446 lines
16 KiB
Rust
446 lines
16 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/*!
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* Name resolution for lifetimes.
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*
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* Name resolution for lifetimes follows MUCH simpler rules than the
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* full resolve. For example, lifetime names are never exported or
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* used between functions, and they operate in a purely top-down
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* way. Therefore we break lifetime name resolution into a separate pass.
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*/
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use driver::session;
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use std::cell::RefCell;
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use std::vec_ng::Vec;
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use util::nodemap::NodeMap;
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use syntax::ast;
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use syntax::codemap::Span;
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use syntax::opt_vec;
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use syntax::opt_vec::OptVec;
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use syntax::parse::token::special_idents;
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use syntax::parse::token;
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use syntax::print::pprust::{lifetime_to_str};
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use syntax::visit;
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use syntax::visit::Visitor;
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// maps the id of each lifetime reference to the lifetime decl
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// that it corresponds to
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pub type NamedRegionMap = NodeMap<ast::DefRegion>;
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// Returns an instance of some type that implements std::fmt::Show
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fn lifetime_show(lt_name: &ast::Name) -> token::InternedString {
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token::get_name(*lt_name)
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}
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struct LifetimeContext {
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sess: session::Session,
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named_region_map: @RefCell<NamedRegionMap>,
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}
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enum ScopeChain<'a> {
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/// EarlyScope(i, ['a, 'b, ...], s) extends s with early-bound
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/// lifetimes, assigning indexes 'a => i, 'b => i+1, ... etc.
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EarlyScope(uint, &'a Vec<ast::Lifetime>, Scope<'a>),
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/// LateScope(binder_id, ['a, 'b, ...], s) extends s with late-bound
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/// lifetimes introduced by the declaration binder_id.
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LateScope(ast::NodeId, &'a Vec<ast::Lifetime>, Scope<'a>),
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/// lifetimes introduced by items within a code block are scoped
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/// to that block.
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BlockScope(ast::NodeId, Scope<'a>),
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RootScope
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}
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type Scope<'a> = &'a ScopeChain<'a>;
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pub fn krate(sess: session::Session, krate: &ast::Crate)
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-> @RefCell<NamedRegionMap> {
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let mut ctxt = LifetimeContext {
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sess: sess,
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named_region_map: @RefCell::new(NodeMap::new())
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};
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visit::walk_crate(&mut ctxt, krate, &RootScope);
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sess.abort_if_errors();
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ctxt.named_region_map
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}
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impl<'a> Visitor<Scope<'a>> for LifetimeContext {
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fn visit_item(&mut self,
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item: &ast::Item,
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_: Scope<'a>) {
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let root = RootScope;
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let scope = match item.node {
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ast::ItemFn(..) | // fn lifetimes get added in visit_fn below
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ast::ItemMod(..) |
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ast::ItemMac(..) |
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ast::ItemForeignMod(..) |
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ast::ItemStatic(..) => {
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RootScope
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}
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ast::ItemTy(_, ref generics) |
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ast::ItemEnum(_, ref generics) |
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ast::ItemStruct(_, ref generics) |
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ast::ItemImpl(ref generics, _, _, _) |
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ast::ItemTrait(ref generics, _, _) => {
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self.check_lifetime_names(&generics.lifetimes);
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EarlyScope(0, &generics.lifetimes, &root)
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}
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};
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debug!("entering scope {:?}", scope);
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visit::walk_item(self, item, &scope);
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debug!("exiting scope {:?}", scope);
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}
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fn visit_fn(&mut self, fk: &visit::FnKind, fd: &ast::FnDecl,
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b: &ast::Block, s: Span, n: ast::NodeId,
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scope: Scope<'a>) {
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match *fk {
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visit::FkItemFn(_, generics, _, _) |
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visit::FkMethod(_, generics, _) => {
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self.visit_fn_decl(
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n, generics, scope,
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|this, scope1| visit::walk_fn(this, fk, fd, b, s, n, scope1))
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}
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visit::FkFnBlock(..) => {
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visit::walk_fn(self, fk, fd, b, s, n, scope)
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}
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}
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}
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fn visit_ty(&mut self, ty: &ast::Ty, scope: Scope<'a>) {
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match ty.node {
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ast::TyClosure(c) => push_fn_scope(self, ty, scope, &c.lifetimes),
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ast::TyBareFn(c) => push_fn_scope(self, ty, scope, &c.lifetimes),
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_ => visit::walk_ty(self, ty, scope),
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}
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fn push_fn_scope(this: &mut LifetimeContext,
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ty: &ast::Ty,
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scope: Scope,
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lifetimes: &Vec<ast::Lifetime>) {
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let scope1 = LateScope(ty.id, lifetimes, scope);
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this.check_lifetime_names(lifetimes);
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debug!("pushing fn scope id={} due to type", ty.id);
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visit::walk_ty(this, ty, &scope1);
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debug!("popping fn scope id={} due to type", ty.id);
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}
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}
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fn visit_ty_method(&mut self,
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m: &ast::TypeMethod,
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scope: Scope<'a>) {
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self.visit_fn_decl(
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m.id, &m.generics, scope,
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|this, scope1| visit::walk_ty_method(this, m, scope1))
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}
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fn visit_block(&mut self,
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b: &ast::Block,
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scope: Scope<'a>) {
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let scope1 = BlockScope(b.id, scope);
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debug!("pushing block scope {}", b.id);
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visit::walk_block(self, b, &scope1);
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debug!("popping block scope {}", b.id);
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}
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fn visit_lifetime_ref(&mut self,
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lifetime_ref: &ast::Lifetime,
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scope: Scope<'a>) {
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if lifetime_ref.name == special_idents::statik.name {
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self.insert_lifetime(lifetime_ref, ast::DefStaticRegion);
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return;
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}
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self.resolve_lifetime_ref(lifetime_ref, scope);
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}
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}
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impl<'a> ScopeChain<'a> {
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fn count_early_params(&self) -> uint {
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/*!
