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 `tcx.types` 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 #![crate_type = "dylib"]
68 #![crate_type = "rlib"]
69 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
70 html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
71 html_root_url = "https://doc.rust-lang.org/nightly/")]
74 #![allow(non_camel_case_types)]
76 #![feature(advanced_slice_patterns)]
77 #![feature(box_patterns)]
78 #![feature(box_syntax)]
79 #![feature(conservative_impl_trait)]
80 #![feature(never_type)]
82 #![feature(rustc_diagnostic_macros)]
83 #![feature(slice_patterns)]
85 #[macro_use] extern crate log;
86 #[macro_use] extern crate syntax;
87 extern crate syntax_pos;
90 extern crate fmt_macros;
91 #[macro_use] extern crate rustc;
92 extern crate rustc_platform_intrinsics as intrinsics;
93 extern crate rustc_back;
94 extern crate rustc_const_math;
95 extern crate rustc_data_structures;
96 extern crate rustc_errors as errors;
98 pub use rustc::dep_graph;
101 pub use rustc::middle;
102 pub use rustc::session;
105 use hir::map as hir_map;
106 use rustc::infer::InferOk;
107 use rustc::ty::subst::Substs;
108 use rustc::ty::{self, Ty, TyCtxt};
109 use rustc::ty::maps::Providers;
110 use rustc::traits::{FulfillmentContext, ObligationCause, ObligationCauseCode, Reveal};
111 use session::{CompileIncomplete, config};
112 use util::common::time;
115 use syntax::abi::Abi;
116 use syntax_pos::Span;
119 // NB: This module needs to be declared first so diagnostics are
120 // registered before they are used.
127 mod constrained_type_params;
132 pub struct TypeAndSubsts<'tcx> {
133 pub substs: &'tcx Substs<'tcx>,
137 fn require_c_abi_if_variadic(tcx: TyCtxt,
141 if decl.variadic && !(abi == Abi::C || abi == Abi::Cdecl) {
142 let mut err = struct_span_err!(tcx.sess, span, E0045,
143 "variadic function must have C or cdecl calling convention");
144 err.span_label(span, "variadics require C or cdecl calling convention").emit();
148 fn require_same_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
149 cause: &ObligationCause<'tcx>,
153 tcx.infer_ctxt().enter(|ref infcx| {
154 let param_env = ty::ParamEnv::empty(Reveal::UserFacing);
155 let mut fulfill_cx = FulfillmentContext::new();
156 match infcx.at(&cause, param_env).eq(expected, actual) {
157 Ok(InferOk { obligations, .. }) => {
158 fulfill_cx.register_predicate_obligations(infcx, obligations);
161 infcx.report_mismatched_types(cause, expected, actual, err).emit();
166 match fulfill_cx.select_all_or_error(infcx) {
169 infcx.report_fulfillment_errors(&errors, None);
176 fn check_main_fn_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
177 main_id: ast::NodeId,
179 let main_def_id = tcx.hir.local_def_id(main_id);
180 let main_t = tcx.type_of(main_def_id);
183 match tcx.hir.find(main_id) {
184 Some(hir_map::NodeItem(it)) => {
186 hir::ItemFn(.., ref generics, _) => {
187 if generics.is_parameterized() {
188 struct_span_err!(tcx.sess, generics.span, E0131,
189 "main function is not allowed to have type parameters")
190 .span_label(generics.span,
191 "main cannot have type parameters")
201 let se_ty = tcx.mk_fn_ptr(ty::Binder(
206 hir::Unsafety::Normal,
213 &ObligationCause::new(main_span, main_id, ObligationCauseCode::MainFunctionType),
215 tcx.mk_fn_ptr(tcx.fn_sig(main_def_id)));
219 "main has a non-function type: found `{}`",
225 fn check_start_fn_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
226 start_id: ast::NodeId,
228 let start_def_id = tcx.hir.local_def_id(start_id);
229 let start_t = tcx.type_of(start_def_id);
232 match tcx.hir.find(start_id) {
233 Some(hir_map::NodeItem(it)) => {
235 hir::ItemFn(..,ref ps,_)
236 if ps.is_parameterized() => {
237 struct_span_err!(tcx.sess, ps.span, E0132,
238 "start function is not allowed to have type parameters")
240 "start function cannot have type parameters")
250 let se_ty = tcx.mk_fn_ptr(ty::Binder(
254 tcx.mk_imm_ptr(tcx.mk_imm_ptr(tcx.types.u8))
258 hir::Unsafety::Normal,
265 &ObligationCause::new(start_span, start_id, ObligationCauseCode::StartFunctionType),
267 tcx.mk_fn_ptr(tcx.fn_sig(start_def_id)));
270 span_bug!(start_span,
271 "start has a non-function type: found `{}`",
277 fn check_for_entry_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
278 if let Some((id, sp)) = *tcx.sess.entry_fn.borrow() {
279 match tcx.sess.entry_type.get() {
280 Some(config::EntryMain) => check_main_fn_ty(tcx, id, sp),
281 Some(config::EntryStart) => check_start_fn_ty(tcx, id, sp),
282 Some(config::EntryNone) => {}
283 None => bug!("entry function without a type")
288 pub fn provide(providers: &mut Providers) {
289 collect::provide(providers);
290 coherence::provide(providers);
291 check::provide(providers);
292 variance::provide(providers);
295 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>)
296 -> Result<(), CompileIncomplete>
298 let time_passes = tcx.sess.time_passes();
300 // this ensures that later parts of type checking can assume that items
301 // have valid types and not error
302 tcx.sess.track_errors(|| {
303 time(time_passes, "type collecting", ||
304 collect::collect_item_types(tcx));
308 tcx.sess.track_errors(|| {
309 time(time_passes, "impl wf inference", ||
310 impl_wf_check::impl_wf_check(tcx));
313 tcx.sess.track_errors(|| {
314 time(time_passes, "coherence checking", ||
315 coherence::check_coherence(tcx));
318 tcx.sess.track_errors(|| {
319 time(time_passes, "variance testing", ||
320 variance::test::test_variance(tcx));
323 time(time_passes, "wf checking", || check::check_wf_new(tcx))?;
325 time(time_passes, "item-types checking", || check::check_item_types(tcx))?;
327 time(time_passes, "item-bodies checking", || check::check_item_bodies(tcx))?;
329 check_unused::check_crate(tcx);
330 check_for_entry_fn(tcx);
332 tcx.sess.compile_status()
335 /// A quasi-deprecated helper used in rustdoc and save-analysis to get
336 /// the type from a HIR node.
337 pub fn hir_ty_to_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, hir_ty: &hir::Ty) -> Ty<'tcx> {
338 // In case there are any projections etc, find the "environment"
339 // def-id that will be used to determine the traits/predicates in
340 // scope. This is derived from the enclosing item-like thing.
341 let env_node_id = tcx.hir.get_parent(hir_ty.id);
342 let env_def_id = tcx.hir.local_def_id(env_node_id);
343 let item_cx = self::collect::ItemCtxt::new(tcx, env_def_id);
344 item_cx.to_ty(hir_ty)
347 __build_diagnostic_array! { librustc_typeck, DIAGNOSTICS }