864 lines
31 KiB
Rust
864 lines
31 KiB
Rust
// Copyright 2014 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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/*!
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* A different sort of visitor for walking fn bodies. Unlike the
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* normal visitor, which just walks the entire body in one shot, the
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* `ExprUseVisitor` determines how expressions are being used.
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*/
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use mc = middle::mem_categorization;
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use middle::def;
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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::MethodCall;
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use middle::typeck;
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use syntax::ast;
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use syntax::codemap::{Span};
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use util::ppaux::Repr;
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use std::gc::Gc;
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///////////////////////////////////////////////////////////////////////////
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// The Delegate trait
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/// This trait defines the callbacks you can expect to receive when
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/// employing the ExprUseVisitor.
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pub trait Delegate {
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// The value found at `cmt` is either copied or moved, depending
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// on mode.
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fn consume(&mut self,
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consume_id: ast::NodeId,
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consume_span: Span,
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cmt: mc::cmt,
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mode: ConsumeMode);
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// The value found at `cmt` is either copied or moved via the
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// pattern binding `consume_pat`, depending on mode.
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fn consume_pat(&mut self,
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consume_pat: &ast::Pat,
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cmt: mc::cmt,
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mode: ConsumeMode);
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// The value found at `borrow` is being borrowed at the point
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// `borrow_id` for the region `loan_region` with kind `bk`.
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fn borrow(&mut self,
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borrow_id: ast::NodeId,
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borrow_span: Span,
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cmt: mc::cmt,
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loan_region: ty::Region,
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bk: ty::BorrowKind,
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loan_cause: LoanCause);
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// The local variable `id` is declared but not initialized.
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fn decl_without_init(&mut self,
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id: ast::NodeId,
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span: Span);
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// The path at `cmt` is being assigned to.
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fn mutate(&mut self,
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assignment_id: ast::NodeId,
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assignment_span: Span,
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assignee_cmt: mc::cmt,
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mode: MutateMode);
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}
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#[deriving(PartialEq)]
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pub enum LoanCause {
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ClosureCapture(Span),
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AddrOf,
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AutoRef,
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RefBinding,
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OverloadedOperator,
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ClosureInvocation
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}
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#[deriving(PartialEq,Show)]
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pub enum ConsumeMode {
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Copy, // reference to x where x has a type that copies
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Move(MoveReason), // reference to x where x has a type that moves
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}
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#[deriving(PartialEq,Show)]
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pub enum MoveReason {
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DirectRefMove,
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PatBindingMove,
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CaptureMove,
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}
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#[deriving(PartialEq,Show)]
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pub enum MutateMode {
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Init,
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JustWrite, // x = y
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WriteAndRead, // x += y
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}
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///////////////////////////////////////////////////////////////////////////
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// The ExprUseVisitor type
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//
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// This is the code that actually walks the tree. Like
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// mem_categorization, it requires a TYPER, which is a type that
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// supplies types from the tree. After type checking is complete, you
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// can just use the tcx as the typer.
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pub struct ExprUseVisitor<'d,'t,TYPER> {
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typer: &'t TYPER,
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mc: mc::MemCategorizationContext<'t,TYPER>,
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delegate: &'d mut Delegate,
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}
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// If the TYPER results in an error, it's because the type check
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// failed (or will fail, when the error is uncovered and reported
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// during writeback). In this case, we just ignore this part of the
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// code.
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//
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// Note that this macro appears similar to try!(), but, unlike try!(),
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// it does not propagate the error.
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macro_rules! return_if_err(
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($inp: expr) => (
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match $inp {
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Ok(v) => v,
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Err(()) => return
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}
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)
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)
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impl<'d,'t,TYPER:mc::Typer> ExprUseVisitor<'d,'t,TYPER> {
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pub fn new(delegate: &'d mut Delegate,
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typer: &'t TYPER)
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-> ExprUseVisitor<'d,'t,TYPER> {
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ExprUseVisitor { typer: typer,
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mc: mc::MemCategorizationContext::new(typer),
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delegate: delegate }
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}
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pub fn walk_fn(&mut self,
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decl: &ast::FnDecl,
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body: &ast::Block) {
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self.walk_arg_patterns(decl, body);
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self.walk_block(body);
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}
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fn walk_arg_patterns(&mut self,
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decl: &ast::FnDecl,
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body: &ast::Block) {
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for arg in decl.inputs.iter() {
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let arg_ty = ty::node_id_to_type(self.tcx(), arg.pat.id);
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let arg_cmt = self.mc.cat_rvalue(
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arg.id,
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arg.pat.span,
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ty::ReScope(body.id), // Args live only as long as the fn body.
