diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs index 1036c97a5ad58..29073e017ea58 100644 --- a/src/librustc/middle/resolve_lifetime.rs +++ b/src/librustc/middle/resolve_lifetime.rs @@ -24,6 +24,7 @@ use middle::region; 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; @@ -70,6 +71,9 @@ struct LifetimeContext<'a> { // 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> { @@ -97,6 +101,7 @@ pub fn krate(sess: &Session, krate: &ast::Crate, def_map: &DefMap) -> NamedRegio scope: &ROOT_SCOPE, def_map: def_map, trait_ref_hack: false, + labels_in_fn: vec![], }, krate); sess.abort_if_errors(); named_region_map @@ -104,6 +109,10 @@ pub fn krate(sess: &Session, krate: &ast::Crate, def_map: &DefMap) -> NamedRegio 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 { @@ -137,6 +146,9 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> { } } }); + + // 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, @@ -144,16 +156,16 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> { 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) } } } @@ -190,6 +202,10 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> { } 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, @@ -197,6 +213,8 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> { } else { visit::walk_trait_item(self, trait_item); } + + replace(&mut self.labels_in_fn, saved); } fn visit_block(&mut self, b: &ast::Block) { @@ -286,7 +304,159 @@ impl<'a, 'v> Visitor<'v> for LifetimeContext<'a> { } } +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_error( + sess: &Session, name: ast::Name, orig: Original, shadower: Shadower) { + sess.span_err(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 an error +// 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_error(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 { + 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_error( + 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(&mut self, wrap_scope: ScopeChain, f: F) where F: FnOnce(Scope, &mut LifetimeContext), { @@ -297,6 +467,7 @@ impl<'a> LifetimeContext<'a> { 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); @@ -494,6 +665,17 @@ impl<'a> LifetimeContext<'a> { 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_error(self.sess, + lifetime.name, + original_label(label_span), + shadower_lifetime(&lifetime)); + return; + } + } + loop { match *old_scope { BlockScope(_, s) => { @@ -507,15 +689,11 @@ impl<'a> LifetimeContext<'a> { 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_error( + self.sess, + lifetime.name, + original_lifetime(&lifetime_def), + shadower_lifetime(&lifetime)); return; }