1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
13 typeck.rs, an introduction
15 The type checker is responsible for:
17 1. Determining the type of each expression
18 2. Resolving methods and traits
19 3. Guaranteeing that most type rules are met ("most?", you say, "why most?"
20 Well, dear reader, read on)
22 The main entry point is `check_crate()`. Type checking operates in
25 1. The collect phase first passes over all items and determines their
26 type, without examining their "innards".
28 2. Variance inference then runs to compute the variance of each parameter
30 3. Coherence checks for overlapping or orphaned impls
32 4. Finally, the check phase then checks function bodies and so forth.
33 Within the check phase, we check each function body one at a time
34 (bodies of function expressions are checked as part of the
35 containing function). Inference is used to supply types wherever
36 they are unknown. The actual checking of a function itself has
37 several phases (check, regionck, writeback), as discussed in the
38 documentation for the `check` module.
40 The type checker is defined into various submodules which are documented
43 - astconv: converts the AST representation of types
44 into the `ty` representation
46 - collect: computes the types of each top-level item and enters them into
47 the `cx.tcache` table for later use
49 - coherence: enforces coherence rules, builds some tables
51 - variance: variance inference
53 - check: walks over function bodies and type checks them, inferring types for
54 local variables, type parameters, etc as necessary.
56 - infer: finds the types to use for each type variable such that
57 all subtyping and assignment constraints are met. In essence, the check
58 module specifies the constraints, and the infer module solves them.
62 This API is completely unstable and subject to change.
66 #![crate_name = "rustc_typeck"]
67 #![unstable(feature = "rustc_private")]
69 #![crate_type = "dylib"]
70 #![crate_type = "rlib"]
71 #![doc(html_logo_url = "http://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
72 html_favicon_url = "http://www.rust-lang.org/favicon.ico",
73 html_root_url = "http://doc.rust-lang.org/nightly/")]
75 #![allow(non_camel_case_types)]
77 #![feature(box_patterns)]
78 #![feature(box_syntax)]
79 #![feature(collections)]
84 #![feature(rustc_diagnostic_macros)]
85 #![feature(rustc_private)]
86 #![feature(unsafe_destructor)]
87 #![feature(staged_api)]
89 #[macro_use] extern crate log;
90 #[macro_use] extern crate syntax;
93 extern crate fmt_macros;
97 pub use rustc::metadata;
98 pub use rustc::middle;
99 pub use rustc::session;
105 use middle::ty::{self, Ty};
107 use util::common::time;
108 use util::ppaux::Repr;
111 use syntax::codemap::Span;
112 use syntax::print::pprust::*;
113 use syntax::{ast, ast_map, abi};
114 use syntax::ast_util::local_def;
116 use std::cell::RefCell;
118 // NB: This module needs to be declared first so diagnostics are
119 // registered before they are used.
129 struct TypeAndSubsts<'tcx> {
130 pub substs: subst::Substs<'tcx>,
134 struct CrateCtxt<'a, 'tcx: 'a> {
135 // A mapping from method call sites to traits that have that method.
136 trait_map: ty::TraitMap,
137 /// A vector of every trait accessible in the whole crate
138 /// (i.e. including those from subcrates). This is used only for
139 /// error reporting, and so is lazily initialised and generally
140 /// shouldn't taint the common path (hence the RefCell).
141 all_traits: RefCell<Option<check::method::AllTraitsVec>>,
142 tcx: &'a ty::ctxt<'tcx>,
145 // Functions that write types into the node type table
146 fn write_ty_to_tcx<'tcx>(tcx: &ty::ctxt<'tcx>, node_id: ast::NodeId, ty: Ty<'tcx>) {
147 debug!("write_ty_to_tcx({}, {})", node_id, ppaux::ty_to_string(tcx, ty));
148 assert!(!ty::type_needs_infer(ty));
149 tcx.node_types.borrow_mut().insert(node_id, ty);
152 fn write_substs_to_tcx<'tcx>(tcx: &ty::ctxt<'tcx>,
153 node_id: ast::NodeId,
154 item_substs: ty::ItemSubsts<'tcx>) {
