939 lines
38 KiB
Rust
939 lines
38 KiB
Rust
#![allow(clippy::float_cmp)]
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use crate::macros::HirNode;
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use crate::source::{SpanRangeExt, walk_span_to_context};
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use crate::{clip, is_direct_expn_of, sext, unsext};
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use rustc_apfloat::Float;
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use rustc_apfloat::ieee::{Half, Quad};
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use rustc_ast::ast::{self, LitFloatType, LitKind};
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use rustc_data_structures::sync::Lrc;
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use rustc_hir::def::{DefKind, Res};
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use rustc_hir::{BinOp, BinOpKind, Block, ConstBlock, Expr, ExprKind, HirId, Item, ItemKind, Node, QPath, UnOp};
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use rustc_lexer::tokenize;
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use rustc_lint::LateContext;
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use rustc_middle::mir::ConstValue;
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use rustc_middle::mir::interpret::{Scalar, alloc_range};
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use rustc_middle::ty::{self, FloatTy, IntTy, ParamEnv, ScalarInt, Ty, TyCtxt, TypeckResults, UintTy};
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use rustc_middle::{bug, mir, span_bug};
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use rustc_span::def_id::DefId;
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use rustc_span::symbol::Ident;
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use rustc_span::{SyntaxContext, sym};
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use rustc_target::abi::Size;
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use std::cell::Cell;
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use std::cmp::Ordering;
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use std::hash::{Hash, Hasher};
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use std::iter;
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/// A `LitKind`-like enum to fold constant `Expr`s into.
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#[derive(Debug, Clone)]
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pub enum Constant<'tcx> {
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Adt(mir::Const<'tcx>),
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/// A `String` (e.g., "abc").
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Str(String),
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/// A binary string (e.g., `b"abc"`).
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Binary(Lrc<[u8]>),
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/// A single `char` (e.g., `'a'`).
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Char(char),
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/// An integer's bit representation.
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Int(u128),
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/// An `f16`.
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F16(f16),
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/// An `f32`.
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F32(f32),
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/// An `f64`.
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F64(f64),
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/// An `f128`.
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F128(f128),
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/// `true` or `false`.
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Bool(bool),
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/// An array of constants.
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Vec(Vec<Constant<'tcx>>),
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/// Also an array, but with only one constant, repeated N times.
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Repeat(Box<Constant<'tcx>>, u64),
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/// A tuple of constants.
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Tuple(Vec<Constant<'tcx>>),
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/// A raw pointer.
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RawPtr(u128),
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/// A reference
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Ref(Box<Constant<'tcx>>),
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/// A literal with syntax error.
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Err,
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}
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trait IntTypeBounds: Sized {
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type Output: PartialOrd;
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fn min_max(self) -> Option<(Self::Output, Self::Output)>;
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fn bits(self) -> Self::Output;
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fn ensure_fits(self, val: Self::Output) -> Option<Self::Output> {
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let (min, max) = self.min_max()?;
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(min <= val && val <= max).then_some(val)
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}
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}
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impl IntTypeBounds for UintTy {
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type Output = u128;
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fn min_max(self) -> Option<(Self::Output, Self::Output)> {
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Some(match self {
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UintTy::U8 => (u8::MIN.into(), u8::MAX.into()),
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UintTy::U16 => (u16::MIN.into(), u16::MAX.into()),
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UintTy::U32 => (u32::MIN.into(), u32::MAX.into()),
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UintTy::U64 => (u64::MIN.into(), u64::MAX.into()),
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UintTy::U128 => (u128::MIN, u128::MAX),
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UintTy::Usize => (usize::MIN.try_into().ok()?, usize::MAX.try_into().ok()?),
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})
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}
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fn bits(self) -> Self::Output {
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match self {
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UintTy::U8 => 8,
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UintTy::U16 => 16,
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UintTy::U32 => 32,
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UintTy::U64 => 64,
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UintTy::U128 => 128,
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UintTy::Usize => usize::BITS.into(),
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}
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}
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}
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impl IntTypeBounds for IntTy {
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type Output = i128;
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fn min_max(self) -> Option<(Self::Output, Self::Output)> {
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Some(match self {
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IntTy::I8 => (i8::MIN.into(), i8::MAX.into()),
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IntTy::I16 => (i16::MIN.into(), i16::MAX.into()),
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IntTy::I32 => (i32::MIN.into(), i32::MAX.into()),
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IntTy::I64 => (i64::MIN.into(), i64::MAX.into()),
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IntTy::I128 => (i128::MIN, i128::MAX),
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IntTy::Isize => (isize::MIN.try_into().ok()?, isize::MAX.try_into().ok()?),
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})
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}
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fn bits(self) -> Self::Output {
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match self {
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IntTy::I8 => 8,
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IntTy::I16 => 16,
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IntTy::I32 => 32,
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IntTy::I64 => 64,
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IntTy::I128 => 128,
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IntTy::Isize => isize::BITS.into(),
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}
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}
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}
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impl PartialEq for Constant<'_> {
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fn eq(&self, other: &Self) -> bool {
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match (self, other) {
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(Self::Str(ls), Self::Str(rs)) => ls == rs,
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(Self::Binary(l), Self::Binary(r)) => l == r,
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(&Self::Char(l), &Self::Char(r)) => l == r,
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(&Self::Int(l), &Self::Int(r)) => l == r,
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(&Self::F64(l), &Self::F64(r)) => {
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// We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
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// `Fw32 == Fw64`, so don’t compare them.
