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lowering.rs
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// 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.
//! Lowers the AST to the HIR.
//!
//! Since the AST and HIR are fairly similar, this is mostly a simple procedure,
//! much like a fold. Where lowering involves a bit more work things get more
//! interesting and there are some invariants you should know about. These mostly
//! concern spans and ids.
//!
//! Spans are assigned to AST nodes during parsing and then are modified during
//! expansion to indicate the origin of a node and the process it went through
//! being expanded. Ids are assigned to AST nodes just before lowering.
//!
//! For the simpler lowering steps, ids and spans should be preserved. Unlike
//! expansion we do not preserve the process of lowering in the spans, so spans
//! should not be modified here. When creating a new node (as opposed to
//! 'folding' an existing one), then you create a new id using `next_id()`.
//!
//! You must ensure that ids are unique. That means that you should only use the
//! id from an AST node in a single HIR node (you can assume that AST node ids
//! are unique). Every new node must have a unique id. Avoid cloning HIR nodes.
//! If you do, you must then set the new node's id to a fresh one.
//!
//! Spans are used for error messages and for tools to map semantics back to
//! source code. It is therefore not as important with spans as ids to be strict
//! about use (you can't break the compiler by screwing up a span). Obviously, a
//! HIR node can only have a single span. But multiple nodes can have the same
//! span and spans don't need to be kept in order, etc. Where code is preserved
//! by lowering, it should have the same span as in the AST. Where HIR nodes are
//! new it is probably best to give a span for the whole AST node being lowered.
//! All nodes should have real spans, don't use dummy spans. Tools are likely to
//! get confused if the spans from leaf AST nodes occur in multiple places
//! in the HIR, especially for multiple identifiers.
use dep_graph::DepGraph;
use hir;
use hir::map::{Definitions, DefKey};
use hir::def_id::{DefIndex, DefId, CRATE_DEF_INDEX};
use hir::def::{Def, PathResolution};
use lint::builtin::PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES;
use middle::cstore::CrateStore;
use rustc_data_structures::indexed_vec::IndexVec;
use session::Session;
use util::common::FN_OUTPUT_NAME;
use util::nodemap::{DefIdMap, FxHashMap, NodeMap};
use std::collections::BTreeMap;
use std::fmt::Debug;
use std::iter;
use std::mem;
use syntax::attr;
use syntax::ast::*;
use syntax::errors;
use syntax::ext::hygiene::{Mark, SyntaxContext};
use syntax::ptr::P;
use syntax::codemap::{self, respan, Spanned, CompilerDesugaringKind};
use syntax::std_inject;
use syntax::symbol::{Symbol, keywords};
use syntax::tokenstream::{TokenStream, TokenTree, Delimited};
use syntax::parse::token::Token;
use syntax::util::small_vector::SmallVector;
use syntax::visit::{self, Visitor};
use syntax_pos::Span;
const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
pub struct LoweringContext<'a> {
crate_root: Option<&'static str>,
// Use to assign ids to hir nodes that do not directly correspond to an ast node
sess: &'a Session,
cstore: &'a CrateStore,
// As we walk the AST we must keep track of the current 'parent' def id (in
// the form of a DefIndex) so that if we create a new node which introduces
// a definition, then we can properly create the def id.
parent_def: Option<DefIndex>,
resolver: &'a mut Resolver,
name_map: FxHashMap<Ident, Name>,
/// The items being lowered are collected here.
items: BTreeMap<NodeId, hir::Item>,
trait_items: BTreeMap<hir::TraitItemId, hir::TraitItem>,
impl_items: BTreeMap<hir::ImplItemId, hir::ImplItem>,
bodies: BTreeMap<hir::BodyId, hir::Body>,
exported_macros: Vec<hir::MacroDef>,
trait_impls: BTreeMap<DefId, Vec<NodeId>>,
trait_default_impl: BTreeMap<DefId, NodeId>,
is_generator: bool,
catch_scopes: Vec<NodeId>,
loop_scopes: Vec<NodeId>,
is_in_loop_condition: bool,
type_def_lifetime_params: DefIdMap<usize>,
current_hir_id_owner: Vec<(DefIndex, u32)>,
item_local_id_counters: NodeMap<u32>,
node_id_to_hir_id: IndexVec<NodeId, hir::HirId>,
}
pub trait Resolver {
/// Resolve a hir path generated by the lowerer when expanding `for`, `if let`, etc.
fn resolve_hir_path(&mut self, path: &mut hir::Path, is_value: bool);
/// Obtain the resolution for a node id
fn get_resolution(&mut self, id: NodeId) -> Option<PathResolution>;
/// We must keep the set of definitions up to date as we add nodes that weren't in the AST.
