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Incorporate MIR const-checker into Pat lowering
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@ecstatic-morse
ecstatic-morse committed Apr 28, 2020
1 parent 6b54829 commit 796c0ca
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Showing 2 changed files with 89 additions and 63 deletions.
21 changes: 18 additions & 3 deletions src/librustc_mir_build/hair/pattern/const_to_pat.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -22,13 +22,14 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
cv: &'tcx ty::Const<'tcx>,
id: hir::HirId,
span: Span,
mir_structural_match_violation: bool,
) -> Pat<'tcx> {
debug!("const_to_pat: cv={:#?} id={:?}", cv, id);
debug!("const_to_pat: cv.ty={:?} span={:?}", cv.ty, span);

self.tcx.infer_ctxt().enter(|infcx| {
let mut convert = ConstToPat::new(self, id, span, infcx);
convert.to_pat(cv)
convert.to_pat(cv, mir_structural_match_violation)
})
}
}
Expand Down Expand Up @@ -81,7 +82,11 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
traits::type_marked_structural(self.id, self.span, &self.infcx, ty)
}

fn to_pat(&mut self, cv: &'tcx ty::Const<'tcx>) -> Pat<'tcx> {
fn to_pat(
&mut self,
cv: &'tcx ty::Const<'tcx>,
mir_structural_match_violation: bool,
) -> Pat<'tcx> {
// This method is just a wrapper handling a validity check; the heavy lifting is
// performed by the recursive `recur` method, which is not meant to be
// invoked except by this method.
Expand All @@ -100,6 +105,11 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
"search_for_structural_match_violation cv.ty: {:?} returned: {:?}",
cv.ty, structural
);

if structural.is_none() && mir_structural_match_violation {
bug!("MIR const-checker found novel structural match violation");
}

if let Some(non_sm_ty) = structural {
let adt_def = match non_sm_ty {
traits::NonStructuralMatchTy::Adt(adt_def) => adt_def,
Expand Down Expand Up @@ -146,13 +156,18 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
if !ty_is_partial_eq {
// span_fatal avoids ICE from resolution of non-existent method (rare case).
self.tcx().sess.span_fatal(self.span, &make_msg());
} else {
} else if mir_structural_match_violation {
self.tcx().struct_span_lint_hir(
lint::builtin::INDIRECT_STRUCTURAL_MATCH,
self.id,
self.span,
|lint| lint.build(&make_msg()).emit(),
);
} else {
debug!(
"`search_for_structural_match_violation` found one, but `CustomEq` was \
not in the qualifs for that `const`"
);
}
}
}
Expand Down
131 changes: 71 additions & 60 deletions src/librustc_mir_build/hair/pattern/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ use rustc_hir::def::{CtorKind, CtorOf, DefKind, Res};
use rustc_hir::pat_util::EnumerateAndAdjustIterator;
use rustc_hir::RangeEnd;
use rustc_index::vec::Idx;
use rustc_middle::mir::interpret::{get_slice_bytes, sign_extend, ConstValue, ErrorHandled};
use rustc_middle::mir::interpret::{get_slice_bytes, sign_extend, ConstValue};
use rustc_middle::mir::interpret::{LitToConstError, LitToConstInput};
use rustc_middle::mir::UserTypeProjection;
use rustc_middle::mir::{BorrowKind, Field, Mutability};
Expand Down Expand Up @@ -762,69 +762,80 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
fn lower_path(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, span: Span) -> Pat<'tcx> {
let ty = self.tables.node_type(id);
let res = self.tables.qpath_res(qpath, id);
let is_associated_const = match res {
Res::Def(DefKind::AssocConst, _) => true,
_ => false,

let pat_from_kind = |kind| Pat { span, ty, kind: Box::new(kind) };

let (def_id, is_associated_const) = match res {
Res::Def(DefKind::Const, def_id) => (def_id, false),
Res::Def(DefKind::AssocConst, def_id) => (def_id, true),

