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.
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 - outlives: outlives inference
55 - check: walks over function bodies and type checks them, inferring types for
56 local variables, type parameters, etc as necessary.
58 - infer: finds the types to use for each type variable such that
59 all subtyping and assignment constraints are met. In essence, the check
60 module specifies the constraints, and the infer module solves them.
64 This API is completely unstable and subject to change.
68 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
69 html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
70 html_root_url = "https://doc.rust-lang.org/nightly/")]
72 #![allow(non_camel_case_types)]
74 #![feature(box_patterns)]
75 #![feature(box_syntax)]
76 #![feature(crate_visibility_modifier)]
77 #![feature(exhaustive_patterns)]
80 #![feature(refcell_replace_swap)]
81 #![feature(rustc_diagnostic_macros)]
82 #![feature(slice_patterns)]
83 #![feature(slice_sort_by_cached_key)]
84 #![feature(never_type)]
86 #![recursion_limit="256"]
88 #[macro_use] extern crate log;
89 #[macro_use] extern crate syntax;
90 extern crate syntax_pos;
93 #[macro_use] extern crate rustc;
94 extern crate rustc_platform_intrinsics as intrinsics;
95 extern crate rustc_data_structures;
96 extern crate rustc_errors as errors;
97 extern crate rustc_target;
98 extern crate smallvec;
100 // N.B., this module needs to be declared first so diagnostics are
101 // registered before they are used.
109 mod constrained_type_params;
110 mod structured_errors;
117 use rustc_target::spec::abi::Abi;
119 use rustc::infer::InferOk;
123 use rustc::traits::{ObligationCause, ObligationCauseCode, TraitEngine, TraitEngineExt};
124 use rustc::ty::subst::Substs;
125 use rustc::ty::{self, Ty, TyCtxt};
126 use rustc::ty::query::Providers;
128 use rustc::util::profiling::ProfileCategory;
129 use session::{CompileIncomplete, config};
130 use syntax_pos::Span;
132 use util::common::time;
136 pub struct TypeAndSubsts<'tcx> {
137 substs: &'tcx Substs<'tcx>,
141 fn require_c_abi_if_variadic(tcx: TyCtxt,
145 if decl.variadic && !(abi == Abi::C || abi == Abi::Cdecl) {
146 let mut err = struct_span_err!(tcx.sess, span, E0045,
147 "variadic function must have C or cdecl calling convention");
148 err.span_label(span, "variadics require C or cdecl calling convention").emit();
152 fn require_same_types<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
153 cause: &ObligationCause<'tcx>,
157 tcx.infer_ctxt().enter(|ref infcx| {
158 let param_env = ty::ParamEnv::empty();
159 let mut fulfill_cx = TraitEngine::new(infcx.tcx);
160 match infcx.at(&cause, param_env).eq(expected, actual) {
161 Ok(InferOk { obligations, .. }) => {
162 fulfill_cx.register_predicate_obligations(infcx, obligations);
165 infcx.report_mismatched_types(cause, expected, actual, err).emit();
170 match fulfill_cx.select_all_or_error(infcx) {
173 infcx.report_fulfillment_errors(&errors, None, false);
180 fn check_main_fn_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
181 main_id: ast::NodeId,
183 let main_def_id = tcx.hir().local_def_id(main_id);
184 let main_t = tcx.type_of(main_def_id);
187 if let Some(Node::Item(it)) = tcx.hir().find(main_id) {
188 if let hir::ItemKind::Fn(.., ref generics, _) = it.node {
189 let mut error = false;
190 if !generics.params.is_empty() {
191 let msg = "`main` function is not allowed to have generic \
192 parameters".to_owned();
193 let label = "`main` cannot have generic parameters".to_string();
194 struct_span_err!(tcx.sess, generics.span, E0131, "{}", msg)
195 .span_label(generics.span, label)
199 if let Some(sp) = generics.where_clause.span() {
200 struct_span_err!(tcx.sess, sp, E0646,
201 "`main` function is not allowed to have a `where` clause")
202 .span_label(sp, "`main` cannot have a `where` clause")
212 let actual = tcx.fn_sig(main_def_id);
213 let expected_return_type = if tcx.lang_items().termination().is_some() {
214 // we take the return type of the given main function, the real check is done
216 actual.output().skip_binder()
218 // standard () main return type
222 let se_ty = tcx.mk_fn_ptr(ty::Binder::bind(
225 expected_return_type,
227 hir::Unsafety::Normal,
234 &ObligationCause::new(main_span, main_id, ObligationCauseCode::MainFunctionType),
236 tcx.mk_fn_ptr(actual));
240 "main has a non-function type: found `{}`",
