cstore.rs

// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// the rustc crate store interface. This also includes types that
// are *mostly* used as a part of that interface, but these should
// probably get a better home if someone can find one.

use hir::def::{self, Def};
use hir::def_id::{CrateNum, DefId, DefIndex};
use hir::map as hir_map;
use hir::map::definitions::{Definitions, DefKey};
use hir::svh::Svh;
use middle::lang_items;
use ty::{self, Ty, TyCtxt};
use mir::Mir;
use session::Session;
use session::search_paths::PathKind;
use util::nodemap::{NodeSet, DefIdMap};
use std::path::PathBuf;
use std::rc::Rc;
use syntax::ast;
use syntax::attr;
use syntax::ext::base::SyntaxExtension;
use syntax::ptr::P;
use syntax::symbol::Symbol;
use syntax_pos::Span;
use rustc_back::target::Target;
use hir;
use hir::intravisit::Visitor;
use rustc_back::PanicStrategy;

pub use self::NativeLibraryKind::{NativeStatic, NativeFramework, NativeUnknown};

// lonely orphan structs and enums looking for a better home

#[derive(Clone, Debug)]
pub struct LinkMeta {
    pub crate_name: Symbol,
    pub crate_hash: Svh,
}

// Where a crate came from on the local filesystem. One of these three options
// must be non-None.
#[derive(PartialEq, Clone, Debug)]
pub struct CrateSource {
    pub dylib: Option<(PathBuf, PathKind)>,
    pub rlib: Option<(PathBuf, PathKind)>,
    pub rmeta: Option<(PathBuf, PathKind)>,
}

#[derive(RustcEncodable, RustcDecodable, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Debug)]
pub enum DepKind {
    /// A dependency that is only used for its macros, none of which are visible from other crates.
    /// These are included in the metadata only as placeholders and are ignored when decoding.
    UnexportedMacrosOnly,
    /// A dependency that is only used for its macros.
    MacrosOnly,
    /// A dependency that is always injected into the dependency list and so
    /// doesn't need to be linked to an rlib, e.g. the injected allocator.
    Implicit,
    /// A dependency that is required by an rlib version of this crate.
    /// Ordinary `extern crate`s result in `Explicit` dependencies.
    Explicit,
}

impl DepKind {
    pub fn macros_only(self) -> bool {
        match self {
            DepKind::UnexportedMacrosOnly | DepKind::MacrosOnly => true,
            DepKind::Implicit | DepKind::Explicit => false,
        }
    }
}

#[derive(PartialEq, Clone, Debug)]
pub enum LibSource {
    Some(PathBuf),
    MetadataOnly,
    None,
}

impl LibSource {
    pub fn is_some(&self) -> bool {
        if let LibSource::Some(_) = *self {
            true
        } else {
            false
        }
    }

    pub fn option(&self) -> Option<PathBuf> {
        match *self {
            LibSource::Some(ref p) => Some(p.clone()),
            LibSource::MetadataOnly | LibSource::None => None,
        }
    }
}

#[derive(Copy, Debug, PartialEq, Clone, RustcEncodable, RustcDecodable)]
pub enum LinkagePreference {
    RequireDynamic,
    RequireStatic,
}

#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
pub enum NativeLibraryKind {
    NativeStatic,    // native static library (.a archive)
    NativeFramework, // OSX-specific
    NativeUnknown,   // default way to specify a dynamic library
}

#[derive(Clone, Hash, RustcEncodable, RustcDecodable)]
pub struct NativeLibrary {
    pub kind: NativeLibraryKind,
    pub name: Symbol,
    pub cfg: Option<ast::MetaItem>,
    pub foreign_items: Vec<DefIndex>,
}

/// The data we save and restore about an inlined item or method.  This is not
/// part of the AST that we parse from a file, but it becomes part of the tree
/// that we trans.
#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
pub struct InlinedItem {
    pub def_id: DefId,
    pub body: P<hir::Expr>,
    pub const_fn_args: Vec<Option<DefId>>,
}

