diff --git a/src/librustc_lint/unused.rs b/src/librustc_lint/unused.rs index 439cc3a4b844..b97920dd18b7 100644 --- a/src/librustc_lint/unused.rs +++ b/src/librustc_lint/unused.rs @@ -153,6 +153,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults { }; let mut fn_warned = false; + let mut op_warned = false; if cx.tcx.sess.features.borrow().fn_must_use { let maybe_def = match expr.node { hir::ExprCall(ref callee, _) => { @@ -172,9 +173,24 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults { let def_id = def.def_id(); fn_warned = check_must_use(cx, def_id, s.span, "return value of "); } + + if let hir::ExprBinary(bin_op, ..) = expr.node { + match bin_op.node { + // Hardcoding the comparison operators here seemed more + // expedient than the refactoring that would be needed to + // look up the `#[must_use]` attribute which does exist on + // the comparison trait methods + hir::BiEq | hir::BiLt | hir::BiLe | hir::BiNe | hir::BiGe | hir::BiGt => { + let msg = "unused comparison which must be used"; + cx.span_lint(UNUSED_MUST_USE, expr.span, msg); + op_warned = true; + }, + _ => {}, + } + } } - if !(ty_warned || fn_warned) { + if !(ty_warned || fn_warned || op_warned) { cx.span_lint(UNUSED_RESULTS, s.span, "unused result"); } diff --git a/src/librustc_mir/borrow_check.rs b/src/librustc_mir/borrow_check.rs index 5133e528b099..10825323e412 100644 --- a/src/librustc_mir/borrow_check.rs +++ b/src/librustc_mir/borrow_check.rs @@ -408,7 +408,7 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx> self.each_borrow_involving_path( context, lvalue_span.0, flow_state, |this, _idx, borrow| { if !borrow.compatible_with(BorrowKind::Mut) { - this.report_move_out_while_borrowed(context, lvalue_span); + this.report_move_out_while_borrowed(context, lvalue_span, borrow); Control::Break } else { Control::Continue @@ -896,20 +896,28 @@ impl<'c, 'b, 'a: 'b+'c, 'gcx, 'tcx: 'a> MirBorrowckCtxt<'c, 'b, 'a, 'gcx, 'tcx> fn report_use_of_moved(&mut self, _context: Context, (lvalue, span): (&Lvalue, Span)) { - let mut err = self.tcx.cannot_act_on_uninitialized_variable( - span, "use", &self.describe_lvalue(lvalue), Origin::Mir); - // FIXME: add span_label for use of uninitialized variable - err.emit(); + self.tcx.cannot_act_on_uninitialized_variable(span, + "use", + &self.describe_lvalue(lvalue), + Origin::Mir) + .span_label(span, format!("use of possibly uninitialized `{}`", + self.describe_lvalue(lvalue))) + .emit(); } fn report_move_out_while_borrowed(&mut self, _context: Context, - (lvalue, span): (&Lvalue, Span)) { - let mut err = self.tcx.cannot_move_when_borrowed( - span, &self.describe_lvalue(lvalue), Origin::Mir); - // FIXME 1: add span_label for "borrow of `()` occurs here" - // FIXME 2: add span_label for "move out of `{}` occurs here" - err.emit(); + (lvalue, span): (&Lvalue, Span), + borrow: &BorrowData) { + self.tcx.cannot_move_when_borrowed(span, + &self.describe_lvalue(lvalue), + Origin::Mir) + .span_label(self.retrieve_borrow_span(borrow), + format!("borrow of `{}` occurs here", + self.describe_lvalue(&borrow.lvalue))) + .span_label(span, format!