//! A simple const eval API, for use on arbitrary HIR expressions. //! //! This cannot use rustc's const eval, aka miri, as arbitrary HIR expressions cannot be lowered to //! executable MIR bodies, so we have to do this instead. #![allow(clippy::float_cmp)] use std::sync::Arc; use crate::source::{SpanRangeExt, walk_span_to_context}; use crate::{clip, is_direct_expn_of, sext, unsext}; use rustc_abi::Size; use rustc_apfloat::Float; use rustc_apfloat::ieee::{Half, Quad}; use rustc_ast::ast::{self, LitFloatType, LitKind}; use rustc_hir::def::{DefKind, Res}; use rustc_hir::{ BinOp, BinOpKind, Block, ConstBlock, Expr, ExprKind, HirId, Item, ItemKind, Node, PatExpr, PatExprKind, QPath, UnOp, }; use rustc_lexer::tokenize; use rustc_lint::LateContext; use rustc_middle::mir::ConstValue; use rustc_middle::mir::interpret::{Scalar, alloc_range}; use rustc_middle::ty::{self, FloatTy, IntTy, ScalarInt, Ty, TyCtxt, TypeckResults, UintTy}; use rustc_middle::{bug, mir, span_bug}; use rustc_span::def_id::DefId; use rustc_span::symbol::Ident; use rustc_span::{SyntaxContext, sym}; use std::cell::Cell; use std::cmp::Ordering; use std::hash::{Hash, Hasher}; use std::iter; /// A `LitKind`-like enum to fold constant `Expr`s into. #[derive(Debug, Clone)] pub enum Constant<'tcx> { Adt(mir::Const<'tcx>), /// A `String` (e.g., "abc"). Str(String), /// A binary string (e.g., `b"abc"`). Binary(Arc<[u8]>), /// A single `char` (e.g., `'a'`). Char(char), /// An integer's bit representation. Int(u128), /// An `f16`. F16(f16), /// An `f32`. F32(f32), /// An `f64`. F64(f64), /// An `f128`. F128(f128), /// `true` or `false`. Bool(bool), /// An array of constants. Vec(Vec>), /// Also an array, but with only one constant, repeated N times. Repeat(Box>, u64), /// A tuple of constants. Tuple(Vec>), /// A raw pointer. RawPtr(u128), /// A reference Ref(Box>), /// A literal with syntax error. Err, } trait IntTypeBounds: Sized { type Output: PartialOrd; fn min_max(self) -> Option<(Self::Output, Self::Output)>; fn bits(self) -> Self::Output; fn ensure_fits(self, val: Self::Output) -> Option { let (min, max) = self.min_max()?; (min <= val && val <= max).then_some(val) } } impl IntTypeBounds for UintTy { type Output = u128; fn min_max(self) -> Option<(Self::Output, Self::Output)> { Some(match self { UintTy::U8 => (u8::MIN.into(), u8::MAX.into()), UintTy::U16 => (u16::MIN.into(), u16::MAX.into()), UintTy::U32 => (u32::MIN.into(), u32::MAX.into()), UintTy::U64 => (u64::MIN.into(), u64::MAX.into()), UintTy::U128 => (u128::MIN, u128::MAX), UintTy::Usize => (usize::MIN.try_into().ok()?, usize::MAX.try_into().ok()?), }) } fn bits(self) -> Self::Output { match self { UintTy::U8 => 8, UintTy::U16 => 16, UintTy::U32 => 32, UintTy::U64 => 64, UintTy::U128 => 128, UintTy::Usize => usize::BITS.into(), } } } impl IntTypeBounds for IntTy { type Output = i128; fn min_max(self) -> Option<(Self::Output, Self::Output)> { Some(match self { IntTy::I8 => (i8::MIN.into(), i8::MAX.into()), IntTy::I16 => (i16::MIN.into(), i16::MAX.into()), IntTy::I32 => (i32::MIN.into(), i32::MAX.into()), IntTy::I64 => (i64::MIN.into(), i64::MAX.into()), IntTy::I128 => (i128::MIN, i128::MAX), IntTy::Isize => (isize::MIN.try_into().ok()?, isize::MAX.try_into().ok()?), }) } fn bits(self) -> Self::Output { match self { IntTy::I8 => 8, IntTy::I16 => 16, IntTy::I32 => 32, IntTy::I64 => 64, IntTy::I128 => 128, IntTy::Isize => isize::BITS.into(), } } } impl PartialEq for Constant<'_> { fn eq(&self, other: &Self) -> bool { match (self, other) { (Self::Str(ls), Self::Str(rs)) => ls == rs, (Self::Binary(l), Self::Binary(r)) => l == r, (&Self::Char(l), &Self::Char(r)) => l == r, (&Self::Int(l), &Self::Int(r)) => l == r, (&Self::F64(l), &Self::F64(r)) => { // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have // `Fw32 == Fw64`, so don’t compare them. // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs. l.to_bits() == r.to_bits() }, (&Self::F32(l), &Self::F32(r)) => { // We want `Fw32 == FwAny` and `FwAny == Fw64`, and by transitivity we must have // `Fw32 == Fw64`, so don’t compare them. // `to_bits` is required to catch non-matching 0.0, -0.0, and NaNs. f64::from(l).to_bits() == f64::from(r).to_bits() }, (&Self::Bool(l), &Self::Bool(r)) => l == r, (&Self::Vec(ref l), &Self::Vec(ref r)) | (&Self::Tuple(ref l), &Self::Tuple(ref r)) => l == r, (Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => ls == rs && lv == rv, (Self::Ref(lb), Self::Ref(rb)) => *lb == *rb, // TODO: are there inter-type equalities? _ => false, } } } impl Hash for Constant<'_> { fn hash(&self, state: &mut H) where H: Hasher, { std::mem::discriminant(self).hash(state); match *self { Self::Adt(ref elem) => { elem.hash(state); }, Self::Str(ref s) => { s.hash(state); }, Self::Binary(ref b) => { b.hash(state); }, Self::Char(c) => { c.hash(state); }, Self::Int(i) => { i.hash(state); }, Self::F16(f) => { // FIXME(f16_f128): once conversions to/from `f128` are available on all platforms, f.to_bits().hash(state); }, Self::F32(f) => { f64::from(f).to_bits().hash(state); }, Self::F64(f) => { f.to_bits().hash(state); }, Self::F128(f) => { f.to_bits().hash(state); }, Self::Bool(b) => { b.hash(state); }, Self::Vec(ref v) | Self::Tuple(ref v) => { v.hash(state); }, Self::Repeat(ref c, l) => { c.hash(state); l.hash(state); }, Self::RawPtr(u) => { u.hash(state); }, Self::Ref(ref r) => { r.hash(state); }, Self::Err => {}, } } } impl Constant<'_> { pub fn partial_cmp(tcx: TyCtxt<'_>, cmp_type: Ty<'_>, left: &Self, right: &Self) -> Option { match (left, right) { (Self::Str(ls), Self::Str(rs)) => Some(ls.cmp(rs)), (Self::Char(l), Self::Char(r)) => Some(l.cmp(r)), (&Self::Int(l), &Self::Int(r)) => match *cmp_type.kind() { ty::Int(int_ty) => Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty))), ty::Uint(_) => Some(l.cmp(&r)), _ => bug!("Not an int type"), }, (&Self::F64(l), &Self::F64(r)) => l.partial_cmp(&r), (&Self::F32(l), &Self::F32(r)) => l.partial_cmp(&r), (Self::Bool(l), Self::Bool(r)) => Some(l.cmp(r)), (Self::Tuple(l), Self::Tuple(r)) if l.len() == r.len() => match *cmp_type.kind() { ty::Tuple(tys) if tys.len() == l.len() => l .iter() .zip(r) .zip(tys) .map(|((li, ri), cmp_type)| Self::partial_cmp(tcx, cmp_type, li, ri)) .find(|r| r.is_none_or(|o| o != Ordering::Equal)) .unwrap_or_else(|| Some(l.len().cmp(&r.len()))), _ => None, }, (Self::Vec(l), Self::Vec(r)) => { let (ty::Array(cmp_type, _) | ty::Slice(cmp_type)) = *cmp_type.kind() else { return None; }; iter::zip(l, r) .map(|(li, ri)| Self::partial_cmp(tcx, cmp_type, li, ri)) .find(|r| r.is_none_or(|o| o != Ordering::Equal)) .unwrap_or_else(|| Some(l.len().cmp(&r.len()))) }, (Self::Repeat(lv, ls), Self::Repeat(rv, rs)) => { match Self::partial_cmp( tcx, match *cmp_type.kind() { ty::Array(ty, _) => ty, _ => return None, }, lv, rv, ) { Some(Ordering::Equal) => Some(ls.cmp(rs)), x => x, } }, (Self::Ref(lb), Self::Ref(rb)) => Self::partial_cmp( tcx, match *cmp_type.kind() { ty::Ref(_, ty, _) => ty, _ => return None, }, lb, rb, ), // TODO: are there any useful inter-type orderings? _ => None, } } /// Returns the integer value or `None` if `self` or `val_type` is not integer type. pub fn int_value(&self, tcx: TyCtxt<'_>, val_type: Ty<'_>) -> Option { if let Constant::Int(const_int) = *self { match *val_type.kind() { ty::Int(ity) => Some(FullInt::S(sext(tcx, const_int, ity))), ty::Uint(_) => Some(FullInt::U(const_int)), _ => None, } } else { None } } #[must_use] pub fn peel_refs(mut self) -> Self { while let Constant::Ref(r) = self { self = *r; } self } fn parse_f16(s: &str) -> Self { let f: Half = s.parse().unwrap(); Self::F16(f16::from_bits(f.to_bits().try_into().unwrap())) } fn parse_f128(s: &str) -> Self { let f: Quad = s.parse().unwrap(); Self::F128(f128::from_bits(f.to_bits())) } } /// Parses a `LitKind` to a `Constant`. pub fn lit_to_mir_constant<'tcx>(lit: &LitKind, ty: Option>) -> Constant<'tcx> { match *lit { LitKind::Str(ref is, _) => Constant::Str(is.to_string()), LitKind::Byte(b) => Constant::Int(u128::from(b)), LitKind::ByteStr(ref s, _) | LitKind::CStr(ref s, _) => Constant::Binary(Arc::clone(s)), LitKind::Char(c) => Constant::Char(c), LitKind::Int(n, _) => Constant::Int(n.get()), LitKind::Float(ref is, LitFloatType::Suffixed(fty)) => match fty { // FIXME(f16_f128): just use `parse()` directly when available for `f16`/`f128` ast::FloatTy::F16 => Constant::parse_f16(is.as_str()), ast::FloatTy::F32 => Constant::F32(is.as_str().parse().unwrap()), ast::FloatTy::F64 => Constant::F64(is.as_str().parse().unwrap()), ast::FloatTy::F128 => Constant::parse_f128(is.as_str()), }, LitKind::Float(ref is, LitFloatType::Unsuffixed) => match ty.expect("type of float is known").kind() { ty::Float(FloatTy::F16) => Constant::parse_f16(is.as_str()), ty::Float(FloatTy::F32) => Constant::F32(is.as_str().parse().unwrap()), ty::Float(FloatTy::F64) => Constant::F64(is.as_str().parse().unwrap()), ty::Float(FloatTy::F128) => Constant::parse_f128(is.as_str()), _ => bug!(), }, LitKind::Bool(b) => Constant::Bool(b), LitKind::Err(_) => Constant::Err, } } /// The source of a constant value. #[derive(Clone, Copy)] pub enum ConstantSource { /// The value is determined solely from the expression. Local, /// The value is dependent on a defined constant. Constant, /// The value is dependent on a constant defined in `core` crate. CoreConstant, } impl ConstantSource { pub fn is_local(self) -> bool { matches!(self, Self::Local) } } #[derive(Copy, Clone, Debug, Eq)] pub enum FullInt { S(i128), U(u128), } impl PartialEq for FullInt { #[must_use] fn eq(&self, other: &Self) -> bool { self.cmp(other) == Ordering::Equal } } impl PartialOrd for FullInt { #[must_use] fn partial_cmp(&self, other: &Self) -> Option { Some(self.cmp(other)) } } impl Ord for FullInt { #[must_use] fn cmp(&self, other: &Self) -> Ordering { use FullInt::{S, U}; fn cmp_s_u(s: i128, u: u128) -> Ordering { u128::try_from(s).map_or(Ordering::Less, |x| x.cmp(&u)) } match (*self, *other) { (S(s), S(o)) => s.cmp(&o), (U(s), U(o)) => s.cmp(&o), (S(s), U(o)) => cmp_s_u(s, o), (U(s), S(o)) => cmp_s_u(o, s).reverse(), } } } /// The context required to evaluate a constant expression. /// /// This is currently limited to constant folding and reading the value of named constants. /// /// See the module level documentation for some context. pub struct ConstEvalCtxt<'tcx> { tcx: TyCtxt<'tcx>, typing_env: ty::TypingEnv<'tcx>, typeck: &'tcx TypeckResults<'tcx>, source: Cell, } impl<'tcx> ConstEvalCtxt<'tcx> { /// Creates the evaluation context from the lint context. This requires the lint context to be /// in a body (i.e. `cx.enclosing_body.is_some()`). pub fn new(cx: &LateContext<'tcx>) -> Self { Self { tcx: cx.tcx, typing_env: cx.typing_env(), typeck: cx.typeck_results(), source: Cell::new(ConstantSource::Local), } } /// Creates an evaluation context. pub fn with_env(tcx: TyCtxt<'tcx>, typing_env: ty::TypingEnv<'tcx>, typeck: &'tcx TypeckResults<'tcx>) -> Self { Self { tcx, typing_env, typeck, source: Cell::new(ConstantSource::Local), } } /// Attempts to evaluate the expression and returns both the value and whether it's dependant on /// other items. pub fn eval_with_source(&self, e: &Expr<'_>) -> Option<(Constant<'tcx>, ConstantSource)> { self.source.set(ConstantSource::Local); self.expr(e).map(|c| (c, self.source.get())) } /// Attempts to evaluate the expression. pub fn eval(&self, e: &Expr<'_>) -> Option> { self.expr(e) } /// Attempts to evaluate the expression without accessing other items. pub fn eval_simple(&self, e: &Expr<'_>) -> Option> { match self.eval_with_source(e) { Some((x, ConstantSource::Local)) => Some(x), _ => None, } } /// Attempts to evaluate the expression as an integer without accessing other items. pub fn eval_full_int(&self, e: &Expr<'_>) -> Option { match self.eval_with_source(e) { Some((x, ConstantSource::Local)) => x.int_value(self.tcx, self.typeck.expr_ty(e)), _ => None, } } pub fn eval_pat_expr(&self, pat_expr: &PatExpr<'_>) -> Option> { match &pat_expr.kind { PatExprKind::Lit { lit, negated } => { let ty = self.typeck.node_type_opt(pat_expr.hir_id); let val = lit_to_mir_constant(&lit.node, ty); if *negated { self.constant_negate(&val, ty?) } else { Some(val) } }, PatExprKind::ConstBlock(ConstBlock { body, .. }) => self.expr(self.tcx.hir_body(*body).value), PatExprKind::Path(qpath) => self.qpath(qpath, pat_expr.hir_id), } } fn qpath(&self, qpath: &QPath<'_>, hir_id: HirId) -> Option> { let is_core_crate = if let Some(def_id) = self.typeck.qpath_res(qpath, hir_id).opt_def_id() { self.tcx.crate_name(def_id.krate) == sym::core } else { false }; self.fetch_path_and_apply(qpath, hir_id, self.typeck.node_type(hir_id), |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) }) } /// Simple constant folding: Insert an expression, get a constant or none. fn expr(&self, e: &Expr<'_>) -> Option> { 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) => self.qpath(qpath, e.hir_id), 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_to_target_usize(self.tcx)?, _ => 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, []) => { // We only handle a few const functions for now. if 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 { 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_to_target_usize(self.tcx)? == 0) } else { span_bug!(e.span, "typeck error"); } }, _ => None, } } #[expect(clippy::cast_possible_wrap)] fn constant_not(&self, o: &Constant<'tcx>, ty: Ty<'_>) -> Option> { 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> { 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.iter().map(|elem| self.expr(elem)).collect::>() } /// Lookup a possibly constant expression from an `ExprKind::Path` and apply a function on it. fn fetch_path_and_apply(&self, qpath: &QPath<'_>, id: HirId, ty: Ty<'tcx>, f: F) -> Option where F: FnOnce(&Self, mir::Const<'tcx>) -> Option, { 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.typing_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> { 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> { 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> { 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> { 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> { 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 { 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> { 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 } }