/// This should only return `None` during testing.
fn definitions(&mut self) -> &mut Definitions;
}
#[derive(Clone, Copy, Debug)]
enum ImplTraitContext {
/// Treat `impl Trait` as shorthand for a new universal generic parameter.
/// Example: `fn foo(x: impl Debug)`, where `impl Debug` is conceptually
/// equivalent to a fresh universal parameter like `fn foo<T: Debug>(x: T)`.
///
/// We store a DefId here so we can look up necessary information later
Universal(DefId),
/// Treat `impl Trait` as shorthand for a new universal existential parameter.
/// Example: `fn foo() -> impl Debug`, where `impl Debug` is conceptually
/// equivalent to a fresh existential parameter like `abstract type T; fn foo() -> T`.
Existential,
/// `impl Trait` is not accepted in this position.
Disallowed,
}
pub fn lower_crate(sess: &Session,
cstore: &CrateStore,
dep_graph: &DepGraph,
krate: &Crate,
resolver: &mut Resolver)
-> hir::Crate {
// We're constructing the HIR here; we don't care what we will
// read, since we haven't even constructed the *input* to
// incr. comp. yet.
let _ignore = dep_graph.in_ignore();
LoweringContext {
crate_root: std_inject::injected_crate_name(krate),
sess,
cstore,
parent_def: None,
resolver,
name_map: FxHashMap(),
items: BTreeMap::new(),
trait_items: BTreeMap::new(),
impl_items: BTreeMap::new(),
bodies: BTreeMap::new(),
trait_impls: BTreeMap::new(),
trait_default_impl: BTreeMap::new(),
exported_macros: Vec::new(),
catch_scopes: Vec::new(),
loop_scopes: Vec::new(),
is_in_loop_condition: false,
type_def_lifetime_params: DefIdMap(),
current_hir_id_owner: vec![(CRATE_DEF_INDEX, 0)],
item_local_id_counters: NodeMap(),
node_id_to_hir_id: IndexVec::new(),
is_generator: false,
}.lower_crate(krate)
}
#[derive(Copy, Clone, PartialEq, Eq)]
enum ParamMode {
/// Any path in a type context.
Explicit,
/// The `module::Type` in `module::Type::method` in an expression.
Optional
}
struct LoweredNodeId {
node_id: NodeId,
hir_id: hir::HirId,
}
enum ParenthesizedGenericArgs {
Ok,
Warn,
Err,
}
impl<'a> LoweringContext<'a> {
fn lower_crate(mut self, c: &Crate) -> hir::Crate {
/// Full-crate AST visitor that inserts into a fresh
/// `LoweringContext` any information that may be
/// needed from arbitrary locations in the crate.
/// E.g. The number of lifetime generic parameters
/// declared for every type and trait definition.
