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
178
179
180
181
182
183
184
185
186
187
use middle::def::*;
use middle::ty;
use util::ppaux;
use syntax::ast;
use syntax::visit::{self, Visitor};
struct CheckCrateVisitor<'a, 'tcx: 'a> {
tcx: &'a ty::ctxt<'tcx>,
in_const: bool
}
impl<'a, 'tcx> CheckCrateVisitor<'a, 'tcx> {
fn with_const<F>(&mut self, in_const: bool, f: F) where
F: FnOnce(&mut CheckCrateVisitor<'a, 'tcx>),
{
let was_const = self.in_const;
self.in_const = in_const;
f(self);
self.in_const = was_const;
}
fn inside_const<F>(&mut self, f: F) where
F: FnOnce(&mut CheckCrateVisitor<'a, 'tcx>),
{
self.with_const(true, f);
}
}
impl<'a, 'tcx, 'v> Visitor<'v> for CheckCrateVisitor<'a, 'tcx> {
fn visit_item(&mut self, i: &ast::Item) {
match i.node {
ast::ItemStatic(_, _, ref ex) |
ast::ItemConst(_, ref ex) => {
self.inside_const(|v| v.visit_expr(&**ex));
}
ast::ItemEnum(ref enum_definition, _) => {
self.inside_const(|v| {
for var in enum_definition.variants.iter() {
if let Some(ref ex) = var.node.disr_expr {
v.visit_expr(&**ex);
}
}
});
}
_ => self.with_const(false, |v| visit::walk_item(v, i))
}
}
fn visit_pat(&mut self, p: &ast::Pat) {
let is_const = match p.node {
ast::PatLit(_) | ast::PatRange(..) => true,
_ => false
};
self.with_const(is_const, |v| visit::walk_pat(v, p))
}
fn visit_expr(&mut self, ex: &ast::Expr) {
if self.in_const {
check_expr(self, ex);
}
visit::walk_expr(self, ex);
}
}
pub fn check_crate(tcx: &ty::ctxt) {
visit::walk_crate(&mut CheckCrateVisitor { tcx: tcx, in_const: false },
tcx.map.krate());
tcx.sess.abort_if_errors();
}
fn check_expr(v: &mut CheckCrateVisitor, e: &ast::Expr) {
match e.node {
ast::ExprUnary(ast::UnDeref, _) => {}
ast::ExprUnary(ast::UnUniq, _) => {
span_err!(v.tcx.sess, e.span, E0010,
"cannot do allocations in constant expressions");
}
ast::ExprBinary(..) | ast::ExprUnary(..) => {
let method_call = ty::MethodCall::expr(e.id);
if v.tcx.method_map.borrow().contains_key(&method_call) {
span_err!(v.tcx.sess, e.span, E0011,
"user-defined operators are not allowed in constant \
expressions");
}
}
ast::ExprLit(_) => {}
ast::ExprCast(ref from, _) => {
let toty = ty::expr_ty(v.tcx, e);
let fromty = ty::expr_ty(v.tcx, &**from);
let is_legal_cast =
ty::type_is_numeric(toty) ||
ty::type_is_unsafe_ptr(toty) ||
(ty::type_is_bare_fn(toty) && ty::type_is_bare_fn_item(fromty));
if !is_legal_cast {
span_err!(v.tcx.sess, e.span, E0012,
"can not cast to `{}` in a constant expression",
ppaux::ty_to_string(v.tcx, toty));
}
if ty::type_is_unsafe_ptr(fromty) && ty::type_is_numeric(toty) {
span_err!(v.tcx.sess, e.span, E0018,
"can not cast a pointer to an integer in a constant \
expression");
}
}
ast::ExprPath(_) => {
match v.tcx.def_map.borrow()[e.id] {
DefStatic(..) | DefConst(..) |
DefFn(..) | DefStaticMethod(..) | DefMethod(..) |
DefStruct(_) | DefVariant(_, _, _) => {}
def => {
debug!("(checking const) found bad def: {:?}", def);
span_err!(v.tcx.sess, e.span, E0014,
"paths in constants may only refer to constants \
or functions");
}
}
}
ast::ExprCall(ref callee, _) => {
match v.tcx.def_map.borrow()[callee.id] {
DefStruct(..) | DefVariant(..) => {}
_ => {
span_err!(v.tcx.sess, e.span, E0015,
"function calls in constants are limited to \
struct and enum constructors");
}
}
}
ast::ExprBlock(ref block) => {
for stmt in block.stmts.iter() {
let block_span_err = |&: span|
span_err!(v.tcx.sess, span, E0016,
"blocks in constants are limited to items and \
tail expressions");
match stmt.node {
ast::StmtDecl(ref decl, _) => {
match decl.node {
ast::DeclLocal(_) => block_span_err(decl.span),
ast::DeclItem(_) => {}
}
}
ast::StmtExpr(ref expr, _) => block_span_err(expr.span),
ast::StmtSemi(ref semi, _) => block_span_err(semi.span),
ast::StmtMac(..) => {
v.tcx.sess.span_bug(e.span, "unexpanded statement \
macro in const?!")
}
}
}
}
ast::ExprVec(_) |
ast::ExprAddrOf(ast::MutImmutable, _) |
ast::ExprParen(..) |
ast::ExprField(..) |
ast::ExprTupField(..) |
ast::ExprIndex(..) |
ast::ExprTup(..) |
ast::ExprRepeat(..) |
ast::ExprStruct(..) => {}
ast::ExprAddrOf(_, ref inner) => {
match inner.node {
ast::ExprVec(_) => {}
_ => span_err!(v.tcx.sess, e.span, E0017,
"references in constants may only refer \
to immutable values")
}
}
_ => span_err!(v.tcx.sess, e.span, E0019,
"constant contains unimplemented expression type")
}
}
