Skip to content

Commit

Permalink
Add a forever unstable opt-out of const qualification checks
Browse files Browse the repository at this point in the history
  • Loading branch information
oli-obk committed Jan 31, 2019
1 parent f40aaa6 commit d0129a6
Show file tree
Hide file tree
Showing 8 changed files with 155 additions and 2 deletions.
2 changes: 2 additions & 0 deletions src/librustc/session/config.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1300,6 +1300,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
"print some statistics about AST and HIR"),
always_encode_mir: bool = (false, parse_bool, [TRACKED],
"encode MIR of all functions into the crate metadata"),
unleash_the_miri_inside_of_you: bool = (false, parse_bool, [TRACKED],
"take the breaks off const evaluation. NOTE: this is unsound"),
osx_rpath_install_name: bool = (false, parse_bool, [TRACKED],
"pass `-install_name @rpath/...` to the macOS linker"),
sanitizer: Option<Sanitizer> = (None, parse_sanitizer, [TRACKED],
Expand Down
29 changes: 27 additions & 2 deletions src/librustc_mir/transform/qualify_consts.rs
Original file line number Diff line number Diff line change
Expand Up @@ -108,6 +108,15 @@ struct Qualifier<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
promotion_candidates: Vec<Candidate>
}

macro_rules! unleash_miri {
($this:expr) => {{
if $this.tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
$this.tcx.sess.span_warn($this.span, "skipping const checks");
return;
}
}}
}

impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
def_id: DefId,
Expand Down Expand Up @@ -147,6 +156,7 @@ impl<'a, 'tcx> Qualifier<'a, 'tcx, 'tcx> {
// categories, but enabling full miri would make that
// slightly pointless (even with feature-gating).
fn not_const(&mut self) {
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
if self.mode != Mode::Fn {
let mut err = struct_span_err!(
Expand Down Expand Up @@ -419,6 +429,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
}
return;
}
unleash_miri!(self);
self.add(Qualif::NOT_CONST);

if self.mode != Mode::Fn {
Expand Down Expand Up @@ -618,6 +629,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
}

if forbidden_mut {
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
if self.mode != Mode::Fn {
let mut err = struct_span_err!(self.tcx.sess, self.span, E0017,
Expand Down Expand Up @@ -660,6 +672,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {

debug!("visit_rvalue: forbidden_mut={:?}", forbidden_mut);
if forbidden_mut {
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
} else {
// We might have a candidate for promotion.
Expand Down Expand Up @@ -700,6 +713,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
match (cast_in, cast_out) {
(CastTy::Ptr(_), CastTy::Int(_)) |
(CastTy::FnPtr, CastTy::Int(_)) => {
unleash_miri!(self);
if let Mode::Fn = self.mode {
// in normal functions, mark such casts as not promotable
self.add(Qualif::NOT_CONST);
Expand Down Expand Up @@ -727,6 +741,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
op == BinOp::Ge || op == BinOp::Gt ||
op == BinOp::Offset);

unleash_miri!(self);
if let Mode::Fn = self.mode {
// raw pointer operations are not allowed inside promoteds
self.add(Qualif::NOT_CONST);
Expand All @@ -745,6 +760,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
}

Rvalue::NullaryOp(NullOp::Box, _) => {
unleash_miri!(self);
self.add(Qualif::NOT_CONST);
if self.mode != Mode::Fn {
let mut err = struct_span_err!(self.tcx.sess, self.span, E0010,
Expand Down Expand Up @@ -861,7 +877,13 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {
} else {
// stable const fns or unstable const fns with their feature gate
// active
if self.tcx.is_const_fn(def_id) {
let unleash_miri = self
.tcx
.sess
.opts
.debugging_opts
.unleash_the_miri_inside_of_you;
if self.tcx.is_const_fn(def_id) || unleash_miri {
is_const_fn = true;
} else if self.is_const_panic_fn(def_id) {
// Check the const_panic feature gate.
Expand Down Expand Up @@ -1030,6 +1052,7 @@ impl<'a, 'tcx> Visitor<'tcx> for Qualifier<'a, 'tcx, 'tcx> {

// Deny *any* live drops anywhere other than functions.
if self.mode != Mode::Fn {
unleash_miri!(self);
// HACK(eddyb): emulate a bit of dataflow analysis,
// conservatively, that drop elaboration will do.
let needs_drop = if let Place::Local(local) = *place {
Expand Down Expand Up @@ -1175,7 +1198,9 @@ impl MirPass for QualifyAndPromoteConstants {
let (temps, candidates) = {
let mut qualifier = Qualifier::new(tcx, def_id, mir, mode);
if mode == Mode::ConstFn {
if tcx.is_min_const_fn(def_id) {
if tcx.sess.opts.debugging_opts.unleash_the_miri_inside_of_you {
qualifier.qualify_const();
} else if tcx.is_min_const_fn(def_id) {
// enforce `min_const_fn` for stable const fns
use super::qualify_min_const_fn::is_min_const_fn;
if let Err((span, err)) = is_min_const_fn(tcx, def_id, mir) {
Expand Down
30 changes: 30 additions & 0 deletions src/test/ui/consts/miri_unleashed/assoc_const.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
// compile-flags: -Zunleash-the-miri-inside-of-you
#![allow(const_err)]

