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Commit | Line | Data |
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74b04a01 XL |
1 | use rustc_ast::attr; |
2 | use rustc_ast::entry::EntryPointType; | |
dfeec247 XL |
3 | use rustc_errors::struct_span_err; |
4 | use rustc_hir::def_id::{CrateNum, DefId, CRATE_DEF_INDEX, LOCAL_CRATE}; | |
5 | use rustc_hir::itemlikevisit::ItemLikeVisitor; | |
6 | use rustc_hir::{HirId, ImplItem, Item, ItemKind, TraitItem}; | |
ba9703b0 XL |
7 | use rustc_middle::hir::map::Map; |
8 | use rustc_middle::ty::query::Providers; | |
9 | use rustc_middle::ty::TyCtxt; | |
10 | use rustc_session::config::EntryFnType; | |
11 | use rustc_session::{config, Session}; | |
dfeec247 XL |
12 | use rustc_span::symbol::sym; |
13 | use rustc_span::{Span, DUMMY_SP}; | |
60c5eb7d | 14 | |
dc9dc135 | 15 | struct EntryContext<'a, 'tcx> { |
1a4d82fc | 16 | session: &'a Session, |
970d7e83 | 17 | |
ba9703b0 | 18 | map: Map<'tcx>, |
970d7e83 | 19 | |
e1599b0c | 20 | /// The top-level function called `main`. |
532ac7d7 | 21 | main_fn: Option<(HirId, Span)>, |
970d7e83 | 22 | |
e1599b0c | 23 | /// The function that has attribute named `main`. |
532ac7d7 | 24 | attr_main_fn: Option<(HirId, Span)>, |
970d7e83 | 25 | |
e1599b0c | 26 | /// The function that has the attribute 'start' on it. |
532ac7d7 | 27 | start_fn: Option<(HirId, Span)>, |
970d7e83 | 28 | |
e1599b0c XL |
29 | /// The functions that one might think are `main` but aren't, e.g. |
30 | /// main functions not defined at the top level. For diagnostics. | |
dfeec247 | 31 | non_main_fns: Vec<(HirId, Span)>, |
970d7e83 LB |
32 | } |
33 | ||
476ff2be | 34 | impl<'a, 'tcx> ItemLikeVisitor<'tcx> for EntryContext<'a, 'tcx> { |
dfeec247 | 35 | fn visit_item(&mut self, item: &'tcx Item<'tcx>) { |
416331ca | 36 | let def_id = self.map.local_def_id(item.hir_id); |
ba9703b0 | 37 | let def_key = self.map.def_key(def_id.expect_local()); |
92a42be0 SL |
38 | let at_root = def_key.parent == Some(CRATE_DEF_INDEX); |
39 | find_item(item, self, at_root); | |
1a4d82fc | 40 | } |
476ff2be | 41 | |
dfeec247 | 42 | fn visit_trait_item(&mut self, _trait_item: &'tcx TraitItem<'tcx>) { |
e1599b0c | 43 | // Entry fn is never a trait item. |
32a655c1 | 44 | } |
476ff2be | 45 | |
dfeec247 | 46 | fn visit_impl_item(&mut self, _impl_item: &'tcx ImplItem<'tcx>) { |
e1599b0c | 47 | // Entry fn is never a trait item. |
476ff2be | 48 | } |
1a4d82fc | 49 | } |
970d7e83 | 50 | |
dc9dc135 | 51 | fn entry_fn(tcx: TyCtxt<'_>, cnum: CrateNum) -> Option<(DefId, EntryFnType)> { |
9fa01778 XL |
52 | assert_eq!(cnum, LOCAL_CRATE); |
53 | ||
dfeec247 XL |
54 | let any_exe = |
55 | tcx.sess.crate_types.borrow().iter().any(|ty| *ty == config::CrateType::Executable); | |
1a4d82fc | 56 | if !any_exe { |
e1599b0c | 57 | // No need to find a main function. |
9fa01778 | 58 | return None; |
970d7e83 LB |
59 | } |
60 | ||
1a4d82fc | 61 | // If the user wants no main function at all, then stop here. |
ba9703b0 | 62 | if attr::contains_name(&tcx.hir().krate().item.attrs, sym::no_main) { |
9fa01778 | 63 | return None; |
1a4d82fc JJ |
64 | } |
65 | ||
66 | let mut ctxt = EntryContext { | |
9fa01778 XL |
67 | session: tcx.sess, |
68 | map: tcx.hir(), | |
970d7e83 LB |
69 | main_fn: None, |
70 | attr_main_fn: None, | |
71 | start_fn: None, | |
1a4d82fc | 72 | non_main_fns: Vec::new(), |
