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Properly check kinds in instantiation of generics
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Issue #1177
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@marijnh
marijnh committed Nov 18, 2011
1 parent 7bef89f commit 0c97fcb
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Showing 3 changed files with 29 additions and 286 deletions.
311 changes: 27 additions & 284 deletions src/comp/middle/kind.rs
View file
Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
import std::option::some;
import std::option::{some, none};
import syntax::{visit, ast_util};
import syntax::ast::*;
import syntax::codemap::span;
Expand Down Expand Up @@ -50,12 +50,33 @@ fn check_expr(e: @expr, cx: ctx, v: visit::vt<ctx>) {
expr_bind(_, args) {
for a in args { alt a { some(ex) { maybe_copy(cx, ex); } _ {} } }
}
// FIXME check for by-copy args
expr_call(_f, _args, _) {

expr_call(f, args, _) {
let i = 0u;
for arg_t in ty::ty_fn_args(cx.tcx, ty::expr_ty(cx.tcx, f)) {
alt arg_t.mode { by_copy. { maybe_copy(cx, args[i]); } _ {} }
i += 1u;
}
}
expr_path(_) {
let substs = ty::node_id_to_ty_param_substs_opt_and_ty(cx.tcx, e.id);
alt substs.substs {
some(ts) {
let did = ast_util::def_id_of_def(cx.tcx.def_map.get(e.id));
let kinds = ty::lookup_item_type(cx.tcx, did).kinds, i = 0u;
for ty in ts {
let kind = ty::type_kind(cx.tcx, ty);
if !ty::kind_lteq(kinds[i], kind) {
cx.tcx.sess.span_err(e.span, "instantiating a " +
kind_to_str(kinds[i]) +
" type parameter with a "
+ kind_to_str(kind) + " type");
}
i += 1u;
}
}
none. {}
}
}
// FIXME: generic instantiation
expr_path(_) {}
expr_fn({proto: proto_shared(_), _}) {
for free in *freevars::get_freevars(cx.tcx, e.id) {
let id = ast_util::def_id_of_def(free).node;
Expand Down Expand Up @@ -114,284 +135,6 @@ fn check_copy(cx: ctx, ty: ty::t, sp: span) {
}
}


/*
* Kinds are types of type.
*
* Every type has a kind. Every type parameter has a set of kind-capabilities
* saying which kind of type may be passed as the parameter.
*
* The kinds are based on two capabilities: move and send. These may each be
* present or absent, though only three of the four combinations can actually
* occur:
*
*
*
* MOVE + SEND = "Unique": no shared substructures or pins, only
* interiors and ~ boxes.
*
* MOVE + NOSEND = "Shared": structures containing @, fixed to the local
* task heap/pool; or ~ structures pointing to
* pinned values.
*
* NOMOVE + NOSEND = "Pinned": structures directly containing resources, or
* by-alias closures as interior or
* uniquely-boxed members.
*
* NOMOVE + SEND = -- : no types are like this.
*
*
* Since this forms a lattice, we denote the capabilites in terms of a
* worst-case requirement. That is, if your function needs to move-and-send (or
* copy) your T, you write fn<uniq T>(...). If you need to move but not send,
* you write fn<T>(...). And if you need neither -- can work with any sort of
* pinned data at all -- then you write fn<pin T>(...).
*
* Most types are unique or shared. Other possible name combinations for these
* two: (tree, graph; pruned, pooled; message, local; owned, common) are
* plausible but nothing stands out as completely pithy-and-obvious.
*
* Pinned values arise in 2 contexts: resources and &-closures (blocks). The
* latter absolutely must not be moved, since they could escape to the heap;
* the former must not be copied, since they'd then be multiply-destructed.
* We achieve the no-copy restriction by recycling the no-move restriction
* in place on pinned kinds for &-closures; and as a benefit we can guarantee
* that a resource passed by reference to C will never move during its life,
* occasionally useful for FFI-code.
*
* Resources cannot be sent because we don't want to oblige the communication
* system to run destructors in some weird limbo context of
* messages-in-transit. It should always be ok to just free messages it's
* dropping. Even if you wanted to send them, you'd need a new sigil for the
* NOMOVE + SEND combination, and you couldn't use the move-mode library
* interface to chan.send in that case (NOMOVE after all), so the whole thing
* wouldn't really work as minimally as the encoding we have here.
*
* Note that obj~ and fn~ -- those that capture a unique environment -- can be
* sent, so satisfy ~T. So can plain obj and fn. They can all also be copied.
*
* Further notes on copying and moving; sending is accomplished by calling a
* move-in operator on something constrained to a unique type ~T.
*
*
* COPYING:
* --------
*
* A copy is made any time you pass-by-value or execute the = operator in a
* non-init expression. Copying requires discriminating on type constructor.
*
* @-boxes copy shallow, copying is always legal.
*
* ~-boxes copy deep, copying is only legal if pointee is unique-kind.
*
* Pinned-kind values (resources, &-closures) can't be copied. All other
* unique-kind (eg. interior) values can be copied, and copy shallow.
*
* Note: If you have no type constructor -- only an opaque typaram -- then
* you can only copy if the typaram is constrained to ~T; this is because @T
* might be a "~resource" box, and making a copy would cause a deep
* resource-copy.
*
*
* MOVING:
* -------
*
* A move is made any time you pass-by-move (that is, with move mode '-') or
* execute the move ('<-') or swap ('<->') operators.
*
*/

