// Copyright 2012-2016 The Rust Project Developers. See the COPYRIGHT // file at the top-level directory of this distribution and at // http://rust-lang.org/COPYRIGHT. // // Licensed under the Apache License, Version 2.0 or the MIT license // , at your // option. This file may not be copied, modified, or distributed // except according to those terms. //#![allow(non_camel_case_types)] use rustc::middle::const_val::ConstVal::*; use rustc::middle::const_val::ConstVal; use self::ErrKind::*; use self::EvalHint::*; use rustc::hir::map as ast_map; use rustc::hir::map::blocks::FnLikeNode; use rustc::middle::cstore::{self, InlinedItem}; use rustc::{infer, traits}; use rustc::hir::def::Def; use rustc::hir::def_id::DefId; use rustc::hir::pat_util::def_to_path; use rustc::ty::{self, Ty, TyCtxt, subst}; use rustc::ty::util::IntTypeExt; use rustc::traits::ProjectionMode; use rustc::middle::astconv_util::ast_ty_to_prim_ty; use rustc::util::nodemap::NodeMap; use rustc::lint; use graphviz::IntoCow; use syntax::ast; use rustc::hir::{Expr, PatKind}; use rustc::hir; use rustc::hir::intravisit::FnKind; use syntax::codemap::Span; use syntax::ptr::P; use syntax::codemap; use syntax::attr::IntType; use std::borrow::Cow; use std::cmp::Ordering; use std::collections::hash_map::Entry::Vacant; use rustc_const_math::*; macro_rules! math { ($e:expr, $op:expr) => { match $op { Ok(val) => val, Err(e) => signal!($e, Math(e)), } } } fn lookup_variant_by_id<'a>(tcx: &'a ty::TyCtxt, enum_def: DefId, variant_def: DefId) -> Option<&'a Expr> { fn variant_expr<'a>(variants: &'a [hir::Variant], id: ast::NodeId) -> Option<&'a Expr> { for variant in variants { if variant.node.data.id() == id { return variant.node.disr_expr.as_ref().map(|e| &**e); } } None } if let Some(enum_node_id) = tcx.map.as_local_node_id(enum_def) { let variant_node_id = tcx.map.as_local_node_id(variant_def).unwrap(); match tcx.map.find(enum_node_id) { None => None, Some(ast_map::NodeItem(it)) => match it.node { hir::ItemEnum(hir::EnumDef { ref variants }, _) => { variant_expr(variants, variant_node_id) } _ => None }, Some(_) => None } } else { None } } /// * `def_id` is the id of the constant. /// * `substs` is the monomorphized substitutions for the expression. /// /// `substs` is optional and is used for associated constants. /// This generally happens in late/trans const evaluation. pub fn lookup_const_by_id<'a, 'tcx: 'a>(tcx: &'a TyCtxt<'tcx>, def_id: DefId, substs: Option>) -> Option<(&'tcx Expr, Option>)> { if let Some(node_id) = tcx.map.as_local_node_id(def_id) { match tcx.map.find(node_id) { None => None, Some(ast_map::NodeItem(it)) => match it.node { hir::ItemConst(ref ty, ref const_expr) => { Some((&const_expr, ast_ty_to_prim_ty(tcx, ty))) } _ => None }, Some(ast_map::NodeTraitItem(ti)) => match ti.node { hir::ConstTraitItem(_, _) => { if let Some(substs) = substs { // If we have a trait item and the substitutions for it, // `resolve_trait_associated_const` will select an impl // or the default. let trait_id = tcx.trait_of_item(def_id).unwrap(); resolve_trait_associated_const(tcx, ti, trait_id, substs) } else { // Technically, without knowing anything about the // expression that generates the obligation, we could // still return the default if there is one. However, // it's safer to return `None` than to return some value // that may differ from what you would get from // correctly selecting an impl. None } } _ => None }, Some(ast_map::NodeImplItem(ii)) => match ii.node { hir::ImplItemKind::Const(ref ty, ref expr) => { Some((&expr, ast_ty_to_prim_ty(tcx, ty))) } _ => None }, Some(_) => None } } else { match tcx.extern_const_statics.borrow().get(&def_id) { Some(&None) => return None, Some(&Some((expr_id, ty))) => { return Some((tcx.map.expect_expr(expr_id), ty)); } None => {} } let mut used_substs = false; let expr_ty = match tcx.sess.cstore.maybe_get_item_ast(tcx, def_id) { cstore::FoundAst::Found(&InlinedItem::Item(ref item)) => match item.node { hir::ItemConst(ref ty, ref const_expr) => { Some((&**const_expr, ast_ty_to_prim_ty(tcx, ty))) }, _ => None }, cstore::FoundAst::Found(&InlinedItem::TraitItem(trait_id, ref ti)) => match ti.node { hir::ConstTraitItem(_, _) => { used_substs = true; if let Some(substs) = substs { // As mentioned in the comments above for in-crate // constants, we only try to find the expression for // a trait-associated const if the caller gives us // the substitutions for the reference to it. resolve_trait_associated_const(tcx, ti, trait_id, substs) } else { None } } _ => None }, cstore::FoundAst::Found(&InlinedItem::ImplItem(_, ref ii)) => match ii.node { hir::ImplItemKind::Const(ref ty, ref expr) => { Some((&**expr, ast_ty_to_prim_ty(tcx, ty))) }, _ => None }, _ => None }; // If we used the substitutions, particularly