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// `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
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l.to_bits() == r.to_bits()
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},
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(&Self::F32(l), &Self::F32(r)) => {
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// We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have
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// `Fw32 == Fw64`, so don’t compare them.
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// `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs.
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f64::from(l).to_bits() == f64::from(r).to_bits()
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},
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(&Self::Bool(l), &Self::Bool(r)) => l == r,
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(&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r,
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(Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => ls == rs && lv == rv,
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(Self::Ref(lb), Self::Ref(rb)) => *lb == *rb,
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// TODO: are there inter-type equalities?
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_ => false,
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}
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}
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}
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impl Hash for Constant<'_> {
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fn hash<H>(&self, state: &mut H)
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where
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H: Hasher,
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{
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std::mem::discriminant(self).hash(state);
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match *self {
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Self::Adt(ref elem) => {
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elem.hash(state);
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},
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Self::Str(ref s) => {
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s.hash(state);
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},
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Self::Binary(ref b) => {
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b.hash(state);
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},
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Self::Char(c) => {
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c.hash(state);
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},
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Self::Int(i) => {
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i.hash(state);
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},
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Self::F16(f) => {
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// FIXME(f16_f128): once conversions to/from `f128` are available on all platforms,
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f.to_bits().hash(state);
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},
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Self::F32(f) => {
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f64::from(f).to_bits().hash(state);
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},
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Self::F64(f) => {
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f.to_bits().hash(state);
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},
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Self::F128(f) => {
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f.to_bits().hash(state);
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},
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Self::Bool(b) => {
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b.hash(state);
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},
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Self::Vec(ref v) | Self::Tuple(ref v) => {
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v.hash(state);
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},
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Self::Repeat(ref c, l) => {
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c.hash(state);
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l.hash(state);
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},
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Self::RawPtr(u) => {
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u.hash(state);
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},
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Self::Ref(ref r) => {
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r.hash(state);
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},
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Self::Err => {},
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}
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}
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}
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impl Constant<'_> {
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pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option<Ordering> {
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match (left, right) {
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(Self::Str(ls), Self::Str(rs)) => Some(ls.cmp(rs)),
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(Self::Char(l), Self::Char(r)) => Some(l.cmp(r)),
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(&Self::Int(l), &Self::Int(r)) => match *cmp_type.kind() {
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ty::Int(int_ty) => Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty))),
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ty::Uint(_) => Some(l.cmp(&r)),
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_ => bug!("Not an int type"),
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},
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(&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r),
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(&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r),
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(Self::Bool(l), Self::Bool(r)) => Some(l.cmp(r)),
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(Self::Tuple(l), Self::Tuple(r)) if l.len() == r.len() => match *cmp_type.kind() {
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ty::Tuple(tys) if tys.len() == l.len() => l
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.iter()
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.zip(r)
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.zip(tys)
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.map(|((li, ri), cmp_type)| Self::partial_cmp(tcx, cmp_type, li, ri))
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.find(|r| r.map_or(true, |o| o != Ordering::Equal))
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.unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
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_ => None,
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},
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(Self::Vec(l), Self::Vec(r)) => {
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let (ty::Array(cmp_type, _) | ty::Slice(cmp_type)) = *cmp_type.kind() else {
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return None;
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};
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iter::zip(l, r)
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.map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri))
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.find(|r| r.map_or(true, |o| o != Ordering::Equal))
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.unwrap_or_else(|| Some(l.len().cmp(&r.len())))
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},
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(Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => {
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match Self::partial_cmp(
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tcx,
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match *cmp_type.kind() {
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ty::Array(ty, _) => ty,
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_ => return None,
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},
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lv,
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rv,
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) {
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Some(Ordering::Equal) => Some(ls.cmp(rs)),
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x => x,
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}
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},
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(Self::Ref(lb), Self::Ref(rb)) => Self::partial_cmp(
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tcx,
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match *cmp_type.kind() {
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ty::Ref(_, ty, _) => ty,
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_ => return None,
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},
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lb,
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rb,
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),
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// TODO: are there any useful inter-type orderings?
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_ => None,
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}
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}
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/// Returns the integer value or `None` if `self` or `val_type` is not integer type.
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pub fn int_value(&self, tcx: TyCtxt<'_>, val_type: Ty<'_>) -> Option<FullInt> {
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if let Constant::Int(const_int) = *self {
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match *val_type.kind() {
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ty::Int(ity) => Some(FullInt::S(sext(tcx, const_int, ity))),
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ty::Uint(_) => Some(FullInt::U(const_int)),
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_ => None,
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}
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} else {
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None
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}
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}
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#[must_use]
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pub fn peel_refs(mut self) -> Self {
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while let Constant::Ref(r) = self {
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self = *r;
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}
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self
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}
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fn parse_f16(s: &str) -> Self {
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let f: Half = s.parse().unwrap();
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Self::F16(f16::from_bits(f.to_bits().try_into().unwrap()))
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}
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fn parse_f128(s: &str) -> Self {
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let f: Quad = s.parse().unwrap();
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Self::F128(f128::from_bits(f.to_bits()))
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}
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}
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/// Parses a `LitKind` to a `Constant`.
