// 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::traits; use rustc::hir::def::Def; use rustc::hir::def_id::DefId; use rustc::ty::{self, Ty, TyCtxt}; use rustc::ty::util::IntTypeExt; use rustc::ty::subst::Substs; use rustc::traits::Reveal; use rustc::util::common::ErrorReported; use rustc::util::nodemap::DefIdMap; use graphviz::IntoCow; use syntax::ast; use rustc::hir::{self, Expr}; use syntax::attr::IntType; use syntax_pos::Span; use std::borrow::Cow; use std::cmp::Ordering; use rustc_const_math::*; use rustc_errors::DiagnosticBuilder; use rustc_i128::{i128, u128}; 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>(tcx: TyCtxt<'a, 'tcx, 'tcx>, variant_def: DefId) -> Option<(&'tcx Expr, Option<&'a ty::TypeckTables<'tcx>>)> { if let Some(variant_node_id) = tcx.map.as_local_node_id(variant_def) { let enum_node_id = tcx.map.get_parent(variant_node_id); if let Some(ast_map::NodeItem(it)) = tcx.map.find(enum_node_id) { if let hir::ItemEnum(ref edef, _) = it.node { for variant in &edef.variants { if variant.node.data.id() == variant_node_id { return variant.node.disr_expr.map(|e| { let def_id = tcx.map.body_owner_def_id(e); (&tcx.map.body(e).value, tcx.tables.borrow().get(&def_id).cloned()) }); } } } } } 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: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId, substs: Option<&'tcx Substs<'tcx>>) -> Option<(&'tcx Expr, Option<&'a ty::TypeckTables<'tcx>>, 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(&hir::Item { node: hir::ItemConst(ref ty, body), .. })) | Some(ast_map::NodeImplItem(&hir::ImplItem { node: hir::ImplItemKind::Const(ref ty, body), .. })) => { Some((&tcx.map.body(body).value, tcx.tables.borrow().get(&def_id).cloned(), tcx.ast_ty_to_prim_ty(ty))) } Some(ast_map::NodeTraitItem(ti)) => match ti.node { hir::TraitItemKind::Const(ref ty, default) => { 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.map.get_parent(node_id); let trait_id = tcx.map.local_def_id(trait_id); let default_value = default.map(|body| { (&tcx.map.body(body).value, tcx.tables.borrow().get(&def_id).cloned(), tcx.ast_ty_to_prim_ty(ty)) }); resolve_trait_associated_const(tcx, def_id, default_value, 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(_) => None } } else { let expr_tables_ty = tcx.sess.cstore.maybe_get_item_body(tcx, def_id).map(|body| { (&body.value, Some(tcx.item_tables(def_id)), Some(tcx.sess.cstore.item_type(tcx, def_id))) }); match tcx.sess.cstore.describe_def(def_id) { Some(Def::AssociatedConst(_)) => { let trait_id = tcx.sess.cstore.trait_of_item(def_id); // 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. if let Some(trait_id) = trait_id { if let Some(substs) = substs { resolve_trait_associated_const(tcx, def_id, expr_tables_ty, trait_id, substs) } else { None } } else { expr_tables_ty } }, Some(Def::Const(..)) => expr_tables_ty, _ => None } } } fn lookup_const_fn_by_id<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Option<(&'tcx hir::Body, Option<&'a ty::TypeckTables<'tcx>>)> { if let Some(node_id) = tcx.map.as_local_node_id(def_id) { FnLikeNode::from_node(tcx.map.get(node_id)).and_then(|fn_like| { if fn_like.constness() == hir::Constness::Const { Some((tcx.map.body(fn_like.body()), tcx.tables.borrow().get(&def_id).cloned())) } else { None } }) } else { if tcx.sess.cstore.is_const_fn(def_id) { tcx.sess.cstore.maybe_get_item_body(tcx, def_id).map(|body| { (body, Some(tcx.item_tables(def_id))) }) } else { None } } } pub fn report_const_eval_err<'a, 'tcx>( tcx: TyCtxt<'a, 'tcx, 'tcx>, err: &ConstEvalErr, primary_span: Span, primary_kind: &str) -> DiagnosticBuilder<'tcx> { let mut err = err; while let &ConstEvalErr { kind: ErroneousReferencedConstant(box ref i_err), .. } = err { err = i_err; } let mut diag = struct_span_err!