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rustc: Implement simple trait inheritance.

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Generic trait inheritance, cross-crate trait inheritance, and vtable-based
trait inheritance don't work yet.
This commit is contained in:
Patrick Walton 2012-10-05 11:50:53 -07:00
parent c56a7e5c25
commit 1b732145ec
4 changed files with 136 additions and 35 deletions
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6
src/rustc/middle/resolve.rs
View File

@ -4181,9 +4181,9 @@ impl Resolver {
}
return self.resolve_identifier(path.idents.last(),
namespace,
check_ribs,
path.span);
namespace,
check_ribs,
path.span);
}
fn resolve_identifier(identifier: ident,

102
src/rustc/middle/typeck/check/vtable.rs
View File

@ -51,8 +51,8 @@ fn lookup_vtables(fcx: @fn_ctxt,
match *bound {
ty::bound_trait(i_ty) => {
let i_ty = ty::subst(tcx, substs, i_ty);
match lookup_vtable(fcx, expr, *ty, i_ty, allow_unsafe,
is_early) {
match lookup_vtable_covariant(fcx, expr, *ty, i_ty,
allow_unsafe, is_early) {
Some(vtable) => result.push(vtable),
None => {
fcx.tcx().sess.span_fatal(
@ -91,20 +91,67 @@ fn relate_trait_tys(fcx: @fn_ctxt, expr: @ast::expr,
demand::suptype(fcx, expr.span, exp_trait_ty, act_trait_ty)
}
/*
Look up the vtable to use when treating an item of type <t>
as if it has type <trait_ty>
*/
fn lookup_vtable(fcx: @fn_ctxt,
expr: @ast::expr,
ty: ty::t,
trait_ty: ty::t,
allow_unsafe: bool,
is_early: bool)
-> Option<vtable_origin>
{
// Look up the vtable to use when treating an item of type `t` as if it has
// type `trait_ty`. This does allow subtraits.
fn lookup_vtable_covariant(fcx: @fn_ctxt,
expr: @ast::expr,
ty: ty::t,
trait_ty: ty::t,
allow_unsafe: bool,
is_early: bool)
-> Option<vtable_origin> {
let worklist = dvec::DVec();
worklist.push(trait_ty);
while worklist.len() > 0 {
let trait_ty = worklist.pop();
let result = lookup_vtable_invariant(fcx, expr, ty, trait_ty,
allow_unsafe, is_early);
if result.is_some() {
return result;
}
debug!("lookup_vtable(ty=%s, trait_ty=%s)",
// Add subtraits to the worklist, if applicable.
match ty::get(trait_ty).sty {
ty::ty_trait(trait_id, _, _) => {
let table = fcx.ccx.coherence_info.supertrait_to_subtraits;
match table.find(trait_id) {
None => {}
Some(subtraits) => {
for subtraits.each |subtrait_id| {
// XXX: This is wrong; subtraits should themselves
// have substs.
let substs =
{ self_r: None, self_ty: None, tps: ~[] };
let trait_ty = ty::mk_trait(fcx.ccx.tcx,
*subtrait_id,
substs,
ty::vstore_box);
worklist.push(trait_ty);
}
}
}
}
_ => {
fcx.ccx.tcx.sess.impossible_case(expr.span,
"lookup_vtable_covariant: \
non-trait in worklist");
}
}
}
return None;
}
// Look up the vtable to use when treating an item of type `t` as if it has
// type `trait_ty`. This does not allow subtraits.
fn lookup_vtable_invariant(fcx: @fn_ctxt,
expr: @ast::expr,
ty: ty::t,
trait_ty: ty::t,
allow_unsafe: bool,
is_early: bool)
-> Option<vtable_origin> {
debug!("lookup_vtable_invariant(ty=%s, trait_ty=%s)",
fcx.infcx().ty_to_str(ty), fcx.inh.infcx.ty_to_str(trait_ty));
let _i = indenter();
@ -112,7 +159,7 @@ fn lookup_vtable(fcx: @fn_ctxt,
let (trait_id, trait_substs) = match ty::get(trait_ty).sty {
ty::ty_trait(did, substs, _) => (did, substs),
_ => tcx.sess.impossible_case(expr.span,
"lookup_vtable: \
"lookup_vtable_invariant: \
don't know how to handle a non-trait")
};
let ty = match fixup_ty(fcx, expr, ty, is_early) {
@ -150,7 +197,7 @@ fn lookup_vtable(fcx: @fn_ctxt,
}
_ => tcx.sess.impossible_case(
expr.span,
"lookup_vtable: in loop, \
"lookup_vtable_invariant: in loop, \
don't know how to handle a non-trait ity")
}
n_bound += 1u;
@ -462,13 +509,14 @@ fn early_resolve_expr(ex: @ast::expr, &&fcx: @fn_ctxt, is_early: bool) {
let target_ty = fcx.expr_ty(ex);
match ty::get(target_ty).sty {
ty::ty_trait(*) => {
/*
Look up vtables for the type we're casting to,
passing in the source and target type
*/
// Look up vtables for the type we're casting to, passing in the
// source and target type.
//
// XXX: This is invariant and shouldn't be. --pcw
let ty = fcx.expr_ty(src);
let vtable_opt = lookup_vtable(fcx, ex, ty, target_ty, true,
is_early);
let vtable_opt = lookup_vtable_invariant(fcx, ex, ty, target_ty,
true, is_early);
match vtable_opt {
None => {
// Try the new-style boxed trait; "@int as @Trait".
@ -476,10 +524,10 @@ fn early_resolve_expr(ex: @ast::expr, &&fcx: @fn_ctxt, is_early: bool) {
let ty = structurally_resolved_type(fcx, ex.span, ty);
match ty::get(ty).sty {
ty::ty_box(boxed_ty) => {
let vtable_opt = lookup_vtable(fcx, ex,
boxed_ty.ty,
target_ty, true,
is_early);
let vtable_opt =
lookup_vtable_invariant(fcx, ex, boxed_ty.ty,
target_ty, true,
is_early);
match vtable_opt {
Some(vtable) => {
/*

