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Auto merge of #132276 - compiler-errors:enforce-fx-in-mir, r=<try>
Double-check conditional constness in MIR To prevent any unchecked `~const` bounds from leaking through during MIR lowering. If this check fails, it will eventually just delay a bug, but for now it reports errors. That error reporting may be redundant if we're calling it from code that already doesn't allow `~const` (i.e. when the `effects` and `const_trait_impl` gates are disabled), but I don't think it's that big of a deal. edit: This also makes sure that we issue a const stability error if we encounter *any* function with const conditions when `const_trait_impl` is not enabled. This ensures that that feature remains airtight.
2 parents 20c909f + 505e083 commit 95d3a79

13 files changed

+185
-54
lines changed

‎compiler/rustc_const_eval/src/check_consts/check.rs‎

Lines changed: 72 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -11,7 +11,6 @@ use rustc_hir::def_id::DefId;
1111
use rustc_hir::{self as hir, LangItem};
1212
use rustc_index::bit_set::BitSet;
1313
use rustc_infer::infer::TyCtxtInferExt;
14-
use rustc_infer::traits::ObligationCause;
1514
use rustc_middle::mir::visit::Visitor;
1615
use rustc_middle::mir::*;
1716
use rustc_middle::span_bug;
@@ -20,9 +19,11 @@ use rustc_middle::ty::{self, Instance, InstanceKind, Ty, TypeVisitableExt, Typin
2019
use rustc_mir_dataflow::Analysis;
2120
use rustc_mir_dataflow::impls::MaybeStorageLive;
2221
use rustc_mir_dataflow::storage::always_storage_live_locals;
23-
use rustc_span::{DUMMY_SP, Span, Symbol, sym};
22+
use rustc_span::{Span, Symbol, sym};
2423
use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
25-
use rustc_trait_selection::traits::{self, ObligationCauseCode, ObligationCtxt};
24+
use rustc_trait_selection::traits::{
25+
Obligation, ObligationCause, ObligationCauseCode, ObligationCtxt,
26+
};
2627
use tracing::{debug, instrument, trace};
2728

2829
use super::ops::{self, NonConstOp, Status};
@@ -360,6 +361,73 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
360361
// end of evaluation.
361362
!is_transient
362363
}
364+
365+
fn revalidate_conditional_constness(
366+
&mut self,
367+
callee: DefId,
368+
callee_args: ty::GenericArgsRef<'tcx>,
369+
call_source: CallSource,
370+
call_span: Span,
371+
) {
372+
let tcx = self.tcx;
373+
if !tcx.is_conditionally_const(callee) {
374+
return;
375+
}
376+
377+
let const_conditions = tcx.const_conditions(callee).instantiate(tcx, callee_args);
378+
// If there are any const conditions on this fn and `const_trait_impl`
379+
// is not enabled, simply bail. We shouldn't be able to call conditionally
380+
// const functions on stable.
381+
if !const_conditions.is_empty() && !tcx.features().const_trait_impl() {
382+
self.check_op(ops::FnCallNonConst {
383+
callee,
384+
args: callee_args,
385+
span: call_span,
386+
call_source,
387+
feature: Some(sym::const_trait_impl),
388+
});
389+
return;
390+
}
391+
392+
let infcx = tcx.infer_ctxt().build(TypingMode::from_param_env(self.param_env));
393+
let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
394+
395+
let body_id = self.body.source.def_id().expect_local();
396+
let host_polarity = match self.const_kind() {
397+
hir::ConstContext::ConstFn => ty::BoundConstness::Maybe,
398+
hir::ConstContext::Static(_) | hir::ConstContext::Const { .. } => {
399+
ty::BoundConstness::Const
400+
}
401+
};
402+
let const_conditions = ocx.normalize(
403+
&ObligationCause::misc(call_span, body_id),
404+
self.param_env,
405+
const_conditions,
406+
);
407+
ocx.register_obligations(const_conditions.into_iter().map(|(trait_ref, span)| {
408+
Obligation::new(
409+
tcx,
410+
ObligationCause::new(
411+
call_span,
412+
body_id,
413+
ObligationCauseCode::WhereClause(callee, span),
414+
),
415+
self.param_env,
416+
trait_ref.to_host_effect_clause(tcx, host_polarity),
417+
)
418+
}));
419+
420+
let errors = ocx.select_all_or_error();
421+
if !errors.is_empty() {
422+
// FIXME(effects): Soon this should be unconditionally delaying a bug.
423+
if matches!(call_source, CallSource::Normal) && tcx.features().effects() {
424+
tcx.dcx()
425+
.span_delayed_bug(call_span, "this should have reported a ~const error in HIR");
426+
} else {
427+
infcx.err_ctxt().report_fulfillment_errors(errors);
428+
}
429+
}
430+
}
363431
}
364432

