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Prevent spurious unreachable pattern lints #115937

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Oct 11, 2023
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Prevent spurious unreachable pattern lints #115937

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d1fd11f
Prevent spurious `unreachable pattern` lints
oli-obk Sep 18, 2023
e83467c
Avoid emitting the non_exhaustive error if other errors already occurred
oli-obk Sep 19, 2023
eca786c
Remember the `ErrorReported` used to silence follow up errors instead…
oli-obk Sep 28, 2023
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13 changes: 8 additions & 5 deletions compiler/rustc_middle/src/thir.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -581,13 +581,13 @@ pub enum BindingMode {
ByRef(BorrowKind),
}

#[derive(Clone, Debug, HashStable)]
#[derive(Clone, Debug, HashStable, TypeVisitable)]
pub struct FieldPat<'tcx> {
pub field: FieldIdx,
pub pattern: Box<Pat<'tcx>>,
}

#[derive(Clone, Debug, HashStable)]
#[derive(Clone, Debug, HashStable, TypeVisitable)]
pub struct Pat<'tcx> {
pub ty: Ty<'tcx>,
pub span: Span,
Expand Down Expand Up @@ -664,7 +664,7 @@ impl<'tcx> IntoDiagnosticArg for Pat<'tcx> {
}
}

#[derive(Clone, Debug, HashStable)]
#[derive(Clone, Debug, HashStable, TypeVisitable)]
pub struct Ascription<'tcx> {
pub annotation: CanonicalUserTypeAnnotation<'tcx>,
/// Variance to use when relating the `user_ty` to the **type of the value being
Expand All @@ -688,7 +688,7 @@ pub struct Ascription<'tcx> {
pub variance: ty::Variance,
}

#[derive(Clone, Debug, HashStable)]
#[derive(Clone, Debug, HashStable, TypeVisitable)]
pub enum PatKind<'tcx> {
/// A wildcard pattern: `_`.
Wild,
Expand All @@ -702,7 +702,9 @@ pub enum PatKind<'tcx> {
Binding {
mutability: Mutability,
name: Symbol,
#[type_visitable(ignore)]
mode: BindingMode,
#[type_visitable(ignore)]
var: LocalVarId,
ty: Ty<'tcx>,
subpattern: Option<Box<Pat<'tcx>>>,
Expand Down Expand Up @@ -771,10 +773,11 @@ pub enum PatKind<'tcx> {
},
}

#[derive(Clone, Debug, PartialEq, HashStable)]
#[derive(Clone, Debug, PartialEq, HashStable, TypeVisitable)]
pub struct PatRange<'tcx> {
pub lo: mir::Const<'tcx>,
pub hi: mir::Const<'tcx>,
#[type_visitable(ignore)]
pub end: RangeEnd,
}

Expand Down
8 changes: 7 additions & 1 deletion compiler/rustc_mir_build/src/thir/pattern/check_match.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ use rustc_hir::HirId;
use rustc_middle::thir::visit::{self, Visitor};
use rustc_middle::thir::*;
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt};
use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt, TypeVisitableExt};
use rustc_session::lint::builtin::{
BINDINGS_WITH_VARIANT_NAME, IRREFUTABLE_LET_PATTERNS, UNREACHABLE_PATTERNS,
};
Expand Down Expand Up @@ -682,6 +682,12 @@ fn non_exhaustive_match<'p, 'tcx>(
arms: &[ArmId],
expr_span: Span,
) -> ErrorGuaranteed {
for &arm in arms {
if let Err(err) = thir[arm].pattern.error_reported() {
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return err;
}
}

let is_empty_match = arms.is_empty();
let non_empty_enum = match scrut_ty.kind() {
ty::Adt(def, _) => def.is_enum() && !def.variants().is_empty(),
Expand Down
85 changes: 48 additions & 37 deletions compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@ use rustc_middle::mir;
use rustc_middle::thir::{FieldPat, Pat, PatKind};
use rustc_middle::ty::{self, Ty, TyCtxt, ValTree};
use rustc_session::lint;
use rustc_span::Span;
use rustc_span::{ErrorGuaranteed, Span};
use rustc_target::abi::{FieldIdx, VariantIdx};
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
use rustc_trait_selection::traits::{self, ObligationCause};
Expand Down Expand Up @@ -48,7 +48,7 @@ struct ConstToPat<'tcx> {
// This tracks if we emitted some hard error for a given const value, so that
// we will not subsequently issue an irrelevant lint for the same const
// value.
saw_const_match_error: Cell<bool>,
saw_const_match_error: Cell<Option<ErrorGuaranteed>>,

