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use std::fmt;
use std::error::Error;
use rustc::hir::{self, def_id::DefId};
use rustc::mir::interpret::ConstEvalErr;
use rustc::mir;
use rustc::ty::{self, TyCtxt, Instance, query::TyCtxtAt};
use rustc::ty::layout::{self, LayoutOf, TyLayout};
use rustc::ty::subst::Subst;
use rustc_data_structures::indexed_vec::IndexVec;
use syntax::ast::Mutability;
use syntax::source_map::Span;
use rustc::mir::interpret::{
EvalResult, EvalError, EvalErrorKind, GlobalId,
Scalar, Allocation, ConstValue,
};
use interpret::{self,
Place, PlaceTy, MemPlace, OpTy, Operand, Value,
EvalContext, StackPopCleanup, MemoryKind,
};
pub fn mk_borrowck_eval_cx<'a, 'mir, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
instance: Instance<'tcx>,
mir: &'mir mir::Mir<'tcx>,
span: Span,
) -> EvalResult<'tcx, EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>> {
debug!("mk_borrowck_eval_cx: {:?}", instance);
let param_env = tcx.param_env(instance.def_id());
let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeEvaluator, ());
ecx.stack.push(interpret::Frame {
block: mir::START_BLOCK,
locals: IndexVec::new(),
instance,
span,
mir,
return_place: Place::null(tcx),
return_to_block: StackPopCleanup::Goto(None),
stmt: 0,
});
Ok(ecx)
}
pub fn mk_eval_cx<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
instance: Instance<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> EvalResult<'tcx, EvalContext<'a, 'tcx, 'tcx, CompileTimeEvaluator>> {
debug!("mk_eval_cx: {:?}, {:?}", instance, param_env);
let span = tcx.def_span(instance.def_id());
let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeEvaluator, ());
let mir = ecx.load_mir(instance.def)?;
ecx.push_stack_frame(
instance,
mir.span,
mir,
Place::null(tcx),
StackPopCleanup::Goto(None),
)?;
Ok(ecx)
}
pub fn eval_promoted<'a, 'mir, 'tcx>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>,
cid: GlobalId<'tcx>,
mir: &'mir mir::Mir<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> EvalResult<'tcx, OpTy<'tcx>> {
ecx.with_fresh_body(|ecx| {
eval_body_using_ecx(ecx, cid, Some(mir), param_env)
})
}
pub fn op_to_const<'tcx>(
ecx: &EvalContext<'_, '_, 'tcx, CompileTimeEvaluator>,
op: OpTy<'tcx>,
may_normalize: bool,
) -> EvalResult<'tcx, &'tcx ty::Const<'tcx>> {
let normalize = may_normalize
&& match op.layout.abi {
layout::Abi::Scalar(..) => true,
layout::Abi::ScalarPair(..) => {
op.layout.ty.builtin_deref(true).is_some()
},
_ => false,
};
let normalized_op = if normalize {
ecx.try_read_value(op)?
} else {
match op.op {
Operand::Indirect(mplace) => Err(mplace),
Operand::Immediate(val) => Ok(val)
}
};
let val = match normalized_op {
Err(MemPlace { ptr, align, extra }) => {
assert!(extra.is_none());
let ptr = ptr.to_ptr()?;
let alloc = ecx.memory.get(ptr.alloc_id)?;
assert!(alloc.align.abi() >= align.abi());
assert!(alloc.bytes.len() as u64 - ptr.offset.bytes() >= op.layout.size.bytes());
let mut alloc = alloc.clone();
alloc.align = align;
let alloc = ecx.tcx.intern_const_alloc(alloc);
ConstValue::ByRef(ptr.alloc_id, alloc, ptr.offset)
},
Ok(Value::Scalar(x)) =>
ConstValue::Scalar(x.not_undef()?),
Ok(Value::ScalarPair(a, b)) =>
ConstValue::ScalarPair(a.not_undef()?, b),
};
Ok(ty::Const::from_const_value(ecx.tcx.tcx, val, op.layout.ty))
}
fn eval_body_and_ecx<'a, 'mir, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
cid: GlobalId<'tcx>,
mir: Option<&'mir mir::Mir<'tcx>>,
param_env: ty::ParamEnv<'tcx>,
) -> (EvalResult<'tcx, OpTy<'tcx>>, EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>) {
let span = tcx.def_span(cid.instance.def_id());
let span = mir.map(|mir| mir.span).unwrap_or(span);
let mut ecx = EvalContext::new(tcx.at(span), param_env, CompileTimeEvaluator, ());
