// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! A different sort of visitor for walking fn bodies. Unlike the
//! normal visitor, which just walks the entire body in one shot, the
//! `ExprUseVisitor` determines how expressions are being used.
pub use self::MutateMode::*;
pub use self::LoanCause::*;
pub use self::ConsumeMode::*;
pub use self::MoveReason::*;
pub use self::MatchMode::*;
use self::TrackMatchMode::*;
use self::OverloadedCallType::*;
use middle::{def, pat_util};
use middle::def_id::{DefId};
use middle::infer;
use middle::mem_categorization as mc;
use middle::ty;
use middle::ty::adjustment;
use rustc_front::hir;
use syntax::ast;
use syntax::ptr::P;
use syntax::codemap::Span;
///////////////////////////////////////////////////////////////////////////
// The Delegate trait
/// This trait defines the callbacks you can expect to receive when
/// employing the ExprUseVisitor.
pub trait Delegate<'tcx> {
// The value found at `cmt` is either copied or moved, depending
// on mode.
fn consume(&mut self,
consume_id: ast::NodeId,
consume_span: Span,
cmt: mc::cmt<'tcx>,
mode: ConsumeMode);
// The value found at `cmt` has been determined to match the
// pattern binding `matched_pat`, and its subparts are being
// copied or moved depending on `mode`. Note that `matched_pat`
// is called on all variant/structs in the pattern (i.e., the
// interior nodes of the pattern's tree structure) while
// consume_pat is called on the binding identifiers in the pattern
// (which are leaves of the pattern's tree structure).
//
// Note that variants/structs and identifiers are disjoint; thus
// `matched_pat` and `consume_pat` are never both called on the
// same input pattern structure (though of `consume_pat` can be
// called on a subpart of an input passed to `matched_pat).
fn matched_pat(&mut self,
matched_pat: &hir::Pat,
cmt: mc::cmt<'tcx>,
mode: MatchMode);
// The value found at `cmt` is either copied or moved via the
// pattern binding `consume_pat`, depending on mode.
fn consume_pat(&mut self,
consume_pat: &hir::Pat,
cmt: mc::cmt<'tcx>,
mode: ConsumeMode);
// The value found at `borrow` is being borrowed at the point
// `borrow_id` for the region `loan_region` with kind `bk`.
fn borrow(&mut self,
borrow_id: ast::NodeId,
borrow_span: Span,
cmt: mc::cmt<'tcx>,
loan_region: ty::Region,
bk: ty::BorrowKind,
loan_cause: LoanCause);
// The local variable `id` is declared but not initialized.
fn decl_without_init(&mut self,
id: ast::NodeId,
span: Span);
// The path at `cmt` is being assigned to.
fn mutate(&mut self,
assignment_id: ast::NodeId,
assignment_span: Span,
assignee_cmt: mc::cmt<'tcx>,
mode: MutateMode);
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum LoanCause {
ClosureCapture(Span),
AddrOf,
AutoRef,
AutoUnsafe,
RefBinding,
OverloadedOperator,
ClosureInvocation,
ForLoop,
MatchDiscriminant
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum ConsumeMode {
Copy, // reference to x where x has a type that copies
Move(MoveReason), // reference to x where x has a type that moves
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum MoveReason {
DirectRefMove,
PatBindingMove,
CaptureMove,
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum MatchMode {
NonBindingMatch,
BorrowingMatch,
CopyingMatch,
MovingMatch,
}
#[derive(Copy, Clone, PartialEq, Debug)]
enum TrackMatchMode {
Unknown,
Definite(MatchMode),
Conflicting,
}
impl TrackMatchMode {
// Builds up the whole match mode for a pattern from its constituent
// parts. The lattice looks like this:
//
// Conflicting
// / \
// / \
// Borrowing Moving
// \ /
// \ /
// Copying
// |
// NonBinding
// |
// Unknown
//
// examples:
//
// * `(_, some_int)` pattern is Copying, since
// NonBinding + Copying => Copying
//
// * `(some_int, some_box)` pattern is Moving, since
// Copying + Moving => Moving
//
// * `(ref x, some_box)` pattern is Conflicting, since
// Borrowing + Moving => Conflicting
//
// Note that the `Unknown` and `Conflicting` states are
// represented separately from the other more interesting
// `Definite` states, which simplifies logic here somewhat.
fn lub(&mut self, mode: MatchMode) {
*self = match (*self, mode) {
// Note that clause order below is very significant.
