
+ sess.span_note(orig.span,
+ &format!("shadowed {} `{}` declared here",
+ orig.kind.desc(), name));
+}
+
+// Adds all labels in `b` to `ctxt.labels_in_fn`, signalling a warning
+// if one of the label shadows a lifetime or another label.
+fn extract_labels<'v, 'a>(ctxt: &mut LifetimeContext<'a>, b: &'v ast::Block) {
+
+ struct GatherLabels<'a> {
+ sess: &'a Session,
+ scope: Scope<'a>,
+ labels_in_fn: &'a mut Vec<(ast::Ident, Span)>,
+ }
+
+ let mut gather = GatherLabels {
+ sess: ctxt.sess,
+ scope: ctxt.scope,
+ labels_in_fn: &mut ctxt.labels_in_fn,
+ };
+ gather.visit_block(b);
+ return;
+
+ impl<'v, 'a> Visitor<'v> for GatherLabels<'a> {
+ fn visit_expr(&mut self, ex: &'v ast::Expr) {
+ if let Some(label) = expression_label(ex) {
+ for &(prior, prior_span) in &self.labels_in_fn[..] {
+ // FIXME (#24278): non-hygienic comparision
+ if label.name == prior.name {
+ signal_shadowing_problem(self.sess,
+ label.name,
+ original_label(prior_span),
+ shadower_label(ex.span));
+ }
+ }
+
+ check_if_label_shadows_lifetime(self.sess,
+ self.scope,
+ label,
+ ex.span);
+
+ self.labels_in_fn.push((label, ex.span));
+ }
+ visit::walk_expr(self, ex)
+ }
+
+ fn visit_item(&mut self, _: &ast::Item) {
+ // do not recurse into items defined in the block
+ }
+ }
+
+ fn expression_label(ex: &ast::Expr) -> Option<ast::Ident> {
+ match ex.node {
+ ast::ExprWhile(_, _, Some(label)) |
+ ast::ExprWhileLet(_, _, _, Some(label)) |
+ ast::ExprForLoop(_, _, _, Some(label)) |
+ ast::ExprLoop(_, Some(label)) => Some(label),
+ _ => None,
+ }
+ }
+
+ fn check_if_label_shadows_lifetime<'a>(sess: &'a Session,
+ mut scope: Scope<'a>,
+ label: ast::Ident,
+ label_span: Span) {
+ loop {
+ match *scope {
+ BlockScope(_, s) => { scope = s; }
+ RootScope => { return; }
+
+ EarlyScope(_, lifetimes, s) |
+ LateScope(lifetimes, s) => {
+ for lifetime_def in lifetimes {
+ // FIXME (#24278): non-hygienic comparision
+ if label.name == lifetime_def.lifetime.name {
+ signal_shadowing_problem(
+ sess,
+ label.name,
+ original_lifetime(&lifetime_def.lifetime),
+ shadower_label(label_span));
+ return;
+ }
+ }
+ scope = s;
+ }
+ }
+ }
+ }
+}
+
impl<'a> LifetimeContext<'a> {
+ // This is just like visit::walk_fn, except that it extracts the
+ // labels of the function body and swaps them in before visiting
+ // the function body itself.
+ fn walk_fn<'b>(&mut self,
+ fk: visit::FnKind,
+ fd: &ast::FnDecl,
+ fb: &'b ast::Block,
+ _span: Span) {
+ match fk {
+ visit::FkItemFn(_, generics, _, _, _) => {
+ visit::walk_fn_decl(self, fd);
+ self.visit_generics(generics);
+ }
+ visit::FkMethod(_, sig, _) => {
+ visit::walk_fn_decl(self, fd);
+ self.visit_generics(&sig.generics);
+ self.visit_explicit_self(&sig.explicit_self);
+ }
+ visit::FkFnBlock(..) => {
+ visit::walk_fn_decl(self, fd);
+ }
+ }
+
+ // After inpsecting the decl, add all labels from the body to
+ // `self.labels_in_fn`.
+ extract_labels(self, fb);
+
+ self.visit_block(fb);
+ }
+
fn with<F>(&mut self, wrap_scope: ScopeChain, f: F) where
F: FnOnce(Scope, &mut LifetimeContext),
{
scope: &wrap_scope,
def_map: self.def_map,
trait_ref_hack: self.trait_ref_hack,
+ labels_in_fn: self.labels_in_fn.clone(),
};
debug!("entering scope {:?}", this.scope);
f(self.scope, &mut this);
mut old_scope: Scope,
lifetime: &ast::Lifetime)
{
+ for &(label, label_span) in &self.labels_in_fn {
+ // FIXME (#24278): non-hygienic comparision
+ if lifetime.name == label.name {
+ signal_shadowing_problem(self.sess,
+ lifetime.name,
+ original_label(label_span),
+ shadower_lifetime(&lifetime));
+ return;
+ }
+ }
+
loop {
match *old_scope {
BlockScope(_, s) => {
EarlyScope(_, lifetimes, s) |
LateScope(lifetimes, s) => {
if let Some((_, lifetime_def)) = search_lifetimes(lifetimes, lifetime) {
- self.sess.span_err(
- lifetime.span,
- &format!("lifetime name `{}` shadows another \
- lifetime name that is already in scope",
- token::get_name(lifetime.name)));
- self.sess.span_note(
- lifetime_def.span,
- &format!("shadowed lifetime `{}` declared here",
- token::get_name(lifetime.name)));
+ signal_shadowing_problem(
+ self.sess,
+ lifetime.name,
+ original_lifetime(&lifetime_def),
+ shadower_lifetime(&lifetime));
return;
}
projects / rust.git / commitdiff