struct MiscCollector<'lcx, 'interner: 'lcx> {
lctx: &'lcx mut LoweringContext<'interner>,
}
impl<'lcx, 'interner> Visitor<'lcx> for MiscCollector<'lcx, 'interner> {
fn visit_item(&mut self, item: &'lcx Item) {
self.lctx.allocate_hir_id_counter(item.id, item);
match item.node {
ItemKind::Struct(_, ref generics) |
ItemKind::Union(_, ref generics) |
ItemKind::Enum(_, ref generics) |
ItemKind::Ty(_, ref generics) |
ItemKind::Trait(_, ref generics, ..) => {
let def_id = self.lctx.resolver.definitions().local_def_id(item.id);
let count = generics.lifetimes.len();
self.lctx.type_def_lifetime_params.insert(def_id, count);
}
_ => {}
}
visit::walk_item(self, item);
}
fn visit_trait_item(&mut self, item: &'lcx TraitItem) {
self.lctx.allocate_hir_id_counter(item.id, item);
visit::walk_trait_item(self, item);
}
fn visit_impl_item(&mut self, item: &'lcx ImplItem) {
self.lctx.allocate_hir_id_counter(item.id, item);
visit::walk_impl_item(self, item);
}
}
struct ItemLowerer<'lcx, 'interner: 'lcx> {
lctx: &'lcx mut LoweringContext<'interner>,
}
impl<'lcx, 'interner> Visitor<'lcx> for ItemLowerer<'lcx, 'interner> {
fn visit_item(&mut self, item: &'lcx Item) {
let mut item_lowered = true;
self.lctx.with_hir_id_owner(item.id, |lctx| {
if let Some(hir_item) = lctx.lower_item(item) {
lctx.items.insert(item.id, hir_item);
} else {
item_lowered = false;
}
});
if item_lowered {
visit::walk_item(self, item);
}
}
fn visit_trait_item(&mut self, item: &'lcx TraitItem) {
self.lctx.with_hir_id_owner(item.id, |lctx| {
let id = hir::TraitItemId { node_id: item.id };
let hir_item = lctx.lower_trait_item(item);
lctx.trait_items.insert(id, hir_item);
});
visit::walk_trait_item(self, item);
}
fn visit_impl_item(&mut self, item: &'lcx ImplItem) {
self.lctx.with_hir_id_owner(item.id, |lctx| {
let id = hir::ImplItemId { node_id: item.id };
let hir_item = lctx.lower_impl_item(item);
lctx.impl_items.insert(id, hir_item);
});
visit::walk_impl_item(self, item);
}
}
self.lower_node_id(CRATE_NODE_ID);
debug_assert!(self.node_id_to_hir_id[CRATE_NODE_ID] == hir::CRATE_HIR_ID);
visit::walk_crate(&mut MiscCollector { lctx: &mut self }, c);
visit::walk_crate(&mut ItemLowerer { lctx: &mut self }, c);
let module = self.lower_mod(&c.module);
let attrs = self.lower_attrs(&c.attrs);
let body_ids = body_ids(&self.bodies);
self.resolver
.definitions()
.init_node_id_to_hir_id_mapping(self.node_id_to_hir_id);
hir::Crate {
module,
attrs,
span: c.span,
exported_macros: hir::HirVec::from(self.exported_macros),
items: self.items,
trait_items: self.trait_items,
impl_items: self.impl_items,
bodies: self.bo
1241
dies,
body_ids,
trait_impls: self.trait_impls,
trait_default_impl: self.trait_default_impl,
}
}
fn allocate_hir_id_counter<T: Debug>(&mut self,
owner: NodeId,
debug: &T) {
if self.item_local_id_counters.insert(owner, 0).is_some() {
bug!("Tried to allocate item_local_id_counter for {:?} twice", debug);
}
// Always allocate the first HirId for the owner itself
self.lower_node_id_with_owner(owner, owner);
}
fn lower_node_id_generic<F>(&mut self,
ast_node_id: NodeId,
alloc_hir_id: F)
-> LoweredNodeId
where F: FnOnce(&mut Self) -> hir::HirId
{
if ast_node_id == DUMMY_NODE_ID {
return LoweredNodeId {
node_id: DUMMY_NODE_ID,
hir_id: hir::DUMMY_HIR_ID,
}
}
let min_size = ast_node_id.as_usize() + 1;
if min_size > self.node_id_to_hir_id.len() {
self.node_id_to_hir_id.resize(min_size, hir::DUMMY_HIR_ID);
}
let existing_hir_id = self.node_id_to_hir_id[ast_node_id];
if existing_hir_id == hir::DUMMY_HIR_ID {
// Generate a new HirId
let hir_id = alloc_hir_id(self);
self.node_id_to_hir_id[ast_node_id] = hir_id;
LoweredNodeId {
node_id: ast_node_id,
hir_id,
}
} else {
LoweredNodeId {
node_id: ast_node_id,
hir_id: existing_hir_id,
}
}
}
fn with_hir_id_owner<F>(&mut self, owner: NodeId, f: F)
where F: FnOnce(&mut Self)
{
let counter = self.item_local_id_counters
.insert(owner, HIR_ID_COUNTER_LOCKED)
.unwrap();
let def_index = self.resolver.definitions().opt_def_index(owner).unwrap();
self.current_hir_id_owner.push((def_index, counter));
f(self);
let (new_def_index, new_counter) = self.current_hir_id_owner.pop().unwrap();
debug_assert!(def_index == new_def_index);
debug_assert!(new_counter >= counter);
let prev = self.item_local_id_counters.insert(owner, new_counter).unwrap();
debug_assert!(prev == HIR_ID_COUNTER_LOCKED);
}
/// This method allocates a new HirId for the given NodeId and stores it in
/// the LoweringContext's NodeId => HirId map.