(tcx.sess, err.span, E0080, "constant evaluation error"); note_const_eval_err(tcx, err, primary_span, primary_kind, &mut diag); diag } pub fn fatal_const_eval_err<'a, 'tcx>( tcx: TyCtxt<'a, 'tcx, 'tcx>, err: &ConstEvalErr, primary_span: Span, primary_kind: &str) -> ! { report_const_eval_err(tcx, err, primary_span, primary_kind).emit(); tcx.sess.abort_if_errors(); unreachable!() } pub fn note_const_eval_err<'a, 'tcx>( _tcx: TyCtxt<'a, 'tcx, 'tcx>, err: &ConstEvalErr, primary_span: Span, primary_kind: &str, diag: &mut DiagnosticBuilder) { match err.description() { ConstEvalErrDescription::Simple(message) => { diag.span_label(err.span, &message); } } if !primary_span.contains(err.span) { diag.span_note(primary_span, &format!("for {} here", primary_kind)); } } pub struct ConstContext<'a, 'tcx: 'a> { tcx: TyCtxt<'a, 'tcx, 'tcx>, tables: Option<&'a ty::TypeckTables<'tcx>>, fn_args: Option> } impl<'a, 'tcx> ConstContext<'a, 'tcx> { pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, body: hir::BodyId) -> Self { let def_id = tcx.map.body_owner_def_id(body); ConstContext { tcx: tcx, tables: tcx.tables.borrow().get(&def_id).cloned(), fn_args: None } } pub fn with_tables(tcx: TyCtxt<'a, 'tcx, 'tcx>, tables: &'a ty::TypeckTables<'tcx>) -> Self { ConstContext { tcx: tcx, tables: Some(tables), fn_args: None } } /// 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(&self, e: &Expr, ty_hint: EvalHint<'tcx>) -> EvalResult { eval_const_expr_partial(self, e, ty_hint) } } #[derive(Clone, Debug)] pub struct ConstEvalErr { pub span: Span, pub kind: ErrKind, } #[derive(Clone, Debug)] 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), MissingStructField, NonConstPath, UnimplementedConstVal(&'static str), UnresolvedPath, ExpectedConstTuple, ExpectedConstStruct, TupleIndexOutOfBounds, IndexedNonVec, IndexNegative, IndexNotInt, IndexOutOfBounds { len: u64, index: u64 }, RepeatCountNotNatural, RepeatCountNotInt, MiscBinaryOp, MiscCatchAll, IndexOpFeatureGated, Math(ConstMathErr), IntermediateUnsignedNegative, /// Expected, Got TypeMismatch(String, ConstInt), BadType(ConstVal), ErroneousReferencedConstant(Box), CharCast(ConstInt), } impl From for ErrKind { fn from(err: ConstMathErr) -> ErrKind { Math(err) } } #[derive(Clone, Debug)] pub enum ConstEvalErrDescription<'a> { Simple(Cow<'a, str>), } impl<'a> ConstEvalErrDescription<'a> { /// Return a one-line description of the error, for lints and such pub fn into_oneline(self) -> Cow<'a, str> { match self { ConstEvalErrDescription::Simple(simple) => simple, } } } impl ConstEvalErr { pub fn description(&self) -> ConstEvalErrDescription { use self::ErrKind::*; use self::ConstEvalErrDescription::*; macro_rules! simple { ($msg:expr) => ({ Simple($msg.into_cow()) }); ($fmt:expr, $($arg:tt)+) => ({ Simple(format!($fmt, $($arg)+).into_cow()) }) } match self.kind { CannotCast => simple!("can't cast this type"), CannotCastTo(s) => simple!("can't cast this type to {}", s), InvalidOpForInts(_) => simple!("can't do this op on integrals"), InvalidOpForBools(_) => simple!("can't do this op on bools"), InvalidOpForFloats(_) => simple!("can't do this op on floats"), InvalidOpForIntUint(..) => simple!("can't do this op on an isize and usize"), InvalidOpForUintInt(..) => simple!("can't do this op on a usize and isize"), NegateOn(ref const_val) => simple!