(Unknown, new) => Definite(new),
(Definite(old), new) if old == new => Definite(old),
(Definite(old), NonBindingMatch) => Definite(old),
(Definite(NonBindingMatch), new) => Definite(new),
(Definite(old), CopyingMatch) => Definite(old),
(Definite(CopyingMatch), new) => Definite(new),
(Definite(_), _) => Conflicting,
(Conflicting, _) => *self,
};
}
fn match_mode(&self) -> MatchMode {
match *self {
Unknown => NonBindingMatch,
Definite(mode) => mode,
Conflicting => {
// Conservatively return MovingMatch to let the
// compiler continue to make progress.
MovingMatch
}
}
}
}
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum MutateMode {
Init,
JustWrite, // x = y
WriteAndRead, // x += y
}
#[derive(Copy, Clone)]
enum OverloadedCallType {
FnOverloadedCall,
FnMutOverloadedCall,
FnOnceOverloadedCall,
}
impl OverloadedCallType {
fn from_trait_id(tcx: &ty::ctxt, trait_id: DefId)
-> OverloadedCallType {
for &(maybe_function_trait, overloaded_call_type) in &[
(tcx.lang_items.fn_once_trait(), FnOnceOverloadedCall),
(tcx.lang_items.fn_mut_trait(), FnMutOverloadedCall),
(tcx.lang_items.fn_trait(), FnOverloadedCall)
] {
match maybe_function_trait {
Some(function_trait) if function_trait == trait_id => {
return overloaded_call_type
}
_ => continue,
}
}
tcx.sess.bug("overloaded call didn't map to known function trait")
}
fn from_method_id(tcx: &ty::ctxt, method_id: DefId)
-> OverloadedCallType {
let method = tcx.impl_or_trait_item(method_id);
OverloadedCallType::from_trait_id(tcx, method.container().id())
}
}
///////////////////////////////////////////////////////////////////////////
// The ExprUseVisitor type
//
// This is the code that actually walks the tree. Like
// mem_categorization, it requires a TYPER, which is a type that
// supplies types from the tree. After type checking is complete, you
// can just use the tcx as the typer.
//
// FIXME(stage0): the :'t here is probably only important for stage0
pub struct ExprUseVisitor<'d, 't, 'a: 't, 'tcx:'a+'d> {
typer: &'t infer::InferCtxt<'a, 'tcx>,
mc: mc::MemCategorizationContext<'t, 'a, 'tcx>,
delegate: &'d mut Delegate<'tcx>,
}
// If the TYPER results in an error, it's because the type check
// failed (or will fail, when the error is uncovered and reported
// during writeback). In this case, we just ignore this part of the
// code.
//
// Note that this macro appears similar to try!(), but, unlike try!(),
// it does not propagate the error.
macro_rules! return_if_err {
($inp: expr) => (
match $inp {
Ok(v) => v,
Err(()) => {
debug!("mc reported err");
return
}
}
)
}
/// Whether the elements of an overloaded operation are passed by value or by reference
enum PassArgs {
ByValue,
ByRef,
}
impl<'d,'t,'a,'tcx> ExprUseVisitor<'d,'t,'a,'tcx> {
pub fn new(delegate: &'d mut (Delegate<'tcx>),
typer: &'t infer::InferCtxt<'a, 'tcx>)
-> ExprUseVisitor<'d,'t,'a,'tcx> where 'tcx:'a+'d
{
let mc: mc::MemCategorizationContext<'t, 'a, 'tcx> =
mc::MemCategorizationContext::new(typer);
ExprUseVisitor { typer: typer, mc: mc, delegate: delegate }
}
pub fn walk_fn(&mut self,
decl: &hir::FnDecl,
body: &hir::Block) {
self.walk_arg_patterns(decl, body);
self.walk_block(body);
}
fn walk_arg_patterns(&mut self,
decl: &hir::FnDecl,
body: &hir::Block) {
for arg in &decl.inputs {
let arg_ty = return_if_err!(self.typer.node_ty(arg.pat.id));
let fn_body_scope = self.tcx().region_maps.node_extent(body.id);
let arg_cmt = self.mc.cat_rvalue(
arg.id,
arg.pat.span,
ty::ReScope(fn_body_scope), // Args live only as long as the fn body.
