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
|
//! See docs in build/expr/mod.rs
use crate::build::{parse_float_into_constval, Builder};
use rustc_ast as ast;
use rustc_middle::mir::interpret::{
Allocation, ConstValue, LitToConstError, LitToConstInput, Scalar,
};
use rustc_middle::mir::*;
use rustc_middle::thir::*;
use rustc_middle::ty::{self, CanonicalUserTypeAnnotation, TyCtxt};
use rustc_target::abi::Size;
impl<'a, 'tcx> Builder<'a, 'tcx> {
/// Compile `expr`, yielding a compile-time constant. Assumes that
/// `expr` is a valid compile-time constant!
pub(crate) fn as_constant(&mut self, expr: &Expr<'tcx>) -> Constant<'tcx> {
let this = self;
let tcx = this.tcx;
let Expr { ty, temp_lifetime: _, span, ref kind } = *expr;
match *kind {
ExprKind::Scope { region_scope: _, lint_level: _, value } => {
this.as_constant(&this.thir[value])
}
ExprKind::Literal { lit, neg } => {
let literal =
match lit_to_mir_constant(tcx, LitToConstInput { lit: &lit.node, ty, neg }) {
Ok(c) => c,
Err(LitToConstError::Reported) => ConstantKind::Ty(tcx.const_error(ty)),
Err(LitToConstError::TypeError) => {
bug!("encountered type error in `lit_to_mir_constant")
}
};
Constant { span, user_ty: None, literal }
}
ExprKind::NonHirLiteral { lit, ref user_ty } => {
let user_ty = user_ty.as_ref().map(|user_ty| {
this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
span,
user_ty: user_ty.clone(),
inferred_ty: ty,
})
});
let literal = ConstantKind::Val(ConstValue::Scalar(Scalar::Int(lit)), ty);
Constant { span, user_ty: user_ty, literal }
}
ExprKind::ZstLiteral { ref user_ty } => {
let user_ty = user_ty.as_ref().map(|user_ty| {
this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
span,
user_ty: user_ty.clone(),
inferred_ty: ty,
})
});
let literal = ConstantKind::Val(ConstValue::ZeroSized, ty);
Constant { span, user_ty: user_ty, literal }
}
ExprKind::NamedConst { def_id, substs, ref user_ty } => {
let user_ty = user_ty.as_ref().map(|user_ty| {
this.canonical_user_type_annotations.push(CanonicalUserTypeAnnotation {
span,
user_ty: user_ty.clone(),
inferred_ty: ty,
})
});
let uneval = ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs);
let literal = ConstantKind::Unevaluated(uneval, ty);
Constant { user_ty, span, literal }
}
ExprKind::ConstParam { param, def_id: _ } => {
let const_param =
tcx.mk_const(ty::ConstS { kind: ty::ConstKind::Param(param), ty: expr.ty });
let literal = ConstantKind::Ty(const_param);
Constant { user_ty: None, span, literal }
}
ExprKind::ConstBlock { did: def_id, substs } => {
let uneval = ty::Unevaluated::new(ty::WithOptConstParam::unknown(def_id), substs);
let literal = ConstantKind::Unevaluated(uneval, ty);
Constant { user_ty: None, span, literal }
}
ExprKind::StaticRef { alloc_id, ty, .. } => {
let const_val = ConstValue::Scalar(Scalar::from_pointer(alloc_id.into(), &tcx));
let literal = ConstantKind::Val(const_val, ty);
Constant { span, user_ty: None, literal }
}
_ => span_bug!(span, "expression is not a valid constant {:?}", kind),
}
}
}
#[instrument(skip(tcx, lit_input))]
pub(crate) fn lit_to_mir_constant<'tcx>(
tcx: TyCtxt<'tcx>,
lit_input: LitToConstInput<'tcx>,
) -> Result<ConstantKind<'tcx>, LitToConstError> {
let LitToConstInput { lit, ty, neg } = lit_input;
let trunc = |n| {
let param_ty = ty::ParamEnv::reveal_all().and(ty);
let width = tcx.layout_of(param_ty).map_err(|_| LitToConstError::Reported)?.size;
trace!("trunc {} with size {} and shift {}", n, width.bits(), 128 - width.bits());
let result = width.truncate(n);
trace!("trunc result: {}", result);
Ok(ConstValue::Scalar(Scalar::from_uint(result, width)))
};
let value = match (lit, &ty.kind()) {
(ast::LitKind::Str(s, _), ty::Ref(_, inner_ty, _)) if inner_ty.is_str() => {
let s = s.as_str();
let allocation = Allocation::from_bytes_byte_aligned_immutable(s.as_bytes());
let allocation = tcx.intern_const_alloc(allocation);
ConstValue::Slice { data: allocation, start: 0, end: s.len() }
}
(ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _))
if matches!(inner_ty.kind(), ty::Slice(_)) =>
{
let allocation = Allocation::from_bytes_byte_aligned_immutable(data as &[u8]);
let allocation = tcx.intern_const_alloc(allocation);
ConstValue::Slice { data: allocation, start: 0, end: data.len() }
}
(ast::LitKind::ByteStr(data), ty::Ref(_, inner_ty, _)) if inner_ty.is_array() => {
let id = tcx.allocate_bytes(data);
ConstValue::Scalar(Scalar::from_pointer(id.into(), &tcx))
}
(ast::LitKind::Byte(n), ty::Uint(ty::UintTy::U8)) => {
ConstValue::Scalar(Scalar::from_uint(*n, Size::from_bytes(1)))
}
(ast::LitKind::Int(n, _), ty::Uint(_)) | (ast::LitKind::Int(n, _), ty::Int(_)) => {
trunc(if neg { (*n as i128).overflowing_neg().0 as u128 } else { *n })?
}
(ast::LitKind::Float(n, _), ty::Float(fty)) => {
parse_float_into_constval(*n, *fty, neg).ok_or(LitToConstError::Reported)?
}
(ast::LitKind::Bool(b), ty::Bool) => ConstValue::Scalar(Scalar::from_bool(*b)),
(ast::LitKind::Char(c), ty::Char) => ConstValue::Scalar(Scalar::from_char(*c)),
(ast::LitKind::Err, _) => return Err(LitToConstError::Reported),
_ => return Err(LitToConstError::TypeError),
};
Ok(ConstantKind::Val(value, ty))
}
|
