Rollup merge of rust-lang#46231 - ritiek:verbs, r=arielb1

MIR: Fix value moved diagnose messages

rust-lang#45960. I believe this will take a different approach. Simply replacing all nouns to verbs (`desired_action`) messes up the message `use of moved value` (although fixes the message in original issue). Here is what happens:

<pre>
$ rustc -Zborrowck-mir src/test/ui/borrowck/borrowck-reinit.rs

error[E0382]: <b>used</b> of moved value: `x` (Mir)
  --> src/test/ui/borrowck/borrowck-reinit.rs:18:16
   |
17 |     drop(x);
   |          - value moved here
18 |     let _ = (1,x);
   |                ^ value used here after move

error: aborting due to 2 previous errors
</pre>
(Notice: *"**used** of moved value: `x`"* instead of *"**use**"*)

Which does not seem to be okay.

After experimenting a bit, it looks like [`report_use_of_moved_value()`](https://github.com/rust-lang/rust/blob/1dc0b573e7ce4314eb196b21b7e0ea4a1bf1f673/src/librustc_mir/borrow_check.rs#L1319) tries to handle both these messages by taking in only one form of`desired_action`.

These messages rise from: *"[{noun} of moved value](https://github.com/rust-lang/rust/blob/1dc0b573e7ce4314eb196b21b7e0ea4a1bf1f673/src/librustc_mir/borrow_check.rs#L1338-L1342)"* and *"[value {verb} here after move](https://github.com/rust-lang/rust/blob/1dc0b573e7ce4314eb196b21b7e0ea4a1bf1f673/src/librustc_mir/borrow_check.rs#L1343)"*.

This PR fixes *"value {verb} here after move"* type messages by passing a corresponding verb (`desired_action`) instead of the original noun.

src/librustc_mir/borrow_check.rs

@@ -484,6 +484,34 @@ enum WriteKind {
  Move,
 }
 
+#[derive(Copy, Clone)]
+enum InitializationRequiringAction {
+ Update,
+ Borrow,
+ Use,
+ Assignment,
+}
+
+impl InitializationRequiringAction {
+ fn as_noun(self) -> &'static str {
+ match self {
+ InitializationRequiringAction::Update => "update",
+ InitializationRequiringAction::Borrow => "borrow",
+ InitializationRequiringAction::Use => "use",
+ InitializationRequiringAction::Assignment => "assign"
+ }
+ }
+
+ fn as_verb_in_past_tense(self) -> &'static str {
+ match self {
+ InitializationRequiringAction::Update => "updated",
+ InitializationRequiringAction::Borrow => "borrowed",
+ InitializationRequiringAction::Use => "used",
+ InitializationRequiringAction::Assignment => "assigned"
+ }
+ }
+}
+
 impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  /// Checks an access to the given lvalue to see if it is allowed. Examines the set of borrows
  /// that are in scope, as well as which paths have been initialized, to ensure that (a) the
@@ -574,7 +602,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  // Write of P[i] or *P, or WriteAndRead of any P, requires P init'd.
  match mode {
  MutateMode::WriteAndRead => {
- self.check_if_path_is_moved(context, "update", lvalue_span, flow_state);
+ self.check_if_path_is_moved(context, InitializationRequiringAction::Update,
+ lvalue_span, flow_state);
  }
  MutateMode::JustWrite => {
  self.check_if_assigned_path_is_moved(context, lvalue_span, flow_state);
@@ -600,7 +629,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  BorrowKind::Mut => (Deep, Write(WriteKind::MutableBorrow(bk))),
  };
  self.access_lvalue(context, (lvalue, span), access_kind, flow_state);
- self.check_if_path_is_moved(context, "borrow", (lvalue, span), flow_state);
+ self.check_if_path_is_moved(context, InitializationRequiringAction::Borrow,
+ (lvalue, span), flow_state);
  }
 
  Rvalue::Use(ref operand) |
@@ -619,7 +649,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  };
  self.access_lvalue(
  context, (lvalue, span), (Shallow(Some(af)), Read(ReadKind::Copy)), flow_state);
- self.check_if_path_is_moved(context, "use", (lvalue, span), flow_state);
+ self.check_if_path_is_moved(context, InitializationRequiringAction::Use,
+ (lvalue, span), flow_state);
  }
 
  Rvalue::BinaryOp(_bin_op, ref operand1, ref operand2) |
@@ -720,7 +751,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  // skip this check in that case).
  }
  ConsumeKind::Consume => {
- self.check_if_path_is_moved(context, "use", lvalue_span, flow_state);
+ self.check_if_path_is_moved(context, InitializationRequiringAction::Use,
+ lvalue_span, flow_state);
  }
  }
  }
@@ -772,7 +804,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
 
  fn check_if_path_is_moved(&mut self,
  context: Context,
- desired_action: &str,
+ desired_action: InitializationRequiringAction,
  lvalue_span: (&Lvalue<'tcx>, Span),
  flow_state: &InProgress<'cx, 'gcx, 'tcx>) {
  // FIXME: analogous code in check_loans first maps `lvalue` to
@@ -943,7 +975,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  // `base` to its base_path.
 
  self.check_if_path_is_moved(
- context, "assignment", (base, span), flow_state);
+ context, InitializationRequiringAction::Assignment,
+ (base, span), flow_state);
 
  // (base initialized; no need to
  // recur further)
@@ -1347,7 +1380,7 @@ mod prefixes {
 impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  fn report_use_of_moved_or_uninitialized(&mut self,
  _context: Context,
- desired_action: &str,
+ desired_action: InitializationRequiringAction,
  (lvalue, span): (&Lvalue<'tcx>, Span),
  mpi: MovePathIndex,
  curr_move_out: &IdxSetBuf<MoveOutIndex>) {
@@ -1357,7 +1390,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
 
  if mois.is_empty() {
  self.tcx.cannot_act_on_uninitialized_variable(span,
- desired_action,
+ desired_action.as_noun(),
  &self.describe_lvalue(lvalue),
  Origin::Mir)
  .span_label(span, format!("use of possibly uninitialized `{}`",
@@ -1367,11 +1400,13 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
  let msg = ""; //FIXME: add "partially " or "collaterally "
 
  let mut err = self.tcx.cannot_act_on_moved_value(span,
- desired_action,
+ desired_action.as_noun(),
  msg,
  &self.describe_lvalue(lvalue),
  Origin::Mir);
- err.span_label(span, format!("value {} here after move", desired_action));
+
+ err.span_label(span, format!("value {} here after move",
+ desired_action.as_verb_in_past_tense()));
  for moi in mois {
  let move_msg = ""; //FIXME: add " (into closure)"
  let move_span = self.mir.source_info(self.move_data.moves[*moi].source).span;

src/test/ui/borrowck/borrowck-reinit.stderr

@@ -14,7 +14,7 @@ error[E0382]: use of moved value: `x` (Mir)
 17 | drop(x);
  | - value moved here
 18 | let _ = (1,x); //~ ERROR use of moved value: `x` (Ast)
- | ^ value use here after move
+ | ^ value used here after move
 
 error: aborting due to 2 previous errors