// a test demonstrating why we do need to run static const qualification on associated constants
// instead of just checking the final constant

trait Foo<T> {
const X: T;
}

trait Bar<T, U: Foo<T>> {
const F: u32 = (U::X, 42).1; //~ WARN skipping const checks
}

impl Foo<u32> for () {
const X: u32 = 42;
}
impl Foo<Vec<u32>> for String {
const X: Vec<u32> = Vec::new();
}

impl Bar<u32, ()> for () {}
impl Bar<Vec<u32>, String> for String {}

fn main() {
// this is fine, but would have been forbidden by the static checks on `F`
let x = <() as Bar<u32, ()>>::F;
// this test only causes errors due to the line below, so post-monomorphization
let y = <String as Bar<Vec<u32>, String>>::F; //~ ERROR erroneous constant
}
15 changes: 15 additions & 0 deletions src/test/ui/consts/miri_unleashed/assoc_const.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
warning: skipping const checks
--> $DIR/assoc_const.rs:12:31
|
LL | const F: u32 = (U::X, 42).1; //~ WARN skipping const checks
| ^

error[E0080]: erroneous constant used
--> $DIR/assoc_const.rs:29:13
|
LL | let y = <String as Bar<Vec<u32>, String>>::F; //~ ERROR erroneous constant
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ referenced constant has errors

error: aborting due to previous error

For more information about this error, try `rustc --explain E0080`.
28 changes: 28 additions & 0 deletions src/test/ui/consts/miri_unleashed/assoc_const_2.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,28 @@
#![allow(const_err)]

// a test demonstrating that const qualification cannot prevent monomorphization time errors

trait Foo {
const X: u32;
}

trait Bar<U: Foo> {
const F: u32 = 100 / U::X;
}

impl Foo for () {
const X: u32 = 42;
}

impl Foo for String {
const X: u32 = 0;
}

impl Bar<()> for () {}
impl Bar<String> for String {}

fn main() {
let x = <() as Bar<()>>::F;
// this test only causes errors due to the line below, so post-monomorphization
let y = <String as Bar<String>>::F; //~ ERROR erroneous constant
}
9 changes: 9 additions & 0 deletions src/test/ui/consts/miri_unleashed/assoc_const_2.stderr
Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
error[E0080]: erroneous constant used
--> $DIR/assoc_const_2.rs:27:13
|
LL | let y = <String as Bar<String>>::F; //~ ERROR erroneous constant
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ referenced constant has errors

error: aborting due to previous error

For more information about this error, try `rustc --explain E0080`.
Original file line number Diff line number Diff line change
@@ -0,0 +1,27 @@
#![allow(const_err)]

// a test demonstrating why we do need to run static const qualification on associated constants
// instead of just checking the final constant

trait Foo<T> {
const X: T;
}

trait Bar<T, U: Foo<T>> {
const F: u32 = (U::X, 42).1; //~ ERROR destructors cannot be evaluated at compile-time
}

impl Foo<u32> for () {
const X: u32 = 42;
}
impl Foo<Vec<u32>> for String {
const X: Vec<u32> = Vec::new(); //~ ERROR not yet stable as a const fn
}

impl Bar<u32, ()> for () {}
impl Bar<Vec<u32>, String> for String {}

fn main() {
let x = <() as Bar<u32, ()>>::F;
let y = <String as Bar<Vec<u32>, String>>::F;
}
Original file line number Diff line number Diff line change
@@ -0,0 +1,17 @@
error[E0493]: destructors cannot be evaluated at compile-time
--> $DIR/feature-gate-unleash_the_miri_inside_of_you.rs:11:20
|
LL | const F: u32 = (U::X, 42).1; //~ ERROR destructors cannot be evaluated at compile-time
| ^^^^^^^^^^ constants cannot evaluate destructors

error: `<std::vec::Vec<T>>::new` is not yet stable as a const fn
--> $DIR/feature-gate-unleash_the_miri_inside_of_you.rs:18:25
|
LL | const X: Vec<u32> = Vec::new(); //~ ERROR not yet stable as a const fn
| ^^^^^^^^^^
|
= help: add `#![feature(const_vec_new)]` to the crate attributes to enable

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0493`.

0 comments on commit d0129a6

Please sign in to comment.