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arg_ty);
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self.walk_pat(arg_cmt, arg.pat.clone());
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}
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}
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fn tcx<'a>(&'a self) -> &'a ty::ctxt {
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self.typer.tcx()
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}
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fn delegate_consume(&mut self,
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consume_id: ast::NodeId,
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consume_span: Span,
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cmt: mc::cmt) {
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let mode = copy_or_move(self.tcx(), cmt.ty, DirectRefMove);
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self.delegate.consume(consume_id, consume_span, cmt, mode);
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}
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fn consume_exprs(&mut self, exprs: &Vec<Gc<ast::Expr>>) {
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for expr in exprs.iter() {
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self.consume_expr(&**expr);
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}
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}
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fn consume_expr(&mut self, expr: &ast::Expr) {
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debug!("consume_expr(expr={})", expr.repr(self.tcx()));
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let cmt = return_if_err!(self.mc.cat_expr(expr));
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self.delegate_consume(expr.id, expr.span, cmt);
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self.walk_expr(expr);
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}
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fn mutate_expr(&mut self,
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assignment_expr: &ast::Expr,
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expr: &ast::Expr,
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mode: MutateMode) {
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let cmt = return_if_err!(self.mc.cat_expr(expr));
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self.delegate.mutate(assignment_expr.id, assignment_expr.span, cmt, mode);
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self.walk_expr(expr);
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}
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fn borrow_expr(&mut self,
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expr: &ast::Expr,
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r: ty::Region,
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bk: ty::BorrowKind,
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cause: LoanCause) {
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debug!("borrow_expr(expr={}, r={}, bk={})",
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expr.repr(self.tcx()), r.repr(self.tcx()), bk.repr(self.tcx()));
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let cmt = return_if_err!(self.mc.cat_expr(expr));
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self.delegate.borrow(expr.id, expr.span, cmt, r, bk, cause);
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// Note: Unlike consume, we can ignore ExprParen. cat_expr
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// already skips over them, and walk will uncover any
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// attachments or whatever.
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self.walk_expr(expr)
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}
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fn select_from_expr(&mut self, expr: &ast::Expr) {
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self.walk_expr(expr)
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}
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fn walk_expr(&mut self, expr: &ast::Expr) {
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debug!("walk_expr(expr={})", expr.repr(self.tcx()));
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self.walk_adjustment(expr);
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match expr.node {
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ast::ExprParen(ref subexpr) => {
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self.walk_expr(&**subexpr)
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}
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ast::ExprPath(..) => { }
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ast::ExprUnary(ast::UnDeref, ref base) => { // *base
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if !self.walk_overloaded_operator(expr, &**base, []) {
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self.select_from_expr(&**base);
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}
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}
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ast::ExprField(ref base, _, _) => { // base.f
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self.select_from_expr(&**base);
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}
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ast::ExprIndex(ref lhs, ref rhs) => { // lhs[rhs]
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if !self.walk_overloaded_operator(expr, &**lhs, [rhs.clone()]) {
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self.select_from_expr(&**lhs);
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self.consume_expr(&**rhs);
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}
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}
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ast::ExprCall(ref callee, ref args) => { // callee(args)
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self.walk_callee(expr, &**callee);
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self.consume_exprs(args);
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}
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ast::ExprMethodCall(_, _, ref args) => { // callee.m(args)
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self.consume_exprs(args);
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}
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ast::ExprStruct(_, ref fields, ref opt_with) => {
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self.walk_struct_expr(expr, fields, opt_with.clone());
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}
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ast::ExprTup(ref exprs) => {
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self.consume_exprs(exprs);
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}
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ast::ExprIf(ref cond_expr, ref then_blk, ref opt_else_expr) => {
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self.consume_expr(&**cond_expr);
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self.walk_block(&**then_blk);
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for else_expr in opt_else_expr.iter() {
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self.consume_expr(&**else_expr);
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}
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}
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ast::ExprMatch(ref discr, ref arms) => {
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// treatment of the discriminant is handled while
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// walking the arms:
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self.walk_expr(&**discr);
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let discr_cmt = return_if_err!(self.mc.cat_expr(&**discr));
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for arm in arms.iter() {
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self.walk_arm(discr_cmt.clone(), arm);
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}
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}
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ast::ExprVec(ref exprs) => {
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self.consume_exprs(exprs);
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}
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ast::ExprAddrOf(m, ref base) => { // &base
