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use clippy_utils::ty::{EnumValue, read_explicit_enum_value};
use rustc_middle::ty::{self, AdtDef, IntTy, Ty, TyCtxt, UintTy, VariantDiscr};
/// Returns the size in bits of an integral type.
/// Will return 0 if the type is not an int or uint variant
pub(super) fn int_ty_to_nbits(typ: Ty<'_>, tcx: TyCtxt<'_>) -> u64 {
match typ.kind() {
ty::Int(i) => match i {
IntTy::Isize => tcx.data_layout.pointer_size.bits(),
IntTy::I8 => 8,
IntTy::I16 => 16,
IntTy::I32 => 32,
IntTy::I64 => 64,
IntTy::I128 => 128,
},
ty::Uint(i) => match i {
UintTy::Usize => tcx.data_layout.pointer_size.bits(),
UintTy::U8 => 8,
UintTy::U16 => 16,
UintTy::U32 => 32,
UintTy::U64 => 64,
UintTy::U128 => 128,
},
_ => 0,
}
}
pub(super) fn enum_value_nbits(value: EnumValue) -> u64 {
match value {
EnumValue::Unsigned(x) => 128 - x.leading_zeros(),
EnumValue::Signed(x) if x < 0 => 128 - (-(x + 1)).leading_zeros() + 1,
EnumValue::Signed(x) => 128 - x.leading_zeros(),
}
.into()
}
pub(super) fn enum_ty_to_nbits(adt: AdtDef<'_>, tcx: TyCtxt<'_>) -> u64 {
let mut explicit = 0i128;
let (start, end) = adt
.variants()
.iter()
.fold((0, i128::MIN), |(start, end), variant| match variant.discr {
VariantDiscr::Relative(x) => match explicit.checked_add(i128::from(x)) {
Some(x) => (start, end.max(x)),
None => (i128::MIN, end),
},
VariantDiscr::Explicit(id) => match read_explicit_enum_value(tcx, id) {
Some(EnumValue::Signed(x)) => {
explicit = x;
(start.min(x), end.max(x))
},
Some(EnumValue::Unsigned(x)) => match i128::try_from(x) {
Ok(x) => {
explicit = x;
(start, end.max(x))
},
Err(_) => (i128::MIN, end),
},
None => (start, end),
},
});
if start > end {
// No variants.
0
} else {
let neg_bits = if start < 0 {
128 - (-(start + 1)).leading_zeros() + 1
} else {
0
};
let pos_bits = if end > 0 { 128 - end.leading_zeros() } else { 0 };
neg_bits.max(pos_bits).into()
}
}
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