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pub fn lit_to_mir_constant<'tcx>(lit: &LitKind, ty: Option<Ty<'tcx>>) -> Constant<'tcx> {
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match *lit {
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LitKind::Str(ref is, _) => Constant::Str(is.to_string()),
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LitKind::Byte(b) => Constant::Int(u128::from(b)),
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LitKind::ByteStr(ref s, _) | LitKind::CStr(ref s, _) => Constant::Binary(Lrc::clone(s)),
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LitKind::Char(c) => Constant::Char(c),
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LitKind::Int(n, _) => Constant::Int(n.get()),
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LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty {
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// FIXME(f16_f128): just use `parse()` directly when available for `f16`/`f128`
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ast::FloatTy::F16 => Constant::parse_f16(is.as_str()),
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ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()),
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ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()),
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ast::FloatTy::F128 => Constant::parse_f128(is.as_str()),
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},
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LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() {
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ty::Float(FloatTy::F16) => Constant::parse_f16(is.as_str()),
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ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()),
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ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()),
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ty::Float(FloatTy::F128) => Constant::parse_f128(is.as_str()),
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_ => bug!(),
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},
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LitKind::Bool(b) => Constant::Bool(b),
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LitKind::Err(_) => Constant::Err,
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}
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}
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/// The source of a constant value.
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#[derive(Clone, Copy)]
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pub enum ConstantSource {
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/// The value is determined solely from the expression.
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Local,
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/// The value is dependent on a defined constant.
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Constant,
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/// The value is dependent on a constant defined in `core` crate.
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CoreConstant,
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}
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impl ConstantSource {
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pub fn is_local(self) -> bool {
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matches!(self, Self::Local)
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}
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}
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#[derive(Copy, Clone, Debug, Eq)]
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pub enum FullInt {
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S(i128),
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U(u128),
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}
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impl PartialEq for FullInt {
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#[must_use]
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fn eq(&self, other: &Self) -> bool {
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self.cmp(other) == Ordering::Equal
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}
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}
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impl PartialOrd for FullInt {
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#[must_use]
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fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
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Some(self.cmp(other))
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}
|
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}
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impl Ord for FullInt {
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#[must_use]
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fn cmp(&self, other: &Self) -> Ordering {
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use FullInt::{S, U};
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fn cmp_s_u(s: i128, u: u128) -> Ordering {
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u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u))
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}
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|
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match (*self, *other) {
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(S(s), S(o)) => s.cmp(&o),
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(U(s), U(o)) => s.cmp(&o),
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(S(s), U(o)) => cmp_s_u(s, o),
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(U(s), S(o)) => cmp_s_u(o, s).reverse(),
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}
|
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}
|
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}
|
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|
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/// The context required to evaluate a constant expression.
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///
|
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/// This is currently limited to constant folding and reading the value of named constants.
|
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pub struct ConstEvalCtxt<'tcx> {
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tcx: TyCtxt<'tcx>,
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param_env: ParamEnv<'tcx>,
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typeck: &'tcx TypeckResults<'tcx>,
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source: Cell<ConstantSource>,
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}
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impl<'tcx> ConstEvalCtxt<'tcx> {
|
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/// Creates the evaluation context from the lint context. This requires the lint context to be
|
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/// in a body (i.e. `cx.enclosing_body.is_some()`).
|
||
pub fn new(cx: &LateContext<'tcx>) -> Self {
|
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Self {
|
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tcx: cx.tcx,
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param_env: cx.param_env,
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typeck: cx.typeck_results(),
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source: Cell::new(ConstantSource::Local),
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}
|
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}
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||
|
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/// Creates an evaluation context.
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pub fn with_env(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, typeck: &'tcx TypeckResults<'tcx>) -> Self {
|
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Self {
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||
tcx,
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||
param_env,
|
||
typeck,
|
||
source: Cell::new(ConstantSource::Local),
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}
|
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}
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|
||
/// Attempts to evaluate the expression and returns both the value and whether it's dependant on
|
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/// other items.
|
||
pub fn eval_with_source(&self, e: &Expr<'_>) -> Option<(Constant<'tcx>, ConstantSource)> {
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||
self.source.set(ConstantSource::Local);
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self.expr(e).map(|c| (c, self.source.get()))
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||
}
|
||
|
||
/// Attempts to evaluate the expression.
|
||
pub fn eval(&self, e: &Expr<'_>) -> Option<Constant<'tcx>> {
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self.expr(e)
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||
}
|
||
|
||
/// Attempts to evaluate the expression without accessing other items.
|
||
pub fn eval_simple(&self, e: &Expr<'_>) -> Option<Constant<'tcx>> {
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||
match self.eval_with_source(e) {
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||
Some((x, ConstantSource::Local)) => Some(x),
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||
_ => None,
|
||
}
|
||
}
|
||
|
||
/// Attempts to evaluate the expression as an integer without accessing other items.