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// make sure that the thing we are pointing out stays valid
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// for the lifetime `scope_r` of the resulting ptr:
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let expr_ty = ty::expr_ty(self.tcx(), expr);
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if !ty::type_is_bot(expr_ty) {
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let r = ty::ty_region(self.tcx(), expr.span, expr_ty);
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let bk = ty::BorrowKind::from_mutbl(m);
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self.borrow_expr(&**base, r, bk, AddrOf);
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} else {
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self.walk_expr(&**base);
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}
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}
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ast::ExprInlineAsm(ref ia) => {
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for &(_, ref input) in ia.inputs.iter() {
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self.consume_expr(&**input);
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}
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for &(_, ref output) in ia.outputs.iter() {
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self.mutate_expr(expr, &**output, JustWrite);
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}
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}
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ast::ExprBreak(..) |
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ast::ExprAgain(..) |
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ast::ExprLit(..) => {}
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ast::ExprLoop(ref blk, _) => {
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self.walk_block(&**blk);
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}
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ast::ExprWhile(ref cond_expr, ref blk) => {
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self.consume_expr(&**cond_expr);
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self.walk_block(&**blk);
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}
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ast::ExprForLoop(..) => fail!("non-desugared expr_for_loop"),
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ast::ExprUnary(_, ref lhs) => {
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if !self.walk_overloaded_operator(expr, &**lhs, []) {
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self.consume_expr(&**lhs);
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}
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}
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ast::ExprBinary(_, ref lhs, ref rhs) => {
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if !self.walk_overloaded_operator(expr, &**lhs, [rhs.clone()]) {
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self.consume_expr(&**lhs);
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self.consume_expr(&**rhs);
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}
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}
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ast::ExprBlock(ref blk) => {
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self.walk_block(&**blk);
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}
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ast::ExprRet(ref opt_expr) => {
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for expr in opt_expr.iter() {
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self.consume_expr(&**expr);
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}
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}
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ast::ExprAssign(ref lhs, ref rhs) => {
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self.mutate_expr(expr, &**lhs, JustWrite);
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self.consume_expr(&**rhs);
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}
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ast::ExprCast(ref base, _) => {
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self.consume_expr(&**base);
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}
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ast::ExprAssignOp(_, ref lhs, ref rhs) => {
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// This will have to change if/when we support
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// overloaded operators for `+=` and so forth.
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self.mutate_expr(expr, &**lhs, WriteAndRead);
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self.consume_expr(&**rhs);
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}
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ast::ExprRepeat(ref base, ref count) => {
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self.consume_expr(&**base);
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self.consume_expr(&**count);
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}
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ast::ExprFnBlock(..) |
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ast::ExprProc(..) => {
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self.walk_captures(expr)
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}
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ast::ExprVstore(ref base, _) => {
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self.consume_expr(&**base);
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}
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ast::ExprBox(ref place, ref base) => {
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self.consume_expr(&**place);
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self.consume_expr(&**base);
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}
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ast::ExprMac(..) => {
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self.tcx().sess.span_bug(
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expr.span,
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"macro expression remains after expansion");
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}
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}
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}
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fn walk_callee(&mut self, call: &ast::Expr, callee: &ast::Expr) {
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let callee_ty = ty::expr_ty_adjusted(self.tcx(), callee);
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debug!("walk_callee: callee={} callee_ty={}",
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callee.repr(self.tcx()), callee_ty.repr(self.tcx()));
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match ty::get(callee_ty).sty {
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ty::ty_bare_fn(..) => {
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self.consume_expr(callee);
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}
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ty::ty_closure(ref f) => {
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match f.onceness {
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ast::Many => {
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self.borrow_expr(callee,
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ty::ReScope(call.id),
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ty::UniqueImmBorrow,
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ClosureInvocation);
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}
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ast::Once => {
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self.consume_expr(callee);
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}
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}
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}
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_ => {
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match self.tcx()
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.method_map
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.borrow()
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.find(&MethodCall::expr(call.id)) {
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Some(_) => {
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// FIXME(#14774, pcwalton): Implement this.