arg_ty);
self.walk_irrefutable_pat(arg_cmt, &*arg.pat);
}
}
fn tcx(&self) -> &'t ty::ctxt<'tcx> {
self.typer.tcx
}
fn delegate_consume(&mut self,
consume_id: ast::NodeId,
consume_span: Span,
cmt: mc::cmt<'tcx>) {
debug!("delegate_consume(consume_id={}, cmt={:?})",
consume_id, cmt);
let mode = copy_or_move(self.typer, &cmt, DirectRefMove);
self.delegate.consume(consume_id, consume_span, cmt, mode);
}
fn consume_exprs(&mut self, exprs: &Vec<P<hir::Expr>>) {
for expr in exprs {
self.consume_expr(&**expr);
}
}
pub fn consume_expr(&mut self, expr: &hir::Expr) {
debug!("consume_expr(expr={:?})", expr);
let cmt = return_if_err!(self.mc.cat_expr(expr));
self.delegate_consume(expr.id, expr.span, cmt);
self.walk_expr(expr);
}
fn mutate_expr(&mut self,
assignment_expr: &hir::Expr,
expr: &hir::Expr,
mode: MutateMode) {
let cmt = return_if_err!(self.mc.cat_expr(expr));
self.delegate.mutate(assignment_expr.id, assignment_expr.span, cmt, mode);
self.walk_expr(expr);
}
fn borrow_expr(&mut self,
expr: &hir::Expr,
r: ty::Region,
bk: ty::BorrowKind,
cause: LoanCause) {
debug!("borrow_expr(expr={:?}, r={:?}, bk={:?})",
expr, r, bk);
let cmt = return_if_err!(self.mc.cat_expr(expr));
self.delegate.borrow(expr.id, expr.span, cmt, r, bk, cause);
self.walk_expr(expr)
}
fn select_from_expr(&mut self, expr: &hir::Expr) {
self.walk_expr(expr)
}
pub fn walk_expr(&mut self, expr: &hir::Expr) {
debug!("walk_expr(expr={:?})", expr);
self.walk_adjustment(expr);
match expr.node {
hir::ExprPath(..) => { }
hir::ExprUnary(hir::UnDeref, ref base) => { // *base
if !self.walk_overloaded_operator(expr, &**base, Vec::new(), PassArgs::ByRef) {
self.select_from_expr(&**base);
}
}
hir::ExprField(ref base, _) => { // base.f
self.select_from_expr(&**base);
}
hir::ExprTupField(ref base, _) => { // base.<n>
self.select_from_expr(&**base);
}
hir::ExprIndex(ref lhs, ref rhs) => { // lhs[rhs]
if !self.walk_overloaded_operator(expr,
&**lhs,
vec![&**rhs],
PassArgs::ByValue) {
self.select_from_expr(&**lhs);
self.consume_expr(&**rhs);
}
}
hir::ExprRange(ref start, ref end) => {
start.as_ref().map(|e| self.consume_expr(&**e));
end.as_ref().map(|e| self.consume_expr(&**e));
}
hir::ExprCall(ref callee, ref args) => { // callee(args)
self.walk_callee(expr, &**callee);
self.consume_exprs(args);
}
hir::ExprMethodCall(_, _, ref args) => { // callee.m(args)
self.consume_exprs(args);
}
hir::ExprStruct(_, ref fields, ref opt_with) => {
self.walk_struct_expr(expr, fields, opt_with);
}
hir::ExprTup(ref exprs) => {
self.consume_exprs(exprs);
}
hir::ExprIf(ref cond_expr, ref then_blk, ref opt_else_expr) => {
self.consume_expr(&**cond_expr);
self.walk_block(&**then_blk);
if let Some(ref else_expr) = *opt_else_expr {
self.consume_expr(&**else_expr);
}
}
hir::ExprMatch(ref discr, ref arms, _) => {
let discr_cmt = return_if_err!(self.mc.cat_expr(&**discr));
self.borrow_expr(&**discr, ty::ReEmpty, ty::ImmBorrow, MatchDiscriminant);
// treatment of the discriminant is handled while walking the arms.