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||
pub fn eval_full_int(&self, e: &Expr<'_>) -> Option<FullInt> {
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||
match self.eval_with_source(e) {
|
||
Some((x, ConstantSource::Local)) => x.int_value(self.tcx, self.typeck.expr_ty(e)),
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
/// Simple constant folding: Insert an expression, get a constant or none.
|
||
fn expr(&self, e: &Expr<'_>) -> Option<Constant<'tcx>> {
|
||
match e.kind {
|
||
ExprKind::ConstBlock(ConstBlock { body, .. }) => self.expr(self.tcx.hir().body(body).value),
|
||
ExprKind::DropTemps(e) => self.expr(e),
|
||
ExprKind::Path(ref qpath) => {
|
||
let is_core_crate = if let Some(def_id) = self.typeck.qpath_res(qpath, e.hir_id()).opt_def_id() {
|
||
self.tcx.crate_name(def_id.krate) == sym::core
|
||
} else {
|
||
false
|
||
};
|
||
self.fetch_path_and_apply(qpath, e.hir_id, self.typeck.expr_ty(e), |self_, result| {
|
||
let result = mir_to_const(self_.tcx, result)?;
|
||
// If source is already Constant we wouldn't want to override it with CoreConstant
|
||
self_.source.set(
|
||
if is_core_crate && !matches!(self_.source.get(), ConstantSource::Constant) {
|
||
ConstantSource::CoreConstant
|
||
} else {
|
||
ConstantSource::Constant
|
||
},
|
||
);
|
||
Some(result)
|
||
})
|
||
},
|
||
ExprKind::Block(block, _) => self.block(block),
|
||
ExprKind::Lit(lit) => {
|
||
if is_direct_expn_of(e.span, "cfg").is_some() {
|
||
None
|
||
} else {
|
||
Some(lit_to_mir_constant(&lit.node, self.typeck.expr_ty_opt(e)))
|
||
}
|
||
},
|
||
ExprKind::Array(vec) => self.multi(vec).map(Constant::Vec),
|
||
ExprKind::Tup(tup) => self.multi(tup).map(Constant::Tuple),
|
||
ExprKind::Repeat(value, _) => {
|
||
let n = match self.typeck.expr_ty(e).kind() {
|
||
ty::Array(_, n) => n.try_eval_target_usize(self.tcx, self.param_env)?,
|
||
_ => span_bug!(e.span, "typeck error"),
|
||
};
|
||
self.expr(value).map(|v| Constant::Repeat(Box::new(v), n))
|
||
},
|
||
ExprKind::Unary(op, operand) => self.expr(operand).and_then(|o| match op {
|
||
UnOp::Not => self.constant_not(&o, self.typeck.expr_ty(e)),
|
||
UnOp::Neg => self.constant_negate(&o, self.typeck.expr_ty(e)),
|
||
UnOp::Deref => Some(if let Constant::Ref(r) = o { *r } else { o }),
|
||
}),
|
||
ExprKind::If(cond, then, ref otherwise) => self.ifthenelse(cond, then, *otherwise),
|
||
ExprKind::Binary(op, left, right) => self.binop(op, left, right),
|
||
ExprKind::Call(callee, args) => {
|
||
// We only handle a few const functions for now.
|
||
if args.is_empty()
|
||
&& let ExprKind::Path(qpath) = &callee.kind
|
||
&& let Some(did) = self.typeck.qpath_res(qpath, callee.hir_id).opt_def_id()
|
||
{
|
||
match self.tcx.get_diagnostic_name(did) {
|
||
Some(sym::i8_legacy_fn_max_value) => Some(Constant::Int(i8::MAX as u128)),
|
||
Some(sym::i16_legacy_fn_max_value) => Some(Constant::Int(i16::MAX as u128)),
|
||
Some(sym::i32_legacy_fn_max_value) => Some(Constant::Int(i32::MAX as u128)),
|
||
Some(sym::i64_legacy_fn_max_value) => Some(Constant::Int(i64::MAX as u128)),
|
||
Some(sym::i128_legacy_fn_max_value) => Some(Constant::Int(i128::MAX as u128)),
|
||
_ => None,
|
||
}
|
||
} else {
|
||
None
|
||
}
|
||
},
|
||
ExprKind::Index(arr, index, _) => self.index(arr, index),
|
||
ExprKind::AddrOf(_, _, inner) => self.expr(inner).map(|r| Constant::Ref(Box::new(r))),
|
||
ExprKind::Field(local_expr, ref field) => {
|
||
let result = self.expr(local_expr);
|
||
if let Some(Constant::Adt(constant)) = &self.expr(local_expr)
|
||
&& let ty::Adt(adt_def, _) = constant.ty().kind()
|
||
&& adt_def.is_struct()
|
||
&& let Some(desired_field) = field_of_struct(*adt_def, self.tcx, *constant, field)
|
||
{
|
||
mir_to_const(self.tcx, desired_field)
|
||
} else {
|
||
result
|
||
}
|
||
},
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
/// Simple constant folding to determine if an expression is an empty slice, str, array, …
|
||
/// `None` will be returned if the constness cannot be determined, or if the resolution
|
||
/// leaves the local crate.