("negate on {}", const_val.description()), NotOn(ref const_val) => simple!("not on {}", const_val.description()), CallOn(ref const_val) => simple!("call on {}", const_val.description()), MissingStructField => simple!("nonexistent struct field"), NonConstPath => simple!("non-constant path in constant expression"), UnimplementedConstVal(what) => simple!("unimplemented constant expression: {}", what), UnresolvedPath => simple!("unresolved path in constant expression"), ExpectedConstTuple => simple!("expected constant tuple"), ExpectedConstStruct => simple!("expected constant struct"), TupleIndexOutOfBounds => simple!("tuple index out of bounds"), IndexedNonVec => simple!("indexing is only supported for arrays"), IndexNegative => simple!("indices must be non-negative integers"), IndexNotInt => simple!("indices must be integers"), IndexOutOfBounds { len, index } => { simple!("index out of bounds: the len is {} but the index is {}", len, index) } RepeatCountNotNatural => simple!("repeat count must be a natural number"), RepeatCountNotInt => simple!("repeat count must be integers"), MiscBinaryOp => simple!("bad operands for binary"), MiscCatchAll => simple!("unsupported constant expr"), IndexOpFeatureGated => simple!("the index operation on const values is unstable"), Math(ref err) => Simple(err.description().into_cow()), IntermediateUnsignedNegative => simple!( "during the computation of an unsigned a negative \ number was encountered. This is most likely a bug in\ the constant evaluator"), TypeMismatch(ref expected, ref got) => { simple!("expected {}, found {}", expected, got.description()) }, BadType(ref i) => simple!("value of wrong type: {:?}", i), ErroneousReferencedConstant(_) => simple!("could not evaluate referenced constant"), CharCast(ref got) => { simple!("only `u8` can be cast as `char`, not `{}`", got.description()) }, } } } 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 }) } } fn eval_const_expr_partial<'a, 'tcx>(cx: &ConstContext<'a, 'tcx>, e: &Expr, ty_hint: EvalHint<'tcx>) -> EvalResult { let tcx = cx.tcx; // 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. cx.tables.map(|tables| tables.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). cx.tables.and_then(|tables| tables.expr_ty_opt(e)) } }; let result = match e.node { hir::ExprUnary(hir::UnNeg, ref inner) => { // unary neg literals already got their sign during creation if let hir::ExprLit(ref lit) = inner.node { use syntax::ast::*; use syntax::ast::LitIntType::*; const I8_OVERFLOW: u128 = i8::min_value() as u8 as u128; const I16_OVERFLOW: u128 = i16::min_value() as u16 as u128; const I32_OVERFLOW: u128 = i32::min_value() as u32 as u128; const I64_OVERFLOW: u128 = i64::min_value() as u64 as u128; const I128_OVERFLOW: u128 = i128::min_value() as u128; match (&lit.node, ety.map(|t| &t.sty)) { (&LitKind::Int(I8_OVERFLOW, _), Some(&ty::TyInt(IntTy::I8))) | (&LitKind::Int(I8_OVERFLOW, Signed(IntTy::I8)), _) => { return Ok(Integral(I8(i8::min_value()))) }, (&LitKind::Int(I16_OVERFLOW, _), Some(&ty::TyInt(IntTy::I16))) | (&LitKind::Int(I16_OVERFLOW, Signed(IntTy::I16)), _) => { return Ok(Integral(I16(i16::min_value()))) }, (&LitKind::Int(I32_OVERFLOW, _), Some(&ty::TyInt(IntTy::I32))) | (&LitKind::Int(I32_OVERFLOW, Signed(IntTy::I32)), _) => { return Ok(Integral(I32(i32::min_value()))) }, (&LitKind::Int(I64_OVERFLOW, _), Some(&ty::TyInt(IntTy::I64))) | (&LitKind::Int(I64_OVERFLOW, Signed(IntTy::I64)), _) => { return Ok(Integral(I64(i64::min_value()))) }, (&LitKind::Int(n, _), Some(&ty::TyInt(IntTy::I128))) | (&LitKind::Int(n, Signed(IntTy::I128)), _) => { // SNAP: replace n in pattern with I128_OVERFLOW and remove this if. if n == I128_OVERFLOW { return Ok(Integral(I128(i128::min_value()))) } }, (&LitKind::Int(n, _), Some(&ty::TyInt(IntTy::Is))) | (&LitKind::Int(n, Signed(IntTy::Is)), _) => { match tcx.sess.target.int_type { IntTy::I16 => if n == I16_OVERFLOW { return Ok(Integral(Isize(Is16(i16::min_value())))); }, IntTy::I32 => if n == I32_OVERFLOW { return Ok(Integral(Isize(Is32(i32::min_value())))); }, IntTy::I64 => if n == I64_OVERFLOW { return Ok(Integral(Isize(Is64(i64::min_value())))); }, _ => bug!(), } }, _ => {}, } } match cx.eval(inner, ty_hint)? { Float(f) => Float(-f), Integral(i) => Integral(math!(e, -i)), const_val => signal!(e, NegateOn(const_val)), } } hir::ExprUnary(hir::UnNot, ref inner) => { match cx.eval(inner, ty_hint)? { 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 (cx.eval(a, ty_hint)?, cx.eval(b, b_ty)?) { (Float(a), Float(b)) => { use std::cmp::Ordering::*; match op.node { hir::BiAdd => Float(math!(e, a + b)), hir::BiSub => Float(math!(e, a - b)), hir::BiMul => Float(math!(e, a * b)), hir::BiDiv => Float(math!(e, a / b)), hir::BiRem => Float(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, 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, hir::BiLt => a < b, hir::BiLe => a <= b, hir::BiGe => a >= b, hir::BiGt => a > b, _ => signal!(e, InvalidOpForBools(op.node)), }) } _ => signal!(e, MiscBinaryOp), } } hir::ExprCast(ref base, ref target_ty) => { let ety = tcx.ast_ty_to_prim_ty(&target_ty).or(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 cx.tables.and_then(|tables| tables.expr_ty_opt(&base)) { Some(t) => UncheckedExprHint(t), None => ty_hint } }; let val = match cx.eval(base, base_hint) { 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!(), }; cx.eval(base, hint)? }, 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(ref qpath) => { let def = cx.tables.map(|tables| tables.qpath_def(qpath, e.id)).unwrap_or_else(|| { // There are no tables so we can only handle already-resolved HIR. match *qpath { hir::QPath::Resolved(_, ref path) => path.def, hir::QPath::TypeRelative(..) => Def::Err } }); match def { Def::Const(def_id) | Def::AssociatedConst(def_id) => { let substs = if let ExprTypeChecked = ty_hint { Some(cx.tables.and_then(|tables| tables.node_id_item_substs(e.id)) .unwrap_or_else(|| tcx.intern_substs(&[]))) } else { None }; if let Some((expr, tables, ty)) = lookup_const_by_id(tcx, def_id, substs) { let item_hint = match ty { Some(ty) => ty_hint.checked_or(ty), None => ty_hint, }; let cx = ConstContext { tcx: tcx, tables: tables, fn_args: None }; match cx.eval(expr, item_hint) { Ok(val) => val, Err(err) => { debug!("bad reference: {:?}, {:?}", err.description(), err.span); signal!(e, ErroneousReferencedConstant(box err)) }, } } else { signal!(e, NonConstPath); } }, Def::VariantCtor(variant_def, ..) => { if let Some((expr, tables)) = lookup_variant_by_id(tcx, variant_def) { let cx = ConstContext { tcx: tcx, tables: tables, fn_args: None }; match cx.eval(expr, ty_hint) { Ok(val) => val, Err(err) => { debug!("bad reference: {:?}, {:?}", err.description(), err.span); signal!(e, ErroneousReferencedConstant(box err)) }, } } else { signal!(e, UnimplementedConstVal("enum variants")); } } Def::StructCtor(..) => { ConstVal::Struct(Default::default()) } Def::Local(def_id) => { debug!("Def::Local({:?}): {:?}", def_id, cx.fn_args); if let Some(val) = cx.fn_args.as_ref().and_then(|args| args.get(&def_id)) { val.clone() } else { signal!