/// A borrowed version of `hir::InlinedItem`. This is what's encoded when saving
/// a crate; it then gets read as an InlinedItem.
#[derive(Clone, PartialEq, Eq, RustcEncodable, Hash, Debug)]
pub struct InlinedItemRef<'a> {
    pub def_id: DefId,
    pub body: &'a hir::Expr,
    pub const_fn_args: Vec<Option<DefId>>,
}

fn get_fn_args(decl: &hir::FnDecl) -> Vec<Option<DefId>> {
    decl.inputs.iter().map(|arg| match arg.pat.node {
        hir::PatKind::Binding(_, def_id, _, _) => Some(def_id),
        _ => None
    }).collect()
}

impl<'a> InlinedItemRef<'a> {
    pub fn from_item<'b, 'tcx>(def_id: DefId,
                               item: &'a hir::Item,
                               tcx: TyCtxt<'b, 'a, 'tcx>)
                               -> InlinedItemRef<'a> {
        let (body, args) = match item.node {
            hir::ItemFn(ref decl, _, _, _, _, body_id) =>
                (tcx.map.expr(body_id), get_fn_args(decl)),
            hir::ItemConst(_, ref body) => (&**body, Vec::new()),
            _ => bug!("InlinedItemRef::from_item wrong kind")
        };
        InlinedItemRef {
            def_id: def_id,
            body: body,
            const_fn_args: args
        }
    }

    pub fn from_trait_item(def_id: DefId,
                           item: &'a hir::TraitItem,
                           _tcx: TyCtxt)
                           -> InlinedItemRef<'a> {
        let (body, args) = match item.node {
            hir::ConstTraitItem(_, Some(ref body)) =>
                (&**body, Vec::new()),
            hir::ConstTraitItem(_, None) => {
                bug!("InlinedItemRef::from_trait_item called for const without body")
            },
            _ => bug!("InlinedItemRef::from_trait_item wrong kind")
        };
        InlinedItemRef {
            def_id: def_id,
            body: body,
            const_fn_args: args
        }
    }

    pub fn from_impl_item<'b, 'tcx>(def_id: DefId,
                                    item: &'a hir::ImplItem,
                                    tcx: TyCtxt<'b, 'a, 'tcx>)
                                    -> InlinedItemRef<'a> {
        let (body, args) = match item.node {
            hir::ImplItemKind::Method(ref sig, body_id) =>
                (tcx.map.expr(body_id), get_fn_args(&sig.decl)),
            hir::ImplItemKind::Const(_, ref body) =>
                (&**body, Vec::new()),
            _ => bug!("InlinedItemRef::from_impl_item wrong kind")
        };
        InlinedItemRef {
            def_id: def_id,
            body: body,
            const_fn_args: args
        }
    }

    pub fn visit<V>(&self, visitor: &mut V)
        where V: Visitor<'a>
    {
        visitor.visit_expr(&self.body);
    }
}

impl InlinedItem {
    pub fn visit<'ast,V>(&'ast self, visitor: &mut V)
        where V: Visitor<'ast>
    {
        visitor.visit_expr(&self.body);
    }
}

pub enum LoadedMacro {
    MacroRules(ast::MacroDef),
    ProcMacro(Rc<SyntaxExtension>),
}

#[derive(Copy, Clone, Debug)]
pub struct ExternCrate {
    /// def_id of an `extern crate` in the current crate that caused
    /// this crate to be loaded; note that there could be multiple
    /// such ids
    pub def_id: DefId,

    /// span of the extern crate that caused this to be loaded
    pub span: Span,

    /// If true, then this crate is the crate named by the extern
    /// crate referenced above. If false, then this crate is a dep
    /// of the crate.
    pub direct: bool,

    /// Number of links to reach the extern crate `def_id`
    /// declaration; used to select the extern crate with the shortest
    /// path
    pub path_len: usize,
}