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* Counts the number of early-bound parameters that are in
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* scope. Used when checking methods: the early-bound
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* lifetime parameters declared on the method are assigned
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* indices that come after the indices from the type. Given
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* something like `impl<'a> Foo { ... fn bar<'b>(...) }`
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* then `'a` gets index 0 and `'b` gets index 1.
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*/
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match *self {
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RootScope => 0,
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EarlyScope(base, lifetimes, _) => base + lifetimes.len(),
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LateScope(_, _, s) => s.count_early_params(),
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BlockScope(_, _) => 0,
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}
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}
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}
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impl LifetimeContext {
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/// Visits self by adding a scope and handling recursive walk over the contents with `walk`.
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fn visit_fn_decl(&mut self,
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n: ast::NodeId,
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generics: &ast::Generics,
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scope: Scope,
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walk: |&mut LifetimeContext, Scope|) {
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/*!
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* Handles visiting fns and methods. These are a bit
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* complicated because we must distinguish early- vs late-bound
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* lifetime parameters. We do this by checking which lifetimes
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* appear within type bounds; those are early bound lifetimes,
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* and the rest are late bound.
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*
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* For example:
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*
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* fn foo<'a,'b,'c,T:Trait<'b>>(...)
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*
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* Here `'a` and `'c` are late bound but `'b` is early
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* bound. Note that early- and late-bound lifetimes may be
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* interspersed together.
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*
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* If early bound lifetimes are present, we separate them into
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* their own list (and likewise for late bound). They will be
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* numbered sequentially, starting from the lowest index that
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* is already in scope (for a fn item, that will be 0, but for
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* a method it might not be). Late bound lifetimes are
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* resolved by name and associated with a binder id (`n`), so
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* the ordering is not important there.
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*/
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self.check_lifetime_names(&generics.lifetimes);
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let early_count = scope.count_early_params();
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let referenced_idents = free_lifetimes(&generics.ty_params);
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debug!("pushing fn scope id={} due to fn item/method\
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referenced_idents={:?} \
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early_count={}",
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n,
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referenced_idents.map(lifetime_show),
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early_count);
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if referenced_idents.is_empty() {
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let scope1 = LateScope(n, &generics.lifetimes, scope);
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walk(self, &scope1)
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} else {
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let (early, late) = generics.lifetimes.clone().partition(
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|l| referenced_idents.iter().any(|&i| i == l.name));
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let scope1 = EarlyScope(early_count, &early, scope);
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let scope2 = LateScope(n, &late, &scope1);
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walk(self, &scope2);
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}
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debug!("popping fn scope id={} due to fn item/method", n);
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}
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fn resolve_lifetime_ref(&self,
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lifetime_ref: &ast::Lifetime,
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scope: Scope) {
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// Walk up the scope chain, tracking the number of fn scopes
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// that we pass through, until we find a lifetime with the
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// given name or we run out of scopes. If we encounter a code
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// block, then the lifetime is not bound but free, so switch
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// over to `resolve_free_lifetime_ref()` to complete the
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// search.
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let mut depth = 0;
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let mut scope = scope;
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loop {
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match *scope {
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BlockScope(id, s) => {
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return self.resolve_free_lifetime_ref(id, lifetime_ref, s);
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}
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RootScope => {
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break;
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}
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EarlyScope(base, lifetimes, s) => {
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match search_lifetimes(lifetimes, lifetime_ref) {
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Some((offset, decl_id)) => {
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let index = base + offset;
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let def = ast::DefEarlyBoundRegion(index, decl_id);
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self.insert_lifetime(lifetime_ref, def);
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return;
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}
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None => {
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depth += 1;
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scope = s;
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}
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}
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}
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LateScope(binder_id, lifetimes, s) => {
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match search_lifetimes(lifetimes, lifetime_ref) {
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Some((_index, decl_id)) => {
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let def = ast::DefLateBoundRegion(binder_id, depth, decl_id);
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self.insert_lifetime(lifetime_ref, def);
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return;
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}
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None => {
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depth += 1;
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scope = s;
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}
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}
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}
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}
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}
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self.unresolved_lifetime_ref(lifetime_ref);
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}
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fn resolve_free_lifetime_ref(&self,
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scope_id: ast::NodeId,
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lifetime_ref: &ast::Lifetime,
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scope: Scope) {
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// Walk up the scope chain, tracking the outermost free scope,
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// until we encounter a scope that contains the named lifetime
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// or we run out of scopes.