// This tracks if we emitted some diagnostic for a given const value, so that
// we will not subsequently issue an irrelevant lint for the same const
Expand Down Expand Up @@ -84,7 +84,7 @@ impl<'tcx> ConstToPat<'tcx> {
span,
infcx,
param_env: pat_ctxt.param_env,
saw_const_match_error: Cell::new(false),
saw_const_match_error: Cell::new(None),
saw_const_match_lint: Cell::new(false),
behind_reference: Cell::new(false),
treat_byte_string_as_slice: pat_ctxt
Expand Down Expand Up @@ -154,7 +154,7 @@ impl<'tcx> ConstToPat<'tcx> {
}),
};

if !self.saw_const_match_error.get() {
if self.saw_const_match_error.get().is_none() {
// If we were able to successfully convert the const to some pat (possibly with some
// lints, but no errors), double-check that all types in the const implement
// `Structural` and `PartialEq`.
Expand All @@ -180,23 +180,26 @@ impl<'tcx> ConstToPat<'tcx> {

if let Some(non_sm_ty) = structural {
if !self.type_has_partial_eq_impl(cv.ty()) {
if let ty::Adt(def, ..) = non_sm_ty.kind() {
let e = if let ty::Adt(def, ..) = non_sm_ty.kind() {
if def.is_union() {
let err = UnionPattern { span: self.span };
self.tcx().sess.emit_err(err);
self.tcx().sess.emit_err(err)
} else {
// fatal avoids ICE from resolution of nonexistent method (rare case).
self.tcx()
.sess
.emit_fatal(TypeNotStructural { span: self.span, non_sm_ty });
.emit_fatal(TypeNotStructural { span: self.span, non_sm_ty })
}
} else {
let err = InvalidPattern { span: self.span, non_sm_ty };
self.tcx().sess.emit_err(err);
}
self.tcx().sess.emit_err(err)
};
// All branches above emitted an error. Don't print any more lints.
// The pattern we return is irrelevant since we errored.
return Box::new(Pat { span: self.span, ty: cv.ty(), kind: PatKind::Wild });
// We errored. Signal that in the pattern, so that follow up errors can be silenced.
let kind = PatKind::Constant {
value: mir::Const::Ty(ty::Const::new_error(self.tcx(), e, cv.ty())),
};
return Box::new(Pat { span: self.span, ty: cv.ty(), kind });
} else if !self.saw_const_match_lint.get() {
if let Some(mir_structural_match_violation) = mir_structural_match_violation {
match non_sm_ty.kind() {
Expand Down Expand Up @@ -330,7 +333,7 @@ impl<'tcx> ConstToPat<'tcx> {
// Backwards compatibility hack because we can't cause hard errors on these
// types, so we compare them via `PartialEq::eq` at runtime.
ty::Adt(..) if !self.type_marked_structural(ty) && self.behind_reference.get() => {
if !self.saw_const_match_error.get() && !self.saw_const_match_lint.get() {
if self.saw_const_match_error.get().is_none() && !self.saw_const_match_lint.get() {
self.saw_const_match_lint.set(true);
tcx.emit_spanned_lint(
lint::builtin::INDIRECT_STRUCTURAL_MATCH,
Expand All @@ -345,18 +348,18 @@ impl<'tcx> ConstToPat<'tcx> {
return Err(FallbackToOpaqueConst);
}
ty::FnDef(..) => {
self.saw_const_match_error.set(true);
tcx.sess.emit_err(InvalidPattern { span, non_sm_ty: ty });
// We errored, so the pattern we generate is irrelevant.
PatKind::Wild
let e = tcx.sess.emit_err(InvalidPattern { span, non_sm_ty: ty });
self.saw_const_match_error.set(Some(e));
// We errored. Signal that in the pattern, so that follow up errors can be silenced.
PatKind::Constant { value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)) }
}
ty::Adt(adt_def, _) if !self.type_marked_structural(ty) => {
debug!("adt_def {:?} has !type_marked_structural for cv.ty: {:?}", adt_def, ty,);
self.saw_const_match_error.set(true);
let err = TypeNotStructural { span, non_sm_ty: ty };
tcx.sess.emit_err(err);
// We errored, so the pattern we generate is irrelevant.
PatKind::Wild
let e = tcx.sess.emit_err(err);
self.saw_const_match_error.set(Some(e));
// We errored. Signal that in the pattern, so that follow up errors can be silenced.
PatKind::Constant { value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)) }
}
ty::Adt(adt_def, args) if adt_def.is_enum() => {
let (&variant_index, fields) = cv.unwrap_branch().split_first().unwrap();
Expand Down Expand Up @@ -416,7 +419,9 @@ impl<'tcx> ConstToPat<'tcx> {
// instead of a hard error.
ty::Adt(_, _) if !self.type_marked_structural(*pointee_ty) => {
if self.behind_reference.get() {
if !self.saw_const_match_error.get() && !self.saw_const_match_lint.get() {
if self.saw_const_match_error.get().is_none()
&& !self.saw_const_match_lint.get()
{
self.saw_const_match_lint.set(true);
tcx.emit_spanned_lint(
lint::builtin::INDIRECT_STRUCTURAL_MATCH,
Expand All @@ -427,14 +432,20 @@ impl<'tcx> ConstToPat<'tcx> {
}
return Err(FallbackToOpaqueConst);
} else {
if !self.saw_const_match_error.get() {
self.saw_const_match_error.set(true);
if let Some(e) = self.saw_const_match_error.get() {
// We already errored. Signal that in the pattern, so that follow up errors can be silenced.
PatKind::Constant {
value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)),
}
} else {
let err = TypeNotStructural { span, non_sm_ty: *pointee_ty };
tcx.sess.emit_err(err);
let e = tcx.sess.emit_err(err);
self.saw_const_match_error.set(Some(e));
// We errored. Signal that in the pattern, so that follow up errors can be silenced.
PatKind::Constant {
value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)),
}
}
tcx.sess.delay_span_bug(span, "`saw_const_match_error` set but no error?");
// We errored, so the pattern we generate is irrelevant.
PatKind::Wild
}
}
// All other references are converted into deref patterns and then recursively
Expand All @@ -443,11 +454,11 @@ impl<'tcx> ConstToPat<'tcx> {
_ => {
if !pointee_ty.is_sized(tcx, param_env) && !pointee_ty.is_slice() {
let err = UnsizedPattern { span, non_sm_ty: *pointee_ty };
tcx.sess.emit_err(err);