let r = eval_body_using_ecx(&mut ecx, cid, mir, param_env);
(r, ecx)
}
fn eval_body_using_ecx<'a, 'mir, 'tcx>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, CompileTimeEvaluator>,
cid: GlobalId<'tcx>,
mir: Option<&'mir mir::Mir<'tcx>>,
param_env: ty::ParamEnv<'tcx>,
) -> EvalResult<'tcx, OpTy<'tcx>> {
debug!("eval_body_using_ecx: {:?}, {:?}", cid, param_env);
let tcx = ecx.tcx.tcx;
let mut mir = match mir {
Some(mir) => mir,
None => ecx.load_mir(cid.instance.def)?,
};
if let Some(index) = cid.promoted {
mir = &mir.promoted[index];
}
let layout = ecx.layout_of(mir.return_ty().subst(tcx, cid.instance.substs))?;
assert!(!layout.is_unsized());
let ret = ecx.allocate(layout, MemoryKind::Stack)?;
let name = ty::tls::with(|tcx| tcx.item_path_str(cid.instance.def_id()));
let prom = cid.promoted.map_or(String::new(), |p| format!("::promoted[{:?}]", p));
trace!("eval_body_using_ecx: pushing stack frame for global: {}{}", name, prom);
assert!(mir.arg_count == 0);
ecx.push_stack_frame(
cid.instance,
mir.span,
mir,
Place::Ptr(*ret),
StackPopCleanup::None { cleanup: false },
)?;
ecx.run()?;
let internally_mutable = !layout.ty.is_freeze(tcx, param_env, mir.span);
let is_static = tcx.is_static(cid.instance.def_id());
let mutability = if is_static == Some(hir::Mutability::MutMutable) || internally_mutable {
Mutability::Mutable
} else {
Mutability::Immutable
};
ecx.memory.intern_static(ret.ptr.to_ptr()?.alloc_id, mutability)?;
debug!("eval_body_using_ecx done: {:?}", *ret);
Ok(ret.into())
}
#[derive(Debug, Clone, Eq, PartialEq, Hash)]
pub struct CompileTimeEvaluator;
impl<'tcx> Into<EvalError<'tcx>> for ConstEvalError {
fn into(self) -> EvalError<'tcx> {
EvalErrorKind::MachineError(self.to_string()).into()
}
}
impl_stable_hash_for!(struct CompileTimeEvaluator {});
#[derive(Clone, Debug)]
enum ConstEvalError {
NeedsRfc(String),
NotConst(String),
}
impl fmt::Display for ConstEvalError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
use self::ConstEvalError::*;
match *self {
NeedsRfc(ref msg) => {
write!(
f,
"\"{}\" needs an rfc before being allowed inside constants",
msg
)
}
NotConst(ref msg) => write!(f, "{}", msg),
}
}
}
impl Error for ConstEvalError {
fn description(&self) -> &str {
use self::ConstEvalError::*;
match *self {
NeedsRfc(_) => "this feature needs an rfc before being allowed inside constants",
NotConst(_) => "this feature is not compatible with constant evaluation",
}
}
fn cause(&self) -> Option<&dyn Error> {
None
}
}
impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeEvaluator {
type MemoryData = ();
type MemoryKinds = !;
const MUT_STATIC_KIND: Option<!> = None;
const DETECT_LOOPS: bool = true;
fn find_fn<'a>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
instance: ty::Instance<'tcx>,
args: &[OpTy<'tcx>],
dest: Option<PlaceTy<'tcx>>,
ret: Option<mir::BasicBlock>,
) -> EvalResult<'tcx, Option<&'mir mir::Mir<'tcx>>> {
debug!("eval_fn_call: {:?}", instance);
if !ecx.tcx.is_const_fn(instance.def_id()) {
if ecx.hook_fn(instance, args, dest)? {
ecx.goto_block(ret)?;
return Ok(None);
}
return Err(
ConstEvalError::NotConst(format!("calling non-const fn `{}`", instance)).into(),
);
}
Ok(Some(match ecx.load_mir(instance.def) {
Ok(mir) => mir,
Err(err) => {
if let EvalErrorKind::NoMirFor(ref path) = err.kind {
return Err(
ConstEvalError::NeedsRfc(format!("calling extern function `{}`", path))
.into(),
);
}
return Err(err);
}
}))
}
fn call_intrinsic<'a>(
ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
instance: ty::Instance<'tcx>,
args: &[OpTy<'tcx>],
dest: PlaceTy<'tcx>,
) -> EvalResult<'tcx> {
if ecx.emulate_intrinsic(instance, args, dest)? {
return Ok(());
}