/*
fn type_and_kind(tcx: ty::ctxt, e: @ast::expr) ->
{ty: ty::t, kind: ast::kind} {
let t = ty::expr_ty(tcx, e);
let k = ty::type_kind(tcx, t);
{ty: t, kind: k}
}
fn need_expr_kind(tcx: ty::ctxt, e: @ast::expr, k_need: ast::kind,
descr: str) {
let tk = type_and_kind(tcx, e);
log #fmt["for %s: want %s type, got %s type %s", descr,
kind_to_str(k_need), kind_to_str(tk.kind),
util::ppaux::ty_to_str(tcx, tk.ty)];
demand_kind(tcx, e.span, tk.ty, k_need, descr);
}
fn demand_kind(tcx: ty::ctxt, sp: codemap::span, t: ty::t,
k_need: ast::kind, descr: str) {
let k = ty::type_kind(tcx, t);
if !kind_lteq(k_need, k) {
let s =
#fmt["mismatched kinds for %s: needed %s type, got %s type %s",
descr, kind_to_str(k_need), kind_to_str(k),
util::ppaux::ty_to_str(tcx, t)];
tcx.sess.span_err(sp, s);
}
}
fn need_shared_lhs_rhs(tcx: ty::ctxt, a: @ast::expr, b: @ast::expr, op: str) {
need_expr_kind(tcx, a, ast::kind_copyable, op + " lhs");
need_expr_kind(tcx, b, ast::kind_copyable, op + " rhs");
}
/*
This ... is a hack (I find myself writing that too often *sadface*).
We need to be able to put pinned kinds into other types but such operations
are conceptually copies, and pinned kinds can't do that, e.g.
let a = my_resource(x);
let b = @a; // no-go
So this function attempts to make a loophole where resources can be put into
other types as long as it's done in a safe way, specifically like
let b = @my_resource(x);
*/
fn need_shared_or_pinned_ctor(tcx: ty::ctxt, a: @ast::expr, descr: str) {
let tk = type_and_kind(tcx, a);
if tk.kind == ast::kind_pinned && !pinned_ctor(a) {
let err =
#fmt["mismatched kinds for %s: cannot copy pinned type %s",
descr, util::ppaux::ty_to_str(tcx, tk.ty)];
tcx.sess.span_err(a.span, err);
let note =
#fmt["try constructing %s directly into %s",
util::ppaux::ty_to_str(tcx, tk.ty), descr];
tcx.sess.span_note(a.span, note);
} else if tk.kind != ast::kind_pinned {
need_expr_kind(tcx, a, ast::kind_shared, descr);
}
fn pinned_ctor(a: @ast::expr) -> bool {
// FIXME: Technically a lambda block is also a pinned ctor
alt a.node {
ast::expr_call(cexpr, _, _) {
// Assuming that if it's a call that it's safe to move in, mostly
// because I don't know offhand how to ensure that it's a call
// specifically to a resource constructor
true
}
ast::expr_rec(_, _) {
true
}
ast::expr_unary(ast::uniq(_), _) {
true
}
ast::expr_tup(_) {
true
}
ast::expr_vec(exprs, _) {
true
}
_ { false }
}
}
}
fn check_expr(tcx: ty::ctxt, e: @ast::expr) {
alt e.node {
// FIXME: These rules do not fully implement the copy type-constructor
// discrimination described by the block comment at the top of this
// file. This code is wrong; it lets you copy anything shared-kind.
ast::expr_move(a, b) { need_shared_lhs_rhs(tcx, a, b, "<-"); }
ast::expr_assign(a, b) {
need_shared_lhs_rhs(tcx, a, b, "=");
}
ast::expr_assign_op(_, a, b) {
need_shared_lhs_rhs(tcx, a, b, "op=");
}
ast::expr_swap(a, b) { need_shared_lhs_rhs(tcx, a, b, "<->"); }
ast::expr_copy(a) {
need_expr_kind(tcx, a, ast::kind_shared, "'copy' operand");
}
ast::expr_ret(option::some(a)) {
need_expr_kind(tcx, a, ast::kind_shared, "'ret' operand");
