Auto merge of #6091 - ebroto:rustup, r=ebroto

Rustup

changelog: none

r? `@ghost`
This commit is contained in:
bors 2020-09-27 13:33:48 +00:00
commit db6fb90bc0
5 changed files with 351 additions and 1 deletions

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@ -6,6 +6,7 @@
#![feature(concat_idents)]
#![feature(crate_visibility_modifier)]
#![feature(drain_filter)]
#![feature(in_band_lifetimes)]
#![feature(or_patterns)]
#![feature(rustc_private)]
#![feature(stmt_expr_attributes)]

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@ -1,10 +1,10 @@
use crate::utils::qualify_min_const_fn::is_min_const_fn;
use crate::utils::{fn_has_unsatisfiable_preds, has_drop, is_entrypoint_fn, span_lint, trait_ref_of_method};
use rustc_hir as hir;
use rustc_hir::intravisit::FnKind;
use rustc_hir::{Body, Constness, FnDecl, GenericParamKind, HirId};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::lint::in_external_macro;
use rustc_mir::transform::qualify_min_const_fn::is_min_const_fn;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::Span;
use rustc_typeck::hir_ty_to_ty;

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@ -87,6 +87,7 @@ fn check_fn(
let maybe_storage_live_result = MaybeStorageLive
.into_engine(cx.tcx, mir, def_id.to_def_id())
.pass_name("redundant_clone")
.iterate_to_fixpoint()
.into_results_cursor(mir);
let mut possible_borrower = {

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@ -18,6 +18,7 @@
pub mod numeric_literal;
pub mod paths;
pub mod ptr;
pub mod qualify_min_const_fn;
pub mod sugg;
pub mod usage;