to choose an impl // of a trait-associated const, don't cache that, because the next // lookup with the same def_id may yield a different result. if !used_substs { tcx.extern_const_statics .borrow_mut() .insert(def_id, expr_ty.map(|(e, t)| (e.id, t))); } expr_ty } } fn inline_const_fn_from_external_crate(tcx: &TyCtxt, def_id: DefId) -> Option { match tcx.extern_const_fns.borrow().get(&def_id) { Some(&ast::DUMMY_NODE_ID) => return None, Some(&fn_id) => return Some(fn_id), None => {} } if !tcx.sess.cstore.is_const_fn(def_id) { tcx.extern_const_fns.borrow_mut().insert(def_id, ast::DUMMY_NODE_ID); return None; } let fn_id = match tcx.sess.cstore.maybe_get_item_ast(tcx, def_id) { cstore::FoundAst::Found(&InlinedItem::Item(ref item)) => Some(item.id), cstore::FoundAst::Found(&InlinedItem::ImplItem(_, ref item)) => Some(item.id), _ => None }; tcx.extern_const_fns.borrow_mut().insert(def_id, fn_id.unwrap_or(ast::DUMMY_NODE_ID)); fn_id } pub fn lookup_const_fn_by_id<'tcx>(tcx: &TyCtxt<'tcx>, def_id: DefId) -> Option> { let fn_id = if let Some(node_id) = tcx.map.as_local_node_id(def_id) { node_id } else { if let Some(fn_id) = inline_const_fn_from_external_crate(tcx, def_id) { fn_id } else { return None; } }; let fn_like = match FnLikeNode::from_node(tcx.map.get(fn_id)) { Some(fn_like) => fn_like, None => return None }; match fn_like.kind() { FnKind::ItemFn(_, _, _, hir::Constness::Const, _, _, _) => { Some(fn_like) } FnKind::Method(_, m, _, _) => { if m.constness == hir::Constness::Const { Some(fn_like) } else { None } } _ => None } } pub fn const_expr_to_pat(tcx: &ty::TyCtxt, expr: &Expr, pat_id: ast::NodeId, span: Span) -> Result, DefId> { let pat_ty = tcx.expr_ty(expr); debug!("expr={:?} pat_ty={:?} pat_id={}", expr, pat_ty, pat_id); match pat_ty.sty { ty::TyFloat(_) => { tcx.sess.add_lint( lint::builtin::ILLEGAL_FLOATING_POINT_CONSTANT_PATTERN, pat_id, span, format!("floating point constants cannot be used in patterns")); } ty::TyEnum(adt_def, _) | ty::TyStruct(adt_def, _) => { if !tcx.has_attr(adt_def.did, "structural_match") { tcx.sess.add_lint( lint::builtin::ILLEGAL_STRUCT_OR_ENUM_CONSTANT_PATTERN, pat_id, span, format!("to use a constant of type `{}` \ in a pattern, \ `{}` must be annotated with `#[derive(PartialEq, Eq)]`", tcx.item_path_str(adt_def.did), tcx.item_path_str(adt_def.did))); } } _ => { } } let pat = match expr.node { hir::ExprTup(ref exprs) => PatKind::Tup(try!(exprs.iter() .map(|expr| const_expr_to_pat(tcx, &expr, pat_id, span)) .collect())), hir::ExprCall(ref callee, ref args) => { let def = *tcx.def_map.borrow().get(&callee.id).unwrap(); if let Vacant(entry) = tcx.def_map.borrow_mut().entry(expr.id) { entry.insert(def); } let path = match def.full_def() { Def::Struct(def_id) => def_to_path(tcx, def_id), Def::Variant(_, variant_did) => def_to_path(tcx, variant_did), Def::Fn(..) | Def::Method(..) => return Ok(P(hir::Pat { id: expr.id, node: PatKind::Lit(P(expr.clone())), span: span, })), _ => bug!() }; let pats = try!(args.iter() .map(|expr| const_expr_to_pat(tcx, &**expr, pat_id, span)) .collect()); PatKind::TupleStruct(path, Some(pats)) } hir::ExprStruct(ref path, ref fields, None) => { let field_pats = try!(fields.iter() .map(|field| Ok(codemap::Spanned { span: codemap::DUMMY_SP, node: hir::FieldPat { name: field.name.node, pat: try!(const_expr_to_pat(tcx, &field.expr, pat_id, span)), is_shorthand: false, }, })) .collect()); PatKind::Struct(path.clone(), field_pats, false) } hir::ExprVec(ref exprs) => { let pats = try!(exprs.iter() .map(|expr| const_expr_to_pat(tcx, &expr, pat_id, span)) .collect()); PatKind::Vec(pats, None, hir::HirVec::new()) } hir::ExprPath(_, ref path) => { let opt_def = tcx.def_map.borrow().get(&expr.id).map(|d| d.full_def()); match opt_def { Some(Def::Struct(..)) | Some(Def::Variant(..)) => PatKind::Path(path.clone()), Some(Def::Const(def_id)) | Some(Def::AssociatedConst(def_id)) => { let substs = Some(tcx.node_id_item_substs(expr.id).substs); let (expr, _ty) = lookup_const_by_id(tcx, def_id, substs).unwrap(); return const_expr_to_pat(tcx, expr, pat_id, span); }, _ => bug!