556 lines
20 KiB
Rust
556 lines
20 KiB
Rust
// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use middle::freevars::freevar_entry;
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use middle::freevars;
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use middle::pat_util;
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use middle::ty;
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use middle::typeck;
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use util::ppaux::{Repr, ty_to_str};
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use util::ppaux::UserString;
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use syntax::ast::*;
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use syntax::attr::attrs_contains_name;
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use syntax::codemap::span;
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use syntax::print::pprust::expr_to_str;
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use syntax::{visit, ast_util};
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// Kind analysis pass.
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//
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// There are several kinds defined by various operations. The most restrictive
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// kind is noncopyable. The noncopyable kind can be extended with any number
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// of the following attributes.
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//
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// send: Things that can be sent on channels or included in spawned closures.
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// copy: Things that can be copied.
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// const: Things thare are deeply immutable. They are guaranteed never to
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// change, and can be safely shared without copying between tasks.
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// owned: Things that do not contain borrowed pointers.
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//
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// Send includes scalar types as well as classes and unique types containing
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// only sendable types.
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//
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// Copy includes boxes, closure and unique types containing copyable types.
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//
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// Const include scalar types, things without non-const fields, and pointers
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// to const things.
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//
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// This pass ensures that type parameters are only instantiated with types
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// whose kinds are equal or less general than the way the type parameter was
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// annotated (with the `send`, `copy` or `const` keyword).
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//
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// It also verifies that noncopyable kinds are not copied. Sendability is not
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// applied, since none of our language primitives send. Instead, the sending
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// primitives in the stdlib are explicitly annotated to only take sendable
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// types.
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pub static try_adding: &'static str = "Try adding a move";
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pub struct Context {
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tcx: ty::ctxt,
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method_map: typeck::method_map,
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current_item: node_id
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}
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pub fn check_crate(tcx: ty::ctxt,
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method_map: typeck::method_map,
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crate: @crate) {
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let ctx = Context {
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tcx: tcx,
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method_map: method_map,
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current_item: -1
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};
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let visit = visit::mk_vt(@visit::Visitor {
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visit_arm: check_arm,
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visit_expr: check_expr,
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visit_fn: check_fn,
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visit_ty: check_ty,
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visit_item: check_item,
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visit_block: check_block,
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.. *visit::default_visitor()
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});
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visit::visit_crate(crate, ctx, visit);
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tcx.sess.abort_if_errors();
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}
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type check_fn = @fn(Context, @freevar_entry);
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fn check_struct_safe_for_destructor(cx: Context,
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span: span,
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struct_did: def_id) {
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let struct_tpt = ty::lookup_item_type(cx.tcx, struct_did);
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if !struct_tpt.generics.has_type_params() {
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let struct_ty = ty::mk_struct(cx.tcx, struct_did, ty::substs {
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self_r: None,
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self_ty: None,
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tps: ~[]
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});
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if !ty::type_is_owned(cx.tcx, struct_ty) {
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cx.tcx.sess.span_err(span,
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"cannot implement a destructor on a struct \
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that is not Owned");
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cx.tcx.sess.span_note(span,
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"use \"#[unsafe_destructor]\" on the \
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implementation to force the compiler to \
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allow this");
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}
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} else {
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cx.tcx.sess.span_err(span,
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"cannot implement a destructor on a struct \
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with type parameters");
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cx.tcx.sess.span_note(span,
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"use \"#[unsafe_destructor]\" on the \
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implementation to force the compiler to \
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allow this");
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}
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}
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fn check_block(block: &blk, cx: Context, visitor: visit::vt<Context>) {
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visit::visit_block(block, cx, visitor);
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}
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fn check_item(item: @item, cx: Context, visitor: visit::vt<Context>) {
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// If this is a destructor, check kinds.