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}
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None => {
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self.tcx().sess.span_bug(
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callee.span,
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format!("unexpected callee type {}",
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callee_ty.repr(self.tcx())).as_slice());
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}
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}
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}
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}
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}
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fn walk_stmt(&mut self, stmt: &ast::Stmt) {
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match stmt.node {
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ast::StmtDecl(ref decl, _) => {
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match decl.node {
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ast::DeclLocal(ref local) => {
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self.walk_local(local.clone());
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}
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ast::DeclItem(_) => {
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// we don't visit nested items in this visitor,
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// only the fn body we were given.
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}
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}
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}
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ast::StmtExpr(ref expr, _) |
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ast::StmtSemi(ref expr, _) => {
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self.consume_expr(&**expr);
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}
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ast::StmtMac(..) => {
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self.tcx().sess.span_bug(stmt.span, "unexpanded stmt macro");
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}
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}
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}
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fn walk_local(&mut self, local: Gc<ast::Local>) {
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match local.init {
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None => {
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let delegate = &mut self.delegate;
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pat_util::pat_bindings(&self.typer.tcx().def_map, &*local.pat,
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|_, id, span, _| {
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delegate.decl_without_init(id, span);
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})
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}
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Some(ref expr) => {
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// Variable declarations with
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// initializers are considered
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// "assigns", which is handled by
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// `walk_pat`:
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self.walk_expr(&**expr);
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let init_cmt = return_if_err!(self.mc.cat_expr(&**expr));
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self.walk_pat(init_cmt, local.pat);
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}
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}
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}
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fn walk_block(&mut self, blk: &ast::Block) {
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/*!
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* Indicates that the value of `blk` will be consumed,
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* meaning either copied or moved depending on its type.
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*/
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debug!("walk_block(blk.id={:?})", blk.id);
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for stmt in blk.stmts.iter() {
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self.walk_stmt(&**stmt);
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}
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for tail_expr in blk.expr.iter() {
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self.consume_expr(&**tail_expr);
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}
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}
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fn walk_struct_expr(&mut self,
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_expr: &ast::Expr,
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fields: &Vec<ast::Field>,
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opt_with: Option<Gc<ast::Expr>>) {
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// Consume the expressions supplying values for each field.
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for field in fields.iter() {
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self.consume_expr(&*field.expr);
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}
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let with_expr = match opt_with {
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Some(ref w) => { w.clone() }
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None => { return; }
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};
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let with_cmt = return_if_err!(self.mc.cat_expr(&*with_expr));
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// Select just those fields of the `with`
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// expression that will actually be used
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let with_fields = match ty::get(with_cmt.ty).sty {
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ty::ty_struct(did, ref substs) => {
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ty::struct_fields(self.tcx(), did, substs)
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}
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_ => {
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self.tcx().sess.span_bug(
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with_expr.span,
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"with expression doesn't evaluate to a struct");
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}
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};
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|
|
// Consume those fields of the with expression that are needed.
|
|
for with_field in with_fields.iter() {
|
|
if !contains_field_named(with_field, fields) {
|
|
let cmt_field = self.mc.cat_field(&*with_expr,
|
|
with_cmt.clone(),
|
|
with_field.ident,
|
|
with_field.mt.ty);
|
|
self.delegate_consume(with_expr.id, with_expr.span, cmt_field);
|
|
}
|
|
}
|
|
|
|
fn contains_field_named(field: &ty::field,
|
|
fields: &Vec<ast::Field>)
|
|
-> bool
|
|
{
|
|
fields.iter().any(
|
|
|f| f.ident.node.name == field.ident.name)
|
|
}
|
|
}
|
|
|
|
// Invoke the appropriate delegate calls for anything that gets
|
|
// consumed or borrowed as part of the automatic adjustment
|
|
// process.
|
|
fn walk_adjustment(&mut self, expr: &ast::Expr) {
|
|
let typer = self.typer;
|
|
match typer.adjustments().borrow().find(&expr.id) {
|
|
None => { }
|
|
Some(adjustment) => {
|
|
match *adjustment {
|
|
ty::AutoAddEnv(..) |
|
|
ty::AutoObject(..) => {
|
|
// Creating an object or closure consumes the
|
|
// input and stores it into the resulting rvalue.
