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Diffstat (limited to 'compiler/rustc_infer/src/infer/resolve.rs')
| -rw-r--r-- | compiler/rustc_infer/src/infer/resolve.rs | 250 |
1 files changed, 250 insertions, 0 deletions
diff --git a/compiler/rustc_infer/src/infer/resolve.rs b/compiler/rustc_infer/src/infer/resolve.rs new file mode 100644 index 00000000000..48b8ee17594 --- /dev/null +++ b/compiler/rustc_infer/src/infer/resolve.rs @@ -0,0 +1,250 @@ +use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; +use super::{FixupError, FixupResult, InferCtxt, Span}; +use rustc_middle::mir; +use rustc_middle::ty::fold::{TypeFolder, TypeVisitor}; +use rustc_middle::ty::{self, Const, InferConst, Ty, TyCtxt, TypeFoldable}; + +use std::ops::ControlFlow; + +/////////////////////////////////////////////////////////////////////////// +// OPPORTUNISTIC VAR RESOLVER + +/// The opportunistic resolver can be used at any time. It simply replaces +/// type/const variables that have been unified with the things they have +/// been unified with (similar to `shallow_resolve`, but deep). This is +/// useful for printing messages etc but also required at various +/// points for correctness. +pub struct OpportunisticVarResolver<'a, 'tcx> { + infcx: &'a InferCtxt<'a, 'tcx>, +} + +impl<'a, 'tcx> OpportunisticVarResolver<'a, 'tcx> { + #[inline] + pub fn new(infcx: &'a InferCtxt<'a, 'tcx>) -> Self { + OpportunisticVarResolver { infcx } + } +} + +impl<'a, 'tcx> TypeFolder<'tcx> for OpportunisticVarResolver<'a, 'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { + self.infcx.tcx + } + + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + if !t.has_infer_types_or_consts() { + t // micro-optimize -- if there is nothing in this type that this fold affects... + } else { + let t = self.infcx.shallow_resolve(t); + t.super_fold_with(self) + } + } + + fn fold_const(&mut self, ct: &'tcx Const<'tcx>) -> &'tcx Const<'tcx> { + if !ct.has_infer_types_or_consts() { + ct // micro-optimize -- if there is nothing in this const that this fold affects... + } else { + let ct = self.infcx.shallow_resolve(ct); + ct.super_fold_with(self) + } + } + + fn fold_mir_const(&mut self, constant: mir::ConstantKind<'tcx>) -> mir::ConstantKind<'tcx> { + constant.super_fold_with(self) + } +} + +/// The opportunistic region resolver opportunistically resolves regions +/// variables to the variable with the least variable id. It is used when +/// normlizing projections to avoid hitting the recursion limit by creating +/// many versions of a predicate for types that in the end have to unify. +/// +/// If you want to resolve type and const variables as well, call +/// [InferCtxt::resolve_vars_if_possible] first. +pub struct OpportunisticRegionResolver<'a, 'tcx> { + infcx: &'a InferCtxt<'a, 'tcx>, +} + +impl<'a, 'tcx> OpportunisticRegionResolver<'a, 'tcx> { + pub fn new(infcx: &'a InferCtxt<'a, 'tcx>) -> Self { + OpportunisticRegionResolver { infcx } + } +} + +impl<'a, 'tcx> TypeFolder<'tcx> for OpportunisticRegionResolver<'a, 'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { + self.infcx.tcx + } + + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + if !t.has_infer_regions() { + t // micro-optimize -- if there is nothing in this type that this fold affects... + } else { + t.super_fold_with(self) + } + } + + fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { + match *r { + ty::ReVar(rid) => { + let resolved = self + .infcx + .inner + .borrow_mut() + .unwrap_region_constraints() + .opportunistic_resolve_var(rid); + self.tcx().reuse_or_mk_region(r, ty::ReVar(resolved)) + } + _ => r, + } + } + + fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> { + if !ct.has_infer_regions() { + ct // micro-optimize -- if there is nothing in this const that this fold affects... + } else { + ct.super_fold_with(self) + } + } +} + +/////////////////////////////////////////////////////////////////////////// +// UNRESOLVED TYPE FINDER + +/// The unresolved type **finder** walks a type