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Auto merge of #36735 - srinivasreddy:typck/variance, r=nrc
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run rustfmt on librustc_typeck/variance folder
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@bors
bors authored Sep 26, 2016
2 parents 3bf4a7a + 765eaac commit c276928
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Showing 5 changed files with 145 additions and 152 deletions.
148 changes: 70 additions & 78 deletions src/librustc_typeck/variance/constraints.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ pub struct ConstraintContext<'a, 'tcx: 'a> {
invariant: VarianceTermPtr<'a>,
bivariant: VarianceTermPtr<'a>,

pub constraints: Vec<Constraint<'a>> ,
pub constraints: Vec<Constraint<'a>>,
}

/// Declares that the variable `decl_id` appears in a location with
Expand All @@ -49,8 +49,7 @@ pub struct Constraint<'a> {
}

pub fn add_constraints_from_crate<'a, 'tcx>(terms_cx: TermsContext<'a, 'tcx>)
-> ConstraintContext<'a, 'tcx>
{
-> ConstraintContext<'a, 'tcx> {
let tcx = terms_cx.tcx;
let covariant = terms_cx.arena.alloc(ConstantTerm(ty::Covariant));
let contravariant = terms_cx.arena.alloc(ConstantTerm(ty::Contravariant));
Expand Down Expand Up @@ -80,7 +79,9 @@ impl<'a, 'tcx, 'v> Visitor<'v> for ConstraintContext<'a, 'tcx> {
debug!("visit_item item={}", tcx.map.node_to_string(item.id));

match item.node {
hir::ItemEnum(..) | hir::ItemStruct(..) | hir::ItemUnion(..) => {
hir::ItemEnum(..) |
hir::ItemStruct(..) |
hir::ItemUnion(..) => {
let scheme = tcx.lookup_item_type(did);

// Not entirely obvious: constraints on structs/enums do not
Expand Down Expand Up @@ -111,16 +112,16 @@ impl<'a, 'tcx, 'v> Visitor<'v> for ConstraintContext<'a, 'tcx> {
hir::ItemForeignMod(..) |
hir::ItemTy(..) |
hir::ItemImpl(..) |
hir::ItemDefaultImpl(..) => {
}
hir::ItemDefaultImpl(..) => {}
}
}
}

/// Is `param_id` a lifetime according to `map`?
fn is_lifetime(map: &hir_map::Map, param_id: ast::NodeId) -> bool {
match map.find(param_id) {
Some(hir_map::NodeLifetime(..)) => true, _ => false
Some(hir_map::NodeLifetime(..)) => true,
_ => false,
}
}

Expand All @@ -143,13 +144,12 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
let tcx = self.terms_cx.tcx;
assert!(is_lifetime(&tcx.map, param_id));
match tcx.named_region_map.defs.get(&param_id) {
Some(&rl::DefEarlyBoundRegion(_, lifetime_decl_id))
=> lifetime_decl_id,
Some(&rl::DefEarlyBoundRegion(_, lifetime_decl_id)) => lifetime_decl_id,
Some(_) => bug!("should not encounter non early-bound cases"),

// The lookup should only fail when `param_id` is
// itself a lifetime binding: use it as the decl_id.
None => param_id,
None => param_id,
}

}
Expand All @@ -163,14 +163,15 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
// parameter (by inspecting parent of its binding declaration
// to see if it is introduced by a type or by a fn/impl).

let check_result = |this:&ConstraintContext| -> bool {
let check_result = |this: &ConstraintContext| -> bool {
let tcx = this.terms_cx.tcx;
let decl_id = this.find_binding_for_lifetime(param_id);
// Currently only called on lifetimes; double-checking that.
assert!(is_lifetime(&tcx.map, param_id));
let parent_id = tcx.map.get_parent(decl_id);
let parent = tcx.map.find(parent_id).unwrap_or_else(
|| bug!("tcx.map missing entry for id: {}", parent_id));
let parent = tcx.map
.find(parent_id)
.unwrap_or_else(|| bug!("tcx.map missing entry for id: {}", parent_id));