/// Take care not to call this method if the resulting HirId is then not
/// actually used in the HIR, as that would trigger an assertion in the
/// HirIdValidator later on, which makes sure that all NodeIds got mapped
/// properly. Calling the method twice with the same NodeId is fine though.
fn lower_node_id(&mut self, ast_node_id: NodeId) -> LoweredNodeId {
self.lower_node_id_generic(ast_node_id, |this| {
let &mut (def_index, ref mut local_id_counter) = this.current_hir_id_owner
.last_mut()
.unwrap();
let local_id = *local_id_counter;
*local_id_counter += 1;
hir::HirId {
owner: def_index,
local_id: hir::ItemLocalId(local_id),
}
})
}
fn lower_node_id_with_owner(&mut self,
ast_node_id: NodeId,
owner: NodeId)
-> LoweredNodeId {
self.lower_node_id_generic(ast_node_id, |this| {
let local_id_counter = this.item_local_id_counters
.get_mut(&owner)
.unwrap();
let local_id = *local_id_counter;
// We want to be sure not to modify the counter in the map while it
// is also on the stack. Otherwise we'll get lost updates when writing
// back from the stack to the map.
debug_assert!(local_id != HIR_ID_COUNTER_LOCKED);
*local_id_counter += 1;
let def_index = this.resolver.definitions().opt_def_index(owner).unwrap();
hir::HirId {
owner: def_index,
local_id: hir::ItemLocalId(local_id),
}
})
}
fn record_body(&mut self, value: hir::Expr, decl: Option<&FnDecl>)
-> hir::BodyId {
let body = hir::Body {
arguments: decl.map_or(hir_vec![], |decl| {
decl.inputs.iter().map(|x| self.lower_arg(x)).collect()
}),
is_generator: self.is_generator,
value,
};
let id = body.id();
self.bodies.insert(id, body);
id
}
fn next_id(&mut self) -> LoweredNodeId {
self.lower_node_id(self.sess.next_node_id())
}
fn expect_full_def(&mut self, id: NodeId) -> Def {
self.resolver.get_resolution(id).map_or(Def::Err, |pr| {
if pr.unresolved_segments() != 0 {
bug!("path not fully resolved: {:?}", pr);
}
pr.base_def()
})
}
fn diagnostic(&self) -> &errors::Handler {
self.sess.diagnostic()
}
fn str_to_ident(&self, s: &'static str) -> Name {
Symbol::gensym(s)
}
fn allow_internal_unstable(&self, reason: CompilerDesugaringKind, span: Span) -> Span
{
let mark = Mark::fresh(Mark::root());
mark.set_expn_info(codemap::ExpnInfo {
call_site: span,
callee: codemap::NameAndSpan {
format: codemap::CompilerDesugaring(reason),
span: Some(span),
allow_internal_unstable: true,
allow_internal_unsafe: false,
},
});
span.with_ctxt(SyntaxContext::empty().apply_mark(mark))
}
fn with_catch_scope<T, F>(&mut self, catch_id: NodeId, f: F) -> T
where F: FnOnce(&mut LoweringContext) -> T
{
let len = self.catch_scopes.len();
self.catch_scopes.push(catch_id);
let result = f(self);
assert_eq!(len + 1, self.catch_scopes.len(),
"catch scopes should be added and removed in stack order");
self.catch_scopes.pop().unwrap();
result
}
fn lower_body<F>(&mut self, decl: Option<&FnDecl>, f: F) -> hir::BodyId
where F: FnOnce(&mut LoweringContext) -> hir::Expr
{
let prev = mem::replace(&mut self.is_generator, false);
let result = f(self);
let r = self.record_body(result, decl);
self.is_generator = prev;
return r
}
fn with_loop_scope<T, F>(&mut self, loop_id: NodeId, f: F) -> T
where F: FnOnce(&mut LoweringContext) -> T
{
// We're no longer in the base loop's condition; we're in another loop.