155 if !item_substs.is_noop() {
156 debug!("write_substs_to_tcx({}, {})",
158 item_substs.repr(tcx));
160 assert!(item_substs.substs.types.all(|t| !ty::type_needs_infer(*t)));
162 tcx.item_substs.borrow_mut().insert(node_id, item_substs);
165 fn lookup_def_tcx(tcx:&ty::ctxt, sp: Span, id: ast::NodeId) -> def::Def {
166 match tcx.def_map.borrow().get(&id) {
167 Some(x) => x.clone(),
169 span_fatal!(tcx.sess, sp, E0242, "internal error looking up a definition")
174 fn lookup_def_ccx(ccx: &CrateCtxt, sp: Span, id: ast::NodeId)
176 lookup_def_tcx(ccx.tcx, sp, id)
179 fn require_same_types<'a, 'tcx, M>(tcx: &ty::ctxt<'tcx>,
180 maybe_infcx: Option<&infer::InferCtxt<'a, 'tcx>>,
181 t1_is_expected: bool,
187 M: FnOnce() -> String,
189 let result = match maybe_infcx {
191 let infcx = infer::new_infer_ctxt(tcx);
192 infer::mk_eqty(&infcx, t1_is_expected, infer::Misc(span), t1, t2)
195 infer::mk_eqty(infcx, t1_is_expected, infer::Misc(span), t1, t2)
202 span_err!(tcx.sess, span, E0211,
205 ty::type_err_to_str(tcx,
207 ty::note_and_explain_type_err(tcx, terr);
213 fn check_main_fn_ty(ccx: &CrateCtxt,
214 main_id: ast::NodeId,
217 let main_t = ty::node_id_to_type(tcx, main_id);
219 ty::ty_bare_fn(..) => {
220 match tcx.map.find(main_id) {
221 Some(ast_map::NodeItem(it)) => {
223 ast::ItemFn(_, _, _, ref ps, _)
224 if ps.is_parameterized() => {
225 span_err!(ccx.tcx.sess, main_span, E0131,
226 "main function is not allowed to have type parameters");
234 let se_ty = ty::mk_bare_fn(tcx, Some(local_def(main_id)), tcx.mk_bare_fn(ty::BareFnTy {
235 unsafety: ast::Unsafety::Normal,
237 sig: ty::Binder(ty::FnSig {
239 output: ty::FnConverging(ty::mk_nil(tcx)),
244 require_same_types(tcx, None, false, main_span, main_t, se_ty,
246 format!("main function expects type: `{}`",
247 ppaux::ty_to_string(ccx.tcx, se_ty))
251 tcx.sess.span_bug(main_span,
252 &format!("main has a non-function type: found \
254 ppaux::ty_to_string(tcx,
260 fn check_start_fn_ty(ccx: &CrateCtxt,
261 start_id: ast::NodeId,
264 let start_t = ty::node_id_to_type(tcx, start_id);
266 ty::ty_bare_fn(..) => {
267 match tcx.map.find(start_id) {
268 Some(ast_map::NodeItem(it)) => {
270 ast::ItemFn(_,_,_,ref ps,_)
271 if ps.is_parameterized() => {
272 span_err!(tcx.sess, start_span, E0132,
273 "start function is not allowed to have type parameters");
282 let se_ty = ty::mk_bare_fn(tcx, Some(local_def(start_id)), tcx.mk_bare_fn(ty::BareFnTy {
283 unsafety: ast::Unsafety::Normal,
285 sig: ty::Binder(ty::FnSig {
288 ty::mk_imm_ptr(tcx, ty::mk_imm_ptr(tcx, tcx.types.u8))
290 output: ty::FnConverging(tcx.types.int),
295 require_same_types(tcx, None, false, start_span, start_t, se_ty,
297 format!("start function expects type: `{}`",
298 ppaux::ty_to_string(ccx.tcx, se_ty))
303 tcx.sess.span_bug(start_span,
304 &format!("start has a non-function type: found \
306 ppaux::ty_to_string(tcx, start_t))[]);
311 fn check_for_entry_fn(ccx: &CrateCtxt) {
313 match *tcx.sess.entry_fn.borrow() {
314 Some((id, sp)) => match tcx.sess.entry_type.get() {
315 Some(config::EntryMain) => check_main_fn_ty(ccx, id, sp),
316 Some(config::EntryStart) => check_start_fn_ty(ccx, id, sp),
317 Some(config::EntryNone) => {}
318 None => tcx.sess.bug("entry function without a type")
324 pub fn check_crate(tcx: &ty::ctxt, trait_map: ty::TraitMap) {
325 let time_passes = tcx.sess.time_passes();
326 let ccx = CrateCtxt {
327 trait_map: trait_map,
328 all_traits: RefCell::new(None),
332 time(time_passes, "type collecting", (), |_|
333 collect::collect_item_types(tcx));
335 // this ensures that later parts of type checking can assume that items
336 // have valid types and not error
337 tcx.sess.abort_if_errors();
339 time(time_passes, "variance inference", (), |_|
340 variance::infer_variance(tcx));
342 time(time_passes, "coherence checking", (), |_|
343 coherence::check_coherence(&ccx));
345 time(time_passes, "type checking", (), |_|
346 check::check_item_types(&ccx));
348 check_for_entry_fn(&ccx);
349 tcx.sess.abort_if_errors();