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@ -0,0 +1,347 @@
use rustc_hir as hir;
use rustc_hir::def_id::DefId;
use rustc_middle::mir::{
Body, CastKind, NullOp, Operand, Place, ProjectionElem, Rvalue, Statement, StatementKind, Terminator,
TerminatorKind,
};
use rustc_middle::ty::subst::GenericArgKind;
use rustc_middle::ty::{self, adjustment::PointerCast, Ty, TyCtxt};
use rustc_span::symbol::sym;
use rustc_span::Span;
use rustc_target::spec::abi::Abi::RustIntrinsic;
use std::borrow::Cow;
type McfResult = Result<(), (Span, Cow<'static, str>)>;
pub fn is_min_const_fn(tcx: TyCtxt<'tcx>, def_id: DefId, body: &'a Body<'tcx>) -> McfResult {
let mut current = def_id;
loop {
let predicates = tcx.predicates_of(current);
for (predicate, _) in predicates.predicates {
match predicate.skip_binders() {
ty::PredicateAtom::RegionOutlives(_)
| ty::PredicateAtom::TypeOutlives(_)
| ty::PredicateAtom::WellFormed(_)
| ty::PredicateAtom::Projection(_)
| ty::PredicateAtom::ConstEvaluatable(..)
| ty::PredicateAtom::ConstEquate(..)
| ty::PredicateAtom::TypeWellFormedFromEnv(..) => continue,
ty::PredicateAtom::ObjectSafe(_) => panic!("object safe predicate on function: {:#?}", predicate),
ty::PredicateAtom::ClosureKind(..) => panic!("closure kind predicate on function: {:#?}", predicate),
ty::PredicateAtom::Subtype(_) => panic!("subtype predicate on function: {:#?}", predicate),
ty::PredicateAtom::Trait(pred, _) => {
if Some(pred.def_id()) == tcx.lang_items().sized_trait() {
continue;
}
match pred.self_ty().kind() {
ty::Param(ref p) => {
let generics = tcx.generics_of(current);
let def = generics.type_param(p, tcx);
let span = tcx.def_span(def.def_id);
return Err((
span,
"trait bounds other than `Sized` \
on const fn parameters are unstable"
.into(),
));
},
// other kinds of bounds are either tautologies
// or cause errors in other passes
_ => continue,
}
},
}
}
match predicates.parent {
Some(parent) => current = parent,
None => break,
}
}
for local in &body.local_decls {
check_ty(tcx, local.ty, local.source_info.span)?;
}
// impl trait is gone in MIR, so check the return type manually
check_ty(
tcx,
tcx.fn_sig(def_id).output().skip_binder(),
body.local_decls.iter().next().unwrap().source_info.span,
)?;
for bb in body.basic_blocks() {
check_terminator(tcx, body, bb.terminator())?;
for stmt in &bb.statements {
check_statement(tcx, body, def_id, stmt)?;
}
}
Ok(())
}
fn check_ty(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, span: Span) -> McfResult {
for arg in ty.walk() {
let ty = match arg.unpack() {
GenericArgKind::Type(ty) => ty,
// No constraints on lifetimes or constants, except potentially
// constants' types, but `walk` will get to them as well.
GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => continue,
};
match ty.kind() {
ty::Ref(_, _, hir::Mutability::Mut) => {
return Err((span, "mutable references in const fn are unstable".into()));
},
ty::Opaque(..) => return Err((span, "`impl Trait` in const fn is unstable".into())),
ty::FnPtr(..) => {
return Err((span, "function pointers in const fn are unstable".into()));
},
ty::Dynamic(preds, _) => {
for pred in preds.iter() {
match pred.skip_binder() {
ty::ExistentialPredicate::AutoTrait(_) | ty::ExistentialPredicate::Projection(_) => {
return Err((
span,
"trait bounds other than `Sized` \
on const fn parameters are unstable"
.into(),
));
},
ty::ExistentialPredicate::Trait(trait_ref) => {
if Some(trait_ref.def_id) != tcx.lang_items().sized_trait() {
return Err((
span,
"trait bounds other than `Sized` \
on const fn parameters are unstable"
.into(),
));
}
},
}
}
},
_ => {},
}
}
Ok(())
}
fn check_rvalue(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, def_id: DefId, rvalue: &Rvalue<'tcx>, span: Span) -> McfResult {
match rvalue {
Rvalue::ThreadLocalRef(_) => Err((span, "cannot access thread local storage in const fn".into())),
Rvalue::Repeat(operand, _) | Rvalue::Use(operand) => check_operand(tcx, operand, span, body),
Rvalue::Len(place) | Rvalue::Discriminant(place) | Rvalue::Ref(_, _, place) | Rvalue::AddressOf(_, place) => {
check_place(tcx, *place, span, body)
},
Rvalue::Cast(CastKind::Misc, operand, cast_ty) => {
use rustc_middle::ty::cast::CastTy;
let cast_in = CastTy::from_ty(operand.ty(body, tcx)).expect("bad input type for cast");
let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast");
match (cast_in, cast_out) {
(CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) => {
Err((span, "casting pointers to ints is unstable in const fn".into()))
},
_ => check_operand(tcx, operand, span, body),
}
},
Rvalue::Cast(CastKind::Pointer(PointerCast::MutToConstPointer | PointerCast::ArrayToPointer), operand, _) => {
check_operand(tcx, operand, span, body)
},
Rvalue::Cast(
CastKind::Pointer(
PointerCast::UnsafeFnPointer | PointerCast::ClosureFnPointer(_) | PointerCast::ReifyFnPointer,
),
_,
_,
) => Err((span, "function pointer casts are not allowed in const fn".into())),
Rvalue::Cast(CastKind::Pointer(PointerCast::Unsize), op, cast_ty) => {
let pointee_ty = if let Some(deref_ty) = cast_ty.builtin_deref(true) {
deref_ty.ty
} else {
// We cannot allow this for now.
return Err((span, "unsizing casts are only allowed for references right now".into()));
};