// FIXME: introduce PatKind::Error to silence follow up diagnostics due to unreachable patterns.
// We errored, so the pattern we generate is irrelevant.
PatKind::Wild
let e = tcx.sess.emit_err(err);
// We errored. Signal that in the pattern, so that follow up errors can be silenced.
PatKind::Constant {
value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)),
}
} else {
let old = self.behind_reference.replace(true);
// `b"foo"` produces a `&[u8; 3]`, but you can't use constants of array type when
Expand All @@ -474,15 +485,15 @@ impl<'tcx> ConstToPat<'tcx> {
}
ty::FnPtr(..) | ty::RawPtr(..) => unreachable!(),
_ => {
self.saw_const_match_error.set(true);
let err = InvalidPattern { span, non_sm_ty: ty };
tcx.sess.emit_err(err);
// We errored, so the pattern we generate is irrelevant.
PatKind::Wild
let e = tcx.sess.emit_err(err);
self.saw_const_match_error.set(Some(e));
// We errored. Signal that in the pattern, so that follow up errors can be silenced.
PatKind::Constant { value: mir::Const::Ty(ty::Const::new_error(tcx, e, ty)) }
}
};

if !self.saw_const_match_error.get()
if self.saw_const_match_error.get().is_none()
&& !self.saw_const_match_lint.get()
&& mir_structural_match_violation
// FIXME(#73448): Find a way to bring const qualification into parity with
Expand Down
6 changes: 6 additions & 0 deletions compiler/rustc_type_ir/src/structural_impls.rs
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Expand Up @@ -153,6 +153,12 @@ impl<I: Interner, T: TypeVisitable<I>> TypeVisitable<I> for &[T] {
}
}