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if !attrs_contains_name(item.attrs, "unsafe_destructor") {
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match item.node {
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item_impl(_, Some(trait_ref), self_type, _) => {
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match cx.tcx.def_map.find(&trait_ref.ref_id) {
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None => cx.tcx.sess.bug(~"trait ref not in def map!"),
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Some(&trait_def) => {
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let trait_def_id = ast_util::def_id_of_def(trait_def);
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if cx.tcx.lang_items.drop_trait() == trait_def_id {
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// Yes, it's a destructor.
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match self_type.node {
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ty_path(_, path_node_id) => {
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let struct_def = cx.tcx.def_map.get_copy(
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&path_node_id);
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let struct_did =
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ast_util::def_id_of_def(struct_def);
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check_struct_safe_for_destructor(
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cx,
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self_type.span,
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struct_did);
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}
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_ => {
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cx.tcx.sess.span_bug(self_type.span,
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"the self type for \
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the Drop trait \
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impl is not a \
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path");
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}
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}
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}
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}
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}
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}
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_ => {}
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}
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}
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let cx = Context { current_item: item.id, ..cx };
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visit::visit_item(item, cx, visitor);
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}
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// Yields the appropriate function to check the kind of closed over
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// variables. `id` is the node_id for some expression that creates the
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// closure.
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fn with_appropriate_checker(cx: Context, id: node_id, b: &fn(check_fn)) {
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fn check_for_uniq(cx: Context, fv: @freevar_entry) {
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// all captured data must be owned, regardless of whether it is
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// moved in or copied in.
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let id = ast_util::def_id_of_def(fv.def).node;
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let var_t = ty::node_id_to_type(cx.tcx, id);
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if !check_owned(cx, var_t, fv.span) { return; }
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// check that only immutable variables are implicitly copied in
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check_imm_free_var(cx, fv.def, fv.span);
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}
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fn check_for_box(cx: Context, fv: @freevar_entry) {
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// all captured data must be owned
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let id = ast_util::def_id_of_def(fv.def).node;
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let var_t = ty::node_id_to_type(cx.tcx, id);
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if !check_durable(cx.tcx, var_t, fv.span) { return; }
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// check that only immutable variables are implicitly copied in
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check_imm_free_var(cx, fv.def, fv.span);
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}
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fn check_for_block(_cx: Context, _fv: @freevar_entry) {
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// no restrictions
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}
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fn check_for_bare(cx: Context, fv: @freevar_entry) {
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cx.tcx.sess.span_err(
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fv.span,
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"attempted dynamic environment capture");
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}
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let fty = ty::node_id_to_type(cx.tcx, id);
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match ty::get(fty).sty {
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ty::ty_closure(ty::ClosureTy {sigil: OwnedSigil, _}) => {
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b(check_for_uniq)
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}
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ty::ty_closure(ty::ClosureTy {sigil: ManagedSigil, _}) => {
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b(check_for_box)
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}
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ty::ty_closure(ty::ClosureTy {sigil: BorrowedSigil, _}) => {
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b(check_for_block)
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}
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ty::ty_bare_fn(_) => {
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b(check_for_bare)
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}
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ref s => {
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cx.tcx.sess.bug(
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fmt!("expect fn type in kind checker, not %?", s));
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}
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}
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}
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// Check that the free variables used in a shared/sendable closure conform
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// to the copy/move kind bounds. Then recursively check the function body.