let was_in_loop_condition = self.is_in_loop_condition;
self.is_in_loop_condition = false;
let len = self.loop_scopes.len();
self.loop_scopes.push(loop_id);
let result = f(self);
assert_eq!(len + 1, self.loop_scopes.len(),
"Loop scopes should be added and removed in stack order");
self.loop_scopes.pop().unwrap();
self.is_in_loop_condition = was_in_loop_condition;
result
}
fn with_loop_condition_scope<T, F>(&mut self, f: F) -> T
where F: FnOnce(&mut LoweringContext) -> T
{
let was_in_loop_condition = self.is_in_loop_condition;
self.is_in_loop_condition = true;
let result = f(self);
self.is_in_loop_condition = was_in_loop_condition;
result
}
fn with_new_scopes<T, F>(&mut self, f: F) -> T
where F: FnOnce(&mut LoweringContext) -> T
{
let was_in_loop_condition = self.is_in_loop_condition;
self.is_in_loop_condition = false;
let catch_scopes = mem::replace(&mut self.catch_scopes, Vec::new());
let loop_scopes = mem::replace(&mut self.loop_scopes, Vec::new());
let result = f(self);
self.catch_scopes = catch_scopes;
self.loop_scopes = loop_scopes;
self.is_in_loop_condition = was_in_loop_condition;
result
}
fn with_parent_def<T, F>(&mut self, parent_id: NodeId, f: F) -> T
where F: FnOnce(&mut LoweringContext) -> T
{
let old_def = self.parent_def;
self.parent_def = {
let defs = self.resolver.definitions();
Some(defs.opt_def_index(parent_id).unwrap())
};
let result = f(self);
self.parent_def = old_def;
result
}
fn def_key(&mut self, id: DefId) -> DefKey {
if id.is_local() {
self.resolver.definitions().def_key(id.index)
} else {
self.cstore.def_key(id)
}
}
fn lower_ident(&mut self, ident: Ident) -> Name {
let ident = ident.modern();
if ident.ctxt == SyntaxContext::empty() {
return ident.name;
}
*self.name_map.entry(ident).or_insert_with(|| Symbol::from_ident(ident))
}
fn lower_opt_sp_ident(&mut self, o_id: Option<Spanned<Ident>>) -> Option<Spanned<Name>> {
o_id.map(|sp_ident| respan(sp_ident.span, sp_ident.node.name))
}
fn lower_loop_destination(&mut self, destination: Option<(NodeId, Spanned<Ident>)>)
-> hir::Destination
{
match destination {
Some((id, label_ident)) => {
let target = if let Def::Label(loop_id) = self.expect_full_def(id) {
hir::LoopIdResult::Ok(self.lower_node_id(loop_id).node_id)
} else {
hir::LoopIdResult::Err(hir::LoopIdError::UnresolvedLabel)
};
hir::Destination {
ident: Some(label_ident),
target_id: hir::ScopeTarget::Loop(target),
}
},
None => {
let loop_id = self.loop_scopes
.last()
.map(|innermost_loop_id| *innermost_loop_id);
hir::Destination {
ident: None,
target_id: hir::ScopeTarget::Loop(
loop_id.map(|id| Ok(self.lower_node_id(id).node_id))
.unwrap_or(Err(hir::LoopIdError::OutsideLoopScope))
.into())
}
}
}
}
fn lower_attrs(&mut self, attrs: &Vec<Attribute>) -> hir::HirVec<Attribute> {
attrs.iter().map(|a| self.lower_attr(a)).collect::<Vec<_>>().into()
}
fn lower_attr(&mut self, attr: &Attribute) -> Attribute {
Attribute {
id: attr.id,
style: attr.style,
path: attr.path.clone(),
tokens: self.lower_token_stream(attr.tokens.clone()),
is_sugared_doc: attr.is_sugared_doc,
span: attr.span,
}
}
fn lower_token_stream(&mut self, tokens: TokenStream) -> TokenStream {
tokens.into_trees()
.flat_map(|tree| self.lower_token_tree(tree).into_trees())
.collect()
}
fn lower_token_tree(&mut self, tree: TokenTree) -> TokenStream {
match tree {
TokenTree::Token(span, token) => {
self.lower_token(token, span)
}
TokenTree::Delimited(span, delimited) => {