}
ast::expr_be(a) {
need_expr_kind(tcx, a, ast::kind_shared, "'be' operand");
}
ast::expr_fail(option::some(a)) {
need_expr_kind(tcx, a, ast::kind_shared, "'fail' operand");
}
ast::expr_call(callee, _, _) {
let tpt = ty::expr_ty_params_and_ty(tcx, callee);
// If we have typarams, we're calling an item; we need to check
// that all the types we're supplying as typarams conform to the
// typaram kind constraints on that item.
if vec::len(tpt.params) != 0u {
let callee_def =
ast_util::def_id_of_def(tcx.def_map.get(callee.id));
let item_tk = ty::lookup_item_type(tcx, callee_def);
let i = 0;
assert (vec::len(item_tk.kinds) == vec::len(tpt.params));
for k_need: ast::kind in item_tk.kinds {
let t = tpt.params[i];
demand_kind(tcx, e.span, t, k_need,
#fmt("typaram %d", i));
i += 1;
}
}
}
ast::expr_unary(op, a) {
alt op {
ast::box(_) {
need_shared_or_pinned_ctor(tcx, a, "'@' operand");
}
ast::uniq(_) {
need_shared_or_pinned_ctor(tcx, a, "'~' operand");
}
_ { /* fall through */ }
}
}
ast::expr_rec(fields, _) {
for field in fields {
need_shared_or_pinned_ctor(tcx, field.node.expr, "record field");
}
}
ast::expr_tup(exprs) {
for expr in exprs {
need_shared_or_pinned_ctor(tcx, expr, "tuple parameter");
}
}
ast::expr_vec(exprs, _) {
// Putting pinned things into vectors is pretty useless since vector
// addition can't work (it's a copy)
for expr in exprs {
need_expr_kind(tcx, expr, ast::kind_shared, "vector element");
}
}
_ { }
}
}
fn check_stmt(tcx: ty::ctxt, stmt: @ast::stmt) {
alt stmt.node {
ast::stmt_decl(@{node: ast::decl_local(locals), _}, _) {
for (let_style, local) in locals {
alt local.node.init {
option::some({op: ast::init_assign., expr}) {
need_shared_or_pinned_ctor(tcx, expr,
"local initializer");
}
option::some({op: ast::init_move., expr}) {
need_shared_or_pinned_ctor(tcx, expr,
"local initializer");
}
option::none. { /* fall through */ }
}
}
}
_ { /* fall through */ }
}
}
*/

//
// Local Variables:
// mode: rust
Expand Down
2 changes: 1 addition & 1 deletion src/comp/middle/trans.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4079,7 +4079,7 @@ fn trans_expr_save_in(bcx: @block_ctxt, e: @ast::expr, dest: ValueRef)

// Call this to compile an expression that you need as an intermediate value,
// and you want to know whether you're dealing with an lval or not (the kind
// field in the returned struct). For non-immediates, use trans_expr or
// field in the returned struct). For non-intermediates, use trans_expr or
// trans_expr_save_in. For intermediates where you don't care about lval-ness,
// use trans_temp_expr.
fn trans_temp_lval(bcx: @block_ctxt, e: @ast::expr) -> lval_result {
Expand Down
2 changes: 1 addition & 1 deletion src/comp/middle/ty.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1143,7 +1143,7 @@ fn type_allows_implicit_copy(cx: ctxt, ty: t) -> bool {
}
_ { false }
};
}) && type_kind(cx, t) != ast::kind_noncopyable;
}) && type_kind(cx, ty) != ast::kind_noncopyable;
}

fn type_structurally_contains_uniques(cx: ctxt, ty: t) -> bool {
Expand Down

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