|
|
debug!("walk_adjustment(AutoAddEnv|AutoObject)");
|
|
let cmt_unadjusted =
|
|
return_if_err!(self.mc.cat_expr_unadjusted(expr));
|
|
self.delegate_consume(expr.id, expr.span, cmt_unadjusted);
|
|
}
|
|
ty::AutoDerefRef(ty::AutoDerefRef {
|
|
autoref: ref opt_autoref,
|
|
autoderefs: n
|
|
}) => {
|
|
self.walk_autoderefs(expr, n);
|
|
|
|
match *opt_autoref {
|
|
None => { }
|
|
Some(ref r) => {
|
|
self.walk_autoref(expr, r, n);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn walk_autoderefs(&mut self,
|
|
expr: &ast::Expr,
|
|
autoderefs: uint) {
|
|
/*!
|
|
* Autoderefs for overloaded Deref calls in fact reference
|
|
* their receiver. That is, if we have `(*x)` where `x` is of
|
|
* type `Rc<T>`, then this in fact is equivalent to
|
|
* `x.deref()`. Since `deref()` is declared with `&self`, this
|
|
* is an autoref of `x`.
|
|
*/
|
|
debug!("walk_autoderefs expr={} autoderefs={}", expr.repr(self.tcx()), autoderefs);
|
|
|
|
for i in range(0, autoderefs) {
|
|
let deref_id = typeck::MethodCall::autoderef(expr.id, i);
|
|
match self.typer.node_method_ty(deref_id) {
|
|
None => {}
|
|
Some(method_ty) => {
|
|
let cmt = return_if_err!(self.mc.cat_expr_autoderefd(expr, i));
|
|
let self_ty = *ty::ty_fn_args(method_ty).get(0);
|
|
let (m, r) = match ty::get(self_ty).sty {
|
|
ty::ty_rptr(r, ref m) => (m.mutbl, r),
|
|
_ => self.tcx().sess.span_bug(expr.span,
|
|
format!("bad overloaded deref type {}",
|
|
method_ty.repr(self.tcx())).as_slice())
|
|
};
|
|
let bk = ty::BorrowKind::from_mutbl(m);
|
|
self.delegate.borrow(expr.id, expr.span, cmt,
|
|
r, bk, AutoRef);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
fn walk_autoref(&mut self,
|
|
expr: &ast::Expr,
|
|
autoref: &ty::AutoRef,
|
|
autoderefs: uint) {
|
|
debug!("walk_autoref expr={} autoderefs={}", expr.repr(self.tcx()), autoderefs);
|
|
|
|
let cmt_derefd = return_if_err!(
|
|
self.mc.cat_expr_autoderefd(expr, autoderefs));
|
|
|
|
debug!("walk_autoref: cmt_derefd={}", cmt_derefd.repr(self.tcx()));
|
|
|
|
match *autoref {
|
|
ty::AutoPtr(r, m) => {
|
|
self.delegate.borrow(expr.id,
|
|
expr.span,
|
|
cmt_derefd,
|
|
r,
|
|
ty::BorrowKind::from_mutbl(m),
|
|
AutoRef)
|
|
}
|
|
ty::AutoBorrowVec(r, m) | ty::AutoBorrowVecRef(r, m) => {
|
|
let cmt_index = self.mc.cat_index(expr, cmt_derefd, autoderefs+1);
|
|
self.delegate.borrow(expr.id,
|
|
expr.span,
|
|
cmt_index,
|
|
r,
|
|
ty::BorrowKind::from_mutbl(m),
|
|
AutoRef)
|
|
}
|
|
ty::AutoBorrowObj(r, m) => {
|
|
let cmt_deref = self.mc.cat_deref_obj(expr, cmt_derefd);
|
|
self.delegate.borrow(expr.id,
|
|
expr.span,
|
|
cmt_deref,
|
|
r,
|
|
ty::BorrowKind::from_mutbl(m),
|
|
AutoRef)
|
|
}
|
|
ty::AutoUnsafe(_) => {}
|
|
}
|
|
}
|
|
|
|
fn walk_overloaded_operator(&mut self,
|
|
expr: &ast::Expr,
|
|
receiver: &ast::Expr,
|
|
args: &[Gc<ast::Expr>])
|
|
-> bool
|
|
{
|
|
if !self.typer.is_method_call(expr.id) {
|
|
return false;
|
|
}
|
|
|
|
self.walk_expr(receiver);
|
|
|
|
// Arguments (but not receivers) to overloaded operator
|
|
// methods are implicitly autoref'd which sadly does not use
|
|
// adjustments, so we must hardcode the borrow here.