TokenTree::Delimited(span, Delimited {
delim: delimited.delim,
tts: self.lower_token_stream(delimited.tts.into()).into(),
}).into()
}
}
}
fn lower_token(&mut self, token: Token, span: Span) -> TokenStream {
match token {
Token::Interpolated(_) => {}
other => return TokenTree::Token(span, other).into(),
}
let tts = token.interpolated_to_tokenstream(&self.sess.parse_sess, span);
self.lower_token_stream(tts)
}
fn lower_arm(&mut self, arm: &Arm) -> hir::Arm {
hir::Arm {
attrs: self.lower_attrs(&arm.attrs),
pats: arm.pats.iter().map(|x| self.lower_pat(x)).collect(),
guard: arm.guard.as_ref().map(|ref x| P(self.lower_expr(x))),
body: P(self.lower_expr(&arm.body)),
}
}
fn lower_ty_binding(&mut self, b: &TypeBinding, itctx: ImplTraitContext) -> hir::TypeBinding {
hir::TypeBinding {
id: self.lower_node_id(b.id).node_id,
name: self.lower_ident(b.ident),
ty: self.lower_ty(&b.ty, itctx),
span: b.span,
}
}
fn lower_ty(&mut self, t: &Ty, itctx: ImplTraitContext) -> P<hir::Ty> {
let kind = match t.node {
TyKind::Infer => hir::TyInfer,
TyKind::Err => hir::TyErr,
TyKind::Slice(ref ty) => hir::TySlice(self.lower_ty(ty, itctx)),
TyKind::Ptr(ref mt) => hir::TyPtr(self.lower_mt(mt, itctx)),
TyKind::Rptr(ref region, ref mt) => {
let span = t.span.with_hi(t.span.lo());
let lifetime = match *region {
Some(ref lt) => self.lower_lifetime(lt),
None => self.elided_lifetime(span)
};
hir::TyRptr(lifetime, self.lower_mt(mt, itctx))
}
TyKind::BareFn(ref f) => {
hir::TyBareFn(P(hir::BareFnTy {
lifetimes: self.lower_lifetime_defs(&f.lifetimes),
unsafety: self.lower_unsafety(f.unsafety),
abi: f.abi,
decl: self.lower_fn_decl(&f.decl, None),
arg_names: self.lower_fn_args_to_names(&f.decl),
}))
}
TyKind::Never => hir::TyNever,
TyKind::Tup(ref tys) => {
hir::TyTup(tys.iter().map(|ty| self.lower_ty(ty, itctx)).collect())
}
TyKind::Paren(ref ty) => {
return self.lower_ty(ty, itctx);
}
TyKind::Path(ref qself, ref path) => {
let id = self.lower_node_id(t.id);
let qpath = self.lower_qpath(t.id, qself, path, ParamMode::Explicit, itctx);
return self.ty_path(id, t.span, qpath);
}
TyKind::ImplicitSelf => {
hir::TyPath(hir::QPath::Resolved(None, P(hir::Path {
def: self.expect_full_def(t.id),
segments: hir_vec![
hir::PathSegment::from_name(keywords::SelfType.name())
],
span: t.span,
})))
}
TyKind::Array(ref ty, ref length) => {
let length = self.lower_body(None, |this| this.lower_expr(length));
hir::TyArray(self.lower_ty(ty, itctx), length)
}
TyKind::Typeof(ref expr) => {
let expr = self.lower_body(None, |this| this.lower_expr(expr));
hir::TyTypeof(expr)
}
TyKind::TraitObject(ref bounds, ..) => {
let mut lifetime_bound = None;
let bounds = bounds.iter().filter_map(|bound| {
match *bound {
TraitTyParamBound(ref ty, TraitBoundModifier::None) => {
Some(self.lower_poly_trait_ref(ty, itctx))
}
TraitTyParamBound(_, TraitBoundModifier::Maybe) => None,
RegionTyParamBound(ref lifetime) => {
if lifetime_bound.is_none() {
lifetime_bound = Some(self.lower_lifetime(lifetime));
}
None
}
}
}).collect();
let lifetime_bound = lifetime_bound.unwrap_or_else(|| {
self.elided_lifetime(t.span)
});
hir::TyTraitObject(bounds, lifetime_bound)
}
TyKind::ImplTrait(ref bounds) => {
match itctx {
ImplTraitContext::Existential =>
hir::TyImplTraitExistential(self.lower_bounds(bounds, itctx)),
ImplTraitContext::Universal(def_id) =>
hir::TyImplTraitUniversal(def_id, self.lower_bounds(bounds, itctx)),
ImplTraitContext::Disallowed => {
10000
