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
use self::Context::*;
use rustc::session::Session;
use rustc::dep_graph::DepNode;
use rustc::hir::map::Map;
use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
use rustc::hir;
use syntax::ast;
use syntax_pos::Span;
#[derive(Clone, Copy, PartialEq)]
enum LoopKind {
Loop(hir::LoopSource),
WhileLoop,
}
impl LoopKind {
fn name(self) -> &'static str {
match self {
LoopKind::Loop(hir::LoopSource::Loop) => "loop",
LoopKind::Loop(hir::LoopSource::WhileLet) => "while let",
LoopKind::Loop(hir::LoopSource::ForLoop) => "for",
LoopKind::WhileLoop => "while",
}
}
}
#[derive(Clone, Copy, PartialEq)]
enum Context {
Normal,
Loop(LoopKind),
Closure,
}
#[derive(Copy, Clone)]
struct CheckLoopVisitor<'a, 'hir: 'a> {
sess: &'a Session,
hir_map: &'a Map<'hir>,
cx: Context,
}
pub fn check_crate(sess: &Session, map: &Map) {
let _task = map.dep_graph.in_task(DepNode::CheckLoops);
let krate = map.krate();
krate.visit_all_item_likes(&mut CheckLoopVisitor {
sess: sess,
hir_map: map,
cx: Normal,
}.as_deep_visitor());
}
impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'hir> {
NestedVisitorMap::OnlyBodies(&self.hir_map)
}
fn visit_item(&mut self, i: &'hir hir::Item) {
self.with_context(Normal, |v| intravisit::walk_item(v, i));
}
fn visit_impl_item(&mut self, i: &'hir hir::ImplItem) {
self.with_context(Normal, |v| intravisit::walk_impl_item(v, i));
}
fn visit_expr(&mut self, e: &'hir hir::Expr) {
match e.node {
hir::ExprWhile(ref e, ref b, _) => {
self.with_context(Loop(LoopKind::WhileLoop), |v| {
v.visit_expr(&e);
v.visit_block(&b);
});
}
hir::ExprLoop(ref b, _, source) => {
self.with_context(Loop(LoopKind::Loop(source)), |v| v.visit_block(&b));
}
hir::ExprClosure(.., b, _) => {
self.with_context(Closure, |v| v.visit_nested_body(b));
}
hir::ExprBreak(label, ref opt_expr) => {
let loop_id = match label.loop_id.into() {
Ok(loop_id) => loop_id,
Err(hir::LoopIdError::OutsideLoopScope) => ast::DUMMY_NODE_ID,
Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
self.emit_unlabled_cf_in_while_condition(e.span, "break");
ast::DUMMY_NODE_ID
},
Err(hir::LoopIdError::UnresolvedLabel) => ast::DUMMY_NODE_ID,
};
if opt_expr.is_some() {
let loop_kind = if loop_id == ast::DUMMY_NODE_ID {
None
} else {
Some(match self.hir_map.expect_expr(loop_id).node {
hir::ExprWhile(..) => LoopKind::WhileLoop,
hir::ExprLoop(_, _, source) => LoopKind::Loop(source),
ref r => span_bug!(e.span,
"break label resolved to a non-loop: {:?}", r),
})
};
match loop_kind {
None | Some(LoopKind::Loop(hir::LoopSource::Loop)) => (),
Some(kind) => {
struct_span_err!(self.sess, e.span, E0571,
"`break` with value from a `{}` loop",
kind.name())
.span_label(e.span,
&format!("can only break with a value inside `loop`"))
.emit();
}
}
}
self.require_loop("break", e.span);
}
hir::ExprAgain(label) => {
if let Err(hir::LoopIdError::UnlabeledCfInWhileCondition) = label.loop_id.into() {
self.emit_unlabled_cf_in_while_condition(e.span, "continue");
}
self.require_loop("continue", e.span)
},
_ => intravisit::walk_expr(self, e),
}
}
}
impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
fn with_context<F>(&mut self, cx: Context, f: F)
where F: FnOnce(&mut CheckLoopVisitor<'a, 'hir>)
{
let old_cx = self.cx;
self.cx = cx;
f(self);
self.cx = old_cx;
}
fn require_loop(&self, name: &str, span: Span) {
match self.cx {
Loop(_) => {}
Closure => {
struct_span_err!(self.sess, span, E0267, "`{}` inside of a closure", name)
.span_label(span, &format!("cannot break inside of a closure"))
.emit();
}
Normal => {
struct_span_err!(self.sess, span, E0268, "`{}` outside of loop", name)
.span_label(span, &format!("cannot break outside of a loop"))
.emit();
}
}
}
fn emit_unlabled_cf_in_while_condition(&mut self, span: Span, cf_type: &str) {
struct_span_err!(self.sess, span, E0590,
"`break` or `continue` with no label in the condition of a `while` loop")
.span_label(span,
&format!("unlabeled `{}` in the condition of a `while` loop", cf_type))
.emit();
}
}