let is_inferred;
macro_rules! cannot_happen { () => { {
Expand All @@ -186,14 +187,14 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
hir::ItemEnum(..) |
hir::ItemStruct(..) |
hir::ItemUnion(..) |
hir::ItemTrait(..) => is_inferred = true,
hir::ItemFn(..) => is_inferred = false,
_ => cannot_happen!(),
hir::ItemTrait(..) => is_inferred = true,
hir::ItemFn(..) => is_inferred = false,
_ => cannot_happen!(),
}
}
hir_map::NodeTraitItem(..) => is_inferred = false,
hir_map::NodeImplItem(..) => is_inferred = false,
_ => cannot_happen!(),
hir_map::NodeTraitItem(..) => is_inferred = false,
hir_map::NodeImplItem(..) => is_inferred = false,
_ => cannot_happen!(),
}

return is_inferred;
Expand Down Expand Up @@ -230,21 +231,18 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
fn add_constraint(&mut self,
InferredIndex(index): InferredIndex,
variance: VarianceTermPtr<'a>) {
debug!("add_constraint(index={}, variance={:?})",
index, variance);
self.constraints.push(Constraint { inferred: InferredIndex(index),
variance: variance });
debug!("add_constraint(index={}, variance={:?})", index, variance);
self.constraints.push(Constraint {
inferred: InferredIndex(index),
variance: variance,
});
}

fn contravariant(&mut self,
variance: VarianceTermPtr<'a>)
-> VarianceTermPtr<'a> {
fn contravariant(&mut self, variance: VarianceTermPtr<'a>) -> VarianceTermPtr<'a> {
self.xform(variance, self.contravariant)
}

fn invariant(&mut self,
variance: VarianceTermPtr<'a>)
-> VarianceTermPtr<'a> {
fn invariant(&mut self, variance: VarianceTermPtr<'a>) -> VarianceTermPtr<'a> {
self.xform(variance, self.invariant)
}

Expand All @@ -257,23 +255,16 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
}
}

fn xform(&mut self,
v1: VarianceTermPtr<'a>,
v2: VarianceTermPtr<'a>)
-> VarianceTermPtr<'a> {
fn xform(&mut self, v1: VarianceTermPtr<'a>, v2: VarianceTermPtr<'a>) -> VarianceTermPtr<'a> {
match (*v1, *v2) {
(_, ConstantTerm(ty::Covariant)) => {
// Applying a "covariant" transform is always a no-op
v1
}

(ConstantTerm(c1), ConstantTerm(c2)) => {
self.constant_term(c1.xform(c2))
}
(ConstantTerm(c1), ConstantTerm(c2)) => self.constant_term(c1.xform(c2)),

_ => {
&*self.terms_cx.arena.alloc(TransformTerm(v1, v2))
}
_ => &*self.terms_cx.arena.alloc(TransformTerm(v1, v2)),
}
}

Expand All @@ -292,13 +283,12 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
// README.md for a discussion on dep-graph management.
self.tcx().dep_graph.read(ItemVariances::to_dep_node(&trait_ref.def_id));

self.add_constraints_from_substs(
generics,
trait_ref.def_id,
&trait_def.generics.types,
&trait_def.generics.regions,
trait_ref.substs,
variance);
self.add_constraints_from_substs(generics,
trait_ref.def_id,
&trait_def.generics.types,
&trait_def.generics.regions,
trait_ref.substs,
variance);
}

/// Adds constraints appropriate for an instance of `ty` appearing
Expand All @@ -313,13 +303,13 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
variance);

match ty.sty {
ty::TyBool |
ty::TyChar | ty::TyInt(_) | ty::TyUint(_) |
ty::TyFloat(_) | ty::TyStr | ty::TyNever => {
/* leaf type -- noop */
ty::TyBool | ty::TyChar | ty::TyInt(_) | ty::TyUint(_) | ty::TyFloat(_) |
ty::TyStr | ty::TyNever => {
// leaf type -- noop
}

ty::TyClosure(..) | ty::TyAnon(..) => {
ty::TyClosure(..) |
ty::TyAnon(..) => {
bug!("Unexpected closure type in variance computation");
}