37
src/rustc/middle/typeck/coherence.rs
View File

@ -126,12 +126,16 @@ struct CoherenceInfo {
// Contains implementations of methods associated with a trait. For these,
// the associated trait must be imported at the call site.
extension_methods: HashMap<def_id,@DVec<@Impl>>,
// A mapping from a supertrait to its subtraits.
supertrait_to_subtraits: HashMap<def_id,@DVec<def_id>>
}
fn CoherenceInfo() -> CoherenceInfo {
CoherenceInfo {
inherent_methods: HashMap(),
extension_methods: HashMap()
extension_methods: HashMap(),
supertrait_to_subtraits: HashMap()
}
}
@ -161,7 +165,6 @@ struct CoherenceChecker {
}
impl CoherenceChecker {
// Create a mapping containing a MethodInfo for every provided
// method in every trait.
fn build_provided_methods_map(crate: @crate) {
@ -225,9 +228,9 @@ impl CoherenceChecker {
}
fn check_coherence(crate: @crate) {
// Check implementations. This populates the tables containing the
// inherent methods and extension methods.
// Check implementations and traits. This populates the tables
// containing the inherent methods and extension methods. It also
// builds up the trait inheritance table.
visit_crate(*crate, (), mk_simple_visitor(@{
visit_item: |item| {
debug!("(checking coherence) item '%s'",
@ -240,6 +243,9 @@ impl CoherenceChecker {
item_class(struct_def, _) => {
self.check_implementation(item, struct_def.traits);
}
item_trait(_, supertraits, _) => {
self.register_inherited_trait(item, supertraits);
}
_ => {
// Nothing to do.
}
@ -324,6 +330,27 @@ impl CoherenceChecker {
}
}
fn register_inherited_trait(item: @item, supertraits: ~[@trait_ref]) {
// XXX: This is wrong. We need to support substitutions; e.g.
// trait Foo : Bar<int>.
let supertrait_to_subtraits =
self.crate_context.coherence_info.supertrait_to_subtraits;
let subtrait_id = local_def(item.id);
for supertraits.each |supertrait| {
let supertrait_id = self.trait_ref_to_trait_def_id(*supertrait);
match supertrait_to_subtraits.find(supertrait_id) {
None => {
let new_vec = @dvec::DVec();
new_vec.push(subtrait_id);
supertrait_to_subtraits.insert(supertrait_id, new_vec);
}
Some(existing_vec) => {
existing_vec.push(subtrait_id);
}
}
}
}
fn add_inherent_method(base_def_id: def_id, implementation: @Impl) {
let implementation_list;
match self.crate_context.coherence_info.inherent_methods

26
src/test/run-pass/trait-inheritance-simple.rs Normal file
View File

@ -0,0 +1,26 @@
trait Foo {
fn f();
}
trait Bar : Foo {
fn g();
}
struct A {
x: int
}
impl A : Bar {
fn g() { io::println("in g"); }
fn f() { io::println("in f"); }
}
fn h<T:Foo>(a: &T) {
a.f();
}
fn main() {
let a = A { x: 3 };
h(&a);
}