searching for +/// type variables that don't yet have a value. The first unresolved type is stored. +/// It does not construct the fully resolved type (which might +/// involve some hashing and so forth). +pub struct UnresolvedTypeFinder<'a, 'tcx> { + infcx: &'a InferCtxt<'a, 'tcx>, +} + +impl<'a, 'tcx> UnresolvedTypeFinder<'a, 'tcx> { + pub fn new(infcx: &'a InferCtxt<'a, 'tcx>) -> Self { + UnresolvedTypeFinder { infcx } + } +} + +impl<'a, 'tcx> TypeVisitor<'tcx> for UnresolvedTypeFinder<'a, 'tcx> { + type BreakTy = (Ty<'tcx>, Option<Span>); + fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> { + let t = self.infcx.shallow_resolve(t); + if t.has_infer_types() { + if let ty::Infer(infer_ty) = *t.kind() { + // Since we called `shallow_resolve` above, this must + // be an (as yet...) unresolved inference variable. + let ty_var_span = if let ty::TyVar(ty_vid) = infer_ty { + let mut inner = self.infcx.inner.borrow_mut(); + let ty_vars = &inner.type_variables(); + if let TypeVariableOrigin { + kind: TypeVariableOriginKind::TypeParameterDefinition(_, _), + span, + } = *ty_vars.var_origin(ty_vid) + { + Some(span) + } else { + None + } + } else { + None + }; + ControlFlow::Break((t, ty_var_span)) + } else { + // Otherwise, visit its contents. + t.super_visit_with(self) + } + } else { + // All type variables in inference types must already be resolved, + // - no need to visit the contents, continue visiting. + ControlFlow::CONTINUE + } + } +} + +/////////////////////////////////////////////////////////////////////////// +// FULL TYPE RESOLUTION + +/// Full type resolution replaces all type and region variables with +/// their concrete results. If any variable cannot be replaced (never unified, etc) +/// then an `Err` result is returned. +pub fn fully_resolve<'a, 'tcx, T>(infcx: &InferCtxt<'a, 'tcx>, value: T) -> FixupResult<'tcx, T> +where + T: TypeFoldable<'tcx>, +{ + let mut full_resolver = FullTypeResolver { infcx, err: None }; + let result = value.fold_with(&mut full_resolver); + match full_resolver.err { + None => Ok(result), + Some(e) => Err(e), + } +} + +// N.B. This type is not public because the protocol around checking the +// `err` field is not enforceable otherwise. +struct FullTypeResolver<'a, 'tcx> { + infcx: &'a InferCtxt<'a, 'tcx>, + err: Option<FixupError<'tcx>>, +} + +impl<'a, 'tcx> TypeFolder<'tcx> for FullTypeResolver<'a, 'tcx> { + fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { + self.infcx.tcx + } + + fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { + if !t.needs_infer() { + t // micro-optimize -- if there is nothing in this type that this fold affects... + } else { + let t = self.infcx.shallow_resolve(t); + match *t.kind() { + ty::Infer(ty::TyVar(vid)) => { + self.err = Some(FixupError::UnresolvedTy(vid)); + self.tcx().ty_error() + } + ty::Infer(ty::IntVar(vid)) => { + self.err = Some(FixupError::UnresolvedIntTy(vid)); + self.tcx().ty_error() + } + ty::Infer(ty::FloatVar(vid)) => { + self.err = Some(FixupError::UnresolvedFloatTy(vid)); + self.tcx().ty_error() + } + ty::Infer(_) => { + bug!("Unexpected type in full type resolver: {:?}", t); + } + _ => t.super_fold_with(self), + } + } + } + + fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { + match *r { + ty::ReVar(rid) => self + .infcx + .lexical_region_resolutions + .borrow() + .as_ref() + .expect("region resolution not performed") + .resolve_var(rid), + _ => r, + } + } + + fn fold_const(&mut self, c: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> { + if !c.needs_infer() { + c // micro-optimize -- if there is nothing in this const that this fold affects... + } else { + let c = self.infcx.shallow_resolve(c); + match c.val { + ty::ConstKind::Infer(InferConst::Var(vid)) => { + self.err = Some(FixupError::UnresolvedConst(vid)); + return self.tcx().const_error(c.ty); + } + ty::ConstKind::Infer(InferConst::Fresh(_)) => { + bug!("Unexpected const in full const resolver: {:?}", c); + } + _ => {} + } + c.super_fold_with(self) + } + } +} |