365433
impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
@@ -566,7 +634,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
566634
};
567635

568636
let ConstCx { tcx, body, param_env, .. } = *self.ccx;
569-
let caller = self.def_id();
570637

571638
let fn_ty = func.ty(body, tcx);
572639

@@ -584,31 +651,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
584651
}
585652
};
586653

587-
// Check that all trait bounds that are marked as `~const` can be satisfied.
588-
//
589-
// Typeck only does a "non-const" check since it operates on HIR and cannot distinguish
590-
// which path expressions are getting called on and which path expressions are only used
591-
// as function pointers. This is required for correctness.
592-
let infcx = tcx.infer_ctxt().build(TypingMode::from_param_env(param_env));
593-
let ocx = ObligationCtxt::new_with_diagnostics(&infcx);
594-
595-
let predicates = tcx.predicates_of(callee).instantiate(tcx, fn_args);
596-
let cause = ObligationCause::new(
597-
terminator.source_info.span,
598-
self.body.source.def_id().expect_local(),
599-
ObligationCauseCode::WhereClause(callee, DUMMY_SP),
600-
);
601-
let normalized_predicates = ocx.normalize(&cause, param_env, predicates);
602-
ocx.register_obligations(traits::predicates_for_generics(
603-
|_, _| cause.clone(),
604-
self.param_env,
605-
normalized_predicates,
606-
));
607-
608-
let errors = ocx.select_all_or_error();
609-
if !errors.is_empty() {
610-
infcx.err_ctxt().report_fulfillment_errors(errors);
611-
}
654+
self.revalidate_conditional_constness(callee, fn_args, call_source, *fn_span);
612655

613656
let mut is_trait = false;
614657
// Attempting to call a trait method?
@@ -648,7 +691,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
648691
None
649692
};
650693
self.check_op(ops::FnCallNonConst {
651-
caller,
652694
callee,
653695
args: fn_args,
654696
span: *fn_span,
@@ -738,7 +780,6 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
738780
// Trait functions are not `const fn` so we have to skip them here.
739781
if !tcx.is_const_fn(callee) && !is_trait {
740782
self.check_op(ops::FnCallNonConst {
741-
caller,
742783
callee,
743784
args: fn_args,
744785
span: *fn_span,

‎compiler/rustc_const_eval/src/check_consts/ops.rs‎

Lines changed: 4 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,5 @@
11
//! Concrete error types for all operations which may be invalid in a certain const context.
22
3-
use hir::def_id::LocalDefId;
43
use hir::{ConstContext, LangItem};
54
use rustc_errors::Diag;
65
use rustc_errors::codes::*;
@@ -74,7 +73,6 @@ impl<'tcx> NonConstOp<'tcx> for FnCallIndirect {
7473
/// A function call where the callee is not marked as `const`.
7574
#[derive(Debug, Clone, Copy)]
7675
pub(crate) struct FnCallNonConst<'tcx> {
77-
pub caller: LocalDefId,
7876
pub callee: DefId,
7977
pub args: GenericArgsRef<'tcx>,
8078
pub span: Span,
@@ -87,8 +85,9 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
8785
#[allow(rustc::diagnostic_outside_of_impl)]
8886
#[allow(rustc::untranslatable_diagnostic)]
8987
fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, _: Span) -> Diag<'tcx> {
90-
let FnCallNonConst { caller, callee, args, span, call_source, feature } = *self;
91-
let ConstCx { tcx, param_env, body, .. } = *ccx;
88+
let FnCallNonConst { callee, args, span, call_source, feature } = *self;
89+
let ConstCx { tcx, param_env, .. } = *ccx;
90+
let caller = ccx.def_id();
9291