(), } } _ => PatKind::Lit(P(expr.clone())) }; Ok(P(hir::Pat { id: expr.id, node: pat, span: span })) } pub fn eval_const_expr(tcx: &TyCtxt, e: &Expr) -> ConstVal { match eval_const_expr_partial(tcx, e, ExprTypeChecked, None) { Ok(r) => r, // non-const path still needs to be a fatal error, because enums are funky Err(s) => { match s.kind { NonConstPath | UnimplementedConstVal(_) => tcx.sess.span_fatal(s.span, &s.description()), _ => { tcx.sess.span_err(s.span, &s.description()); Dummy } } }, } } pub type FnArgMap<'a> = Option<&'a NodeMap>; #[derive(Clone)] pub struct ConstEvalErr { pub span: Span, pub kind: ErrKind, } #[derive(Clone)] pub enum ErrKind { CannotCast, CannotCastTo(&'static str), InvalidOpForInts(hir::BinOp_), InvalidOpForBools(hir::BinOp_), InvalidOpForFloats(hir::BinOp_), InvalidOpForIntUint(hir::BinOp_), InvalidOpForUintInt(hir::BinOp_), NegateOn(ConstVal), NotOn(ConstVal), CallOn(ConstVal), NegateWithOverflow(i64), AddiWithOverflow(i64, i64), SubiWithOverflow(i64, i64), MuliWithOverflow(i64, i64), AdduWithOverflow(u64, u64), SubuWithOverflow(u64, u64), MuluWithOverflow(u64, u64), DivideByZero, DivideWithOverflow, ModuloByZero, ModuloWithOverflow, ShiftLeftWithOverflow, ShiftRightWithOverflow, MissingStructField, NonConstPath, UnimplementedConstVal(&'static str), UnresolvedPath, ExpectedConstTuple, ExpectedConstStruct, TupleIndexOutOfBounds, IndexedNonVec, IndexNegative, IndexNotInt, IndexOutOfBounds, RepeatCountNotNatural, RepeatCountNotInt, MiscBinaryOp, MiscCatchAll, IndexOpFeatureGated, Math(ConstMathErr), IntermediateUnsignedNegative, /// Expected, Got TypeMismatch(String, ConstInt), BadType(ConstVal), ErroneousReferencedConstant(Box), } impl From for ErrKind { fn from(err: ConstMathErr) -> ErrKind { Math(err) } } impl ConstEvalErr { pub fn description(&self) -> Cow { use self::ErrKind::*; match self.kind { CannotCast => "can't cast this type".into_cow(), CannotCastTo(s) => format!("can't cast this type to {}", s).into_cow(), InvalidOpForInts(_) => "can't do this op on integrals".into_cow(), InvalidOpForBools(_) => "can't do this op on bools".into_cow(), InvalidOpForFloats(_) => "can't do this op on floats".into_cow(), InvalidOpForIntUint(..) => "can't do this op on an isize and usize".into_cow(), InvalidOpForUintInt(..) => "can't do this op on a usize and isize".into_cow(), NegateOn(ref const_val) => format!("negate on {}", const_val.description()).into_cow(), NotOn(ref const_val) => format!("not on {}", const_val.description()).into_cow(), CallOn(ref const_val) => format!("call on {}", const_val.description()).into_cow(), NegateWithOverflow(..) => "attempted to negate with overflow".into_cow(), AddiWithOverflow(..) => "attempted to add with overflow".into_cow(), SubiWithOverflow(..) => "attempted to sub with overflow".into_cow(), MuliWithOverflow(..) => "attempted to mul with overflow".into_cow(), AdduWithOverflow(..) => "attempted to add with overflow".into_cow(), SubuWithOverflow(..) => "attempted to sub with overflow".into_cow(), MuluWithOverflow(..) => "attempted to mul with overflow".into_cow(), DivideByZero => "attempted to divide by zero".into_cow(), DivideWithOverflow => "attempted to divide with overflow".into_cow(), ModuloByZero => "attempted remainder with a divisor of zero".into_cow(), ModuloWithOverflow => "attempted remainder with overflow".into_cow(), ShiftLeftWithOverflow => "attempted left shift with overflow".into_cow(), ShiftRightWithOverflow => "attempted right shift with overflow".into_cow(), MissingStructField => "nonexistent struct field".into_cow(), NonConstPath => "non-constant path in constant expression".into_cow(), UnimplementedConstVal(what) => format!("unimplemented constant expression: {}", what).into_cow(), UnresolvedPath => "unresolved path in constant expression".into_cow(), ExpectedConstTuple => "expected constant tuple".into_cow(), ExpectedConstStruct => "expected constant struct".into_cow(), TupleIndexOutOfBounds => "tuple index out of bounds".into_cow(), IndexedNonVec => "indexing is only supported for arrays".into_cow(), IndexNegative => "indices must be non-negative integers".into_cow(), IndexNotInt => "indices must be integers".into_cow(), IndexOutOfBounds => "array index out of bounds".into_cow(), RepeatCountNotNatural => "repeat count must be a natural number".into_cow(), RepeatCountNotInt => "repeat count must be integers".into_cow(), MiscBinaryOp => "bad operands for binary".into_cow(), MiscCatchAll => "unsupported constant expr".into_cow(), IndexOpFeatureGated => "the index operation on const values is unstable".into_cow(), Math(ref err) => err.description().into_cow(), IntermediateUnsignedNegative => "during the computation of an unsigned a negative \ number was encountered. This is most likely a bug in\ the constant evaluator".into_cow(), TypeMismatch(ref expected, ref got) => { format!("mismatched types: expected `{}`, found `{}`", expected, got.description()).into_cow() }, BadType(ref i) => format!("value of wrong type: {:?