(e, NonConstPath); } }, Def::Method(id) | Def::Fn(id) => Function(id), Def::Err => signal!(e, UnresolvedPath), _ => signal!(e, NonConstPath), } } hir::ExprCall(ref callee, ref args) => { let sub_ty_hint = ty_hint.erase_hint(); let callee_val = cx.eval(callee, sub_ty_hint)?; let did = match callee_val { Function(did) => did, Struct(_) => signal!(e, UnimplementedConstVal("tuple struct constructors")), callee => signal!(e, CallOn(callee)), }; let (body, tables) = match lookup_const_fn_by_id(tcx, did) { Some(x) => x, None => signal!(e, NonConstPath), }; let arg_defs = body.arguments.iter().map(|arg| match arg.pat.node { hir::PatKind::Binding(_, def_id, _, _) => Some(def_id), _ => None }).collect::>(); assert_eq!(arg_defs.len(), args.len()); let mut call_args = DefIdMap(); for (arg, arg_expr) in arg_defs.into_iter().zip(args.iter()) { let arg_hint = ty_hint.erase_hint(); let arg_val = cx.eval(arg_expr, arg_hint)?; debug!("const call arg: {:?}", arg); if let Some(def_id) = arg { assert!(call_args.insert(def_id, arg_val).is_none()); } } debug!("const call({:?})", call_args); let callee_cx = ConstContext { tcx: tcx, tables: tables, fn_args: Some(call_args) }; callee_cx.eval(&body.value, ty_hint)? }, hir::ExprLit(ref lit) => match lit_to_const(&lit.node, tcx, ety) { Ok(val) => val, Err(err) => signal!(e, err), }, hir::ExprBlock(ref block) => { match block.expr { Some(ref expr) => cx.eval(expr, ty_hint)?, None => signal!(e, UnimplementedConstVal("empty block")), } } hir::ExprType(ref e, _) => cx.eval(e, ty_hint)?, hir::ExprTup(ref fields) => { let field_hint = ty_hint.erase_hint(); Tuple(fields.iter().map(|e| cx.eval(e, field_hint)).collect::>()?) } hir::ExprStruct(_, ref fields, _) => { let field_hint = ty_hint.erase_hint(); Struct(fields.iter().map(|f| { cx.eval(&f.expr, field_hint).map(|v| (f.name.node, v)) }).collect::>()?) } 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 = cx.eval(arr, arr_hint)?; let idx_hint = ty_hint.checked_or(tcx.types.usize); let idx = match cx.eval(idx, idx_hint)? { 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(ref v) => { if let Some(elem) = v.get(idx as usize) { elem.clone() } else { let n = v.len() as u64; assert_eq!(n as usize as u64, n); signal!(e, IndexOutOfBounds { len: n, index: idx }) } } Repeat(.., n) if idx >= n => { signal!(e, IndexOutOfBounds { len: n, index: idx }) } Repeat(ref elem, _) => (**elem).clone(), ByteStr(ref data) if idx >= data.len() as u64 => { signal!(e, IndexOutOfBounds { len: data.len() as u64, index: idx }) } ByteStr(data) => { Integral(U8(data[idx as usize])) }, _ => signal!(e, IndexedNonVec), } } hir::ExprArray(ref v) => { let elem_hint = ty_hint.erase_hint(); Array(v.iter().map(|e| cx.eval(e, elem_hint)).collect::>()?) } hir::ExprRepeat(ref elem, count) => { let elem_hint = ty_hint.erase_hint(); let len_hint = ty_hint.checked_or(tcx.types.usize); let n = if let Some(ty) = ety { // For cross-crate constants, we have the type already, // but not the body for `count`, so use the type. match ty.sty { ty::TyArray(_, n) => n as u64, _ => bug!() } } else { let n = &tcx.map.body(count).value; match ConstContext::new(tcx, count).eval(n, len_hint)? { Integral(Usize(i)) => i.as_u64(tcx.sess.target.uint_type), Integral(_) => signal!(e, RepeatCountNotNatural), _ => signal!(e, RepeatCountNotInt), } }; Repeat(Box::new(cx.eval(elem, elem_hint)?), n) }, hir::ExprTupField(ref base, index) => { let base_hint = ty_hint.erase_hint(); let c = cx.eval(base, base_hint)?; if let Tuple(ref fields) = c { if let Some(elem) = fields.get(index.node) { elem.clone() } else { signal!