for arm in arms {
let mode = self.arm_move_mode(discr_cmt.clone(), arm);
let mode = mode.match_mode();
self.walk_arm(discr_cmt.clone(), arm, mode);
}
}
hir::ExprVec(ref exprs) => {
self.consume_exprs(exprs);
}
hir::ExprAddrOf(m, ref base) => { // &base
// make sure that the thing we are pointing out stays valid
// for the lifetime `scope_r` of the resulting ptr:
let expr_ty = return_if_err!(self.typer.node_ty(expr.id));
if let ty::TyRef(&r, _) = expr_ty.sty {
let bk = ty::BorrowKind::from_mutbl(m);
self.borrow_expr(&**base, r, bk, AddrOf);
}
}
hir::ExprInlineAsm(ref ia) => {
for &(_, ref input) in &ia.inputs {
self.consume_expr(&**input);
}
for &(_, ref output, is_rw) in &ia.outputs {
self.mutate_expr(expr, &**output,
if is_rw { WriteAndRead } else { JustWrite });
}
}
hir::ExprBreak(..) |
hir::ExprAgain(..) |
hir::ExprLit(..) => {}
hir::ExprLoop(ref blk, _) => {
self.walk_block(&**blk);
}
hir::ExprWhile(ref cond_expr, ref blk, _) => {
self.consume_expr(&**cond_expr);
self.walk_block(&**blk);
}
hir::ExprUnary(op, ref lhs) => {
let pass_args = if ::rustc_front::util::is_by_value_unop(op) {
PassArgs::ByValue
} else {
PassArgs::ByRef
};
if !self.walk_overloaded_operator(expr, &**lhs, Vec::new(), pass_args) {
self.consume_expr(&**lhs);
}
}
hir::ExprBinary(op, ref lhs, ref rhs) => {
let pass_args = if ::rustc_front::util::is_by_value_binop(op.node) {
PassArgs::ByValue
} else {
PassArgs::ByRef
};
if !self.walk_overloaded_operator(expr, &**lhs, vec![&**rhs], pass_args) {
self.consume_expr(&**lhs);
self.consume_expr(&**rhs);
}
}
hir::ExprBlock(ref blk) => {
self.walk_block(&**blk);
}
hir::ExprRet(ref opt_expr) => {
if let Some(ref expr) = *opt_expr {
self.consume_expr(&**expr);
}
}
hir::ExprAssign(ref lhs, ref rhs) => {
self.mutate_expr(expr, &**lhs, JustWrite);
self.consume_expr(&**rhs);
}
hir::ExprCast(ref base, _) => {
self.consume_expr(&**base);
}
hir::ExprAssignOp(op, ref lhs, ref rhs) => {
// NB All our assignment operations take the RHS by value
assert!(::rustc_front::util::is_by_value_binop(op.node));
if !self.walk_overloaded_operator(expr, lhs, vec![rhs], PassArgs::ByValue) {
self.mutate_expr(expr, &**lhs, WriteAndRead);
self.consume_expr(&**rhs);
}
}
hir::ExprRepeat(ref base, ref count) => {
self.consume_expr(&**base);
self.consume_expr(&**count);
}
hir::ExprClosure(..) => {
self.walk_captures(expr)
}
hir::ExprBox(ref base) => {
self.consume_expr(&**base);
}
}
}
fn walk_callee(&mut self, call: &hir::Expr, callee: &hir::Expr) {
let callee_ty = return_if_err!(self.typer.expr_ty_adjusted(callee));
debug!("walk_callee: callee={:?} callee_ty={:?}",
callee, callee_ty);
let call_scope = self.tcx().region_maps.node_extent(call.id);
match callee_ty.sty {
ty::TyBareFn(..) => {
self.consume_expr(callee);
}
ty::TyError => { }
_ => {
let overloaded_call_type =
match self.typer.node_method_id(ty::MethodCall::expr(call.id)) {
Some(method_id) => {
OverloadedCallType::from_method_id(self.tcx(), method_id)
}
None => {
self.tcx().sess.span_bug(
callee.span,
&format!("unexpected callee type {}", callee_ty))
}
};
match overloaded_call_type {
FnMutOverloadedCall => {
self.borrow_expr(callee,
ty::ReScope(call_scope),
ty::MutBorrow,
ClosureInvocation);
}
FnOverloadedCall => {
self.borrow_expr(callee,
ty::ReScope(call_scope),
ty::ImmBorrow,
ClosureInvocation);
}
FnOnceOverloadedCall => self.consume_expr(callee),
}
}
}
}
fn walk_stmt(&mut self, stmt: &hir::Stmt) {
match stmt.node {
hir::StmtDecl(ref decl, _) => {
match decl.node {
hir::DeclLocal(ref local) => {
self.walk_local(&**local);
}
hir::DeclItem(_) => {
// we don't visit nested items in this visitor,
// only the fn body we were given.
