forked from rust-lang/rust
/
as_constant.rs
51 lines (48 loc) · 1.51 KB
/
as_constant.rs
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
//! See docs in build/expr/mod.rs
use crate::build::Builder;
use crate::hair::*;
use rustc::mir::*;
use rustc::ty::CanonicalUserTypeAnnotation;
impl<'a, 'tcx> Builder<'a, 'tcx> {
/// Compile `expr`, yielding a compile-time constant. Assumes that
/// `expr` is a valid compile-time constant!
pub fn as_constant<M>(&mut self, expr: M) -> Constant<'tcx>
where
M: Mirror<'tcx, Output = Expr<'tcx>>,
{
let expr = self.hir.mirror(expr);
self.expr_as_constant(expr)
}
fn expr_as_constant(&mut self, expr: Expr<'tcx>) -> Constant<'tcx> {
let this = self;
let Expr {
ty,
temp_lifetime: _,
span,
kind,
} = expr;
match kind {
ExprKind::Scope {
region_scope: _,
lint_level: _,
value,
} => this.as_constant(value),
ExprKind::Literal { literal, user_ty } => {
let user_ty = user_ty.map(|user_ty| {
this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
span,
user_ty,
inferred_ty: ty,
})
});
assert_eq!(literal.ty, ty);
Constant {
span,
user_ty,
literal,
}
},
_ => span_bug!(span, "expression is not a valid constant {:?}", kind),
}
}
}