From de90afc72e2393efad0fb9cdfd765703a044fe02 Mon Sep 17 00:00:00 2001 From: Aaron Hill Date: Tue, 22 Dec 2020 22:15:40 -0500 Subject: [PATCH] Explain method-call move errors in loops PR #73708 added a more detailed explanation of move errors that occur due to a call to a method that takes `self`. This PR extends that logic to work when a move error occurs due to a method call in the previous iteration of a loop. --- .../diagnostics/conflict_errors.rs | 142 +++++++++--------- src/test/ui/moves/move-fn-self-receiver.rs | 5 + .../ui/moves/move-fn-self-receiver.stderr | 11 +- .../suggestions/borrow-for-loop-head.stderr | 8 +- 4 files changed, 90 insertions(+), 76 deletions(-) diff --git a/compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs b/compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs index 0bb09e26f03e8..c2a14840fb85e 100644 --- a/compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs +++ b/compiler/rustc_mir/src/borrow_check/diagnostics/conflict_errors.rs @@ -151,95 +151,88 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { let move_msg = if move_spans.for_closure() { " into closure" } else { "" }; + let loop_message = if location == move_out.source || move_site.traversed_back_edge { + ", in previous iteration of loop" + } else { + "" + }; + if location == move_out.source { - err.span_label( - span, - format!( - "value {}moved{} here, in previous iteration of loop", - partially_str, move_msg - ), - ); is_loop_move = true; - } else if move_site.traversed_back_edge { - err.span_label( - move_span, - format!( - "value {}moved{} here, in previous iteration of loop", - partially_str, move_msg - ), - ); - } else { - if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = - move_spans - { - let place_name = self - .describe_place(moved_place.as_ref()) - .map(|n| format!("`{}`", n)) - .unwrap_or_else(|| "value".to_owned()); - match kind { - FnSelfUseKind::FnOnceCall => { + } + + if let UseSpans::FnSelfUse { var_span, fn_call_span, fn_span, kind } = move_spans { + let place_name = self + .describe_place(moved_place.as_ref()) + .map(|n| format!("`{}`", n)) + .unwrap_or_else(|| "value".to_owned()); + match kind { + FnSelfUseKind::FnOnceCall => { + err.span_label( + fn_call_span, + &format!( + "{} {}moved due to this call{}", + place_name, partially_str, loop_message + ), + ); + err.span_note( + var_span, + "this value implements `FnOnce`, which causes it to be moved when called", + ); + } + FnSelfUseKind::Operator { self_arg } => { + err.span_label( + fn_call_span, + &format!( + "{} {}moved due to usage in operator{}", + place_name, partially_str, loop_message + ), + ); + if self.fn_self_span_reported.insert(fn_span) { + err.span_note( + self_arg.span, + "calling this operator moves the left-hand side", + ); + } + } + FnSelfUseKind::Normal { self_arg, implicit_into_iter } => { + if implicit_into_iter { err.span_label( fn_call_span, &format!( - "{} {}moved due to this call", - place_name, partially_str + "{} {}moved due to this implicit call to `.into_iter()`{}", + place_name, partially_str, loop_message ), ); - err.span_note( - var_span, - "this value implements `FnOnce`, which causes it to be moved when called", - ); - } - FnSelfUseKind::Operator { self_arg } => { + } else { err.span_label( fn_call_span, &format!( - "{} {}moved due to usage in operator", - place_name, partially_str + "{} {}moved due to this method call{}", + place_name, partially_str, loop_message ), ); - if self.fn_self_span_reported.insert(fn_span) { - err.span_note( - self_arg.span, - "calling this operator moves the left-hand side", - ); - } } - FnSelfUseKind::Normal { self_arg, implicit_into_iter } => { - if implicit_into_iter { - err.span_label( - fn_call_span, - &format!