}
}
}
hir::StmtExpr(ref expr, _) |
hir::StmtSemi(ref expr, _) => {
self.consume_expr(&**expr);
}
}
}
fn walk_local(&mut self, local: &hir::Local) {
match local.init {
None => {
let delegate = &mut self.delegate;
pat_util::pat_bindings(&self.typer.tcx.def_map, &*local.pat,
|_, id, span, _| {
delegate.decl_without_init(id, span);
})
}
Some(ref expr) => {
// Variable declarations with
// initializers are considered
// "assigns", which is handled by
// `walk_pat`:
self.walk_expr(&**expr);
let init_cmt = return_if_err!(self.mc.cat_expr(&**expr));
self.walk_irrefutable_pat(init_cmt, &*local.pat);
}
}
}
/// Indicates that the value of `blk` will be consumed, meaning either copied or moved
/// depending on its type.
fn walk_block(&mut self, blk: &hir::Block) {
debug!("walk_block(blk.id={})", blk.id);
for stmt in &blk.stmts {
self.walk_stmt(&**stmt);
}
if let Some(ref tail_expr) = blk.expr {
self.consume_expr(&**tail_expr);
}
}
fn walk_struct_expr(&mut self,
_expr: &hir::Expr,
fields: &Vec<hir::Field>,
opt_with: &Option<P<hir::Expr>>) {
// Consume the expressions supplying values for each field.
for field in fields {
self.consume_expr(&*field.expr);
}
let with_expr = match *opt_with {
Some(ref w) => &**w,
None => { return; }
};
let with_cmt = return_if_err!(self.mc.cat_expr(&*with_expr));
// Select just those fields of the `with`
// expression that will actually be used
if let ty::TyStruct(def, substs) = with_cmt.ty.sty {
// Consume those fields of the with expression that are needed.
for with_field in &def.struct_variant().fields {
if !contains_field_named(with_field, fields) {
let cmt_field = self.mc.cat_field(
&*with_expr,
with_cmt.clone(),
with_field.name,
with_field.ty(self.tcx(), substs)
);
self.delegate_consume(with_expr.id, with_expr.span, cmt_field);
}
}
} else {
// the base expression should always evaluate to a
// struct; however, when EUV is run during typeck, it
// may not. This will generate an error earlier in typeck,
// so we can just ignore it.
if !self.tcx().sess.has_errors() {
self.tcx().sess.span_bug(
with_expr.span,
"with expression doesn't evaluate to a struct");
}
};
// walk the with expression so that complex expressions
// are properly handled.
self.walk_expr(with_expr);
fn contains_field_named(field: ty::FieldDef,
fields: &Vec<hir::Field>)
-> bool
{
fields.iter().any(
|f| f.name.node == field.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: &hir::Expr) {
let typer = self.typer;
//NOTE(@jroesch): mixed RefCell borrow causes crash
let adj = typer.adjustments().get(&expr.id).map(|x| x.clone());
if let Some(adjustment) = adj {
match adjustment {
adjustment::AdjustReifyFnPointer |
adjustment::AdjustUnsafeFnPointer => {
// Creating a closure/fn-pointer or unsizing consumes
// the input and stores it into the resulting rvalue.
debug!("walk_adjustment(AdjustReifyFnPointer|AdjustUnsafeFnPointer)");
let cmt_unadjusted =
return_if_err!(self.mc.cat_expr_unadjusted(expr));
self.delegate_consume(expr.id, expr.span, cmt_unadjusted);
}
adjustment::AdjustDerefRef(ref adj) => {
self.walk_autoderefref(expr, adj);
}
}
}
}
/// 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`.