/// A store of Rust crates, through with their metadata
/// can be accessed.
pub trait CrateStore<'tcx> {
    // item info
    fn describe_def(&self, def: DefId) -> Option<Def>;
    fn def_span(&self, sess: &Session, def: DefId) -> Span;
    fn stability(&self, def: DefId) -> Option<attr::Stability>;
    fn deprecation(&self, def: DefId) -> Option<attr::Deprecation>;
    fn visibility(&self, def: DefId) -> ty::Visibility;
    fn closure_kind(&self, def_id: DefId) -> ty::ClosureKind;
    fn closure_ty<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
                      -> ty::ClosureTy<'tcx>;
    fn item_variances(&self, def: DefId) -> Vec<ty::Variance>;
    fn item_type<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                     -> Ty<'tcx>;
    fn visible_parent_map<'a>(&'a self) -> ::std::cell::RefMut<'a, DefIdMap<DefId>>;
    fn item_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                           -> ty::GenericPredicates<'tcx>;
    fn item_super_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                                 -> ty::GenericPredicates<'tcx>;
    fn item_generics<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                         -> ty::Generics<'tcx>;
    fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute>;
    fn trait_def<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)-> ty::TraitDef;
    fn adt_def<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId) -> &'tcx ty::AdtDef;
    fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name>;
    fn inherent_implementations_for_type(&self, def_id: DefId) -> Vec<DefId>;

    // trait info
    fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId>;

    // impl info
    fn associated_item_def_ids(&self, def_id: DefId) -> Vec<DefId>;
    fn impl_trait_ref<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                          -> Option<ty::TraitRef<'tcx>>;
    fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity;
    fn custom_coerce_unsized_kind(&self, def: DefId)
                                  -> Option<ty::adjustment::CustomCoerceUnsized>;
    fn impl_parent(&self, impl_def_id: DefId) -> Option<DefId>;

    // trait/impl-item info
    fn trait_of_item(&self, def_id: DefId) -> Option<DefId>;
    fn associated_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                           -> Option<ty::AssociatedItem>;

    // flags
    fn is_const_fn(&self, did: DefId) -> bool;
    fn is_defaulted_trait(&self, did: DefId) -> bool;
    fn is_default_impl(&self, impl_did: DefId) -> bool;
    fn is_foreign_item(&self, did: DefId) -> bool;
    fn is_dllimport_foreign_item(&self, def: DefId) -> bool;
    fn is_statically_included_foreign_item(&self, def_id: DefId) -> bool;

    // crate metadata
    fn dylib_dependency_formats(&self, cnum: CrateNum)
                                    -> Vec<(CrateNum, LinkagePreference)>;
    fn dep_kind(&self, cnum: CrateNum) -> DepKind;
    fn export_macros(&self, cnum: CrateNum);
    fn lang_items(&self, cnum: CrateNum) -> Vec<(DefIndex, usize)>;
    fn missing_lang_items(&self, cnum: CrateNum) -> Vec<lang_items::LangItem>;
    fn is_staged_api(&self, cnum: CrateNum) -> bool;
    fn is_allocator(&self, cnum: CrateNum) -> bool;
    fn is_panic_runtime(&self, cnum: CrateNum) -> bool;
    fn is_compiler_builtins(&self, cnum: CrateNum) -> bool;
    fn panic_strategy(&self, cnum: CrateNum) -> PanicStrategy;
    fn extern_crate(&self, cnum: CrateNum) -> Option<ExternCrate>;
    /// The name of the crate as it is referred to in source code of the current
    /// crate.
    fn crate_name(&self, cnum: CrateNum) -> Symbol;
    /// The name of the crate as it is stored in the crate's metadata.
    fn original_crate_name(&self, cnum: CrateNum) -> Symbol;
    fn crate_hash(&self, cnum: CrateNum) -> Svh;
    fn crate_disambiguator(&self, cnum: CrateNum) -> Symbol;
    fn plugin_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>;
    fn derive_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>;
    fn native_libraries(&self, cnum: CrateNum) -> Vec<NativeLibrary>;
    fn exported_symbols(&self, cnum: CrateNum) -> Vec<DefId>;
    fn is_no_builtins(&self, cnum: CrateNum) -> bool;