9392
let diag_trait = |err, self_ty: Ty<'_>, trait_id| {
9493
let trait_ref = TraitRef::from_method(tcx, trait_id, args);
@@ -289,7 +288,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
289288
if let Some(feature) = feature {
290289
ccx.tcx.disabled_nightly_features(
291290
&mut err,
292-
body.source.def_id().as_local().map(|local| ccx.tcx.local_def_id_to_hir_id(local)),
291+
Some(ccx.tcx.local_def_id_to_hir_id(caller)),
293292
[(String::new(), feature)],
294293
);
295294
}

‎tests/ui/traits/const-traits/const-drop-fail-2.stderr‎

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -29,6 +29,12 @@ LL | const fn check<T: ~const Destruct>(_: T) {}
2929
| |
3030
| the destructor for this type cannot be evaluated in constant functions
3131

32+
error[E0277]: the trait bound `T: ~const A` is not satisfied
33+
--> $DIR/const-drop-fail-2.rs:41:9
34+
|
35+
LL | T::a();
36+
| ^^^^^^
37+
3238
error[E0015]: cannot call non-const fn `<T as A>::a` in constant functions
3339
--> $DIR/const-drop-fail-2.rs:41:9
3440
|
@@ -41,7 +47,7 @@ help: add `#![feature(effects)]` to the crate attributes to enable
4147
LL + #![feature(effects)]
4248
|
4349

44-
error: aborting due to 5 previous errors
50+
error: aborting due to 6 previous errors
4551

46-
Some errors have detailed explanations: E0015, E0493.
52+
Some errors have detailed explanations: E0015, E0277, E0493.
4753
For more information about an error, try `rustc --explain E0015`.

‎tests/ui/traits/const-traits/const-drop.precise.stderr‎

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -78,6 +78,12 @@ error[E0493]: destructor of `T` cannot be evaluated at compile-time
7878
LL | const fn a<T: ~const Destruct>(_: T) {}
7979
| ^ the destructor for this type cannot be evaluated in constant functions
8080

81+
error[E0277]: the trait bound `T: ~const SomeTrait` is not satisfied
82+
--> $DIR/const-drop.rs:69:13
83+
|
84+
LL | T::foo();
85+
| ^^^^^^^^
86+
8187
error[E0015]: cannot call non-const fn `<T as SomeTrait>::foo` in constant functions
8288
--> $DIR/const-drop.rs:69:13
8389
|
@@ -90,7 +96,7 @@ help: add `#![feature(effects)]` to the crate attributes to enable
9096
LL + #![feature(effects)]
9197
|
9298

93-
error: aborting due to 10 previous errors
99+
error: aborting due to 11 previous errors
94100

95101
Some errors have detailed explanations: E0015, E0277, E0493.
96102
For more information about an error, try `rustc --explain E0015`.

‎tests/ui/traits/const-traits/const-drop.stock.stderr‎

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -80,6 +80,12 @@ LL | const fn a<T: ~const Destruct>(_: T) {}
8080
| |
8181
| the destructor for this type cannot be evaluated in constant functions
8282

83+
error[E0277]: the trait bound `T: ~const SomeTrait` is not satisfied
84+
--> $DIR/const-drop.rs:69:13
85+
|
86+
LL | T::foo();
87+
| ^^^^^^^^
88+
8389
error[E0015]: cannot call non-const fn `<T as SomeTrait>::foo` in constant functions
8490
--> $DIR/const-drop.rs:69:13
8591
|
@@ -92,7 +98,7 @@ help: add `#![feature(effects)]` to the crate attributes to enable
9298
LL + #![feature(effects)]
9399
|
94100

95-
error: aborting due to 10 previous errors
101+
error: aborting due to 11 previous errors
96102

97103
Some errors have detailed explanations: E0015, E0277, E0493.
98104
For more information about an error, try `rustc --explain E0015`.

‎tests/ui/traits/const-traits/cross-crate.rs‎

Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -18,10 +18,11 @@ const fn const_context() {
1818
#[cfg(any(stocknc, gatednc))]
1919
NonConst.func();
2020
//[stocknc]~^ ERROR: cannot call
21-
//[gatednc]~^^ ERROR: the trait bound
21+
//[stocknc]~| ERROR: cannot call
22+
//[gatednc]~^^^ ERROR: the trait bound
2223
Const.func();
23-
//[stock]~^ ERROR: cannot call
24-
//[stocknc]~^^ ERROR: cannot call
24+
//[stock,stocknc]~^ ERROR: cannot call
25+
//[stock,stocknc]~| ERROR: cannot call
2526
}
2627