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fn check_fn(
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fk: &visit::fn_kind,
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decl: &fn_decl,
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body: &blk,
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sp: span,
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fn_id: node_id,
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cx: Context,
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v: visit::vt<Context>) {
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// Check kinds on free variables:
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do with_appropriate_checker(cx, fn_id) |chk| {
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for vec::each(*freevars::get_freevars(cx.tcx, fn_id)) |fv| {
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chk(cx, *fv);
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}
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}
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visit::visit_fn(fk, decl, body, sp, fn_id, cx, v);
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}
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fn check_arm(a: &arm, cx: Context, v: visit::vt<Context>) {
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for a.pats.each |p| {
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do pat_util::pat_bindings(cx.tcx.def_map, *p) |mode, id, span, _pth| {
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if mode == bind_by_copy {
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let t = ty::node_id_to_type(cx.tcx, id);
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let reason = "consider binding with `ref` or `move` instead";
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check_copy(cx, t, span, reason);
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}
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}
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}
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visit::visit_arm(a, cx, v);
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}
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pub fn check_expr(e: @expr, cx: Context, v: visit::vt<Context>) {
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debug!("kind::check_expr(%s)", expr_to_str(e, cx.tcx.sess.intr()));
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// Handle any kind bounds on type parameters
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let type_parameter_id = match e.node {
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expr_index(*)|expr_assign_op(*)|
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expr_unary(*)|expr_binary(*)|expr_method_call(*) => e.callee_id,
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_ => e.id
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};
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for cx.tcx.node_type_substs.find(&type_parameter_id).each |ts| {
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let type_param_defs = match e.node {
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expr_path(_) => {
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let did = ast_util::def_id_of_def(cx.tcx.def_map.get_copy(&e.id));
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ty::lookup_item_type(cx.tcx, did).generics.type_param_defs
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}
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_ => {
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// Type substitutions should only occur on paths and
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// method calls, so this needs to be a method call.
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// Even though the callee_id may have been the id with
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// node_type_substs, e.id is correct here.
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ty::method_call_type_param_defs(cx.tcx, cx.method_map, e.id).expect(
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~"non path/method call expr has type substs??")
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}
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};
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if ts.len() != type_param_defs.len() {
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// Fail earlier to make debugging easier
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fail!("internal error: in kind::check_expr, length \
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mismatch between actual and declared bounds: actual = \
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%s, declared = %s",
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ts.repr(cx.tcx),
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type_param_defs.repr(cx.tcx));
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}
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for vec::each2(**ts, *type_param_defs) |&ty, type_param_def| {
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check_bounds(cx, type_parameter_id, e.span, ty, type_param_def)
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}
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}
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match e.node {
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expr_cast(source, _) => {
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check_cast_for_escaping_regions(cx, source, e);
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check_kind_bounds_of_cast(cx, source, e);
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}
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expr_copy(expr) => {
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// Note: This is the only place where we must check whether the
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// argument is copyable. This is not because this is the only
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// kind of expression that may copy things, but rather because all
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// other copies will have been converted to moves by by the
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// `moves` pass if the value is not copyable.
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check_copy(cx,
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ty::expr_ty(cx.tcx, expr),
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expr.span,
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"explicit copy requires a copyable argument");
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}
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expr_repeat(element, count_expr, _) => {
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let count = ty::eval_repeat_count(cx.tcx, count_expr);
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if count > 1 {
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let element_ty = ty::expr_ty(cx.tcx, element);
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check_copy(cx, element_ty, element.span,
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"repeated element will be copied");
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}
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}
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_ => {}
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}
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visit::visit_expr(e, cx, v);
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}
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fn check_ty(aty: @Ty, cx: Context, v: visit::vt<Context>) {
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match aty.node {
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ty_path(_, id) => {
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for cx.tcx.node_type_substs.find(&id).each |ts| {
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let did = ast_util::def_id_of_def(cx.tcx.def_map.get_copy(&id));
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let type_param_defs =
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ty::lookup_item_type(cx.tcx, did).generics.type_param_defs;
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for vec::each2(**ts, *type_param_defs) |&ty, type_param_def| {
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check_bounds(cx, aty.id, aty.span, ty, type_param_def)
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}
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}
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}
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_ => {}
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}
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visit::visit_ty(aty, cx, v);
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}
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pub fn check_bounds(cx: Context,
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_type_parameter_id: node_id,
