1 // Copyright 2012 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 use rustc::infer::InferOk;
14 use rustc::traits::ObligationCause;
17 use syntax_pos::{self, Span};
19 use rustc::hir::def::Def;
20 use rustc::ty::{self, Ty, AssociatedItem};
21 use errors::DiagnosticBuilder;
23 use super::method::probe;
25 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
26 // Requires that the two types unify, and prints an error message if
28 pub fn demand_suptype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
29 let cause = self.misc(sp);
30 match self.sub_types(false, &cause, actual, expected) {
31 Ok(InferOk { obligations, value: () }) => {
32 self.register_predicates(obligations);
35 self.report_mismatched_types(&cause, expected, actual, e).emit();
40 pub fn demand_eqtype(&self, sp: Span, expected: Ty<'tcx>, actual: Ty<'tcx>) {
41 if let Some(mut err) = self.demand_eqtype_diag(sp, expected, actual) {
46 pub fn demand_eqtype_diag(&self,
49 actual: Ty<'tcx>) -> Option<DiagnosticBuilder<'tcx>> {
50 self.demand_eqtype_with_origin(&self.misc(sp), expected, actual)
53 pub fn demand_eqtype_with_origin(&self,
54 cause: &ObligationCause<'tcx>,
56 actual: Ty<'tcx>) -> Option<DiagnosticBuilder<'tcx>> {
57 match self.eq_types(false, cause, actual, expected) {
58 Ok(InferOk { obligations, value: () }) => {
59 self.register_predicates(obligations);
63 Some(self.report_mismatched_types(cause, expected, actual, e))
68 // Checks that the type of `expr` can be coerced to `expected`.
70 // NB: This code relies on `self.diverges` to be accurate. In
71 // particular, assignments to `!` will be permitted if the
72 // diverges flag is currently "always".
73 pub fn demand_coerce(&self,
77 let expected = self.resolve_type_vars_with_obligations(expected);
79 if let Err(e) = self.try_coerce(expr, checked_ty, self.diverges.get(), expected) {
80 let cause = self.misc(expr.span);
81 let expr_ty = self.resolve_type_vars_with_obligations(checked_ty);
82 let mut err = self.report_mismatched_types(&cause, expected, expr_ty, e);
83 if let Some(suggestion) = self.check_ref(expr,
86 err.help(&suggestion);
88 let mode = probe::Mode::MethodCall;
89 let suggestions = self.probe_for_return_type(syntax_pos::DUMMY_SP,
94 if suggestions.len() > 0 {
95 err.help(&format!("here are some functions which \
96 might fulfill your needs:\n{}",
97 self.get_best_match(&suggestions).join("\n")));
104 fn format_method_suggestion(&self, method: &AssociatedItem) -> String {
107 if self.has_no_input_arg(method) {
114 fn display_suggested_methods(&self, methods: &[AssociatedItem]) -> Vec<String> {
117 .map(|method| self.format_method_suggestion(&*method))
118 .collect::<Vec<String>>()
121 fn get_best_match(&self, methods: &[AssociatedItem]) -> Vec<String> {
122 let no_argument_methods: Vec<_> =
124 .filter(|ref x| self.has_no_input_arg(&*x))
127 if no_argument_methods.len() > 0 {
128 self.display_suggested_methods(&no_argument_methods)
130 self.display_suggested_methods(&methods)
134 // This function checks if the method isn't static and takes other arguments than `self`.
135 fn has_no_input_arg(&self, method: &AssociatedItem) -> bool {
137 Def::Method(def_id) => {
138 match self.tcx.type_of(def_id).sty {
139 ty::TypeVariants::TyFnDef(_, _, sig) => {
140 sig.inputs().skip_binder().len() == 1
149 /// This function is used to determine potential "simple" improvements or users' errors and
150 /// provide them useful help. For example:
153 /// fn some_fn(s: &str) {}
155 /// let x = "hey!".to_owned();
156 /// some_fn(x); // error
159 /// No need to find every potential function which could make a coercion to transform a
160 /// `String` into a `&str` since a `&` would do the trick!
162 /// In addition of this check, it also checks between references mutability state. If the
163 /// expected is mutable but the provided isn't, maybe we could just say "Hey, try with
167 checked_ty: Ty<'tcx>,
170 match (&expected.sty, &checked_ty.sty) {
171 (&ty::TyRef(_, _), &ty::TyRef(_, _)) => None,
172 (&ty::TyRef(_, mutability), _) => {
173 // Check if it can work when put into a ref. For example:
176 // fn bar(x: &mut i32) {}
179 // bar(&x); // error, expected &mut
181 let ref_ty = match mutability.mutbl {
182 hir::Mutability::MutMutable => self.tcx.mk_mut_ref(
183 self.tcx.mk_region(ty::ReStatic),
185 hir::Mutability::MutImmutable => self.tcx.mk_imm_ref(
186 self.tcx.mk_region(ty::ReStatic),
189 if self.can_coerce(ref_ty, expected) {
190 if let Ok(src) = self.tcx.sess.codemap().span_to_snippet(expr.span) {
191 return Some(format!("try with `{}{}`",
192 match mutability.mutbl {
193 hir::Mutability::MutMutable => "&mut ",
194 hir::Mutability::MutImmutable => "&",