(e, TupleIndexOutOfBounds); } } else { signal!(base, ExpectedConstTuple); } } hir::ExprField(ref base, field_name) => { let base_hint = ty_hint.erase_hint(); let c = cx.eval(base, base_hint)?; if let Struct(ref fields) = c { if let Some(f) = fields.get(&field_name.node) { f.clone() } else { signal!(e, MissingStructField); } } 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)) => match infer(i, tcx, ty_hint) { Ok(inferred) => Ok(Integral(inferred)), Err(err) => signal!(e, err), }, (_, result) => Ok(result), } } fn infer<'a, 'tcx>(i: ConstInt, tcx: TyCtxt<'a, 'tcx, 'tcx>, ty_hint: &ty::TypeVariants<'tcx>) -> Result { use syntax::ast::*; 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::I128), result @ I128(_)) => 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::U128), result @ U128(_)) => Ok(result), (&ty::TyUint(UintTy::Us), result @ Usize(_)) => Ok(result), (&ty::TyInt(IntTy::I8), Infer(i)) => Ok(I8(i as i128 as i8)), (&ty::TyInt(IntTy::I16), Infer(i)) => Ok(I16(i as i128 as i16)), (&ty::TyInt(IntTy::I32), Infer(i)) => Ok(I32(i as i128 as i32)), (&ty::TyInt(IntTy::I64), Infer(i)) => Ok(I64(i as i128 as i64)), (&ty::TyInt(IntTy::I128), Infer(i)) => Ok(I128(i as i128)), (&ty::TyInt(IntTy::Is), Infer(i)) => { Ok(Isize(ConstIsize::new_truncating(i as i128, tcx.sess.target.int_type))) }, (&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 as i64)), (&ty::TyInt(IntTy::I128), InferSigned(i)) => Ok(I128(i)), (&ty::TyInt(IntTy::Is), InferSigned(i)) => { Ok(Isize(ConstIsize::new_truncating(i, tcx.sess.target.int_type))) }, (&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 as u64)), (&ty::TyUint(UintTy::U128), Infer(i)) => Ok(U128(i)), (&ty::TyUint(UintTy::Us), Infer(i)) => { Ok(Usize(ConstUsize::new_truncating(i, tcx.sess.target.uint_type))) }, (&ty::TyUint(_), InferSigned(_)) => Err(IntermediateUnsignedNegative), (&ty::TyInt(ity), i) => Err(TypeMismatch(ity.to_string(), i)), (&ty::TyUint(ity), i) => Err(TypeMismatch(ity.to_string(), i)), (&ty::TyAdt(adt, _), i) if adt.is_enum() => { 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) }, (_, i) => Err(BadType(ConstVal::Integral(i))), } } fn resolve_trait_associated_const<'a, 'tcx: 'a>( tcx: TyCtxt<'a, 'tcx, 'tcx>, trait_item_id: DefId, default_value: Option<(&'tcx Expr, Option<&'a ty::TypeckTables<'tcx>>, Option>)>, trait_id: DefId, rcvr_substs: &'tcx Substs<'tcx> ) -> Option<(&'tcx Expr, Option<&'a ty::TypeckTables<'tcx>>, Option>)> { let trait_ref = ty::Binder(ty::TraitRef::new(trait_id, rcvr_substs)); debug!("resolve_trait_associated_const: trait_ref={:?}", trait_ref); tcx.populate_implementations_for_trait_if_necessary(trait_id); tcx.infer_ctxt((), Reveal::NotSpecializable).enter(|infcx| { 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 Reveal 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 Reveal // when constructing the inference context above. match selection { traits::VtableImpl(ref impl_data) => { let name = tcx.associated_item(trait_item_id).name; let ac = tcx.associated_items(impl_data.impl_def_id) .find(|item| item.kind == ty::AssociatedKind::Const && item.name == name); match ac { Some(ic) => lookup_const_by_id(tcx, ic.def_id, None), None => default_value, } } _ => { bug!