impl<I: Interner, T: TypeVisitable<I>> TypeVisitable<I> for Box<[T]> {
fn visit_with<V: TypeVisitor<I>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
self.iter().try_for_each(|t| t.visit_with(visitor))
}
}

impl<I: Interner, T: TypeFoldable<I>, Ix: Idx> TypeFoldable<I> for IndexVec<Ix, T> {
fn try_fold_with<F: FallibleTypeFolder<I>>(self, folder: &mut F) -> Result<Self, F::Error> {
self.try_map_id(|x| x.try_fold_with(folder))
Expand Down
14 changes: 13 additions & 1 deletion tests/ui/const-generics/generic_const_exprs/typeid-equality-by-subtyping.stderr
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Expand Up @@ -7,5 +7,17 @@ LL | WHAT_A_TYPE => 0,
= note: the traits must be derived, manual `impl`s are not sufficient
= note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details

error: aborting due to previous error
error[E0015]: cannot match on `TypeId` in constant functions
--> $DIR/typeid-equality-by-subtyping.rs:18:9
|
LL | WHAT_A_TYPE => 0,
| ^^^^^^^^^^^
|
= note: `TypeId` cannot be compared in compile-time, and therefore cannot be used in `match`es
note: impl defined here, but it is not `const`
--> $SRC_DIR/core/src/any.rs:LL:COL
= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants

error: aborting due to 2 previous errors
Comment on lines +10 to +21
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Where is this error coming from? I guess it was there before but got skipped because of previous errors?

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oh yea. We're actually generating a PartialEq call for it now, because we have an actual pattern now instead of a wildcard, which has no additional code.


For more information about this error, try `rustc --explain E0015`.
1 change: 0 additions & 1 deletion tests/ui/consts/const_in_pattern/issue-78057.rs
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Expand Up @@ -12,6 +12,5 @@ fn main() {
FOO => {},
//~^ ERROR must be annotated with `#[derive(PartialEq, Eq)]`
_ => {}
//~^ ERROR unreachable pattern
}
}
17 changes: 1 addition & 16 deletions tests/ui/consts/const_in_pattern/issue-78057.stderr
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Expand Up @@ -7,20 +7,5 @@ LL | FOO => {},
= note: the traits must be derived, manual `impl`s are not sufficient
= note: see https://doc.rust-lang.org/stable/std/marker/trait.StructuralEq.html for details

error: unreachable pattern
--> $DIR/issue-78057.rs:14:9
|
LL | FOO => {},
| --- matches any value
LL |
LL | _ => {}
| ^ unreachable pattern
|
note: the lint level is defined here
--> $DIR/issue-78057.rs:1:9
|
LL | #![deny(unreachable_patterns)]
| ^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors
error: aborting due to previous error

4 changes: 2 additions & 2 deletions tests/ui/pattern/non-structural-match-types.rs
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Expand Up @@ -6,9 +6,9 @@

fn main() {
match loop {} {
const { || {} } => {}, //~ ERROR cannot be used in patterns
const { || {} } => {} //~ ERROR cannot be used in patterns
}
match loop {} {
const { async {} } => {}, //~ ERROR cannot be used in patterns
const { async {} } => {} //~ ERROR cannot be used in patterns
}
}
4 changes: 2 additions & 2 deletions tests/ui/pattern/non-structural-match-types.stderr
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@@ -1,13 +1,13 @@
error: `{closure@$DIR/non-structural-match-types.rs:9:17: 9:19}` cannot be used in patterns
--> $DIR/non-structural-match-types.rs:9:9
|
LL | const { || {} } => {},
LL | const { || {} } => {}
| ^^^^^^^^^^^^^^^

error: `{async block@$DIR/non-structural-match-types.rs:12:17: 12:25}` cannot be used in patterns
--> $DIR/non-structural-match-types.rs:12:9
|
LL | const { async {} } => {},
LL | const { async {} } => {}
| ^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors
Expand Down
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