|
||
pub fn eval_is_empty(&self, e: &Expr<'_>) -> Option<bool> {
|
||
match e.kind {
|
||
ExprKind::ConstBlock(ConstBlock { body, .. }) => self.eval_is_empty(self.tcx.hir().body(body).value),
|
||
ExprKind::DropTemps(e) => self.eval_is_empty(e),
|
||
ExprKind::Path(ref qpath) => {
|
||
if !self
|
||
.typeck
|
||
.qpath_res(qpath, e.hir_id)
|
||
.opt_def_id()
|
||
.is_some_and(DefId::is_local)
|
||
{
|
||
return None;
|
||
}
|
||
self.fetch_path_and_apply(qpath, e.hir_id, self.typeck.expr_ty(e), |self_, result| {
|
||
mir_is_empty(self_.tcx, result)
|
||
})
|
||
},
|
||
ExprKind::Lit(lit) => {
|
||
if is_direct_expn_of(e.span, "cfg").is_some() {
|
||
None
|
||
} else {
|
||
match &lit.node {
|
||
LitKind::Str(is, _) => Some(is.is_empty()),
|
||
LitKind::ByteStr(s, _) | LitKind::CStr(s, _) => Some(s.is_empty()),
|
||
_ => None,
|
||
}
|
||
}
|
||
},
|
||
ExprKind::Array(vec) => self.multi(vec).map(|v| v.is_empty()),
|
||
ExprKind::Repeat(..) => {
|
||
if let ty::Array(_, n) = self.typeck.expr_ty(e).kind() {
|
||
Some(n.try_eval_target_usize(self.tcx, self.param_env)? == 0)
|
||
} else {
|
||
span_bug!(e.span, "typeck error");
|
||
}
|
||
},
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
#[expect(clippy::cast_possible_wrap)]
|
||
fn constant_not(&self, o: &Constant<'tcx>, ty: Ty<'_>) -> Option<Constant<'tcx>> {
|
||
use self::Constant::{Bool, Int};
|
||
match *o {
|
||
Bool(b) => Some(Bool(!b)),
|
||
Int(value) => {
|
||
let value = !value;
|
||
match *ty.kind() {
|
||
ty::Int(ity) => Some(Int(unsext(self.tcx, value as i128, ity))),
|
||
ty::Uint(ity) => Some(Int(clip(self.tcx, value, ity))),
|
||
_ => None,
|
||
}
|
||
},
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
fn constant_negate(&self, o: &Constant<'tcx>, ty: Ty<'_>) -> Option<Constant<'tcx>> {
|
||
use self::Constant::{F32, F64, Int};
|
||
match *o {
|
||
Int(value) => {
|
||
let ty::Int(ity) = *ty.kind() else { return None };
|
||
let (min, _) = ity.min_max()?;
|
||
// sign extend
|
||
let value = sext(self.tcx, value, ity);
|
||
|
||
// Applying unary - to the most negative value of any signed integer type panics.
|
||
if value == min {
|
||
return None;
|
||
}
|
||
|
||
let value = value.checked_neg()?;
|
||
// clear unused bits
|
||
Some(Int(unsext(self.tcx, value, ity)))
|
||
},
|
||
F32(f) => Some(F32(-f)),
|
||
F64(f) => Some(F64(-f)),
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
/// Create `Some(Vec![..])` of all constants, unless there is any
|
||
/// non-constant part.
|
||
fn multi(&self, vec: &[Expr<'_>]) -> Option<Vec<Constant<'tcx>>> {
|
||
vec.iter().map(|elem| self.expr(elem)).collect::<Option<_>>()
|
||
}
|
||
|
||
/// Lookup a possibly constant expression from an `ExprKind::Path` and apply a function on it.
|
||
fn fetch_path_and_apply<T, F>(&self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>, f: F) -> Option<T>
|
||
where
|
||
F: FnOnce(&Self, mir::Const<'tcx>) -> Option<T>,
|
||
{
|
||
let res = self.typeck.qpath_res(qpath, id);
|
||
match res {
|
||
Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
|
||
// Check if this constant is based on `cfg!(..)`,
|
||
// which is NOT constant for our purposes.
|
||
if let Some(node) = self.tcx.hir().get_if_local(def_id)
|
||
&& let Node::Item(Item {
|
||
kind: ItemKind::Const(.., body_id),
|
||
..
|
||
}) = node
|
||
&& let Node::Expr(Expr {
|
||
kind: ExprKind::Lit(_),
|
||
span,
|
||
..
|
||
}) = self.tcx.hir_node(body_id.hir_id)
|
||
&& is_direct_expn_of(*span, "cfg").is_some()
|
||
{
|
||
return None;
|
||
}
|
||
|
||
let args = self.typeck.node_args(id);
|
||
let result = self
|
||
.tcx
|
||
.const_eval_resolve(self.param_env, mir::UnevaluatedConst::new(def_id, args), qpath.span())
|
||
.ok()
|
||
.map(|val| mir::Const::from_value(val, ty))?;
|
||
f(self, result)
|
||
},
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
fn index(&self, lhs: &'_ Expr<'_>, index: &'_ Expr<'_>) -> Option<Constant<'tcx>> {
|
||
let lhs = self.expr(lhs);
|
||
let index = self.expr(index);
|
||
|
||
match (lhs, index) {
|
||
(Some(Constant::Vec(vec)), Some(Constant::Int(index))) => match vec.get(index as usize) {
|
||
Some(Constant::F16(x)) => Some(Constant::F16(*x)),
|
||
Some(Constant::F32(x)) => Some(Constant::F32(*x)),
|
||
Some(Constant::F64(x)) => Some(Constant::F64(*x)),
|
||
Some(Constant::F128(x)) => Some(Constant::F128(*x)),
|
||
_ => None,
|
||
},
|
||
(Some(Constant::Vec(vec)), _) => {
|
||
if !vec.is_empty() && vec.iter().all(|x| *x == vec[0]) {
|
||
match vec.first() {
|
||
Some(Constant::F16(x)) => Some(Constant::F16(*x)),
|
||
Some(Constant::F32(x)) => Some(Constant::F32(*x)),
|
||
Some(Constant::F64(x)) => Some(Constant::F64(*x)),
|
||
Some(Constant::F128(x)) => Some(Constant::F128(*x)),
|
||
_ => None,
|
||
}
|
||
} else {
|
||
None
|
||
}
|
||
},
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
/// A block can only yield a constant if it has exactly one constant expression.