("resolve_trait_associated_const: unexpected vtable type") } } }) } fn cast_const_int<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, val: ConstInt, ty: ty::Ty) -> CastResult { let v = val.to_u128_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 i128 as i8))), ty::TyInt(ast::IntTy::I16) => Ok(Integral(I16(v as i128 as i16))), ty::TyInt(ast::IntTy::I32) => Ok(Integral(I32(v as i128 as i32))), ty::TyInt(ast::IntTy::I64) => Ok(Integral(I64(v as i128 as i64))), ty::TyInt(ast::IntTy::I128) => Ok(Integral(I128(v as i128))), ty::TyInt(ast::IntTy::Is) => { Ok(Integral(Isize(ConstIsize::new_truncating(v as i128, tcx.sess.target.int_type)))) }, 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 as u64))), ty::TyUint(ast::UintTy::U128) => Ok(Integral(U128(v as u128))), ty::TyUint(ast::UintTy::Us) => { Ok(Integral(Usize(ConstUsize::new_truncating(v, tcx.sess.target.uint_type)))) }, ty::TyFloat(ast::FloatTy::F64) => match val.erase_type() { Infer(u) => Ok(Float(F64(u as f64))), InferSigned(i) => Ok(Float(F64(i as f64))), _ => bug!("ConstInt::erase_type returned something other than Infer/InferSigned"), }, ty::TyFloat(ast::FloatTy::F32) => match val.erase_type() { Infer(u) => Ok(Float(F32(u as f32))), InferSigned(i) => Ok(Float(F32(i as f32))), _ => bug!("ConstInt::erase_type returned something other than Infer/InferSigned"), }, ty::TyRawPtr(_) => Err(ErrKind::UnimplementedConstVal("casting an address to a raw ptr")), ty::TyChar => match infer(val, tcx, &ty::TyUint(ast::UintTy::U8)) { Ok(U8(u)) => Ok(Char(u as char)), // can only occur before typeck, typeck blocks `T as char` for `T` != `u8` _ => Err(CharCast(val)), }, _ => Err(CannotCast), } } fn cast_const_float<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, val: ConstFloat, ty: ty::Ty) -> CastResult { match ty.sty { ty::TyInt(_) | ty::TyUint(_) => { let i = match val { F32(f) if f >= 0.0 => Infer(f as u128), FInfer { f64: f, .. } | F64(f) if f >= 0.0 => Infer(f as u128), F32(f) => InferSigned(f as i128), FInfer { f64: f, .. } | F64(f) => InferSigned(f as i128) }; if let (InferSigned(_), &ty::TyUint(_)) = (i, &ty.sty) { return Err(CannotCast); } cast_const_int(tcx, i, ty) } ty::TyFloat(ast::FloatTy::F64) => Ok(Float(F64(match val { F32(f) => f as f64, FInfer { f64: f, .. } | F64(f) => f }))), ty::TyFloat(ast::FloatTy::F32) => Ok(Float(F32(match val { F64(f) => f as f32, FInfer { f32: f, .. } | F32(f) => f }))), _ => Err(CannotCast), } } fn cast_const<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, '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 u128), ty), Float(f) => cast_const_float(tcx, f, ty), Char(c) => cast_const_int(tcx, Infer(c as u128), ty), Function(_) => Err(UnimplementedConstVal("casting fn pointers")), ByteStr(b) => match ty.sty { ty::TyRawPtr(_) => { Err(ErrKind::UnimplementedConstVal("casting a bytestr to a raw ptr")) }, ty::TyRef(_, ty::TypeAndMut { ref ty, mutbl: hir::MutImmutable }) => match ty.sty { ty::TyArray(ty, n) if ty == tcx.types.u8 && n == b.len() => Ok(ByteStr(b)), ty::TySlice(_) => { Err(ErrKind::UnimplementedConstVal("casting a bytestr to slice")) }, _ => Err(CannotCast), }, _ => Err(CannotCast), }, Str(s) => match ty.sty { ty::TyRawPtr(_) => Err(ErrKind::UnimplementedConstVal("casting a str to a raw ptr")), ty::TyRef(_, ty::TypeAndMut { ref ty, mutbl: hir::MutImmutable }) => match ty.sty { ty::TyStr => Ok(Str(s)), _ => Err(CannotCast), }, _ => Err(CannotCast), }, _ => Err(CannotCast), } } fn lit_to_const<'a, 'tcx>(lit: &ast::LitKind, tcx: TyCtxt<'a, 'tcx, 'tcx>, ty_hint: Option>) -> Result { use syntax::ast::*; use syntax::ast::LitIntType::*; match *lit { LitKind::Str(ref s, _) => Ok(Str(s.as_str())), LitKind::ByteStr(ref data) => Ok(ByteStr(data.clone())), LitKind::Byte(n) => Ok(Integral(U8(n))), LitKind::Int(n, Signed(ity)) => { infer(InferSigned(n as