970d7e83 LB |
73 | }; |
74 | ||
9fa01778 | 75 | tcx.hir().krate().visit_all_item_likes(&mut ctxt); |
970d7e83 | 76 | |
9fa01778 | 77 | configure_main(tcx, &ctxt) |
970d7e83 LB |
78 | } |
79 | ||
74b04a01 | 80 | // Beware, this is duplicated in `librustc_ast/entry.rs`, so make sure to keep |
e9174d1e | 81 | // them in sync. |
dfeec247 | 82 | fn entry_point_type(item: &Item<'_>, at_root: bool) -> EntryPointType { |
e74abb32 | 83 | match item.kind { |
8faf50e0 | 84 | ItemKind::Fn(..) => { |
48663c56 | 85 | if attr::contains_name(&item.attrs, sym::start) { |
e9174d1e | 86 | EntryPointType::Start |
48663c56 | 87 | } else if attr::contains_name(&item.attrs, sym::main) { |
e9174d1e | 88 | EntryPointType::MainAttr |
48663c56 | 89 | } else if item.ident.name == sym::main { |
92a42be0 | 90 | if at_root { |
e1599b0c | 91 | // This is a top-level function so can be `main`. |
e9174d1e | 92 | EntryPointType::MainNamed |
970d7e83 | 93 | } else { |
e9174d1e | 94 | EntryPointType::OtherMain |
970d7e83 | 95 | } |
e9174d1e SL |
96 | } else { |
97 | EntryPointType::None | |
970d7e83 LB |
98 | } |
99 | } | |
e9174d1e SL |
100 | _ => EntryPointType::None, |
101 | } | |
102 | } | |
103 | ||
dfeec247 | 104 | fn find_item(item: &Item<'_>, ctxt: &mut EntryContext<'_, '_>, at_root: bool) { |
92a42be0 | 105 | match entry_point_type(item, at_root) { |
e9174d1e SL |
106 | EntryPointType::MainNamed => { |
107 | if ctxt.main_fn.is_none() { | |
532ac7d7 | 108 | ctxt.main_fn = Some((item.hir_id, item.span)); |
e9174d1e | 109 | } else { |
dfeec247 XL |
110 | struct_span_err!(ctxt.session, item.span, E0136, "multiple `main` functions") |
111 | .emit(); | |
e9174d1e | 112 | } |
dfeec247 | 113 | } |
e9174d1e | 114 | EntryPointType::OtherMain => { |
532ac7d7 | 115 | ctxt.non_main_fns.push((item.hir_id, item.span)); |
dfeec247 | 116 | } |
e9174d1e SL |
117 | EntryPointType::MainAttr => { |
118 | if ctxt.attr_main_fn.is_none() { | |
532ac7d7 | 119 | ctxt.attr_main_fn = Some((item.hir_id, item.span)); |
e9174d1e | 120 | } else { |
dfeec247 XL |
121 | struct_span_err!( |
122 | ctxt.session, | |
123 | item.span, | |
124 | E0137, | |
125 | "multiple functions with a `#[main]` attribute" | |
126 | ) | |
416331ca XL |
127 | .span_label(item.span, "additional `#[main]` function") |
128 | .span_label(ctxt.attr_main_fn.unwrap().1, "first `#[main]` function") | |
5bcae85e | 129 | .emit(); |
e9174d1e | 130 | } |
dfeec247 | 131 | } |
e9174d1e SL |
132 | EntryPointType::Start => { |
133 | if ctxt.start_fn.is_none() { | |
532ac7d7 | 134 | ctxt.start_fn = Some((item.hir_id, item.span)); |
e9174d1e | 135 | } else { |
e1599b0c | 136 | struct_span_err!(ctxt.session, item.span, E0138, "multiple `start` functions") |
dfeec247 | 137 | .span_label(ctxt.start_fn.unwrap().1, "previous `#[start]` function here") |
7cac9316 | 138 | .span_label(item.span, "multiple `start` functions") |
5bcae85e | 139 | .emit(); |
e9174d1e | 140 | } |
9fa01778 XL |
141 | } |
142 | EntryPointType::None => (), | |
970d7e83 | 143 | } |
970d7e83 LB |
144 | } |
145 | ||
dc9dc135 | 146 | fn configure_main(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) -> Option<(DefId, EntryFnType)> { |
532ac7d7 | 147 | if let Some((hir_id, _)) = visitor.start_fn { |
416331ca | 148 | Some((tcx.hir().local_def_id(hir_id), EntryFnType::Start)) |
532ac7d7 | 149 | } else if let Some((hir_id, _)) = visitor.attr_main_fn { |