Expand All @@ -329,11 +319,12 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
self.add_constraints_from_mt(generics, mt, variance);
}

ty::TyBox(typ) | ty::TyArray(typ, _) | ty::TySlice(typ) => {
ty::TyBox(typ) |
ty::TyArray(typ, _) |
ty::TySlice(typ) => {
self.add_constraints_from_ty(generics, typ, variance);
}


ty::TyRawPtr(ref mt) => {
self.add_constraints_from_mt(generics, mt, variance);
}
Expand All @@ -352,13 +343,12 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
// README.md for a discussion on dep-graph management.
self.tcx().dep_graph.read(ItemVariances::to_dep_node(&def.did));

self.add_constraints_from_substs(
generics,
def.did,
&item_type.generics.types,
&item_type.generics.regions,
substs,
variance);
self.add_constraints_from_substs(generics,
def.did,
&item_type.generics.types,
&item_type.generics.regions,
substs,
variance);
}

ty::TyProjection(ref data) => {
Expand All @@ -370,22 +360,20 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
// README.md for a discussion on dep-graph management.
self.tcx().dep_graph.read(ItemVariances::to_dep_node(&trait_ref.def_id));

self.add_constraints_from_substs(
generics,
trait_ref.def_id,
&trait_def.generics.types,
&trait_def.generics.regions,
trait_ref.substs,
variance);
self.add_constraints_from_substs(generics,
trait_ref.def_id,
&trait_def.generics.types,
&trait_def.generics.regions,
trait_ref.substs,
variance);
}

ty::TyTrait(ref data) => {
// The type `Foo<T+'a>` is contravariant w/r/t `'a`:
let contra = self.contravariant(variance);
self.add_constraints_from_region(generics, data.region_bound, contra);

let poly_trait_ref =
data.principal.with_self_ty(self.tcx(), self.tcx().types.err);
let poly_trait_ref = data.principal.with_self_ty(self.tcx(), self.tcx().types.err);
self.add_constraints_from_trait_ref(generics, poly_trait_ref.0, variance);

for projection in &data.projection_bounds {
Expand Down Expand Up @@ -425,7 +413,8 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {

ty::TyInfer(..) => {
bug!("unexpected type encountered in \
variance inference: {}", ty);
variance inference: {}",
ty);
}
}
}
Expand All @@ -445,18 +434,17 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
variance);

for p in type_param_defs {
let variance_decl =
self.declared_variance(p.def_id, def_id, p.index as usize);
let variance_decl = self.declared_variance(p.def_id, def_id, p.index as usize);
let variance_i = self.xform(variance, variance_decl);
let substs_ty = substs.type_for_def(p);
debug!("add_constraints_from_substs: variance_decl={:?} variance_i={:?}",
variance_decl, variance_i);
variance_decl,
variance_i);
self.add_constraints_from_ty(generics, substs_ty, variance_i);
}

for p in region_param_defs {
let variance_decl =
self.declared_variance(p.def_id, def_id, p.index as usize);
let variance_decl = self.declared_variance(p.def_id, def_id, p.index as usize);
let variance_i = self.xform(variance, variance_decl);
let substs_r = substs.region_for_def(p);
self.add_constraints_from_region(generics, substs_r, variance_i);
Expand Down Expand Up @@ -494,15 +482,19 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
}
}

ty::ReStatic => { }
ty::ReStatic => {}

ty::ReLateBound(..) => {
// We do not infer variance for region parameters on
// methods or in fn types.
}

ty::ReFree(..) | ty::ReScope(..) | ty::ReVar(..) |
ty::ReSkolemized(..) | ty::ReEmpty | ty::ReErased => {
ty::ReFree(..) |
ty::ReScope(..) |
ty::ReVar(..) |
ty::ReSkolemized(..) |
ty::ReEmpty |
ty::ReErased => {
// We don't expect to see anything but 'static or bound
// regions when visiting member types or method types.
bug!("unexpected region encountered in variance \
Expand Down
1 change: 0 additions & 1 deletion src/librustc_typeck/variance/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -34,4 +34,3 @@ pub fn infer_variance<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
solve::solve_constraints(constraints_cx);
tcx.variance_computed.set(true);
}

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