|
||
fn block(&self, block: &Block<'_>) -> Option<Constant<'tcx>> {
|
||
if block.stmts.is_empty()
|
||
&& let Some(expr) = block.expr
|
||
{
|
||
// Try to detect any `cfg`ed statements or empty macro expansions.
|
||
let span = block.span.data();
|
||
if span.ctxt == SyntaxContext::root() {
|
||
if let Some(expr_span) = walk_span_to_context(expr.span, span.ctxt)
|
||
&& let expr_lo = expr_span.lo()
|
||
&& expr_lo >= span.lo
|
||
&& let Some(src) = (span.lo..expr_lo).get_source_range(&self.tcx)
|
||
&& let Some(src) = src.as_str()
|
||
{
|
||
use rustc_lexer::TokenKind::{BlockComment, LineComment, OpenBrace, Semi, Whitespace};
|
||
if !tokenize(src)
|
||
.map(|t| t.kind)
|
||
.filter(|t| !matches!(t, Whitespace | LineComment { .. } | BlockComment { .. } | Semi))
|
||
.eq([OpenBrace])
|
||
{
|
||
self.source.set(ConstantSource::Constant);
|
||
}
|
||
} else {
|
||
// Unable to access the source. Assume a non-local dependency.
|
||
self.source.set(ConstantSource::Constant);
|
||
}
|
||
}
|
||
|
||
self.expr(expr)
|
||
} else {
|
||
None
|
||
}
|
||
}
|
||
|
||
fn ifthenelse(&self, cond: &Expr<'_>, then: &Expr<'_>, otherwise: Option<&Expr<'_>>) -> Option<Constant<'tcx>> {
|
||
if let Some(Constant::Bool(b)) = self.expr(cond) {
|
||
if b {
|
||
self.expr(then)
|
||
} else {
|
||
otherwise.as_ref().and_then(|expr| self.expr(expr))
|
||
}
|
||
} else {
|
||
None
|
||
}
|
||
}
|
||
|
||
fn binop(&self, op: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> Option<Constant<'tcx>> {
|
||
let l = self.expr(left)?;
|
||
let r = self.expr(right);
|
||
match (l, r) {
|
||
(Constant::Int(l), Some(Constant::Int(r))) => match *self.typeck.expr_ty_opt(left)?.kind() {
|
||
ty::Int(ity) => {
|
||
let (ty_min_value, _) = ity.min_max()?;
|
||
let bits = ity.bits();
|
||
let l = sext(self.tcx, l, ity);
|
||
let r = sext(self.tcx, r, ity);
|
||
|
||
// Using / or %, where the left-hand argument is the smallest integer of a signed integer type and
|
||
// the right-hand argument is -1 always panics, even with overflow-checks disabled
|
||
if let BinOpKind::Div | BinOpKind::Rem = op.node
|
||
&& l == ty_min_value
|
||
&& r == -1
|
||
{
|
||
return None;
|
||
}
|
||
|
||
let zext = |n: i128| Constant::Int(unsext(self.tcx, n, ity));
|
||
match op.node {
|
||
// When +, * or binary - create a value greater than the maximum value, or less than
|
||
// the minimum value that can be stored, it panics.
|
||
BinOpKind::Add => l.checked_add(r).and_then(|n| ity.ensure_fits(n)).map(zext),
|
||
BinOpKind::Sub => l.checked_sub(r).and_then(|n| ity.ensure_fits(n)).map(zext),
|
||
BinOpKind::Mul => l.checked_mul(r).and_then(|n| ity.ensure_fits(n)).map(zext),
|
||
BinOpKind::Div if r != 0 => l.checked_div(r).map(zext),
|
||
BinOpKind::Rem if r != 0 => l.checked_rem(r).map(zext),
|
||
// Using << or >> where the right-hand argument is greater than or equal to the number of bits
|
||
// in the type of the left-hand argument, or is negative panics.