fn walk_autoderefs(&mut self,
expr: &hir::Expr,
autoderefs: usize) {
debug!("walk_autoderefs expr={:?} autoderefs={}", expr, autoderefs);
for i in 0..autoderefs {
let deref_id = ty::MethodCall::autoderef(expr.id, i as u32);
match self.typer.node_method_ty(deref_id) {
None => {}
Some(method_ty) => {
let cmt = return_if_err!(self.mc.cat_expr_autoderefd(expr, i));
// the method call infrastructure should have
// replaced all late-bound regions with variables:
let self_ty = method_ty.fn_sig().input(0);
let self_ty = self.tcx().no_late_bound_regions(&self_ty).unwrap();
let (m, r) = match self_ty.sty {
ty::TyRef(r, ref m) => (m.mutbl, r),
_ => self.tcx().sess.span_bug(expr.span,
&format!("bad overloaded deref type {:?}",
method_ty))
};
let bk = ty::BorrowKind::from_mutbl(m);
self.delegate.borrow(expr.id, expr.span, cmt,
*r, bk, AutoRef);
}
}
}
}
fn walk_autoderefref(&mut self,
expr: &hir::Expr,
adj: &adjustment::AutoDerefRef<'tcx>) {
debug!("walk_autoderefref expr={:?} adj={:?}",
expr,
adj);
self.walk_autoderefs(expr, adj.autoderefs);
let cmt_derefd =
return_if_err!(self.mc.cat_expr_autoderefd(expr, adj.autoderefs));
let cmt_refd =
self.walk_autoref(expr, cmt_derefd, adj.autoref);
if adj.unsize.is_some() {
// Unsizing consumes the thin pointer and produces a fat one.
self.delegate_consume(expr.id, expr.span, cmt_refd);
}
}
/// Walks the autoref `opt_autoref` applied to the autoderef'd
/// `expr`. `cmt_derefd` is the mem-categorized form of `expr`
/// after all relevant autoderefs have occurred. Because AutoRefs
/// can be recursive, this function is recursive: it first walks
/// deeply all the way down the autoref chain, and then processes
/// the autorefs on the way out. At each point, it returns the
/// `cmt` for the rvalue that will be produced by introduced an
/// autoref.
fn walk_autoref(&mut self,
expr: &hir::Expr,
cmt_base: mc::cmt<'tcx>,
opt_autoref: Option<adjustment::AutoRef<'tcx>>)
-> mc::cmt<'tcx>
{
debug!("walk_autoref(expr.id={} cmt_derefd={:?} opt_autoref={:?})",
expr.id,
cmt_base,
opt_autoref);
let cmt_base_ty = cmt_base.ty;
let autoref = match opt_autoref {
Some(ref autoref) => autoref,
None => {
// No AutoRef.
return cmt_base;
}
};
match *autoref {
adjustment::AutoPtr(r, m) => {
self.delegate.borrow(expr.id,
expr.span,
cmt_base,
*r,
ty::BorrowKind::from_mutbl(m),
AutoRef);
}
adjustment::AutoUnsafe(m) => {
debug!("walk_autoref: expr.id={} cmt_base={:?}",
expr.id,
cmt_base);
// Converting from a &T to *T (or &mut T to *mut T) is
// treated as borrowing it for the enclosing temporary
// scope.
let r = ty::ReScope(self.tcx().region_maps.node_extent(expr.id));
self.delegate.borrow(expr.id,
expr.span,
cmt_base,
r,
ty::BorrowKind::from_mutbl(m),
AutoUnsafe);
}
}
// Construct the categorization for the result of the autoref.
// This is always an rvalue, since we are producing a new
// (temporary) indirection.
let adj_ty = cmt_base_ty.adjust_for_autoref(self.tcx(), opt_autoref);
self.mc.cat_rvalue_node(expr.id, expr.span, adj_ty)
}
// When this returns true, it means that the expression *is* a
// method-call (i.e. via the operator-overload). This true result
// also implies that walk_overloaded_operator already took care of
// recursively processing the input arguments, and thus the caller
// should not do so.
fn walk_overloaded_operator(&mut self,
expr: &hir::Expr,
receiver: &hir::Expr,
rhs: Vec<&hir::Expr>,
pass_args: PassArgs)
-> bool
{
if !self.typer.is_method_call(expr.id) {
return false;
}
match pass_args {
PassArgs::ByValue => {
self.consume_expr(receiver);
for &arg in &rhs {
self.consume_expr(arg);
}
return true;
},
PassArgs::ByRef => {},
}
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(self.tcx().region_maps.node_extent(expr.id));
let bk = ty::ImmBorrow;
for &arg in &rhs {
self.borrow_expr(arg, r, bk, OverloadedOperator);
}
return true;
}
fn arm_move_mode(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm) -> TrackMatchMode {
let mut mode = Unknown;
for pat in &arm.pats {
self.determine_pat_move_mode(discr_cmt.clone(), &**pat, &mut mode);
}
mode
}
fn walk_arm(&mut self, discr_cmt: mc::cmt<'tcx>, arm: &hir::Arm, mode: MatchMode) {
for pat in &arm.pats {
self.walk_pat(discr_cmt.clone(), &**pat, mode);
}
if let Some(ref guard) = arm.guard {
self.consume_expr(&**guard);
}
self.consume_expr(&*arm.body);
}
/// Walks a pat that occurs in isolation (i.e. top-level of fn
/// arg or let binding. *Not* a match arm or nested pat.)