|
|
|
|
let r = ty::ReScope(expr.id);
|
|
let bk = ty::ImmBorrow;
|
|
|
|
for arg in args.iter() {
|
|
self.borrow_expr(&**arg, r, bk, OverloadedOperator);
|
|
}
|
|
return true;
|
|
}
|
|
|
|
fn walk_arm(&mut self, discr_cmt: mc::cmt, arm: &ast::Arm) {
|
|
for &pat in arm.pats.iter() {
|
|
self.walk_pat(discr_cmt.clone(), pat);
|
|
}
|
|
|
|
for guard in arm.guard.iter() {
|
|
self.consume_expr(&**guard);
|
|
}
|
|
|
|
self.consume_expr(&*arm.body);
|
|
}
|
|
|
|
fn walk_pat(&mut self, cmt_discr: mc::cmt, pat: Gc<ast::Pat>) {
|
|
debug!("walk_pat cmt_discr={} pat={}", cmt_discr.repr(self.tcx()),
|
|
pat.repr(self.tcx()));
|
|
let mc = &self.mc;
|
|
let typer = self.typer;
|
|
let tcx = typer.tcx();
|
|
let def_map = &self.typer.tcx().def_map;
|
|
let delegate = &mut self.delegate;
|
|
return_if_err!(mc.cat_pattern(cmt_discr, &*pat, |mc, cmt_pat, pat| {
|
|
if pat_util::pat_is_binding(def_map, pat) {
|
|
let tcx = typer.tcx();
|
|
|
|
debug!("binding cmt_pat={} pat={}",
|
|
cmt_pat.repr(tcx),
|
|
pat.repr(tcx));
|
|
|
|
// pat_ty: the type of the binding being produced.
|
|
let pat_ty = ty::node_id_to_type(tcx, pat.id);
|
|
|
|
// Each match binding is effectively an assignment to the
|
|
// binding being produced.
|
|
let def = def_map.borrow().get_copy(&pat.id);
|
|
match mc.cat_def(pat.id, pat.span, pat_ty, def) {
|
|
Ok(binding_cmt) => {
|
|
delegate.mutate(pat.id, pat.span, binding_cmt, Init);
|
|
}
|
|
Err(_) => { }
|
|
}
|
|
|
|
// It is also a borrow or copy/move of the value being matched.
|
|
match pat.node {
|
|
ast::PatIdent(ast::BindByRef(m), _, _) => {
|
|
let (r, bk) = {
|
|
(ty::ty_region(tcx, pat.span, pat_ty),
|
|
ty::BorrowKind::from_mutbl(m))
|
|
};
|
|
delegate.borrow(pat.id, pat.span, cmt_pat,
|
|
r, bk, RefBinding);
|
|
}
|
|
ast::PatIdent(ast::BindByValue(_), _, _) => {
|
|
let mode = copy_or_move(typer.tcx(), cmt_pat.ty, PatBindingMove);
|
|
delegate.consume_pat(pat, cmt_pat, mode);
|
|
}
|
|
_ => {
|
|
typer.tcx().sess.span_bug(
|
|
pat.span,
|
|
"binding pattern not an identifier");
|
|
}
|
|
}
|
|
} else {
|
|
match pat.node {
|
|
ast::PatVec(_, Some(slice_pat), _) => {
|
|
// The `slice_pat` here creates a slice into
|
|
// the original vector. This is effectively a
|
|
// borrow of the elements of the vector being
|
|
// matched.
|
|
|
|
let (slice_cmt, slice_mutbl, slice_r) = {
|
|
match mc.cat_slice_pattern(cmt_pat, &*slice_pat) {
|
|
Ok(v) => v,
|
|
Err(()) => {
|
|
tcx.sess.span_bug(slice_pat.span,
|
|
"Err from mc")
|
|
}
|
|
}
|
|
};
|
|
|
|
// Note: We declare here that the borrow
|
|
// occurs upon entering the `[...]`
|
|
// pattern. This implies that something like
|
|
// `[a, ..b]` where `a` is a move is illegal,
|
|
// because the borrow is already in effect.