( - "{} {}moved due to this implicit call to `.into_iter()`", - place_name, partially_str - ), - ); - } else { - err.span_label( - fn_call_span, - &format!( - "{} {}moved due to this method call", - place_name, partially_str - ), - ); - } - // Avoid pointing to the same function in multiple different - // error messages - if self.fn_self_span_reported.insert(self_arg.span) { - err.span_note( - self_arg.span, - &format!("this function consumes the receiver `self` by taking ownership of it, which moves {}", place_name) - ); - } + // Avoid pointing to the same function in multiple different + // error messages + if self.fn_self_span_reported.insert(self_arg.span) { + err.span_note( + self_arg.span, + &format!("this function consumes the receiver `self` by taking ownership of it, which moves {}", place_name) + ); } - // Deref::deref takes &self, which cannot cause a move - FnSelfUseKind::DerefCoercion { .. } => unreachable!(), } - } else { - err.span_label( - move_span, - format!("value {}moved{} here", partially_str, move_msg), - ); + // Deref::deref takes &self, which cannot cause a move + FnSelfUseKind::DerefCoercion { .. } => unreachable!(), + } + } else { + err.span_label( + move_span, + format!("value {}moved{} here{}", partially_str, move_msg, loop_message), + ); + // If the move error occurs due to a loop, don't show + // another message for the same span + if loop_message.is_empty() { move_spans.var_span_label( &mut err, format!( @@ -250,6 +243,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> { ); } } + if let UseSpans::PatUse(span) = move_spans { err.span_suggestion_verbose( span.shrink_to_lo(), diff --git a/src/test/ui/moves/move-fn-self-receiver.rs b/src/test/ui/moves/move-fn-self-receiver.rs index 6107f53fa1960..946642ef6f3ad 100644 --- a/src/test/ui/moves/move-fn-self-receiver.rs +++ b/src/test/ui/moves/move-fn-self-receiver.rs @@ -69,6 +69,11 @@ fn move_out(val: Container) { let container = Container(vec![]); for _val in container.custom_into_iter() {} container; //~ ERROR use of moved + + let foo2 = Foo; + loop { + foo2.use_self(); //~ ERROR use of moved + } } fn main() {} diff --git a/src/test/ui/moves/move-fn-self-receiver.stderr b/src/test/ui/moves/move-fn-self-receiver.stderr index dd263c1e90677..8c509363d02d1 100644 --- a/src/test/ui/moves/move-fn-self-receiver.stderr +++ b/src/test/ui/moves/move-fn-self-receiver.stderr @@ -152,7 +152,16 @@ note: this function consumes the receiver `self` by taking ownership of it, whic LL | fn custom_into_iter(self) -> impl Iterator { | ^^^^ -error: aborting due to 11 previous errors +error[E0382]: use of moved value: `foo2` + --> $DIR/move-fn-self-receiver.rs:75:9 + | +LL | let foo2 = Foo; + | ---- move occurs because `foo2` has type `Foo`, which does not implement the `Copy` trait +LL | loop { +LL | foo2.use_self(); + | ^^^^ ---------- `foo2` moved due to this method call, in previous iteration of loop + +error: aborting due to 12 previous errors Some errors have detailed explanations: E0382, E0505. For more information about an error, try `rustc --explain E0382`. diff --git a/src/test/ui/suggestions/borrow-for-loop-head.stderr b/src/test/ui/suggestions/borrow-for-loop-head.stderr index de342a969f4eb..64ce6c1e16d4b 100644 --- a/src/test/ui/suggestions/borrow-for-loop-head.stderr +++ b/src/test/ui/suggestions/borrow-for-loop-head.stderr @@ -15,8 +15,14 @@ LL | for i in &a { LL | for j in a { | ^ | | - | value moved here, in previous iteration of loop + | `a` moved due to this implicit call to `.into_iter()`, in previous iteration of loop | help: consider borrowing to avoid moving into the for loop: `&a` + | +note: this function consumes the receiver `self` by taking ownership of it, which moves `a` + --> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL + | +LL | fn into_iter(self) -> Self::IntoIter; + | ^^^^ error: aborting due to 2 previous errors