fn walk_irrefutable_pat(&mut self, cmt_discr: mc::cmt<'tcx>, pat: &hir::Pat) {
let mut mode = Unknown;
self.determine_pat_move_mode(cmt_discr.clone(), pat, &mut mode);
let mode = mode.match_mode();
self.walk_pat(cmt_discr, pat, mode);
}
/// Identifies any bindings within `pat` and accumulates within
/// `mode` whether the overall pattern/match structure is a move,
/// copy, or borrow.
fn determine_pat_move_mode(&mut self,
cmt_discr: mc::cmt<'tcx>,
pat: &hir::Pat,
mode: &mut TrackMatchMode) {
debug!("determine_pat_move_mode cmt_discr={:?} pat={:?}", cmt_discr,
pat);
return_if_err!(self.mc.cat_pattern(cmt_discr, pat, |_mc, cmt_pat, pat| {
let tcx = self.tcx();
let def_map = &self.tcx().def_map;
if pat_util::pat_is_binding(def_map, pat) {
match pat.node {
hir::PatIdent(hir::BindByRef(_), _, _) =>
mode.lub(BorrowingMatch),
hir::PatIdent(hir::BindByValue(_), _, _) => {
match copy_or_move(self.typer, &cmt_pat, PatBindingMove) {
Copy => mode.lub(CopyingMatch),
Move(_) => mode.lub(MovingMatch),
}
}
_ => {
tcx.sess.span_bug(
pat.span,
"binding pattern not an identifier");
}
}
}
}));
}
/// The core driver for walking a pattern; `match_mode` must be
/// established up front, e.g. via `determine_pat_move_mode` (see
/// also `walk_irrefutable_pat` for patterns that stand alone).
fn walk_pat(&mut self,
cmt_discr: mc::cmt<'tcx>,
pat: &hir::Pat,
match_mode: MatchMode) {
debug!("walk_pat cmt_discr={:?} pat={:?}", cmt_discr,
pat);
let mc = &self.mc;
let typer = self.typer;
let def_map = &self.tcx().def_map;
let delegate = &mut self.delegate;
return_if_err!(mc.cat_pattern(cmt_discr.clone(), pat, |mc, cmt_pat, pat| {
if pat_util::pat_is_binding(def_map, pat) {
let tcx = typer.tcx;
debug!("binding cmt_pat={:?} pat={:?} match_mode={:?}",
cmt_pat,
pat,
match_mode);
// pat_ty: the type of the binding being produced.
let pat_ty = return_if_err!(typer.node_ty(pat.id));
// Each match binding is effectively an assignment to the
// binding being produced.
let def = def_map.borrow().get(&pat.id).unwrap().full_def();
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 {
hir::PatIdent(hir::BindByRef(m), _, _) => {
if let ty::TyRef(&r, _) = pat_ty.sty {
let bk = ty::BorrowKind::from_mutbl(m);
delegate.borrow(pat.id, pat.span, cmt_pat,
r, bk, RefBinding);
}
}
hir::PatIdent(hir::BindByValue(_), _, _) => {
let mode = copy_or_move(typer, &cmt_pat, PatBindingMove);
debug!("walk_pat binding consuming pat");
delegate.consume_pat(pat, cmt_pat, mode);
}
_ => {
tcx.sess.span_bug(
pat.span,
"binding pattern not an identifier");
}
}
} else {
match pat.node {
hir::PatVec(_, Some(ref 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) =
return_if_err!(mc.cat_slice_pattern(cmt_pat, &**slice_pat));
// 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 `Box<[T]>`s. 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);
}
_ => { }
}
}
}));
// Do a second pass over the pattern, calling `matched_pat` on
// the interior nodes (enum variants and structs), as opposed
// to the above loop's visit of than the bindings that form
// the leaves of the pattern tree structure.
return_if_err!(mc.cat_pattern(cmt_discr, pat, |mc, cmt_pat, pat| {
let def_map = def_map.borrow();
let tcx = typer.tcx;
match pat.node {
hir::PatEnum(_, _) | hir::PatQPath(..) |
hir::PatIdent(_, _, None) | hir::PatStruct(..) => {
match def_map.get(&pat.id).map(|d| d.full_def()) {
None => {
// no definition found: pat is not a
// struct or enum pattern.