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sp: span,
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ty: ty::t,
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type_param_def: &ty::TypeParameterDef)
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{
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let kind = ty::type_contents(cx.tcx, ty);
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let mut missing = ty::EmptyBuiltinBounds();
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for type_param_def.bounds.builtin_bounds.each |bound| {
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if !kind.meets_bound(cx.tcx, bound) {
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missing.add(bound);
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}
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}
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if !missing.is_empty() {
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cx.tcx.sess.span_err(
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sp,
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fmt!("instantiating a type parameter with an incompatible type \
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`%s`, which does not fulfill `%s`",
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ty_to_str(cx.tcx, ty),
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missing.user_string(cx.tcx)));
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}
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}
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fn is_nullary_variant(cx: Context, ex: @expr) -> bool {
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match ex.node {
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expr_path(_) => {
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match cx.tcx.def_map.get_copy(&ex.id) {
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def_variant(edid, vdid) => {
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vec::len(ty::enum_variant_with_id(cx.tcx, edid, vdid).args) == 0u
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}
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_ => false
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}
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}
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_ => false
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}
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}
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fn check_imm_free_var(cx: Context, def: def, sp: span) {
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match def {
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def_local(_, is_mutbl) => {
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if is_mutbl {
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cx.tcx.sess.span_err(
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sp,
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"mutable variables cannot be implicitly captured");
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}
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}
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def_arg(*) => { /* ok */ }
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def_upvar(_, def1, _, _) => { check_imm_free_var(cx, *def1, sp); }
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def_binding(*) | def_self(*) => { /*ok*/ }
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_ => {
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cx.tcx.sess.span_bug(
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sp,
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fmt!("unknown def for free variable: %?", def));
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}
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}
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}
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fn check_copy(cx: Context, ty: ty::t, sp: span, reason: &str) {
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debug!("type_contents(%s)=%s",
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ty_to_str(cx.tcx, ty),
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ty::type_contents(cx.tcx, ty).to_str());
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if !ty::type_is_copyable(cx.tcx, ty) {
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cx.tcx.sess.span_err(
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sp, fmt!("copying a value of non-copyable type `%s`",
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ty_to_str(cx.tcx, ty)));
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cx.tcx.sess.span_note(sp, fmt!("%s", reason));
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}
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}
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pub fn check_owned(cx: Context, ty: ty::t, sp: span) -> bool {
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if !ty::type_is_owned(cx.tcx, ty) {
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cx.tcx.sess.span_err(
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sp, fmt!("value has non-owned type `%s`",
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ty_to_str(cx.tcx, ty)));
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false
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} else {
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true
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}
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}
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// note: also used from middle::typeck::regionck!
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pub fn check_durable(tcx: ty::ctxt, ty: ty::t, sp: span) -> bool {
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if !ty::type_is_static(tcx, ty) {
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match ty::get(ty).sty {
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ty::ty_param(*) => {
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tcx.sess.span_err(sp, "value may contain borrowed \
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pointers; use `'static` bound");
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}
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_ => {
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tcx.sess.span_err(sp, "value may contain borrowed \
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pointers");
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}
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}
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false
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} else {
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true
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}
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}
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/// This is rather subtle. When we are casting a value to a instantiated
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/// trait like `a as trait<'r>`, regionck already ensures that any borrowed
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/// pointers that appear in the type of `a` are bounded by `'r` (ed.: rem
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/// FIXME(#5723)). However, it is possible that there are *type parameters*
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/// in the type of `a`, and those *type parameters* may have borrowed pointers
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/// within them. We have to guarantee that the regions which appear in those
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/// type parameters are not obscured.
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///
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/// Therefore, we ensure that one of three conditions holds:
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///
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/// (1) The trait instance cannot escape the current fn. This is
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/// guaranteed if the region bound `&r` is some scope within the fn
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/// itself. This case is safe because whatever borrowed pointers are
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/// found within the type parameter, they must enclose the fn body
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/// itself.
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///
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/// (2) The type parameter appears in the type of the trait. For
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/// example, if the type parameter is `T` and the trait type is
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/// `deque<T>`, then whatever borrowed ptrs may appear in `T` also
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/// appear in `deque<T>`.