}", i).into_cow(), ErroneousReferencedConstant(_) => "could not evaluate referenced constant".into_cow(), } } } pub type EvalResult = Result; pub type CastResult = Result; // FIXME: Long-term, this enum should go away: trying to evaluate // an expression which hasn't been type-checked is a recipe for // disaster. That said, it's not clear how to fix ast_ty_to_ty // to avoid the ordering issue. /// Hint to determine how to evaluate constant expressions which /// might not be type-checked. #[derive(Copy, Clone, Debug)] pub enum EvalHint<'tcx> { /// We have a type-checked expression. ExprTypeChecked, /// We have an expression which hasn't been type-checked, but we have /// an idea of what the type will be because of the context. For example, /// the length of an array is always `usize`. (This is referred to as /// a hint because it isn't guaranteed to be consistent with what /// type-checking would compute.) UncheckedExprHint(Ty<'tcx>), /// We have an expression which has not yet been type-checked, and /// and we have no clue what the type will be. UncheckedExprNoHint, } impl<'tcx> EvalHint<'tcx> { fn erase_hint(&self) -> EvalHint<'tcx> { match *self { ExprTypeChecked => ExprTypeChecked, UncheckedExprHint(_) | UncheckedExprNoHint => UncheckedExprNoHint, } } fn checked_or(&self, ty: Ty<'tcx>) -> EvalHint<'tcx> { match *self { ExprTypeChecked => ExprTypeChecked, _ => UncheckedExprHint(ty), } } } macro_rules! signal { ($e:expr, $exn:expr) => { return Err(ConstEvalErr { span: $e.span, kind: $exn }) } } /// Evaluate a constant expression in a context where the expression isn't /// guaranteed to be evaluatable. `ty_hint` is usually ExprTypeChecked, /// but a few places need to evaluate constants during type-checking, like /// computing the length of an array. (See also the FIXME above EvalHint.) pub fn eval_const_expr_partial<'tcx>(tcx: &TyCtxt<'tcx>, e: &Expr, ty_hint: EvalHint<'tcx>, fn_args: FnArgMap) -> EvalResult { // Try to compute the type of the expression based on the EvalHint. // (See also the definition of EvalHint, and the FIXME above EvalHint.) let ety = match ty_hint { ExprTypeChecked => { // After type-checking, expr_ty is guaranteed to succeed. Some(tcx.expr_ty(e)) } UncheckedExprHint(ty) => { // Use the type hint; it's not guaranteed to be right, but it's // usually good enough. Some(ty) } UncheckedExprNoHint => { // This expression might not be type-checked, and we have no hint. // Try to query the context for a type anyway; we might get lucky // (for example, if the expression was imported from another crate). tcx.expr_ty_opt(e) } }; let result = match e.node { hir::ExprUnary(hir::UnNeg, ref inner) => { // unary neg literals already got their sign during creation match inner.node { hir::ExprLit(ref lit) => { use syntax::ast::*; use syntax::ast::LitIntType::*; const I8_OVERFLOW: u64 = ::std::i8::MAX as u64 + 1; const I16_OVERFLOW: u64 = ::std::i16::MAX as u64 + 1; const I32_OVERFLOW: u64 = ::std::i32::MAX as u64 + 1; const I64_OVERFLOW: u64 = ::std::i64::MAX as u64 + 1; match (&lit.node, ety.map(|t| &t.sty)) { (&LitKind::Int(I8_OVERFLOW, Unsuffixed), Some(&ty::TyInt(IntTy::I8))) | (&LitKind::Int(I8_OVERFLOW, Signed(IntTy::I8)), _) => { return Ok(Integral(I8(::std::i8::MIN))) }, (&LitKind::Int(I16_OVERFLOW, Unsuffixed), Some(&ty::TyInt(IntTy::I16))) | (&LitKind::Int(I16_OVERFLOW, Signed(IntTy::I16)), _) => { return Ok(Integral(I16(::std::i16::MIN))) }, (&LitKind::Int(I32_OVERFLOW, Unsuffixed), Some(&ty::TyInt(IntTy::I32))) | (&LitKind::Int(I32_OVERFLOW, Signed(IntTy::I32)), _) => { return Ok(Integral(I32(::std::i32::MIN))) }, (&LitKind::Int(I64_OVERFLOW, Unsuffixed), Some(&ty::TyInt(IntTy::I64))) | (&LitKind::Int(I64_OVERFLOW, Signed(IntTy::I64)), _) => { return Ok(Integral(I64(::std::i64::MIN))) }, (&LitKind::Int(n, Unsuffixed), Some(&ty::TyInt(IntTy::Is))) | (&LitKind::Int(n, Signed(IntTy::Is)), _) => { match tcx.sess.target.int_type { IntTy::I32 => if n == I32_OVERFLOW { return Ok(Integral(Isize(Is32(::std::i32::MIN)))); }, IntTy::I64 => if n == I64_OVERFLOW { return Ok(Integral(Isize(Is64(::std::i64::MIN)))); }, _ => bug!(), } }, _ => {}, } }, hir::ExprUnary(hir::UnNeg, ref inner) => { // skip `--$expr` return eval_const_expr_partial(tcx, inner, ty_hint, fn_args); }, _ => {}, } match eval_const_expr_partial(tcx, &inner, ty_hint, fn_args)? { Float(f) => Float(-f), Integral(i) => Integral(math!(e, -i)), const_val => signal!(e, NegateOn(const_val)), } } hir::ExprUnary(hir::UnNot, ref inner) => { match eval_const_expr_partial(tcx, &inner, ty_hint, fn_args)? { Integral(i) => Integral(math!(e, !i)), Bool(b) => Bool(!b), const_val => signal!(e, NotOn(const_val)), } } hir::ExprUnary(hir::UnDeref, _) => signal!(e, UnimplementedConstVal("deref operation")), hir::ExprBinary(op, ref a, ref b) => { let b_ty = match op.node { hir::BiShl | hir::BiShr => ty_hint.erase_hint(), _ => ty_hint }; // technically, if we don't have type hints, but integral eval // gives us a type through a type-suffix, cast or const def type // we need to re-eval the other value of the BinOp if it was // not inferred match (eval_const_expr_partial(tcx, &a, ty_hint, fn_args)?, eval_const_expr_partial(tcx, &b, b_ty, fn_args)?) { (Float(a), Float(b)) => { match op.node { hir::BiAdd => Float(a + b), hir::BiSub => Float(a - b), hir::BiMul => Float(a * b), hir::BiDiv => Float(a / b), hir::BiRem => Float(a % b), hir::BiEq => Bool(a == b), hir::BiLt => Bool(a < b), hir::BiLe => Bool(a <= b), hir::BiNe => Bool(a != b), hir::BiGe => Bool(a >= b), hir::BiGt => Bool(a > b), _ => signal!