416331ca | 150 | Some((tcx.hir().local_def_id(hir_id), EntryFnType::Main)) |
532ac7d7 | 151 | } else if let Some((hir_id, _)) = visitor.main_fn { |
416331ca | 152 | Some((tcx.hir().local_def_id(hir_id), EntryFnType::Main)) |
970d7e83 | 153 | } else { |
e1599b0c | 154 | no_main_err(tcx, visitor); |
9fa01778 | 155 | None |
970d7e83 LB |
156 | } |
157 | } | |
9fa01778 | 158 | |
e1599b0c | 159 | fn no_main_err(tcx: TyCtxt<'_>, visitor: &EntryContext<'_, '_>) { |
ba9703b0 | 160 | let sp = tcx.hir().krate().item.span; |
e74abb32 XL |
161 | if *tcx.sess.parse_sess.reached_eof.borrow() { |
162 | // There's an unclosed brace that made the parser reach `Eof`, we shouldn't complain about | |
163 | // the missing `fn main()` then as it might have been hidden inside an unclosed block. | |
164 | tcx.sess.delay_span_bug(sp, "`main` not found, but expected unclosed brace error"); | |
165 | return; | |
166 | } | |
167 | ||
e1599b0c | 168 | // There is no main function. |
dfeec247 XL |
169 | let mut err = struct_span_err!( |
170 | tcx.sess, | |
171 | DUMMY_SP, | |
172 | E0601, | |
173 | "`main` function not found in crate `{}`", | |
174 | tcx.crate_name(LOCAL_CRATE) | |
175 | ); | |
e1599b0c XL |
176 | let filename = &tcx.sess.local_crate_source_file; |
177 | let note = if !visitor.non_main_fns.is_empty() { | |
178 | for &(_, span) in &visitor.non_main_fns { | |
179 | err.span_note(span, "here is a function named `main`"); | |
180 | } | |
181 | err.note("you have one or more functions named `main` not defined at the crate level"); | |
dfeec247 XL |
182 | err.help( |
183 | "either move the `main` function definitions or attach the `#[main]` attribute \ | |
184 | to one of them", | |
185 | ); | |
e1599b0c | 186 | // There were some functions named `main` though. Try to give the user a hint. |
dfeec247 XL |
187 | format!( |
188 | "the main function must be defined at the crate level{}", | |
189 | filename.as_ref().map(|f| format!(" (in `{}`)", f.display())).unwrap_or_default() | |
190 | ) | |
e1599b0c XL |
191 | } else if let Some(filename) = filename { |
192 | format!("consider adding a `main` function to `{}`", filename.display()) | |
193 | } else { | |
194 | String::from("consider adding a `main` function at the crate level") | |
195 | }; | |
e1599b0c XL |
196 | // The file may be empty, which leads to the diagnostic machinery not emitting this |
197 | // note. This is a relatively simple way to detect that case and emit a span-less | |
198 | // note instead. | |
74b04a01 | 199 | if tcx.sess.source_map().lookup_line(sp.lo()).is_ok() { |
e1599b0c XL |
200 | err.set_span(sp); |
201 | err.span_label(sp, ¬e); | |
202 | } else { | |
203 | err.note(¬e); | |
204 | } | |
205 | if tcx.sess.teach(&err.get_code().unwrap()) { | |
dfeec247 XL |
206 | err.note( |
207 | "If you don't know the basics of Rust, you can go look to the Rust Book \ | |
208 | to get started: https://doc.rust-lang.org/book/", | |
209 | ); | |
e1599b0c XL |
210 | } |
211 | err.emit(); | |
212 | } | |
213 | ||
dc9dc135 | 214 | pub fn find_entry_point(tcx: TyCtxt<'_>) -> Option<(DefId, EntryFnType)> { |
9fa01778 XL |
215 | tcx.entry_fn(LOCAL_CRATE) |
216 | } | |
217 | ||
218 | pub fn provide(providers: &mut Providers<'_>) { | |
dfeec247 | 219 | *providers = Providers { entry_fn, ..*providers }; |
9fa01778 | 220 | } |