1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
|
use hir::map as hir_map;
use hir::def_id::{CRATE_DEF_INDEX};
use session::{config, Session};
use session::config::EntryFnType;
use syntax::ast::NodeId;
use syntax::attr;
use syntax::entry::EntryPointType;
use syntax_pos::Span;
use hir::{Item, ItemKind, ImplItem, TraitItem};
use hir::itemlikevisit::ItemLikeVisitor;
struct EntryContext<'a, 'tcx: 'a> {
session: &'a Session,
map: &'a hir_map::Map<'tcx>,
// The top-level function called 'main'
main_fn: Option<(NodeId, Span)>,
// The function that has attribute named 'main'
attr_main_fn: Option<(NodeId, Span)>,
// The function that has the attribute 'start' on it
start_fn: Option<(NodeId, Span)>,
// The functions that one might think are 'main' but aren't, e.g.
// main functions not defined at the top level. For diagnostics.
non_main_fns: Vec<(NodeId, Span)> ,
}
impl<'a, 'tcx> ItemLikeVisitor<'tcx> for EntryContext<'a, 'tcx> {
fn visit_item(&mut self, item: &'tcx Item) {
let def_id = self.map.local_def_id(item.id);
let def_key = self.map.def_key(def_id);
let at_root = def_key.parent == Some(CRATE_DEF_INDEX);
find_item(item, self, at_root);
}
fn visit_trait_item(&mut self, _trait_item: &'tcx TraitItem) {
// entry fn is never a trait item
}
fn visit_impl_item(&mut self, _impl_item: &'tcx ImplItem) {
// entry fn is never an impl item
}
}
pub fn find_entry_point(session: &Session,
hir_map: &hir_map::Map<'_>,
crate_name: &str) {
let any_exe = session.crate_types.borrow().iter().any(|ty| {
*ty == config::CrateType::Executable
});
if !any_exe {
// No need to find a main function
session.entry_fn.set(None);
return
}
// If the user wants no main function at all, then stop here.
if attr::contains_name(&hir_map.krate().attrs, "no_main") {
session.entry_fn.set(None);
return
}
let mut ctxt = EntryContext {
session,
map: hir_map,
main_fn: None,
attr_main_fn: None,
start_fn: None,
non_main_fns: Vec::new(),
};
hir_map.krate().visit_all_item_likes(&mut ctxt);
configure_main(&mut ctxt, crate_name);
}
// Beware, this is duplicated in `libsyntax/entry.rs`, so make sure to keep
// them in sync.
fn entry_point_type(item: &Item, at_root: bool) -> EntryPointType {
match item.node {
ItemKind::Fn(..) => {
if attr::contains_name(&item.attrs, "start") {
EntryPointType::Start
} else if attr::contains_name(&item.attrs, "main") {
EntryPointType::MainAttr
} else if item.name == "main" {
if at_root {
// This is a top-level function so can be 'main'.
EntryPointType::MainNamed
} else {
EntryPointType::OtherMain
}
} else {
EntryPointType::None
}
}
_ => EntryPointType::None,
}
}
fn find_item(item: &Item, ctxt: &mut EntryContext<'_, '_>, at_root: bool) {
match entry_point_type(item, at_root) {
EntryPointType::MainNamed => {
if ctxt.main_fn.is_none() {
ctxt.main_fn = Some((item.id, item.span));
} else {
span_err!(ctxt.session, item.span, E0136,
"multiple 'main' functions");
}
},
EntryPointType::OtherMain => {
ctxt.non_main_fns.push((item.id, item.span));
},
EntryPointType::MainAttr => {
if ctxt.attr_main_fn.is_none() {
ctxt.attr_main_fn = Some((item.id, item.span));
} else {
struct_span_err!(ctxt.session, item.span, E0137,
"multiple functions with a #[main] attribute")
.span_label(item.span, "additional #[main] function")
.span_label(ctxt.attr_main_fn.unwrap().1, "first #[main] function")
.emit();
}
},
EntryPointType::Start => {
if ctxt.start_fn.is_none() {
ctxt.start_fn = Some((item.id, item.span));
} else {
struct_span_err!(ctxt.session, item.span, E0138, "multiple 'start' functions")
.span_label(ctxt.start_fn.unwrap().1, "previous `start` function here")
.span_label(item.span, "multiple `start` functions")
.emit();
}
},
EntryPointType::None => ()
}
}
fn configure_main(this: &mut EntryContext<'_, '_>, crate_name: &str) {
if let Some((node_id, span)) = this.start_fn {
this.session.entry_fn.set(Some((node_id, span, EntryFnType::Start)));
} else if let Some((node_id, span)) = this.attr_main_fn {
this.session.entry_fn.set(Some((node_id, span, EntryFnType::Main)));
} else if let Some((node_id, span)) = this.main_fn {
this.session.entry_fn.set(Some((node_id, span, EntryFnType::Main)));
} else {
// No main function
this.session.entry_fn.set(None);
let mut err = struct_err!(this.session, E0601,
"`main` function not found in crate `{}`", crate_name);
if !this.non_main_fns.is_empty() {
// There were some functions named 'main' though. Try to give the user a hint.
err.note("the main function must be defined at the crate level \
but you have one or more functions named 'main' that are not \
defined at the crate level. Either move the definition or \
attach the `#[main]` attribute to override this behavior.");
for &(_, span) in &this.non_main_fns {
err.span_note(span, "here is a function named 'main'");
}
err.emit();
this.session.abort_if_errors();
} else {
if let Some(ref filename) = this.session.local_crate_source_file {
err.note(&format!("consider adding a `main` function to `{}`", filename.display()));
}
if this.session.teach(&err.get_code().unwrap()) {
err.note("If you don't know the basics of Rust, you can go look to the Rust Book \
to get started: https://doc.rust-lang.org/book/");
}
err.emit();
}
}
}
|