(e, InvalidOpForFloats(op.node)), } } (Integral(a), Integral(b)) => { use std::cmp::Ordering::*; match op.node { hir::BiAdd => Integral(math!(e, a + b)), hir::BiSub => Integral(math!(e, a - b)), hir::BiMul => Integral(math!(e, a * b)), hir::BiDiv => Integral(math!(e, a / b)), hir::BiRem => Integral(math!(e, a % b)), hir::BiBitAnd => Integral(math!(e, a & b)), hir::BiBitOr => Integral(math!(e, a | b)), hir::BiBitXor => Integral(math!(e, a ^ b)), hir::BiShl => Integral(math!(e, a << b)), hir::BiShr => Integral(math!(e, a >> b)), hir::BiEq => Bool(math!(e, a.try_cmp(b)) == Equal), hir::BiLt => Bool(math!(e, a.try_cmp(b)) == Less), hir::BiLe => Bool(math!(e, a.try_cmp(b)) != Greater), hir::BiNe => Bool(math!(e, a.try_cmp(b)) != Equal), hir::BiGe => Bool(math!(e, a.try_cmp(b)) != Less), hir::BiGt => Bool(math!(e, a.try_cmp(b)) == Greater), _ => signal!(e, InvalidOpForInts(op.node)), } } (Bool(a), Bool(b)) => { Bool(match op.node { hir::BiAnd => a && b, hir::BiOr => a || b, hir::BiBitXor => a ^ b, hir::BiBitAnd => a & b, hir::BiBitOr => a | b, hir::BiEq => a == b, hir::BiNe => a != b, _ => signal!(e, InvalidOpForBools(op.node)), }) } _ => signal!(e, MiscBinaryOp), } } hir::ExprCast(ref base, ref target_ty) => { let ety = ast_ty_to_prim_ty(tcx, &target_ty).or_else(|| ety) .unwrap_or_else(|| { tcx.sess.span_fatal(target_ty.span, "target type not found for const cast") }); let base_hint = if let ExprTypeChecked = ty_hint { ExprTypeChecked } else { match tcx.expr_ty_opt(&base) { Some(t) => UncheckedExprHint(t), None => ty_hint } }; let val = match eval_const_expr_partial(tcx, &base, base_hint, fn_args) { Ok(val) => val, Err(ConstEvalErr { kind: ErroneousReferencedConstant( box ConstEvalErr { kind: TypeMismatch(_, val), .. }), .. }) | Err(ConstEvalErr { kind: TypeMismatch(_, val), .. }) => { // Something like `5i8 as usize` doesn't need a type hint for the base // instead take the type hint from the inner value let hint = match val.int_type() { Some(IntType::UnsignedInt(ty)) => ty_hint.checked_or(tcx.mk_mach_uint(ty)), Some(IntType::SignedInt(ty)) => ty_hint.checked_or(tcx.mk_mach_int(ty)), // we had a type hint, so we can't have an unknown type None => bug!(), }; eval_const_expr_partial(tcx, &base, hint, fn_args)? }, Err(e) => return Err(e), }; match cast_const(tcx, val, ety) { Ok(val) => val, Err(kind) => return Err(ConstEvalErr { span: e.span, kind: kind }), } } hir::ExprPath(..) => { let opt_def = if let Some(def) = tcx.def_map.borrow().get(&e.id) { // After type-checking, def_map contains definition of the // item referred to by the path. During type-checking, it // can contain the raw output of path resolution, which // might be a partially resolved path. // FIXME: There's probably a better way to make sure we don't // panic here. if def.depth != 0 { signal!(e, UnresolvedPath); } def.full_def() } else { signal!(e, NonConstPath); }; match opt_def { Def::Const(def_id) | Def::AssociatedConst(def_id) => { let substs = if let ExprTypeChecked = ty_hint { Some(tcx.node_id_item_substs(e.id).substs) } else { None }; if let Some((expr, ty)) = lookup_const_by_id(tcx, def_id, substs) { let item_hint = match ty { Some(ty) => ty_hint.checked_or(ty), None => ty_hint, }; match eval_const_expr_partial(tcx, expr, item_hint, None) { Ok(val) => val, Err(err) => { debug!("bad reference: {:?}, {:?}", err.description(), err.span); signal!(e, ErroneousReferencedConstant(box err)) }, } } else { signal!(e, NonConstPath); } }, Def::Variant(enum_def, variant_def) => { if let Some(const_expr) = lookup_variant_by_id(tcx, enum_def, variant_def) { match eval_const_expr_partial(tcx, const_expr, ty_hint, None) { Ok(val) => val, Err(err) => { debug!("bad reference: {:?}, {:?}", err.description(), err.span); signal!(e, ErroneousReferencedConstant(box err)) }, } } else { signal!(e, UnimplementedConstVal("enum variants")); } } Def::Struct(..) => { ConstVal::Struct(e.id) } Def::Local(_, id) => { debug!("Def::Local({:?}): {:?}", id, fn_args); if let Some(val) = fn_args.and_then(|args| args.get(&id)) { val.clone() } else { signal!(e, NonConstPath); } }, Def::Method(id) | Def::Fn(id) => Function(id), _ => signal!(e, NonConstPath), } } hir::ExprCall(ref callee, ref args) => { let sub_ty_hint = ty_hint.erase_hint(); let callee_val = eval_const_expr_partial(tcx, callee, sub_ty_hint, fn_args)?; let did = match callee_val { Function(did) => did, Struct(_) => signal!(e, UnimplementedConstVal("tuple struct constructors")), callee => signal!