    // resolve
    fn def_index_for_def_key(&self,
                             cnum: CrateNum,
                             def: DefKey)
                             -> Option<DefIndex>;
    fn def_key(&self, def: DefId) -> hir_map::DefKey;
    fn relative_def_path(&self, def: DefId) -> Option<hir_map::DefPath>;
    fn struct_field_names(&self, def: DefId) -> Vec<ast::Name>;
    fn item_children(&self, did: DefId) -> Vec<def::Export>;
    fn load_macro(&self, did: DefId, sess: &Session) -> LoadedMacro;

    // misc. metadata
    fn maybe_get_item_ast<'a>(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                              -> Option<(&'tcx InlinedItem, ast::NodeId)>;
    fn local_node_for_inlined_defid(&'tcx self, def_id: DefId) -> Option<ast::NodeId>;
    fn defid_for_inlined_node(&'tcx self, node_id: ast::NodeId) -> Option<DefId>;

    fn get_item_mir<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId) -> Mir<'tcx>;
    fn is_item_mir_available(&self, def: DefId) -> bool;

    /// Take a look if we need to inline or monomorphize this. If so, we
    /// will emit code for this item in the local crate, and thus
    /// create a translation item for it.
    fn can_have_local_instance<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId) -> bool;

    // This is basically a 1-based range of ints, which is a little
    // silly - I may fix that.
    fn crates(&self) -> Vec<CrateNum>;
    fn used_libraries(&self) -> Vec<NativeLibrary>;
    fn used_link_args(&self) -> Vec<String>;

    // utility functions
    fn metadata_filename(&self) -> &str;
    fn metadata_section_name(&self, target: &Target) -> &str;
    fn used_crates(&self, prefer: LinkagePreference) -> Vec<(CrateNum, LibSource)>;
    fn used_crate_source(&self, cnum: CrateNum) -> CrateSource;
    fn extern_mod_stmt_cnum(&self, emod_id: ast::NodeId) -> Option<CrateNum>;
    fn encode_metadata<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           reexports: &def::ExportMap,
                           link_meta: &LinkMeta,
                           reachable: &NodeSet) -> Vec<u8>;
    fn metadata_encoding_version(&self) -> &[u8];
}

// FIXME: find a better place for this?
pub fn validate_crate_name(sess: Option<&Session>, s: &str, sp: Option<Span>) {
    let mut err_count = 0;
    {
        let mut say = |s: &str| {
            match (sp, sess) {
                (_, None) => bug!("{}", s),
                (Some(sp), Some(sess)) => sess.span_err(sp, s),
                (None, Some(sess)) => sess.err(s),
            }
            err_count += 1;
        };
        if s.is_empty() {
            say("crate name must not be empty");
        }
        for c in s.chars() {
            if c.is_alphanumeric() { continue }
            if c == '_'  { continue }
            say(&format!("invalid character `{}` in crate name: `{}`", c, s));
        }
    }