|
|
// In fact such a move would be safe-ish, but
|
|
// it effectively *requires* that we use the
|
|
// nulling out semantics to indicate when a
|
|
// value has been moved, which we are trying
|
|
// to move away from. Otherwise, how can we
|
|
// indicate that the first element in the
|
|
// vector has been moved? Eventually, we
|
|
// could perhaps modify this rule to permit
|
|
// `[..a, b]` where `b` is a move, because in
|
|
// that case we can adjust the length of the
|
|
// original vec accordingly, but we'd have to
|
|
// make trans do the right thing, and it would
|
|
// only work for `~` vectors. It seems simpler
|
|
// to just require that people call
|
|
// `vec.pop()` or `vec.unshift()`.
|
|
let slice_bk = ty::BorrowKind::from_mutbl(slice_mutbl);
|
|
delegate.borrow(pat.id, pat.span,
|
|
slice_cmt, slice_r,
|
|
slice_bk, RefBinding);
|
|
}
|
|
_ => { }
|
|
}
|
|
}
|
|
}));
|
|
}
|
|
|
|
fn walk_captures(&mut self, closure_expr: &ast::Expr) {
|
|
debug!("walk_captures({})", closure_expr.repr(self.tcx()));
|
|
|
|
let tcx = self.typer.tcx();
|
|
freevars::with_freevars(tcx, closure_expr.id, |freevars| {
|
|
match freevars::get_capture_mode(self.tcx(), closure_expr.id) {
|
|
freevars::CaptureByRef => {
|
|
self.walk_by_ref_captures(closure_expr, freevars);
|
|
}
|
|
freevars::CaptureByValue => {
|
|
self.walk_by_value_captures(closure_expr, freevars);
|
|
}
|
|
}
|
|
});
|
|
}
|
|
|
|
fn walk_by_ref_captures(&mut self,
|
|
closure_expr: &ast::Expr,
|
|
freevars: &[freevars::freevar_entry]) {
|
|
for freevar in freevars.iter() {
|
|
let id_var = freevar.def.def_id().node;
|
|
let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.id,
|
|
closure_expr.span,
|
|
freevar.def));
|
|
|
|
// Lookup the kind of borrow the callee requires, as
|
|
// inferred by regionbk
|
|
let upvar_id = ty::UpvarId { var_id: id_var,
|
|
closure_expr_id: closure_expr.id };
|
|
let upvar_borrow = self.tcx().upvar_borrow_map.borrow()
|
|
.get_copy(&upvar_id);
|
|
|
|
self.delegate.borrow(closure_expr.id,
|
|
closure_expr.span,
|
|
cmt_var,
|
|
upvar_borrow.region,
|
|
upvar_borrow.kind,
|
|
ClosureCapture(freevar.span));
|
|
}
|
|
}
|
|
|
|
fn walk_by_value_captures(&mut self,
|
|
closure_expr: &ast::Expr,
|
|
freevars: &[freevars::freevar_entry]) {
|
|
for freevar in freevars.iter() {
|
|
let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.id,
|
|
closure_expr.span,
|
|
freevar.def));
|
|
let mode = copy_or_move(self.tcx(), cmt_var.ty, CaptureMove);
|
|
self.delegate.consume(closure_expr.id, freevar.span, cmt_var, mode);
|
|
}
|
|
}
|
|
|
|
fn cat_captured_var(&mut self,
|
|
closure_id: ast::NodeId,
|
|
closure_span: Span,
|
|
upvar_def: def::Def)
|
|
-> mc::McResult<mc::cmt> {
|
|
// Create the cmt for the variable being borrowed, from the
|
|
// caller's perspective
|
|
let var_id = upvar_def.def_id().node;
|
|
let var_ty = ty::node_id_to_type(self.tcx(), var_id);
|
|
self.mc.cat_def(closure_id, closure_span, var_ty, upvar_def)
|
|
}
|
|
}
|
|
|
|
fn copy_or_move(tcx: &ty::ctxt, ty: ty::t, move_reason: MoveReason) -> ConsumeMode {
|
|
if ty::type_moves_by_default(tcx, ty) { Move(move_reason) } else { Copy }
|
|
}
|
|
|