let unsized_ty = tcx.struct_tail_erasing_lifetimes(pointee_ty, tcx.param_env(def_id));
if let ty::Slice(_) | ty::Str = unsized_ty.kind() {
check_operand(tcx, op, span, body)?;
// Casting/coercing things to slices is fine.
Ok(())
} else {
// We just can't allow trait objects until we have figured out trait method calls.
Err((span, "unsizing casts are not allowed in const fn".into()))
}
},
// binops are fine on integers
Rvalue::BinaryOp(_, lhs, rhs) | Rvalue::CheckedBinaryOp(_, lhs, rhs) => {
check_operand(tcx, lhs, span, body)?;
check_operand(tcx, rhs, span, body)?;
let ty = lhs.ty(body, tcx);
if ty.is_integral() || ty.is_bool() || ty.is_char() {
Ok(())
} else {
Err((
span,
"only int, `bool` and `char` operations are stable in const fn".into(),
))
}
},
Rvalue::NullaryOp(NullOp::SizeOf, _) => Ok(()),
Rvalue::NullaryOp(NullOp::Box, _) => Err((span, "heap allocations are not allowed in const fn".into())),
Rvalue::UnaryOp(_, operand) => {
let ty = operand.ty(body, tcx);
if ty.is_integral() || ty.is_bool() {
check_operand(tcx, operand, span, body)
} else {
Err((span, "only int and `bool` operations are stable in const fn".into()))
}
},
Rvalue::Aggregate(_, operands) => {
for operand in operands {
check_operand(tcx, operand, span, body)?;
}
Ok(())
},
}
}
fn check_statement(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, def_id: DefId, statement: &Statement<'tcx>) -> McfResult {
let span = statement.source_info.span;
match &statement.kind {
StatementKind::Assign(box (place, rval)) => {
check_place(tcx, *place, span, body)?;
check_rvalue(tcx, body, def_id, rval, span)
},
StatementKind::FakeRead(_, place) |
// just an assignment
StatementKind::SetDiscriminant { place, .. } => check_place(tcx, **place, span, body),
StatementKind::LlvmInlineAsm { .. } => Err((span, "cannot use inline assembly in const fn".into())),
// These are all NOPs
StatementKind::StorageLive(_)
| StatementKind::StorageDead(_)
| StatementKind::Retag { .. }
| StatementKind::AscribeUserType(..)
| StatementKind::Coverage(..)
| StatementKind::Nop => Ok(()),
}
}
fn check_operand(tcx: TyCtxt<'tcx>, operand: &Operand<'tcx>, span: Span, body: &Body<'tcx>) -> McfResult {
match operand {
Operand::Move(place) | Operand::Copy(place) => check_place(tcx, *place, span, body),
Operand::Constant(c) => match c.check_static_ptr(tcx) {
Some(_) => Err((span, "cannot access `static` items in const fn".into())),
None => Ok(()),
},
}
}
fn check_place(tcx: TyCtxt<'tcx>, place: Place<'tcx>, span: Span, body: &Body<'tcx>) -> McfResult {
let mut cursor = place.projection.as_ref();
while let [ref proj_base @ .., elem] = *cursor {
cursor = proj_base;
match elem {
ProjectionElem::Field(..) => {
let base_ty = Place::ty_from(place.local, &proj_base, body, tcx).ty;
if let Some(def) = base_ty.ty_adt_def() {
// No union field accesses in `const fn`
if def.is_union() {
return Err((span, "accessing union fields is unstable".into()));
}
}
},
ProjectionElem::ConstantIndex { .. }
| ProjectionElem::Downcast(..)
| ProjectionElem::Subslice { .. }
| ProjectionElem::Deref
| ProjectionElem::Index(_) => {},
}
}
Ok(())
}
fn check_terminator(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, terminator: &Terminator<'tcx>) -> McfResult {
let span = terminator.source_info.span;
match &terminator.kind {
TerminatorKind::FalseEdge { .. }
| TerminatorKind::FalseUnwind { .. }
| TerminatorKind::Goto { .. }
| TerminatorKind::Return
| TerminatorKind::Resume
| TerminatorKind::Unreachable => Ok(()),
TerminatorKind::Drop { place, .. } => check_place(tcx, *place, span, body),
TerminatorKind::DropAndReplace { place, value, .. } => {
check_place(tcx, *place, span, body)?;
check_operand(tcx, value, span, body)
},
TerminatorKind::SwitchInt {
discr,
switch_ty: _,
values: _,
targets: _,
} => check_operand(tcx, discr, span, body),
TerminatorKind::Abort => Err((span, "abort is not stable in const fn".into())),
TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => {
Err((span, "const fn generators are unstable".into()))
},
TerminatorKind::Call {
func,
args,
from_hir_call: _,
destination: _,
cleanup: _,
fn_span: _,
} => {
let fn_ty = func.ty(body, tcx);
if let ty::FnDef(fn_def_id, _) = *fn_ty.kind() {
if !rustc_mir::const_eval::is_min_const_fn(tcx, fn_def_id) {
return Err((
span,
format!(
"can only call other `const fn` within a `const fn`, \
but `{:?}` is not stable as `const fn`",
func,
)
.into(),
));
}
// HACK: This is to "unstabilize" the `transmute` intrinsic
// within const fns. `transmute` is allowed in all other const contexts.
// This won't really scale to more intrinsics or functions. Let's allow const
// transmutes in const fn before we add more hacks to this.
if tcx.fn_sig(fn_def_id).abi() == RustIntrinsic && tcx.item_name(fn_def_id) == sym::transmute {
return Err((
span,
"can only call `transmute` from const items, not `const fn`".into(),
));
}
check_operand(tcx, func, span, body)?;
for arg in args {
check_operand(tcx, arg, span, body)?;
}
Ok(())
} else {
Err((span, "can only call other const fns within const fn".into()))
}
},
TerminatorKind::Assert {
cond,
expected: _,
msg: _,
target: _,
cleanup: _,
} => check_operand(tcx, cond, span, body),
TerminatorKind::InlineAsm { .. } => Err((span, "cannot use inline assembly in const fn".into())),
}
}