    if err_count > 0 {
        sess.unwrap().abort_if_errors();
    }
}

/// A dummy crate store that does not support any non-local crates,
/// for test purposes.
pub struct DummyCrateStore;
#[allow(unused_variables)]
impl<'tcx> CrateStore<'tcx> for DummyCrateStore {
    // item info
    fn describe_def(&self, def: DefId) -> Option<Def> { bug!("describe_def") }
    fn def_span(&self, sess: &Session, def: DefId) -> Span { bug!("def_span") }
    fn stability(&self, def: DefId) -> Option<attr::Stability> { bug!("stability") }
    fn deprecation(&self, def: DefId) -> Option<attr::Deprecation> { bug!("deprecation") }
    fn visibility(&self, def: DefId) -> ty::Visibility { bug!("visibility") }
    fn closure_kind(&self, def_id: DefId) -> ty::ClosureKind { bug!("closure_kind") }
    fn closure_ty<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId)
                      -> ty::ClosureTy<'tcx>  { bug!("closure_ty") }
    fn item_variances(&self, def: DefId) -> Vec<ty::Variance> { bug!("item_variances") }
    fn item_type<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                     -> Ty<'tcx> { bug!("item_type") }
    fn visible_parent_map<'a>(&'a self) -> ::std::cell::RefMut<'a, DefIdMap<DefId>> {
        bug!("visible_parent_map")
    }
    fn item_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                           -> ty::GenericPredicates<'tcx> { bug!("item_predicates") }
    fn item_super_predicates<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                                 -> ty::GenericPredicates<'tcx> { bug!("item_super_predicates") }
    fn item_generics<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                         -> ty::Generics<'tcx> { bug!("item_generics") }
    fn item_attrs(&self, def_id: DefId) -> Vec<ast::Attribute> { bug!("item_attrs") }
    fn trait_def<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)-> ty::TraitDef
        { bug!("trait_def") }
    fn adt_def<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId) -> &'tcx ty::AdtDef
        { bug!("adt_def") }
    fn fn_arg_names(&self, did: DefId) -> Vec<ast::Name> { bug!("fn_arg_names") }
    fn inherent_implementations_for_type(&self, def_id: DefId) -> Vec<DefId> { vec![] }

    // trait info
    fn implementations_of_trait(&self, filter: Option<DefId>) -> Vec<DefId> { vec![] }
    fn def_index_for_def_key(&self,
                             cnum: CrateNum,
                             def: DefKey)
                             -> Option<DefIndex> {
        None
    }

    // impl info
    fn associated_item_def_ids(&self, def_id: DefId) -> Vec<DefId>
        { bug!("associated_items") }
    fn impl_trait_ref<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                          -> Option<ty::TraitRef<'tcx>> { bug!("impl_trait_ref") }
    fn impl_polarity(&self, def: DefId) -> hir::ImplPolarity { bug!("impl_polarity") }
    fn custom_coerce_unsized_kind(&self, def: DefId)
                                  -> Option<ty::adjustment::CustomCoerceUnsized>
        { bug!("custom_coerce_unsized_kind") }
    fn impl_parent(&self, def: DefId) -> Option<DefId> { bug!("impl_parent") }

    // trait/impl-item info
    fn trait_of_item(&self, def_id: DefId) -> Option<DefId> { bug!("trait_of_item") }
    fn associated_item<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                           -> Option<ty::AssociatedItem> { bug!("associated_item") }

    // flags
    fn is_const_fn(&self, did: DefId) -> bool { bug!("is_const_fn") }
    fn is_defaulted_trait(&self, did: DefId) -> bool { bug!("is_defaulted_trait") }
    fn is_default_impl(&self, impl_did: DefId) -> bool { bug!("is_default_impl") }
    fn is_foreign_item(&self, did: DefId) -> bool { bug!("is_foreign_item") }
    fn is_dllimport_foreign_item(&self, id: DefId) -> bool { false }
    fn is_statically_included_foreign_item(&self, def_id: DefId) -> bool { false }