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///
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/// (3) The type parameter is owned (and therefore does not contain
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/// borrowed ptrs).
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///
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/// FIXME(#5723)---This code should probably move into regionck.
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pub fn check_cast_for_escaping_regions(
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cx: Context,
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source: @expr,
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target: @expr)
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{
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// Determine what type we are casting to; if it is not an trait, then no
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// worries.
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let target_ty = ty::expr_ty(cx.tcx, target);
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match ty::get(target_ty).sty {
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ty::ty_trait(*) => {}
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_ => { return; }
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}
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// Collect up the regions that appear in the target type. We want to
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// ensure that these lifetimes are shorter than all lifetimes that are in
|
|
// the source type. See test `src/test/compile-fail/regions-trait-2.rs`
|
|
let mut target_regions = ~[];
|
|
ty::walk_regions_and_ty(
|
|
cx.tcx,
|
|
target_ty,
|
|
|r| {
|
|
if !r.is_bound() {
|
|
target_regions.push(r);
|
|
}
|
|
},
|
|
|_| true);
|
|
|
|
// Check, based on the region associated with the trait, whether it can
|
|
// possibly escape the enclosing fn item (note that all type parameters
|
|
// must have been declared on the enclosing fn item).
|
|
if target_regions.any(|r| is_re_scope(*r)) {
|
|
return; /* case (1) */
|
|
}
|
|
|
|
// Assuming the trait instance can escape, then ensure that each parameter
|
|
// either appears in the trait type or is owned.
|
|
let target_params = ty::param_tys_in_type(target_ty);
|
|
let source_ty = ty::expr_ty(cx.tcx, source);
|
|
ty::walk_regions_and_ty(
|
|
cx.tcx,
|
|
source_ty,
|
|
|
|
|_r| {
|
|
// FIXME(#5723) --- turn this check on once &Objects are usable
|
|
//
|
|
// if !target_regions.any(|t_r| is_subregion_of(cx, *t_r, r)) {
|
|
// cx.tcx.sess.span_err(
|
|
// source.span,
|
|
// fmt!("source contains borrowed pointer with lifetime \
|
|
// not found in the target type `%s`",
|
|
// ty_to_str(cx.tcx, target_ty)));
|
|
// note_and_explain_region(
|
|
// cx.tcx, "source data is only valid for ", r, "");
|
|
// }
|
|
},
|
|
|
|
|ty| {
|
|
match ty::get(ty).sty {
|
|
ty::ty_param(source_param) => {
|
|
if target_params.contains(&source_param) {
|
|
/* case (2) */
|
|
} else {
|
|
check_durable(cx.tcx, ty, source.span); /* case (3) */
|
|
}
|
|
}
|
|
_ => {}
|
|
}
|
|
true
|
|
});
|
|
|
|
fn is_re_scope(r: ty::Region) -> bool {
|
|
match r {
|
|
ty::re_scope(*) => true,
|
|
_ => false
|
|
}
|
|
}
|
|
|
|
fn is_subregion_of(cx: Context, r_sub: ty::Region, r_sup: ty::Region) -> bool {
|
|
cx.tcx.region_maps.is_subregion_of(r_sub, r_sup)
|
|
}
|
|
}
|
|
|
|
/// Ensures that values placed into a ~Trait are copyable and sendable.
|
|
pub fn check_kind_bounds_of_cast(cx: Context, source: @expr, target: @expr) {
|
|
let target_ty = ty::expr_ty(cx.tcx, target);
|
|
match ty::get(target_ty).sty {
|
|
ty::ty_trait(_, _, ty::UniqTraitStore, _) => {
|
|
let source_ty = ty::expr_ty(cx.tcx, source);
|
|
if !ty::type_is_owned(cx.tcx, source_ty) {
|
|
cx.tcx.sess.span_err(
|
|
target.span,
|
|
"uniquely-owned trait objects must be sendable");
|
|
}
|
|
}
|
|
_ => {} // Nothing to do.
|
|
}
|
|
}
|