|
||
BinOpKind::Shr if r < bits && !r.is_negative() => l.checked_shr(r.try_into().ok()?).map(zext),
|
||
BinOpKind::Shl if r < bits && !r.is_negative() => l.checked_shl(r.try_into().ok()?).map(zext),
|
||
BinOpKind::BitXor => Some(zext(l ^ r)),
|
||
BinOpKind::BitOr => Some(zext(l | r)),
|
||
BinOpKind::BitAnd => Some(zext(l & r)),
|
||
BinOpKind::Eq => Some(Constant::Bool(l == r)),
|
||
BinOpKind::Ne => Some(Constant::Bool(l != r)),
|
||
BinOpKind::Lt => Some(Constant::Bool(l < r)),
|
||
BinOpKind::Le => Some(Constant::Bool(l <= r)),
|
||
BinOpKind::Ge => Some(Constant::Bool(l >= r)),
|
||
BinOpKind::Gt => Some(Constant::Bool(l > r)),
|
||
_ => None,
|
||
}
|
||
},
|
||
ty::Uint(ity) => {
|
||
let bits = ity.bits();
|
||
|
||
match op.node {
|
||
BinOpKind::Add => l.checked_add(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
|
||
BinOpKind::Sub => l.checked_sub(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
|
||
BinOpKind::Mul => l.checked_mul(r).and_then(|n| ity.ensure_fits(n)).map(Constant::Int),
|
||
BinOpKind::Div => l.checked_div(r).map(Constant::Int),
|
||
BinOpKind::Rem => l.checked_rem(r).map(Constant::Int),
|
||
BinOpKind::Shr if r < bits => l.checked_shr(r.try_into().ok()?).map(Constant::Int),
|
||
BinOpKind::Shl if r < bits => l.checked_shl(r.try_into().ok()?).map(Constant::Int),
|
||
BinOpKind::BitXor => Some(Constant::Int(l ^ r)),
|
||
BinOpKind::BitOr => Some(Constant::Int(l | r)),
|
||
BinOpKind::BitAnd => Some(Constant::Int(l & r)),
|
||
BinOpKind::Eq => Some(Constant::Bool(l == r)),
|
||
BinOpKind::Ne => Some(Constant::Bool(l != r)),
|
||
BinOpKind::Lt => Some(Constant::Bool(l < r)),
|
||
BinOpKind::Le => Some(Constant::Bool(l <= r)),
|
||
BinOpKind::Ge => Some(Constant::Bool(l >= r)),
|
||
BinOpKind::Gt => Some(Constant::Bool(l > r)),
|
||
_ => None,
|
||
}
|
||
},
|
||
_ => None,
|
||
},
|
||
// FIXME(f16_f128): add these types when binary operations are available on all platforms
|
||
(Constant::F32(l), Some(Constant::F32(r))) => match op.node {
|
||
BinOpKind::Add => Some(Constant::F32(l + r)),
|
||
BinOpKind::Sub => Some(Constant::F32(l - r)),
|
||
BinOpKind::Mul => Some(Constant::F32(l * r)),
|
||
BinOpKind::Div => Some(Constant::F32(l / r)),
|
||
BinOpKind::Rem => Some(Constant::F32(l % r)),
|
||
BinOpKind::Eq => Some(Constant::Bool(l == r)),
|
||
BinOpKind::Ne => Some(Constant::Bool(l != r)),
|
||
BinOpKind::Lt => Some(Constant::Bool(l < r)),
|
||
BinOpKind::Le => Some(Constant::Bool(l <= r)),
|
||
BinOpKind::Ge => Some(Constant::Bool(l >= r)),
|
||
BinOpKind::Gt => Some(Constant::Bool(l > r)),
|
||
_ => None,
|
||
},
|
||
(Constant::F64(l), Some(Constant::F64(r))) => match op.node {
|
||
BinOpKind::Add => Some(Constant::F64(l + r)),
|
||
BinOpKind::Sub => Some(Constant::F64(l - r)),
|
||
BinOpKind::Mul => Some(Constant::F64(l * r)),
|
||
BinOpKind::Div => Some(Constant::F64(l / r)),
|
||
BinOpKind::Rem => Some(Constant::F64(l % r)),
|
||
BinOpKind::Eq => Some(Constant::Bool(l == r)),
|
||
BinOpKind::Ne => Some(Constant::Bool(l != r)),
|
||
BinOpKind::Lt => Some(Constant::Bool(l < r)),
|
||
BinOpKind::Le => Some(Constant::Bool(l <= r)),
|
||
BinOpKind::Ge => Some(Constant::Bool(l >= r)),
|
||
BinOpKind::Gt => Some(Constant::Bool(l > r)),
|
||
_ => None,
|
||
},
|
||
(l, r) => match (op.node, l, r) {
|
||
(BinOpKind::And, Constant::Bool(false), _) => Some(Constant::Bool(false)),
|
||
(BinOpKind::Or, Constant::Bool(true), _) => Some(Constant::Bool(true)),
|
||
(BinOpKind::And, Constant::Bool(true), Some(r)) | (BinOpKind::Or, Constant::Bool(false), Some(r)) => {
|
||
Some(r)
|
||
},
|
||
(BinOpKind::BitXor, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l ^ r)),
|
||
(BinOpKind::BitAnd, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l & r)),
|
||
(BinOpKind::BitOr, Constant::Bool(l), Some(Constant::Bool(r))) => Some(Constant::Bool(l | r)),
|
||
_ => None,
|
||
},
|
||
}
|
||
}
|
||
}
|
||
|
||
pub fn mir_to_const<'tcx>(tcx: TyCtxt<'tcx>, result: mir::Const<'tcx>) -> Option<Constant<'tcx>> {
|
||
let mir::Const::Val(val, _) = result else {
|
||
// We only work on evaluated consts.