246 fn check_start_fn_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
247 start_id: ast::NodeId,
249 let start_def_id = tcx.hir().local_def_id(start_id);
250 let start_t = tcx.type_of(start_def_id);
253 if let Some(Node::Item(it)) = tcx.hir().find(start_id) {
254 if let hir::ItemKind::Fn(.., ref generics, _) = it.node {
255 let mut error = false;
256 if !generics.params.is_empty() {
257 struct_span_err!(tcx.sess, generics.span, E0132,
258 "start function is not allowed to have type parameters")
259 .span_label(generics.span,
260 "start function cannot have type parameters")
264 if let Some(sp) = generics.where_clause.span() {
265 struct_span_err!(tcx.sess, sp, E0647,
266 "start function is not allowed to have a `where` clause")
267 .span_label(sp, "start function cannot have a `where` clause")
277 let se_ty = tcx.mk_fn_ptr(ty::Binder::bind(
281 tcx.mk_imm_ptr(tcx.mk_imm_ptr(tcx.types.u8))
285 hir::Unsafety::Normal,
292 &ObligationCause::new(start_span, start_id, ObligationCauseCode::StartFunctionType),
294 tcx.mk_fn_ptr(tcx.fn_sig(start_def_id)));
297 span_bug!(start_span,
298 "start has a non-function type: found `{}`",
304 fn check_for_entry_fn<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
305 if let Some((id, sp, entry_type)) = *tcx.sess.entry_fn.borrow() {
307 config::EntryFnType::Main => check_main_fn_ty(tcx, id, sp),
308 config::EntryFnType::Start => check_start_fn_ty(tcx, id, sp),
313 pub fn provide(providers: &mut Providers) {
314 collect::provide(providers);
315 coherence::provide(providers);
316 check::provide(providers);
317 variance::provide(providers);
318 outlives::provide(providers);
321 pub fn check_crate<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>)
322 -> Result<(), CompileIncomplete>
324 tcx.sess.profiler(|p| p.start_activity(ProfileCategory::TypeChecking));
326 // this ensures that later parts of type checking can assume that items
327 // have valid types and not error
328 tcx.sess.track_errors(|| {
329 time(tcx.sess, "type collecting", ||
330 collect::collect_item_types(tcx));
334 tcx.sess.track_errors(|| {
335 time(tcx.sess, "outlives testing", ||
336 outlives::test::test_inferred_outlives(tcx));
339 tcx.sess.track_errors(|| {
340 time(tcx.sess, "impl wf inference", ||
341 impl_wf_check::impl_wf_check(tcx));
344 tcx.sess.track_errors(|| {
345 time(tcx.sess, "coherence checking", ||
346 coherence::check_coherence(tcx));
349 tcx.sess.track_errors(|| {
350 time(tcx.sess, "variance testing", ||
351 variance::test::test_variance(tcx));
354 time(tcx.sess, "wf checking", || check::check_wf_new(tcx))?;
356 time(tcx.sess, "item-types checking", || check::check_item_types(tcx))?;
358 time(tcx.sess, "item-bodies checking", || check::check_item_bodies(tcx))?;
360 check_unused::check_crate(tcx);
361 check_for_entry_fn(tcx);
363 tcx.sess.profiler(|p| p.end_activity(ProfileCategory::TypeChecking));
365 tcx.sess.compile_status()
368 /// A quasi-deprecated helper used in rustdoc and save-analysis to get
369 /// the type from a HIR node.
370 pub fn hir_ty_to_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, hir_ty: &hir::Ty) -> Ty<'tcx> {
371 // In case there are any projections etc, find the "environment"
372 // def-id that will be used to determine the traits/predicates in
373 // scope. This is derived from the enclosing item-like thing.
374 let env_node_id = tcx.hir().get_parent(hir_ty.id);
375 let env_def_id = tcx.hir().local_def_id(env_node_id);
376 let item_cx = self::collect::ItemCtxt::new(tcx, env_def_id);
378 astconv::AstConv::ast_ty_to_ty(&item_cx, hir_ty)
381 pub fn hir_trait_to_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, hir_trait: &hir::TraitRef)
382 -> (ty::PolyTraitRef<'tcx>, Vec<(ty::PolyProjectionPredicate<'tcx>, Span)>) {
383 // In case there are any projections etc, find the "environment"
384 // def-id that will be used to determine the traits/predicates in
385 // scope. This is derived from the enclosing item-like thing.
386 let env_node_id = tcx.hir().get_parent(hir_trait.ref_id);
387 let env_def_id = tcx.hir().local_def_id(env_node_id);
388 let item_cx = self::collect::ItemCtxt::new(tcx, env_def_id);
389 let mut projections = Vec::new();
390 let (principal, _) = astconv::AstConv::instantiate_poly_trait_ref_inner(
391 &item_cx, hir_trait, tcx.types.err, &mut projections, true
394 (principal, projections)
397 __build_diagnostic_array! { librustc_typeck, DIAGNOSTICS }