    // crate metadata
    fn dylib_dependency_formats(&self, cnum: CrateNum)
                                    -> Vec<(CrateNum, LinkagePreference)>
        { bug!("dylib_dependency_formats") }
    fn lang_items(&self, cnum: CrateNum) -> Vec<(DefIndex, usize)>
        { bug!("lang_items") }
    fn missing_lang_items(&self, cnum: CrateNum) -> Vec<lang_items::LangItem>
        { bug!("missing_lang_items") }
    fn is_staged_api(&self, cnum: CrateNum) -> bool { bug!("is_staged_api") }
    fn dep_kind(&self, cnum: CrateNum) -> DepKind { bug!("is_explicitly_linked") }
    fn export_macros(&self, cnum: CrateNum) { bug!("export_macros") }
    fn is_allocator(&self, cnum: CrateNum) -> bool { bug!("is_allocator") }
    fn is_panic_runtime(&self, cnum: CrateNum) -> bool { bug!("is_panic_runtime") }
    fn is_compiler_builtins(&self, cnum: CrateNum) -> bool { bug!("is_compiler_builtins") }
    fn panic_strategy(&self, cnum: CrateNum) -> PanicStrategy {
        bug!("panic_strategy")
    }
    fn extern_crate(&self, cnum: CrateNum) -> Option<ExternCrate> { bug!("extern_crate") }
    fn crate_name(&self, cnum: CrateNum) -> Symbol { bug!("crate_name") }
    fn original_crate_name(&self, cnum: CrateNum) -> Symbol {
        bug!("original_crate_name")
    }
    fn crate_hash(&self, cnum: CrateNum) -> Svh { bug!("crate_hash") }
    fn crate_disambiguator(&self, cnum: CrateNum)
                           -> Symbol { bug!("crate_disambiguator") }
    fn plugin_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>
        { bug!("plugin_registrar_fn") }
    fn derive_registrar_fn(&self, cnum: CrateNum) -> Option<DefId>
        { bug!("derive_registrar_fn") }
    fn native_libraries(&self, cnum: CrateNum) -> Vec<NativeLibrary>
        { bug!("native_libraries") }
    fn exported_symbols(&self, cnum: CrateNum) -> Vec<DefId> { bug!("exported_symbols") }
    fn is_no_builtins(&self, cnum: CrateNum) -> bool { bug!("is_no_builtins") }

    // resolve
    fn def_key(&self, def: DefId) -> hir_map::DefKey { bug!("def_key") }
    fn relative_def_path(&self, def: DefId) -> Option<hir_map::DefPath> {
        bug!("relative_def_path")
    }
    fn struct_field_names(&self, def: DefId) -> Vec<ast::Name> { bug!("struct_field_names") }
    fn item_children(&self, did: DefId) -> Vec<def::Export> { bug!("item_children") }
    fn load_macro(&self, did: DefId, sess: &Session) -> LoadedMacro { bug!("load_macro") }

    // misc. metadata
    fn maybe_get_item_ast<'a>(&'tcx self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                              -> Option<(&'tcx InlinedItem, ast::NodeId)> {
        bug!("maybe_get_item_ast")
    }
    fn local_node_for_inlined_defid(&'tcx self, def_id: DefId) -> Option<ast::NodeId> {
        bug!("local_node_for_inlined_defid")
    }
    fn defid_for_inlined_node(&'tcx self, node_id: ast::NodeId) -> Option<DefId> {
        bug!("defid_for_inlined_node")
    }

    fn get_item_mir<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId)
                        -> Mir<'tcx> { bug!("get_item_mir") }
    fn is_item_mir_available(&self, def: DefId) -> bool {
        bug!("is_item_mir_available")
    }
    fn can_have_local_instance<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, def: DefId) -> bool {
        bug!("can_have_local_instance")
    }

    // This is basically a 1-based range of ints, which is a little
    // silly - I may fix that.
    fn crates(&self) -> Vec<CrateNum> { vec![] }
    fn used_libraries(&self) -> Vec<NativeLibrary> { vec![] }
    fn used_link_args(&self) -> Vec<String> { vec![] }

    // utility functions
    fn metadata_filename(&self) -> &str { bug!("metadata_filename") }
    fn metadata_section_name(&self, target: &Target) -> &str { bug!("metadata_section_name") }
    fn used_crates(&self, prefer: LinkagePreference) -> Vec<(CrateNum, LibSource)>
        { vec![] }
    fn used_crate_source(&self, cnum: CrateNum) -> CrateSource { bug!("used_crate_source") }
    fn extern_mod_stmt_cnum(&self, emod_id: ast::NodeId) -> Option<CrateNum> { None }
    fn encode_metadata<'a>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           reexports: &def::ExportMap,
                           link_meta: &LinkMeta,
                           reachable: &NodeSet) -> Vec<u8> { vec![] }
    fn metadata_encoding_version(&self) -> &[u8] { bug!("metadata_encoding_version") }
}

pub trait CrateLoader {
    fn process_item(&mut self, item: &ast::Item, defs: &Definitions);
    fn postprocess(&mut self, krate: &ast::Crate);
}