(e, CallOn(callee)), }; let (decl, result) = if let Some(fn_like) = lookup_const_fn_by_id(tcx, did) { (fn_like.decl(), &fn_like.body().expr) } else { signal!(e, NonConstPath) }; let result = result.as_ref().expect("const fn has no result expression"); assert_eq!(decl.inputs.len(), args.len()); let mut call_args = NodeMap(); for (arg, arg_expr) in decl.inputs.iter().zip(args.iter()) { let arg_hint = ty_hint.erase_hint(); let arg_val = eval_const_expr_partial( tcx, arg_expr, arg_hint, fn_args )?; debug!("const call arg: {:?}", arg); let old = call_args.insert(arg.pat.id, arg_val); assert!(old.is_none()); } debug!("const call({:?})", call_args); eval_const_expr_partial(tcx, &result, ty_hint, Some(&call_args))? }, hir::ExprLit(ref lit) => lit_to_const(&lit.node, tcx, ety, lit.span)?, hir::ExprBlock(ref block) => { match block.expr { Some(ref expr) => eval_const_expr_partial(tcx, &expr, ty_hint, fn_args)?, None => signal!(e, UnimplementedConstVal("empty block")), } } hir::ExprType(ref e, _) => eval_const_expr_partial(tcx, &e, ty_hint, fn_args)?, hir::ExprTup(_) => Tuple(e.id), hir::ExprStruct(..) => Struct(e.id), hir::ExprIndex(ref arr, ref idx) => { if !tcx.sess.features.borrow().const_indexing { signal!(e, IndexOpFeatureGated); } let arr_hint = ty_hint.erase_hint(); let arr = eval_const_expr_partial(tcx, arr, arr_hint, fn_args)?; let idx_hint = ty_hint.checked_or(tcx.types.usize); let idx = match eval_const_expr_partial(tcx, idx, idx_hint, fn_args)? { Integral(Usize(i)) => i.as_u64(tcx.sess.target.uint_type), Integral(_) => bug!(), _ => signal!(idx, IndexNotInt), }; assert_eq!(idx as usize as u64, idx); match arr { Array(_, n) if idx >= n => signal!(e, IndexOutOfBounds), Array(v, n) => if let hir::ExprVec(ref v) = tcx.map.expect_expr(v).node { assert_eq!(n as usize as u64, n); eval_const_expr_partial(tcx, &v[idx as usize], ty_hint, fn_args)? } else { bug!() }, Repeat(_, n) if idx >= n => signal!(e, IndexOutOfBounds), Repeat(elem, _) => eval_const_expr_partial( tcx, &tcx.map.expect_expr(elem), ty_hint, fn_args, )?, ByteStr(ref data) if idx >= data.len() as u64 => signal!(e, IndexOutOfBounds), ByteStr(data) => { Integral(U8(data[idx as usize])) }, Str(ref s) if idx as usize >= s.len() => signal!(e, IndexOutOfBounds), // FIXME: return a const char Str(_) => signal!(e, UnimplementedConstVal("indexing into str")), _ => signal!(e, IndexedNonVec), } } hir::ExprVec(ref v) => Array(e.id, v.len() as u64), hir::ExprRepeat(_, ref n) => { let len_hint = ty_hint.checked_or(tcx.types.usize); Repeat( e.id, match eval_const_expr_partial(tcx, &n, len_hint, fn_args)? { Integral(Usize(i)) => i.as_u64(tcx.sess.target.uint_type), Integral(_) => signal!(e, RepeatCountNotNatural), _ => signal!(e, RepeatCountNotInt), }, ) }, hir::ExprTupField(ref base, index) => { let base_hint = ty_hint.erase_hint(); let c = eval_const_expr_partial(tcx, base, base_hint, fn_args)?; if let Tuple(tup_id) = c { if let hir::ExprTup(ref fields) = tcx.map.expect_expr(tup_id).node { if index.node < fields.len() { eval_const_expr_partial(tcx, &fields[index.node], ty_hint, fn_args)? } else { signal!(e, TupleIndexOutOfBounds); } } else { bug!() } } else { signal!(base, ExpectedConstTuple); } } hir::ExprField(ref base, field_name) => { let base_hint = ty_hint.erase_hint(); // Get the base expression if it is a struct and it is constant let c = eval_const_expr_partial(tcx, base, base_hint, fn_args)?; if let Struct(struct_id) = c { if let hir::ExprStruct(_, ref fields, _) = tcx.map.expect_expr(struct_id).node { // Check that the given field exists and evaluate it // if the idents are compared run-pass/issue-19244 fails if let Some(f) = fields.iter().find(|f| f.name.node == field_name.node) { eval_const_expr_partial(tcx, &f.expr, ty_hint, fn_args)? } else { signal!(e, MissingStructField); } } else { bug!() } } else { signal!(base, ExpectedConstStruct); } } hir::ExprAddrOf(..) => signal!(e, UnimplementedConstVal("address operator")), _ => signal!(e, MiscCatchAll) }; match (ety.map(|t| &t.sty), result) { (Some(ref ty_hint), Integral(i)) => Ok(Integral(infer(i, tcx, ty_hint, e.span)?)), (_, result) => Ok(result), } } fn infer<'tcx>( i: ConstInt, tcx: &TyCtxt<'tcx>, ty_hint: &ty::TypeVariants<'tcx>, span: Span ) -> Result { use syntax::ast::*; let err = |e| ConstEvalErr { span: span, kind: e, }; match (ty_hint, i) { (&ty::TyInt(IntTy::I8), result @ I8(_)) => Ok(result), (&ty::TyInt(IntTy::I16), result @ I16(_)) => Ok(result), (&ty::TyInt(IntTy::I32), result @ I32(_)) => Ok(result), (&ty::TyInt(IntTy::I64), result @ I64(_)) => Ok(result), (&ty::TyInt(IntTy::Is), result @ Isize(_)) => Ok(result), (&ty::TyUint(UintTy::U8), result @ U8(_)) => Ok(result), (&ty::TyUint(UintTy::U16), result @ U16(_)) => Ok(result), (&ty::TyUint(UintTy::U32), result @ U32(_)) => Ok(result), (&ty::TyUint(UintTy::U64), result @ U64(_)) => Ok(result), (&ty::TyUint(UintTy::Us), result @ Usize(_)) => Ok(result), (&ty::TyInt(IntTy::I8), Infer(i)) => Ok(I8(i as i64 as i8)), (&ty::TyInt(IntTy::I16), Infer(i)) => Ok(I16(i as i64 as i16)), (&ty::TyInt(IntTy::I32), Infer(i)) => Ok(I32(i as i64 as i32)), (&ty::TyInt(IntTy::I64), Infer(i)) => Ok(I64(i as i64)), (&ty::TyInt(IntTy::Is), Infer(i)) => { match ConstIsize::new(i as i64, tcx.sess.target.int_type) { Ok(val) => Ok(Isize(val)), Err(_) => Ok(Isize(ConstIsize::Is32(i as i64 as i32))), } }, (&ty::TyInt(IntTy::I8), InferSigned(i)) => Ok(I8(i as i8)), (&ty::TyInt(IntTy::I16), InferSigned(i)) => Ok(I16(i as i16)), (&ty::TyInt(IntTy::I32), InferSigned(i)) => Ok(I32(i as i32)), (&ty::TyInt(IntTy::I64), InferSigned(i)) => Ok(I64(i)), (&ty::TyInt(IntTy::Is), InferSigned(i)) => { match ConstIsize::new(i, tcx.sess.target.int_type) { Ok(val) => Ok(Isize(val)), Err(_) => Ok(Isize(ConstIsize::Is32(i as i32))), } }, (&ty::TyUint(UintTy::U8), Infer(i)) => Ok(U8(i as u8)), (&ty::TyUint(UintTy::U16), Infer(i)) => Ok(U16(i as u16)), (&ty::TyUint(UintTy::U32), Infer(i)) => Ok(U32(i as u32)), (&ty::TyUint(UintTy::U64), Infer(i)) => Ok(U64(i)), (&ty::TyUint(UintTy::Us), Infer(i)) => { match ConstUsize::new(i, tcx.sess.target.uint_type) { Ok(val) => Ok(Usize(val)), Err(_) => Ok(Usize(ConstUsize::Us32(i as u32))), } }, (&ty::TyUint(_), InferSigned(_)) => Err(err(IntermediateUnsignedNegative)), (&ty::TyInt(ity), i) => Err(err(TypeMismatch(ity.to_string(), i))), (&ty::TyUint(ity), i) => Err(err(TypeMismatch(ity.to_string(), i))), (&ty::TyEnum(ref adt, _), i) => { let hints = tcx.lookup_repr_hints(adt.did); let int_ty = tcx.enum_repr_type(hints.iter().next()); infer(i, tcx, &int_ty.to_ty(tcx).sty, span) }, (_, i) => Err(err(BadType(ConstVal::Integral(i)))), } } fn resolve_trait_associated_const<'a, 'tcx: 'a>(tcx: &'a TyCtxt<'tcx>, ti: &'tcx hir::TraitItem, trait_id: DefId, rcvr_substs: subst::Substs<'tcx>) -> Option<(&'tcx Expr, Option>)> { let trait_ref = ty::Binder( rcvr_substs.erase_regions().to_trait_ref(tcx, trait_id) ); debug!("resolve_trait_associated_const: trait_ref={:?}", trait_ref); tcx.populate_implementations_for_trait_if_necessary(trait_ref.def_id()); let infcx = infer::new_infer_ctxt(tcx, &tcx.tables, None, ProjectionMode::AnyFinal); let mut selcx = traits::SelectionContext::new(&infcx); let obligation = traits::Obligation::new(traits::ObligationCause::dummy(), trait_ref.to_poly_trait_predicate()); let selection = match selcx.select(&obligation) { Ok(Some(vtable)) => vtable, // Still ambiguous, so give up and let the caller decide whether this // expression is really needed yet. Some associated constant values // can't be evaluated until monomorphization is done in trans. Ok(None) => { return None } Err(_) => { return None } }; // NOTE: this code does not currently account for specialization, but when // it does so, it should hook into the ProjectionMode to determine when the // constant should resolve; this will also require plumbing through to this // function whether we are in "trans mode" to pick the right ProjectionMode // when constructing the inference context above. match selection { traits::VtableImpl(ref impl_data) => { match tcx.associated_consts(impl_data.impl_def_id) .iter().find(|ic| ic.name == ti.name) { Some(ic) => lookup_const_by_id(tcx, ic.def_id, None), None => match ti.node { hir::ConstTraitItem(ref ty, Some(ref expr)) => { Some((&*expr, ast_ty_to_prim_ty(tcx, ty))) }, _ => None, }, } } _ => { span_bug!( ti.span, "resolve_trait_associated_const: unexpected vtable type") } } } fn cast_const_int<'tcx>(tcx: &TyCtxt<'tcx>, val: ConstInt, ty: ty::Ty) -> CastResult { let v = val.to_u64_unchecked(); match ty.sty { ty::TyBool if v == 0 => Ok(Bool(false)), ty::TyBool if v == 1 => Ok(Bool(true)), ty::TyInt(ast::IntTy::I8) => Ok(Integral(I8(v as i64 as i8))), ty::TyInt(ast::IntTy::I16) => Ok(Integral(I16(v as i64 as i16))), ty::TyInt(ast::IntTy::I32) => Ok(Integral(I32(v as i64 as i32))), ty::TyInt(ast::IntTy::I64) => Ok(Integral(I64(v as i64))), ty::TyInt(ast::IntTy::Is) => { match ConstIsize::new(v as i64, tcx.sess.target.int_type) { Ok(val) => Ok(Integral(Isize(val))), Err(_) => Ok(Integral(Isize(ConstIsize::Is32(v as i64 as i32)))), } }, ty::TyUint(ast::UintTy::U8) => Ok(Integral(U8(v as u8))), ty::TyUint(ast::UintTy::U16) => Ok(Integral(U16(v as u16))), ty::TyUint(ast::UintTy::U32) => Ok(Integral(U32(v as u32))), ty::TyUint(ast::UintTy::U64) => Ok(Integral(U64(v))), ty::TyUint(ast::UintTy::Us) => { match ConstUsize::new(v, tcx.sess.target.uint_type) { Ok(val) => Ok(Integral(Usize(val))), Err(_) => Ok(Integral(Usize(ConstUsize::Us32(v as u32)))), } }, ty::TyFloat(ast::FloatTy::F64) if