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Issue #4715: Give a better error message when move results from a binding.. #6674

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Issue #4715: Give a better error message when move results from a binding.. #6674

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2 changes: 1 addition & 1 deletion src/librustc/middle/check_match.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -803,7 +803,7 @@ pub fn check_legality_of_move_bindings(cx: @MatchCheckCtxt,

if !any_by_move { return; } // pointless micro-optimization
for pats.each |pat| {
do walk_pat(*pat) |p| {
for walk_pat(*pat) |p| {
if pat_is_binding(def_map, p) {
match p.node {
pat_ident(_, _, sub) => {
Expand Down
2 changes: 1 addition & 1 deletion src/librustc/middle/dataflow.rs
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Expand Up @@ -824,7 +824,7 @@ impl<'self, O:DataFlowOperator> PropagationContext<'self, O> {
debug!("DataFlowContext::walk_pat(pat=%s, in_out=%s)",
pat.repr(self.dfcx.tcx), bits_to_str(reslice(in_out)));

do ast_util::walk_pat(pat) |p| {
for ast_util::walk_pat(pat) |p| {
debug!(" p.id=%? in_out=%s", p.id, bits_to_str(reslice(in_out)));
self.merge_with_entry_set(p.id, in_out);
self.dfcx.apply_gen_kill(p.id, in_out);
Expand Down
137 changes: 65 additions & 72 deletions src/librustc/middle/liveness.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1443,10 +1443,10 @@ fn check_expr(expr: @expr, this: @Liveness, vt: vt<@Liveness>) {

match this.ir.variable_moves_map.find(&expr.id) {
None => {}
Some(&entire_expr) => {
Some(&reason) => {
debug!("(checking expr) is a move: `%s`",
expr_to_str(expr, this.tcx.sess.intr()));
this.check_move_from_var(ln, *var, entire_expr);
this.check_move_from_var(ln, *var, reason);
}
}
}
Expand All @@ -1459,7 +1459,7 @@ fn check_expr(expr: @expr, this: @Liveness, vt: vt<@Liveness>) {
for caps.each |cap| {
let var = this.variable(cap.var_nid, expr.span);
if cap.is_move {
this.check_move_from_var(cap.ln, var, expr);
this.check_move_from_var(cap.ln, var, moves::MovedByExpr(expr));
}
}

Expand Down Expand Up @@ -1549,24 +1549,20 @@ pub impl Liveness {
fn check_move_from_var(&self,
ln: LiveNode,
var: Variable,
move_expr: @expr) {
move_reason: moves::Reason) {
/*!
* Checks whether `var` is live on entry to any of the
* successors of `ln`. If it is, report an error.
* `move_expr` is the expression which caused the variable
* `move_reason` is the reason which caused the variable
* to be moved.
*
* Note that `move_expr` is not necessarily a reference to the
* variable. It might be an expression like `x.f` which could
* cause a move of the variable `x`, or a closure creation.
*/

debug!("check_move_from_var(%s, %s)",
ln.to_str(), var.to_str());

match self.live_on_exit(ln, var) {
None => {}
Some(lnk) => self.report_illegal_move(lnk, var, move_expr)
Some(lnk) => self.report_illegal_move(lnk, var, move_reason)
}
}

Expand Down Expand Up @@ -1640,82 +1636,79 @@ pub impl Liveness {

fn report_illegal_move(&self, lnk: LiveNodeKind,
var: Variable,
move_expr: @expr) {
// the only time that it is possible to have a moved variable
// used by ExitNode would be arguments or fields in a ctor.
// we give a slightly different error message in those cases.
if lnk == ExitNode {
// FIXME #4715: this seems like it should be reported in the
// borrow checker
let vk = self.ir.var_kinds[*var];
match vk {
Arg(_, name) => {
self.tcx.sess.span_err(
move_expr.span,
fmt!("illegal move from argument `%s`, which is not \
copy or move mode", *self.tcx.sess.str_of(name)));
return;
}
Local(*) | ImplicitRet => {
self.tcx.sess.span_bug(
move_expr.span,
fmt!("illegal reader (%?) for `%?`",
lnk, vk));
}
move_reason: moves::Reason) {
match move_reason {
moves::MovedByExpr(move_expr) => {
match move_expr.node {
expr_fn_block(*) => {
self.report_illegal_read(
move_expr.span, lnk, var, MovedValue);
let name = self.ir.variable_name(var);
self.tcx.sess.span_note(
move_expr.span,
fmt!("`%s` moved into closure environment here \
because its type is moved by default",
*name));
}
expr_path(*) => {
self.report_illegal_read(
move_expr.span, lnk, var, MovedValue);
self.report_move_location(
move_expr.id, move_expr.span, var,
"", "it", "copy");
}
expr_field(*) => {
self.report_illegal_read(
move_expr.span, lnk, var, PartiallyMovedValue);
self.report_move_location(
move_expr.id, move_expr.span, var,
"field of ", "the field", "copy");
}
expr_index(*) => {
self.report_illegal_read(
move_expr.span, lnk, var, PartiallyMovedValue);
self.report_move_location(
move_expr.id, move_expr.span, var,
"element of ", "the element", "copy");
}
_ => {
self.report_illegal_read(
move_expr.span, lnk, var, PartiallyMovedValue);
self.report_move_location(
move_expr.id, move_expr.span, var,
"subcomponent of ", "the subcomponent", "copy");
}
}
}
}

match move_expr.node {
expr_fn_block(*) => {
self.report_illegal_read(
move_expr.span, lnk, var, MovedValue);
let name = self.ir.variable_name(var);
self.tcx.sess.span_note(
move_expr.span,
fmt!("`%s` moved into closure environment here \
because its type is moved by default",
*name));
}
expr_path(*) => {
self.report_illegal_read(
move_expr.span, lnk, var, MovedValue);
self.report_move_location(
move_expr, var, "", "it");
}
expr_field(*) => {
self.report_illegal_read(
move_expr.span, lnk, var, PartiallyMovedValue);
self.report_move_location(
move_expr, var, "field of ", "the field");
}
expr_index(*) => {
self.report_illegal_read(
move_expr.span, lnk, var, PartiallyMovedValue);
self.report_move_location(
move_expr, var, "element of ", "the element");
}
_ => {
moves::MovedByPat(move_binding) => {
self.report_illegal_read(
move_expr.span, lnk, var, PartiallyMovedValue);
move_binding.span, lnk, var, PartiallyMovedValue);
self.report_move_location(
move_expr, var, "subcomponent of ", "the subcomponent");
move_binding.id, move_binding.span, var,
"", "the binding", "ref");
}
};
}

fn report_move_location(&self,
move_expr: @expr,
move_loc_id: node_id,
move_loc_span: span,
var: Variable,
expr_descr: &str,
pronoun: &str) {
let move_expr_ty = ty::expr_ty(self.tcx, move_expr);
pronoun: &str,
override: &str) {
let move_expr_ty = ty::node_id_to_type(self.tcx, move_loc_id);
let name = self.ir.variable_name(var);
self.tcx.sess.span_note(
move_expr.span,
move_loc_span,
fmt!("%s`%s` moved here because %s has type %s, \
which is moved by default (use `copy` to override)",
expr_descr, *name, pronoun,
ty_to_str(self.tcx, move_expr_ty)));
which is moved by default (use `%s` to override)",
expr_descr,
*name,
pronoun,
ty_to_str(self.tcx, move_expr_ty),
override));
}

fn report_illegal_read(&self,
Expand Down
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