i128), tcx, &ty::TyInt(ity)).map(Integral) }, // FIXME: this should become u128. LitKind::Int(n, Unsuffixed) => { match ty_hint.map(|t| &t.sty) { Some(&ty::TyInt(ity)) => { infer(InferSigned(n as i128), tcx, &ty::TyInt(ity)).map(Integral) }, Some(&ty::TyUint(uty)) => { infer(Infer(n as u128), tcx, &ty::TyUint(uty)).map(Integral) }, None => Ok(Integral(Infer(n as u128))), Some(&ty::TyAdt(adt, _)) => { let hints = tcx.lookup_repr_hints(adt.did); let int_ty = tcx.enum_repr_type(hints.iter().next()); infer(Infer(n as u128), tcx, &int_ty.to_ty(tcx).sty).map(Integral) }, Some(ty_hint) => bug!("bad ty_hint: {:?}, {:?}", ty_hint, lit), } }, LitKind::Int(n, Unsigned(ity)) => { infer(Infer(n as u128), tcx, &ty::TyUint(ity)).map(Integral) }, LitKind::Float(n, fty) => { parse_float(&n.as_str(), Some(fty)).map(Float) } LitKind::FloatUnsuffixed(n) => { let fty_hint = match ty_hint.map(|t| &t.sty) { Some(&ty::TyFloat(fty)) => Some(fty), _ => None }; parse_float(&n.as_str(), fty_hint).map(Float) } LitKind::Bool(b) => Ok(Bool(b)), LitKind::Char(c) => Ok(Char(c)), } } fn parse_float(num: &str, fty_hint: Option) -> Result { let val = match fty_hint { Some(ast::FloatTy::F32) => num.parse::().map(F32), Some(ast::FloatTy::F64) => num.parse::().map(F64), None => { num.parse::().and_then(|f32| { num.parse::().map(|f64| { FInfer { f32: f32, f64: f64 } }) }) } }; val.map_err(|_| { // FIXME(#31407) this is only necessary because float parsing is buggy UnimplementedConstVal("could not evaluate float literal (see issue #31407)") }) } pub fn compare_const_vals(tcx: TyCtxt, span: Span, a: &ConstVal, b: &ConstVal) -> Result { let result = match (a, b) { (&Integral(a), &Integral(b)) => a.try_cmp(b).ok(), (&Float(a), &Float(b)) => a.try_cmp(b).ok(), (&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, }; match result { Some(result) => Ok(result), None => { // FIXME: can this ever be reached? span_err!(tcx.sess, span, E0298, "type mismatch comparing {} and {}", a.description(), b.description()); Err(ErrorReported) } } } impl<'a, 'tcx> ConstContext<'a, 'tcx> { pub fn compare_lit_exprs(&self, span: Span, a: &Expr, b: &Expr) -> Result { let tcx = self.tcx; let a = match self.eval(a, ExprTypeChecked) { Ok(a) => a, Err(e) => { report_const_eval_err(tcx, &e, a.span, "expression").emit(); return Err(ErrorReported); } }; let b = match self.eval(b, ExprTypeChecked) { Ok(b) => b, Err(e) => { report_const_eval_err(tcx, &e, b.span, "expression").emit(); return Err(ErrorReported); } }; compare_const_vals(tcx, span, &a, &b) } } /// Returns the value of the length-valued expression pub fn eval_length<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, count: hir::BodyId, reason: &str) -> Result { let hint = UncheckedExprHint(tcx.types.usize); let count_expr = &tcx.map.body(count).value; match ConstContext::new(tcx, count).eval(count_expr, hint) { Ok(Integral(Usize(count))) => { let val = count.as_u64(tcx.sess.target.uint_type); assert_eq!(val as usize as u64, val); Ok(val as usize) }, Ok(const_val) => { struct_span_err!(tcx.sess, count_expr.span, E0306, "expected `usize` for {}, found {}", reason, const_val.description()) .span_label(count_expr.span, &format!("expected `usize`")) .emit(); Err(ErrorReported) } Err(err) => { let mut diag = report_const_eval_err( tcx, &err, count_expr.span, reason); if let hir::ExprPath(hir::QPath::Resolved(None, ref path)) = count_expr.node { if let Def::Local(..) = path.def { diag.note(&format!("`{}` is a variable", tcx.map.node_to_pretty_string(count_expr.id))); } } diag.emit(); Err(ErrorReported) } } }