self.impl_trait_err(t.span);
hir::TyErr
}
}
}
TyKind::Mac(_) => panic!("TyMac should have been expanded by now."),
};
let LoweredNodeId { node_id, hir_id } = self.lower_node_id(t.id);
P(hir::Ty {
id: node_id,
node: kind,
span: t.span,
hir_id,
})
}
fn lower_foreign_mod(&mut self, fm: &ForeignMod) -> hir::ForeignMod {
hir::ForeignMod {
abi: fm.abi,
items: fm.items.iter().map(|x| self.lower_foreign_item(x)).collect(),
}
}
fn lower_global_asm(&mut self, ga: &GlobalAsm) -> P<hir::GlobalAsm> {
P(hir::GlobalAsm {
asm: ga.asm,
ctxt: ga.ctxt,
})
}
fn lower_variant(&mut self, v: &Variant) -> hir::Variant {
Spanned {
node: hir::Variant_ {
name: v.node.name.name,
attrs: self.lower_attrs(&v.node.attrs),
data: self.lower_variant_data(&v.node.data),
disr_expr: v.node.disr_expr.as_ref().map(|e| {
self.lower_body(None, |this| this.lower_expr(e))
}),
},
span: v.span,
}
}
fn lower_qpath(&mut self,
id: NodeId,
qself: &Option<QSelf>,
p: &Path,
param_mode: ParamMode,
itctx: ImplTraitContext)
-> hir::QPath {
let qself_position = qself.as_ref().map(|q| q.position);
let qself = qself.as_ref().map(|q| self.lower_ty(&q.ty, itctx));
let resolution = self.resolver.get_resolution(id)
.unwrap_or(PathResolution::new(Def::Err));
let proj_start = p.segments.len() - resolution.unresolved_segments();
let path = P(hir::Path {
def: resolution.base_def(),
segments: p.segments[..proj_start].iter().enumerate().map(|(i, segment)| {
let param_mode = match (qself_position, param_mode) {
(Some(j), ParamMode::Optional) if i < j => {
// This segment is part of the trait path in a
// qualified path - one of `a`, `b` or `Trait`
// in `<X as a::b::Trait>::T::U::method`.
ParamMode::Explicit
}
_ => param_mode
};
// Figure out if this is a type/trait segment,
// which may need lifetime elision performed.
let parent_def_id = |this: &mut Self, def_id: DefId| {
DefId {
krate: def_id.krate,
index: this.def_key(def_id).parent.expect("missing parent")
}
};
let type_def_id = match resolution.base_def() {
Def::AssociatedTy(def_id) if i + 2 == proj_start => {
Some(parent_def_id(self, def_id))
}
Def::Variant(def_id) if i + 1 == proj_start => {
Some(parent_def_id(self, def_id))
}
Def::Struct(def_id) |
Def::Union(def_id) |
Def::Enum(def_id) |
Def::TyAlias(def_id) |
Def::Trait(def_id) if i + 1 == proj_start => Some(def_id),
_ => None
};
let parenthesized_generic_args = match resolution.base_def() {
// `a::b::Trait(Args)`
Def::Trait(..) if i + 1 == proj_start => ParenthesizedGenericArgs::Ok,
// `a::b::Trait(Args)::TraitItem`
Def::Method(..) |
Def::AssociatedConst(..) |
Def::AssociatedTy(..) if i + 2 == proj_start => ParenthesizedGenericArgs::Ok,
// Avoid duplicated errors
Def::Err => ParenthesizedGenericArgs::Ok,
// An error
Def::Struct(..) | Def::Enum(..) | Def::Union(..) | Def::TyAlias(..) |
Def::Variant(..) if i + 1 == proj_start => ParenthesizedGenericArgs::Err,
// A warning for now, for compatibility reasons
_ => ParenthesizedGenericArgs::Warn,
};
let num_lifetimes = type_def_id.map_or(0, |def_id| {
if let Some(&n) = self.type_def_lifetime_params.get(&def_id) {
return n;
}
assert!(!def_id.is_local());
let n = self.cstore.item_generics_cloned_untracked(def_id).regions.len();
self.type_def_lifetime_params.insert(def_id, n);
n
});
self.lower_path_segment(p.span, segment, param_mode, num_lifetimes,
parenthesized_generic_args, itctx)
}).collect(),
span: p.span,
});
// Simple case, either no projections, or only fully-qualified.