2728
fn main() {}

‎tests/ui/traits/const-traits/cross-crate.stock.stderr‎

Lines changed: 15 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,5 @@
11
error[E0015]: cannot call non-const fn `<cross_crate::Const as cross_crate::MyTrait>::func` in constant functions
2-
--> $DIR/cross-crate.rs:22:11
2+
--> $DIR/cross-crate.rs:23:11
33
|
44
LL | Const.func();
55
| ^^^^^^
@@ -10,6 +10,19 @@ help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
1010
LL + #![feature(const_trait_impl)]
1111
|
1212

13-
error: aborting due to 1 previous error
13+
error[E0015]: cannot call non-const fn `<cross_crate::Const as cross_crate::MyTrait>::func` in constant functions
14+
--> $DIR/cross-crate.rs:23:11
15+
|
16+
LL | Const.func();
17+
| ^^^^^^
18+
|
19+
= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
20+
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
21+
help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
22+
|
23+
LL + #![feature(const_trait_impl)]
24+
|
25+
26+
error: aborting due to 2 previous errors
1427

1528
For more information about this error, try `rustc --explain E0015`.

‎tests/ui/traits/const-traits/cross-crate.stocknc.stderr‎

Lines changed: 28 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -10,18 +10,44 @@ help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
1010
LL + #![feature(const_trait_impl)]
1111
|
1212

13+
error[E0015]: cannot call non-const fn `<cross_crate::NonConst as cross_crate::MyTrait>::func` in constant functions
14+
--> $DIR/cross-crate.rs:19:14
15+
|
16+
LL | NonConst.func();
17+
| ^^^^^^
18+
|
19+
= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
20+
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
21+
help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
22+
|
23+
LL + #![feature(const_trait_impl)]
24+
|
25+
26+
error[E0015]: cannot call non-const fn `<cross_crate::Const as cross_crate::MyTrait>::func` in constant functions
27+
--> $DIR/cross-crate.rs:23:11
28+
|
29+
LL | Const.func();
30+
| ^^^^^^
31+
|
32+
= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
33+
help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
34+
|
35+
LL + #![feature(const_trait_impl)]
36+
|
37+
1338
error[E0015]: cannot call non-const fn `<cross_crate::Const as cross_crate::MyTrait>::func` in constant functions
14-
--> $DIR/cross-crate.rs:22:11
39+
--> $DIR/cross-crate.rs:23:11
1540
|
1641
LL | Const.func();
1742
| ^^^^^^
1843
|
1944
= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
45+
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
2046
help: add `#![feature(const_trait_impl)]` to the crate attributes to enable
2147
|
2248
LL + #![feature(const_trait_impl)]
2349
|
2450

25-
error: aborting due to 2 previous errors
51+
error: aborting due to 4 previous errors
2652

2753
For more information about this error, try `rustc --explain E0015`.

‎tests/ui/traits/const-traits/default-method-body-is-const-body-checking.rs‎

Lines changed: 1 addition & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,3 @@
1-
//@ known-bug: #110395
2-
//@ check-pass
3-
41
#![feature(const_trait_impl)]
52

63
#[const_trait]
@@ -13,7 +10,7 @@ const fn foo<T>() where T: ~const Tr {}
1310
pub trait Foo {
1411
fn foo() {
1512
foo::<()>();
16-
//FIXME ~^ ERROR the trait bound `(): Tr` is not satisfied
13+
//~^ ERROR the trait bound `(): ~const Tr` is not satisfied
1714
}
1815
}
1916

‎tests/ui/traits/const-traits/default-method-body-is-const-body-checking.stderr‎

Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
1+
error[E0277]: the trait bound `(): ~const Tr` is not satisfied
2+
--> $DIR/default-method-body-is-const-body-checking.rs:12:9
3+
|
4+
LL | foo::<()>();
5+
| ^^^^^^^^^^^
6+
|
7+
note: required by a bound in `foo`
8+
--> $DIR/default-method-body-is-const-body-checking.rs:7:28
9+
|
10+
LL | const fn foo<T>() where T: ~const Tr {}
11+
| ^^^^^^ required by this bound in `foo`
12+
13+
error: aborting due to 1 previous error
14+
15+
For more information about this error, try `rustc --explain E0277`.

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