val.is_negative() => { // FIXME: this could probably be prettier // there's no easy way to turn an `Infer` into a f64 let val = (-val).map_err(Math)?; let val = val.to_u64().unwrap() as f64; let val = -val; Ok(Float(val)) }, ty::TyFloat(ast::FloatTy::F64) => Ok(Float(val.to_u64().unwrap() as f64)), ty::TyFloat(ast::FloatTy::F32) if val.is_negative() => { let val = (-val).map_err(Math)?; let val = val.to_u64().unwrap() as f32; let val = -val; Ok(Float(val as f64)) }, ty::TyFloat(ast::FloatTy::F32) => Ok(Float(val.to_u64().unwrap() as f32 as f64)), ty::TyRawPtr(_) => Err(ErrKind::UnimplementedConstVal("casting an address to a raw ptr")), _ => Err(CannotCast), } } fn cast_const_float<'tcx>(tcx: &TyCtxt<'tcx>, f: f64, ty: ty::Ty) -> CastResult { match ty.sty { ty::TyInt(_) if f >= 0.0 => cast_const_int(tcx, Infer(f as u64), ty), ty::TyInt(_) => cast_const_int(tcx, InferSigned(f as i64), ty), ty::TyUint(_) if f >= 0.0 => cast_const_int(tcx, Infer(f as u64), ty), ty::TyFloat(ast::FloatTy::F64) => Ok(Float(f)), ty::TyFloat(ast::FloatTy::F32) => Ok(Float(f as f32 as f64)), _ => Err(CannotCast), } } fn cast_const<'tcx>(tcx: &TyCtxt<'tcx>, val: ConstVal, ty: ty::Ty) -> CastResult { match val { Integral(i) => cast_const_int(tcx, i, ty), Bool(b) => cast_const_int(tcx, Infer(b as u64), ty), Float(f) => cast_const_float(tcx, f, ty), Char(c) => cast_const_int(tcx, Infer(c as u64), ty), Function(_) => Err(UnimplementedConstVal("casting fn pointers")), _ => Err(CannotCast), } } fn lit_to_const<'tcx>(lit: &ast::LitKind, tcx: &TyCtxt<'tcx>, ty_hint: Option>, span: Span, ) -> Result { use syntax::ast::*; use syntax::ast::LitIntType::*; match *lit { LitKind::Str(ref s, _) => Ok(Str((*s).clone())), LitKind::ByteStr(ref data) => Ok(ByteStr(data.clone())), LitKind::Byte(n) => Ok(Integral(U8(n))), LitKind::Int(n, Signed(ity)) => { infer(InferSigned(n as i64), tcx, &ty::TyInt(ity), span).map(Integral) }, LitKind::Int(n, Unsuffixed) => { match ty_hint.map(|t| &t.sty) { Some(&ty::TyInt(ity)) => { infer(InferSigned(n as i64), tcx, &ty::TyInt(ity), span).map(Integral) }, Some(&ty::TyUint(uty)) => { infer(Infer(n), tcx, &ty::TyUint(uty), span).map(Integral) }, None => Ok(Integral(Infer(n))), Some(&ty::TyEnum(ref adt, _)) => { let hints = tcx.lookup_repr_hints(adt.did); let int_ty = tcx.enum_repr_type(hints.iter().next()); infer(Infer(n), tcx, &int_ty.to_ty(tcx).sty, span).map(Integral) }, Some(ty_hint) => bug!("bad ty_hint: {:?}, {:?}", ty_hint, lit), } }, LitKind::Int(n, Unsigned(ity)) => { infer(Infer(n), tcx, &ty::TyUint(ity), span).map(Integral) }, LitKind::Float(ref n, _) | LitKind::FloatUnsuffixed(ref n) => { if let Ok(x) = n.parse::() { Ok(Float(x)) } else { // FIXME(#31407) this is only necessary because float parsing is buggy span_bug!(span, "could not evaluate float literal (see issue #31407)"); } } LitKind::Bool(b) => Ok(Bool(b)), LitKind::Char(c) => Ok(Char(c)), } } pub fn compare_const_vals(a: &ConstVal, b: &ConstVal) -> Option { match (a, b) { (&Integral(a), &Integral(b)) => a.try_cmp(b).ok(), (&Float(a), &Float(b)) => { // This is pretty bad but it is the existing behavior. Some(if a == b { Ordering::Equal } else if a < b { Ordering::Less } else { Ordering::Greater }) } (&Str(ref a), &Str(ref b)) => Some(a.cmp(b)), (&Bool(a), &Bool(b)) => Some(a.cmp(&b)), (&ByteStr(ref a), &ByteStr(ref b)) => Some(a.cmp(b)), (&Char(a), &Char(ref b)) => Some(a.cmp(b)), _ => None, } } pub fn compare_lit_exprs<'tcx>(tcx: &TyCtxt<'tcx>, a: &Expr, b: &Expr) -> Option { let a = match eval_const_expr_partial(tcx, a, ExprTypeChecked, None) { Ok(a) => a, Err(e) => { tcx.sess.span_err(a.span, &e.description()); return None; } }; let b = match eval_const_expr_partial(tcx, b, ExprTypeChecked, None) { Ok(b) => b, Err(e) => { tcx.sess.span_err(b.span, &e.description()); return None; } }; compare_const_vals(&a, &b) } /// Returns the repeat count for a repeating vector expression. pub fn eval_repeat_count(tcx: &TyCtxt, count_expr: &hir::Expr) -> usize { let hint = UncheckedExprHint(tcx.types.usize); match eval_const_expr_partial(tcx, count_expr, hint, None) { Ok(Integral(Usize(count))) => { let val = count.as_u64(tcx.sess.target.uint_type); assert_eq!(val as usize as u64, val); val as usize }, Ok(const_val) => { span_err!(tcx.sess, count_expr.span, E0306, "expected positive integer for repeat count, found {}", const_val.description()); 0 } Err(err) => { let err_msg = match count_expr.node { hir::ExprPath(None, hir::Path { global: false, ref segments, .. }) if segments.len() == 1 => format!("found variable"), _ => match err.kind { MiscCatchAll => format!("but found {}", err.description()), _ => format!("but {}", err.description()) } }; span_err!(tcx.sess, count_expr.span, E0307, "expected constant integer for repeat count, {}", err_msg); 0 } } }