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let mut scope_id = scope_id;
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let mut scope = scope;
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let mut search_result = None;
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loop {
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match *scope {
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BlockScope(id, s) => {
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scope_id = id;
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scope = s;
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}
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RootScope => {
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break;
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}
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EarlyScope(_, lifetimes, s) |
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LateScope(_, lifetimes, s) => {
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search_result = search_lifetimes(lifetimes, lifetime_ref);
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if search_result.is_some() {
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break;
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}
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scope = s;
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}
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}
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}
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match search_result {
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Some((_depth, decl_id)) => {
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let def = ast::DefFreeRegion(scope_id, decl_id);
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self.insert_lifetime(lifetime_ref, def);
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}
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None => {
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self.unresolved_lifetime_ref(lifetime_ref);
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}
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}
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}
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fn unresolved_lifetime_ref(&self,
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lifetime_ref: &ast::Lifetime) {
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self.sess.span_err(
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lifetime_ref.span,
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format!("use of undeclared lifetime name `'{}`",
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token::get_name(lifetime_ref.name)));
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}
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fn check_lifetime_names(&self, lifetimes: &Vec<ast::Lifetime>) {
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for i in range(0, lifetimes.len()) {
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let lifetime_i = lifetimes.get(i);
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let special_idents = [special_idents::statik];
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for lifetime in lifetimes.iter() {
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if special_idents.iter().any(|&i| i.name == lifetime.name) {
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self.sess.span_err(
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lifetime.span,
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format!("illegal lifetime parameter name: `{}`",
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token::get_name(lifetime.name)));
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}
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}
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for j in range(i + 1, lifetimes.len()) {
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let lifetime_j = lifetimes.get(j);
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if lifetime_i.name == lifetime_j.name {
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self.sess.span_err(
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lifetime_j.span,
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format!("lifetime name `'{}` declared twice in \
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the same scope",
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token::get_name(lifetime_j.name)));
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}
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}
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}
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}
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fn insert_lifetime(&self,
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lifetime_ref: &ast::Lifetime,
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def: ast::DefRegion) {
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if lifetime_ref.id == ast::DUMMY_NODE_ID {
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self.sess.span_bug(lifetime_ref.span,
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"lifetime reference not renumbered, \
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probably a bug in syntax::fold");
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}
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debug!("lifetime_ref={} id={} resolved to {:?}",
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lifetime_to_str(lifetime_ref),
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lifetime_ref.id,
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def);
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let mut named_region_map = self.named_region_map.borrow_mut();
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named_region_map.get().insert(lifetime_ref.id, def);
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}
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}
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fn search_lifetimes(lifetimes: &Vec<ast::Lifetime>,
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lifetime_ref: &ast::Lifetime)
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-> Option<(uint, ast::NodeId)> {
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for (i, lifetime_decl) in lifetimes.iter().enumerate() {
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if lifetime_decl.name == lifetime_ref.name {
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return Some((i, lifetime_decl.id));
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}
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}
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return None;
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}
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///////////////////////////////////////////////////////////////////////////
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pub fn early_bound_lifetimes<'a>(generics: &'a ast::Generics) -> Vec<ast::Lifetime> {
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let referenced_idents = free_lifetimes(&generics.ty_params);
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if referenced_idents.is_empty() {
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return Vec::new();
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}
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generics.lifetimes.iter()
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.filter(|l| referenced_idents.iter().any(|&i| i == l.name))
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.map(|l| *l)
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.collect()
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}
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pub fn free_lifetimes(ty_params: &OptVec<ast::TyParam>) -> OptVec<ast::Name> {
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/*!
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* Gathers up and returns the names of any lifetimes that appear
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* free in `ty_params`. Of course, right now, all lifetimes appear
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* free, since we don't currently have any binders in type parameter
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* declarations; just being forwards compatible with future extensions.
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*/
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let mut collector = FreeLifetimeCollector { names: opt_vec::Empty };
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for ty_param in ty_params.iter() {
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visit::walk_ty_param_bounds(&mut collector, &ty_param.bounds, ());
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}
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return collector.names;
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struct FreeLifetimeCollector {
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names: OptVec<ast::Name>,
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}
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impl Visitor<()> for FreeLifetimeCollector {
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fn visit_lifetime_ref(&mut self,
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lifetime_ref: &ast::Lifetime,
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_: ()) {
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self.names.push(lifetime_ref.name);
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}
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}
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}
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