_ => return pat_from_kind(self.lower_variant_or_leaf(res, id, span, ty, vec![])),
};
let kind = match res {
Res::Def(DefKind::Const | DefKind::AssocConst, def_id) => {
let substs = self.tables.node_substs(id);
// Use `Reveal::All` here because patterns are always monomorphic even if their function isn't.
match self.tcx.const_eval_resolve(
self.param_env.with_reveal_all(),
def_id,
substs,
None,
Some(span),
) {
Ok(value) => {
let const_ =
ty::Const::from_value(self.tcx, value, self.tables.node_type(id));

let pattern = self.const_to_pat(&const_, id, span);
if !is_associated_const {
return pattern;
}

let user_provided_types = self.tables().user_provided_types();
return if let Some(u_ty) = user_provided_types.get(id) {
let user_ty = PatTyProj::from_user_type(*u_ty);
Pat {
span,
kind: Box::new(PatKind::AscribeUserType {
subpattern: pattern,
ascription: Ascription {
/// Note that use `Contravariant` here. See the
/// `variance` field documentation for details.
variance: ty::Variance::Contravariant,
user_ty,
user_ty_span: span,
},
}),
ty: const_.ty,
}
} else {
pattern
};
}
Err(ErrorHandled::TooGeneric) => {
self.errors.push(if is_associated_const {
PatternError::AssocConstInPattern(span)
} else {
PatternError::StaticInPattern(span)
});
PatKind::Wild
}
Err(_) => {
self.tcx.sess.span_err(span, "could not evaluate constant pattern");
PatKind::Wild
}
}
// Use `Reveal::All` here because patterns are always monomorphic even if their function
// isn't.
let param_env_reveal_all = self.param_env.with_reveal_all();
let substs = self.tables.node_substs(id);
let instance = match ty::Instance::resolve(self.tcx, param_env_reveal_all, def_id, substs) {
Ok(Some(i)) => i,
Ok(None) => {
self.errors.push(if is_associated_const {
PatternError::AssocConstInPattern(span)
} else {
PatternError::StaticInPattern(span)
});

return pat_from_kind(PatKind::Wild);
}

Err(_) => {
self.tcx.sess.span_err(span, "could not evaluate constant pattern");
return pat_from_kind(PatKind::Wild);
}
_ => self.lower_variant_or_leaf(res, id, span, ty, vec![]),
};

Pat { span, ty, kind: Box::new(kind) }
// `mir_const_qualif` must be called with the `DefId` of the item where the const is
// defined, not where it is declared. The difference is significant for associated
// constants.
let mir_structural_match_violation = self.tcx.mir_const_qualif(instance.def_id()).custom_eq;
debug!("mir_structural_match_violation({:?}) -> {}", qpath, mir_structural_match_violation);

match self.tcx.const_eval_instance(param_env_reveal_all, instance, Some(span)) {
Ok(value) => {
let const_ = ty::Const::from_value(self.tcx, value, self.tables.node_type(id));

let pattern = self.const_to_pat(&const_, id, span, mir_structural_match_violation);

if !is_associated_const {
return pattern;
}

let user_provided_types = self.tables().user_provided_types();
if let Some(u_ty) = user_provided_types.get(id) {
let user_ty = PatTyProj::from_user_type(*u_ty);
Pat {
span,
kind: Box::new(PatKind::AscribeUserType {
subpattern: pattern,
ascription: Ascription {
/// Note that use `Contravariant` here. See the
/// `variance` field documentation for details.
variance: ty::Variance::Contravariant,
user_ty,
user_ty_span: span,
},
}),
ty: const_.ty,
}
} else {
pattern
}
}
Err(_) => {
self.tcx.sess.span_err(span, "could not evaluate constant pattern");
pat_from_kind(PatKind::Wild)
}
}
}

/// Converts literals, paths and negation of literals to patterns.
Expand All @@ -849,7 +860,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {

let lit_input = LitToConstInput { lit: &lit.node, ty: self.tables.expr_ty(expr), neg };
match self.tcx.at(expr.span).lit_to_const(lit_input) {
Ok(val) => *self.const_to_pat(val, expr.hir_id, lit.span).kind,
Ok(val) => *self.const_to_pat(val, expr.hir_id, lit.span, false).kind,
Err(LitToConstError::UnparseableFloat) => {
self.errors.push(PatternError::FloatBug);
PatKind::Wild
Expand Down

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