}
Some(def::DefVariant(enum_did, variant_did, _is_struct)) => {
let downcast_cmt =
if tcx.lookup_adt_def(enum_did).is_univariant() {
cmt_pat
} else {
let cmt_pat_ty = cmt_pat.ty;
mc.cat_downcast(pat, cmt_pat, cmt_pat_ty, variant_did)
};
debug!("variant downcast_cmt={:?} pat={:?}",
downcast_cmt,
pat);
delegate.matched_pat(pat, downcast_cmt, match_mode);
}
Some(def::DefStruct(..)) | Some(def::DefTy(_, false)) => {
// A struct (in either the value or type
// namespace; we encounter the former on
// e.g. patterns for unit structs).
debug!("struct cmt_pat={:?} pat={:?}",
cmt_pat,
pat);
delegate.matched_pat(pat, cmt_pat, match_mode);
}
Some(def::DefConst(..)) |
Some(def::DefAssociatedConst(..)) |
Some(def::DefLocal(..)) => {
// This is a leaf (i.e. identifier binding
// or constant value to match); thus no
// `matched_pat` call.
}
Some(def @ def::DefTy(_, true)) => {
// An enum's type -- should never be in a
// pattern.
if !tcx.sess.has_errors() {
let msg = format!("Pattern has unexpected type: {:?} and type {:?}",
def,
cmt_pat.ty);
tcx.sess.span_bug(pat.span, &msg)
}
}
Some(def) => {
// Remaining cases are e.g. DefFn, to
// which identifiers within patterns
// should not resolve. However, we do
// encouter this when using the
// expr-use-visitor during typeck. So just
// ignore it, an error should have been
// reported.
if !tcx.sess.has_errors() {
let msg = format!("Pattern has unexpected def: {:?} and type {:?}",
def,
cmt_pat.ty);
tcx.sess.span_bug(pat.span, &msg[..])
}
}
}
}
hir::PatIdent(_, _, Some(_)) => {
// Do nothing; this is a binding (not an enum
// variant or struct), and the cat_pattern call
// will visit the substructure recursively.
}
hir::PatWild | hir::PatTup(..) | hir::PatBox(..) |
hir::PatRegion(..) | hir::PatLit(..) | hir::PatRange(..) |
hir::PatVec(..) => {
// Similarly, each of these cases does not
// correspond to an enum variant or struct, so we
// do not do any `matched_pat` calls for these
// cases either.
}
}
}));
}
fn walk_captures(&mut self, closure_expr: &hir::Expr) {
debug!("walk_captures({:?})", closure_expr);
self.tcx().with_freevars(closure_expr.id, |freevars| {
for freevar in freevars {
let id_var = freevar.def.var_id();
let upvar_id = ty::UpvarId { var_id: id_var,
closure_expr_id: closure_expr.id };
let upvar_capture = self.typer.upvar_capture(upvar_id).unwrap();
let cmt_var = return_if_err!(self.cat_captured_var(closure_expr.id,
closure_expr.span,
freevar.def));
match upvar_capture {
ty::UpvarCapture::ByValue => {
let mode = copy_or_move(self.typer, &cmt_var, CaptureMove);
self.delegate.consume(closure_expr.id, freevar.span, cmt_var, mode);
}
ty::UpvarCapture::ByRef(upvar_borrow) => {
self.delegate.borrow(closure_expr.id,
closure_expr.span,
cmt_var,
upvar_borrow.region,
upvar_borrow.kind,
ClosureCapture(freevar.span));
}
}
}
});
}
fn cat_captured_var(&mut self,
closure_id: ast::NodeId,
closure_span: Span,
upvar_def: def::Def)
-> mc::McResult<mc::cmt<'tcx>> {
// Create the cmt for the variable being borrowed, from the
// caller's perspective
let var_id = upvar_def.var_id();
let var_ty = try!(self.typer.node_ty(var_id));
self.mc.cat_def(closure_id, closure_span, var_ty, upvar_def)
}
}
fn copy_or_move<'a, 'tcx>(typer: &infer::InferCtxt<'a, 'tcx>,
cmt: &mc::cmt<'tcx>,
move_reason: MoveReason)
-> ConsumeMode
{
if typer.type_moves_by_default(cmt.ty, cmt.span) {
Move(move_reason)
} else {
Copy
}
}