let intrinsic_name = &ecx.tcx.item_name(instance.def_id()).as_str()[..];
Err(
ConstEvalError::NeedsRfc(format!("calling intrinsic `{}`", intrinsic_name)).into()
)
}
fn ptr_op<'a>(
_ecx: &EvalContext<'a, 'mir, 'tcx, Self>,
_bin_op: mir::BinOp,
_left: Scalar,
_left_layout: TyLayout<'tcx>,
_right: Scalar,
_right_layout: TyLayout<'tcx>,
) -> EvalResult<'tcx, (Scalar, bool)> {
Err(
ConstEvalError::NeedsRfc("pointer arithmetic or comparison".to_string()).into(),
)
}
fn find_foreign_static<'a>(
_tcx: TyCtxtAt<'a, 'tcx, 'tcx>,
_def_id: DefId,
) -> EvalResult<'tcx, &'tcx Allocation> {
err!(ReadForeignStatic)
}
fn box_alloc<'a>(
_ecx: &mut EvalContext<'a, 'mir, 'tcx, Self>,
_dest: PlaceTy<'tcx>,
) -> EvalResult<'tcx> {
Err(
ConstEvalError::NeedsRfc("heap allocations via `box` keyword".to_string()).into(),
)
}
}
pub fn const_field<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
instance: ty::Instance<'tcx>,
variant: Option<usize>,
field: mir::Field,
value: &'tcx ty::Const<'tcx>,
) -> ::rustc::mir::interpret::ConstEvalResult<'tcx> {
trace!("const_field: {:?}, {:?}, {:?}", instance, field, value);
let ecx = mk_eval_cx(tcx, instance, param_env).unwrap();
let result = (|| {
let op = ecx.const_to_op(value)?;
let down = match variant {
None => op,
Some(variant) => ecx.operand_downcast(op, variant)?
};
let field = ecx.operand_field(down, field.index() as u64)?;
op_to_const(&ecx, field, true)
})();
result.map_err(|err| {
let (trace, span) = ecx.generate_stacktrace(None);
ConstEvalErr {
error: err,
stacktrace: trace,
span,
}.into()
})
}
pub fn const_variant_index<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
param_env: ty::ParamEnv<'tcx>,
instance: ty::Instance<'tcx>,
val: &'tcx ty::Const<'tcx>,
) -> EvalResult<'tcx, usize> {
trace!("const_variant_index: {:?}, {:?}", instance, val);
let ecx = mk_eval_cx(tcx, instance, param_env).unwrap();
let op = ecx.const_to_op(val)?;
Ok(ecx.read_discriminant(op)?.1)
}
pub fn const_to_allocation_provider<'a, 'tcx>(
_tcx: TyCtxt<'a, 'tcx, 'tcx>,
val: &'tcx ty::Const<'tcx>,
) -> &'tcx Allocation {
match val.val {
ConstValue::ByRef(_, alloc, offset) => {
assert_eq!(offset.bytes(), 0);
return alloc;
},
_ => bug!("const_to_allocation called on non-static"),
}
}
pub fn const_eval_provider<'a, 'tcx>(
tcx: TyCtxt<'a, 'tcx, 'tcx>,
key: ty::ParamEnvAnd<'tcx, GlobalId<'tcx>>,
) -> ::rustc::mir::interpret::ConstEvalResult<'tcx> {
trace!("const eval: {:?}", key);
let cid = key.value;
let def_id = cid.instance.def.def_id();
if let Some(id) = tcx.hir.as_local_node_id(def_id) {
let tables = tcx.typeck_tables_of(def_id);
let span = tcx.def_span(def_id);
if tcx.check_match(def_id).is_err() {
return Err(ConstEvalErr {
error: EvalErrorKind::CheckMatchError.into(),
stacktrace: vec![],
span,
}.into());
}
if let hir::BodyOwnerKind::Const = tcx.hir.body_owner_kind(id) {
tcx.mir_const_qualif(def_id);
}
if tables.tainted_by_errors {
return Err(ConstEvalErr {
error: EvalErrorKind::CheckMatchError.into(),
stacktrace: vec![],
span,
}.into());
}
};
let (res, ecx) = eval_body_and_ecx(tcx, cid, None, key.param_env);
res.and_then(|op| {
let normalize = tcx.is_static(def_id).is_none() && cid.promoted.is_none();
if !normalize {
match op.op {
Operand::Indirect(_) => { },
Operand::Immediate(_) => bug!("const eval gave us an Immediate"),
}
}
op_to_const(&ecx, op, normalize)
}).map_err(|err| {
let (trace, span) = ecx.generate_stacktrace(None);
let err = ConstEvalErr {
error: err,
stacktrace: trace,
span,
};
if tcx.is_static(def_id).is_some() {
err.report_as_error(ecx.tcx, "could not evaluate static initializer");
if tcx.sess.err_count() == 0 {
span_bug!(span, "static eval failure didn't emit an error: {:#?}", err);
}
}
err.into()
})
}