// E.g. `std::mem::size_of` or `<I as Iterator>::Item`.
if resolution.unresolved_segments() == 0 {
return hir::QPath::Resolved(qself, path);
}
// Create the innermost type that we're projecting from.
let mut ty = if path.segments.is_empty() {
// If the base path is empty that means there exists a
// syntactical `Self`, e.g. `&i32` in `<&i32>::clone`.
qself.expect("missing QSelf for <T>::...")
} else {
// Otherwise, the base path is an implicit `Self` type path,
// e.g. `Vec` in `Vec::new` or `<I as Iterator>::Item` in
// `<I as Iterator>::Item::default`.
let new_id = self.next_id();
self.ty_path(new_id, p.span, hir::QPath::Resolved(qself, path))
};
// Anything after the base path are associated "extensions",
// out of which all but the last one are associated types,
// e.g. for `std::vec::Vec::<T>::IntoIter::Item::clone`:
// * base path is `std::vec::Vec<T>`
// * "extensions" are `IntoIter`, `Item` and `clone`
// * type nodes are:
// 1. `std::vec::Vec<T>` (created above)
// 2. `<std::vec::Vec<T>>::IntoIter`
// 3. `<<std::vec::Vec<T>>::IntoIter>::Item`
// * final path is `<<<std::vec::Vec<T>>::IntoIter>::Item>::clone`
for (i, segment) in p.segments.iter().enumerate().skip(proj_start) {
let segment = P(self.lower_path_segment(p.span, segment, param_mode, 0,
ParenthesizedGenericArgs::Warn,
itctx));
let qpath = hir::QPath::TypeRelative(ty, segment);
// It's finished, return the extension of the right node type.
if i == p.segments.len() - 1 {
return qpath;
}
// Wrap the associated extension in another type node.
let new_id = self.next_id();
ty = self.ty_path(new_id, p.span, qpath);
}
// Should've returned in the for loop above.
span_bug!(p.span, "lower_qpath: no final extension segment in {}..{}",
proj_start, p.segments.len())
}
fn lower_path_extra(&mut self,
id: NodeId,
p: &Path,
name: Option<Name>,
param_mode: ParamMode,
defaults_to_global: bool)
-> hir::Path {
let mut segments = p.segments.iter();
if defaults_to_global && p.is_global() {
segments.next();
}
hir::Path {
def: self.expect_full_def(id),
segments: segments.map(|segment| {
self.lower_path_segment(p.span, segment, param_mode, 0,
ParenthesizedGenericArgs::Err,
ImplTraitContext::Disallowed)
}).chain(name.map(|name| hir::PathSegment::from_name(name)))
.collect(),
span: p.span,
}
}
fn lower_path(&mut self,
id: NodeId,
p: &Path,
param_mode: ParamMode,
defaults_to_global: bool)
-> hir::Path {
self.lower_path_extra(id, p, None, param_mode, defaults_to_global)
}
fn lower_path_segment(&mut self,
path_span: Span,
segment: &PathSegment,
param_mode: ParamMode,
expected_lifetimes: usize,
parenthesized_generic_args: ParenthesizedGenericArgs,
itctx: ImplTraitContext)
-> hir::PathSegment {
let (mut parameters, infer_types) = if let Some(ref parameters) = segment.parameters {
let msg = "parenthesized parameters may only be used with a trait";
<
4FF8
/div> match **parameters {
PathParameters::AngleBracketed(ref data) => {
self.lower_angle_bracketed_parameter_data(data, param_mode, itctx)
}
PathParameters::Parenthesized(ref data) => match parenthesized_generic_args {
ParenthesizedGenericArgs::Ok =>
self.lower_parenthesized_parameter_data(data, itctx),
ParenthesizedGenericArgs::Warn => {
self.sess.buffer_lint(PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
CRATE_NODE_ID, data.span, msg.into());
(hir::PathParameters::none(), true)
}
ParenthesizedGenericArgs::Err => {
struct_span_err!(self.sess, data.span, E0214, "{}", msg)
.span_label(data.span, "only traits may use parentheses").emit();
(hir::PathParameters::none(), true)
}
}
}
} else {
self.lower_angle_bracketed_parameter_data(&Default::default(), param_mode, itctx)
};
if !parameters.parenthesized && parameters.lifetimes.is_empty() {
parameters.lifetimes = (0..expected_lifetimes).map(|_| {
self.elided_lifetime(path_span)
}).collect();
}
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