|
||
return None;
|
||
};
|
||
match (val, result.ty().kind()) {
|
||
(ConstValue::Scalar(Scalar::Int(int)), _) => match result.ty().kind() {
|
||
ty::Adt(adt_def, _) if adt_def.is_struct() => Some(Constant::Adt(result)),
|
||
ty::Bool => Some(Constant::Bool(int == ScalarInt::TRUE)),
|
||
ty::Uint(_) | ty::Int(_) => Some(Constant::Int(int.to_bits(int.size()))),
|
||
ty::Float(FloatTy::F16) => Some(Constant::F16(f16::from_bits(int.into()))),
|
||
ty::Float(FloatTy::F32) => Some(Constant::F32(f32::from_bits(int.into()))),
|
||
ty::Float(FloatTy::F64) => Some(Constant::F64(f64::from_bits(int.into()))),
|
||
ty::Float(FloatTy::F128) => Some(Constant::F128(f128::from_bits(int.into()))),
|
||
ty::RawPtr(_, _) => Some(Constant::RawPtr(int.to_bits(int.size()))),
|
||
_ => None,
|
||
},
|
||
(_, ty::Ref(_, inner_ty, _)) if matches!(inner_ty.kind(), ty::Str) => {
|
||
let data = val.try_get_slice_bytes_for_diagnostics(tcx)?;
|
||
String::from_utf8(data.to_owned()).ok().map(Constant::Str)
|
||
},
|
||
(_, ty::Adt(adt_def, _)) if adt_def.is_struct() => Some(Constant::Adt(result)),
|
||
(ConstValue::Indirect { alloc_id, offset }, ty::Array(sub_type, len)) => {
|
||
let alloc = tcx.global_alloc(alloc_id).unwrap_memory().inner();
|
||
let len = len.try_to_target_usize(tcx)?;
|
||
let ty::Float(flt) = sub_type.kind() else {
|
||
return None;
|
||
};
|
||
let size = Size::from_bits(flt.bit_width());
|
||
let mut res = Vec::new();
|
||
for idx in 0..len {
|
||
let range = alloc_range(offset + size * idx, size);
|
||
let val = alloc.read_scalar(&tcx, range, /* read_provenance */ false).ok()?;
|
||
res.push(match flt {
|
||
FloatTy::F16 => Constant::F16(f16::from_bits(val.to_u16().discard_err()?)),
|
||
FloatTy::F32 => Constant::F32(f32::from_bits(val.to_u32().discard_err()?)),
|
||
FloatTy::F64 => Constant::F64(f64::from_bits(val.to_u64().discard_err()?)),
|
||
FloatTy::F128 => Constant::F128(f128::from_bits(val.to_u128().discard_err()?)),
|
||
});
|
||
}
|
||
Some(Constant::Vec(res))
|
||
},
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
fn mir_is_empty<'tcx>(tcx: TyCtxt<'tcx>, result: mir::Const<'tcx>) -> Option<bool> {
|
||
let mir::Const::Val(val, _) = result else {
|
||
// We only work on evaluated consts.
|
||
return None;
|
||
};
|
||
match (val, result.ty().kind()) {
|
||
(_, ty::Ref(_, inner_ty, _)) => match inner_ty.kind() {
|
||
ty::Str | ty::Slice(_) => {
|
||
if let ConstValue::Indirect { alloc_id, offset } = val {
|
||
// Get the length from the slice, using the same formula as
|
||
// [`ConstValue::try_get_slice_bytes_for_diagnostics`].
|
||
let a = tcx.global_alloc(alloc_id).unwrap_memory().inner();
|
||
let ptr_size = tcx.data_layout.pointer_size;
|
||
if a.size() < offset + 2 * ptr_size {
|
||
// (partially) dangling reference
|
||
return None;
|
||
}
|
||
let len = a
|
||
.read_scalar(&tcx, alloc_range(offset + ptr_size, ptr_size), false)
|
||
.ok()?
|
||
.to_target_usize(&tcx)
|
||
.discard_err()?;
|
||
Some(len == 0)
|
||
} else {
|
||
None
|
||
}
|
||
},
|
||
ty::Array(_, len) => Some(len.try_to_target_usize(tcx)? == 0),
|
||
_ => None,
|
||
},
|
||
(ConstValue::Indirect { .. }, ty::Array(_, len)) => Some(len.try_to_target_usize(tcx)? == 0),
|
||
(ConstValue::ZeroSized, _) => Some(true),
|
||
_ => None,
|
||
}
|
||
}
|
||
|
||
fn field_of_struct<'tcx>(
|
||
adt_def: ty::AdtDef<'tcx>,
|
||
tcx: TyCtxt<'tcx>,
|
||
result: mir::Const<'tcx>,
|
||
field: &Ident,
|
||
) -> Option<mir::Const<'tcx>> {
|
||
if let mir::Const::Val(result, ty) = result
|
||
&& let Some(dc) = tcx.try_destructure_mir_constant_for_user_output(result, ty)
|
||
&& let Some(dc_variant) = dc.variant
|
||
&& let Some(variant) = adt_def.variants().get(dc_variant)
|
||
&& let Some(field_idx) = variant.fields.iter().position(|el| el.name == field.name)
|
||
&& let Some(&(val, ty)) = dc.fields.get(field_idx)
|
||
{
|
||
Some(mir::Const::Val(val, ty))
|
||
} else {
|
||
None
|
||
}
|
||
}
|