("move out of `{}` occurs here", + self.describe_lvalue(lvalue))) + .emit(); } fn report_use_while_mutably_borrowed(&mut self, diff --git a/src/librustdoc/html/static/rustdoc.css b/src/librustdoc/html/static/rustdoc.css index 5727d3c5f706..1b7232bf1bca 100644 --- a/src/librustdoc/html/static/rustdoc.css +++ b/src/librustdoc/html/static/rustdoc.css @@ -823,7 +823,7 @@ span.since { .information { position: absolute; - left: -1px; + left: -20px; margin-top: 7px; z-index: 1; } diff --git a/src/libstd/process.rs b/src/libstd/process.rs index a3a7e91dd807..1869ad3ed707 100644 --- a/src/libstd/process.rs +++ b/src/libstd/process.rs @@ -106,15 +106,18 @@ use sys_common::{AsInner, AsInnerMut, FromInner, IntoInner}; pub struct Child { handle: imp::Process, - /// The handle for writing to the child's stdin, if it has been captured + /// The handle for writing to the child's standard input (stdin), if it has + /// been captured. #[stable(feature = "process", since = "1.0.0")] pub stdin: Option, - /// The handle for reading from the child's stdout, if it has been captured + /// The handle for reading from the child's standard output (stdout), if it + /// has been captured. #[stable(feature = "process", since = "1.0.0")] pub stdout: Option, - /// The handle for reading from the child's stderr, if it has been captured + /// The handle for reading from the child's standard error (stderr), if it + /// has been captured. #[stable(feature = "process", since = "1.0.0")] pub stderr: Option, } @@ -149,12 +152,17 @@ impl fmt::Debug for Child { } } -/// A handle to a child process's stdin. +/// A handle to a child process's standard input (stdin). /// /// This struct is used in the [`stdin`] field on [`Child`]. /// +/// When an instance of `ChildStdin` is [dropped], the `ChildStdin`'s underlying +/// file handle will be closed. If the child process was blocked on input prior +/// to being dropped, it will become unblocked after dropping. +/// /// [`Child`]: struct.Child.html /// [`stdin`]: struct.Child.html#structfield.stdin +/// [dropped]: ../ops/trait.Drop.html #[stable(feature = "process", since = "1.0.0")] pub struct ChildStdin { inner: AnonPipe @@ -192,12 +200,16 @@ impl fmt::Debug for ChildStdin { } } -/// A handle to a child process's stdout. +/// A handle to a child process's standard output (stdout). /// /// This struct is used in the [`stdout`] field on [`Child`]. /// +/// When an instance of `ChildStdout` is [dropped], the `ChildStdout`'s +/// underlying file handle will be closed. +/// /// [`Child`]: struct.Child.html /// [`stdout`]: struct.Child.html#structfield.stdout +/// [dropped]: ../ops/trait.Drop.html #[stable(feature = "process", since = "1.0.0")] pub struct ChildStdout { inner: AnonPipe @@ -239,8 +251,12 @@ impl fmt::Debug for ChildStdout { /// /// This struct is used in the [`stderr`] field on [`Child`]. /// +/// When an instance of `ChildStderr` is [dropped], the `ChildStderr`'s +/// underlying file handle will be closed. +/// /// [`Child`]: struct.Child.html /// [`stderr`]: struct.Child.html#structfield.stderr +/// [dropped]: ../ops/trait.Drop.html #[stable(feature = "process", since = "1.0.0")] pub struct ChildStderr { inner: AnonPipe @@ -534,7 +550,7 @@ impl Command { self } - /// Configuration for the child process's stdin handle (file descriptor 0). + /// Configuration for the child process's standard input (stdin) handle. /// /// # Examples /// @@ -554,7 +570,7 @@ impl Command { self } - /// Configuration for the child process's stdout handle (file descriptor 1). + /// Configuration for the child process's standard output (stdout) handle. /// /// # Examples /// @@ -574,7 +590,7 @@ impl Command { self } - /// Configuration for the child process's stderr handle (file descriptor 2). + /// Configuration for the child process's standard error (stderr) handle. /// /// # Examples /// diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs index 1fef382c83a3..5c730aaa8d0f 100644 --- a/src/libsyntax/feature_gate.rs +++ b/src/libsyntax/feature_gate.rs @@ -380,7 +380,7 @@ declare_features! ( // #[doc(masked)] (active, doc_masked, "1.21.0", None), - // allow `#[must_use]` on functions (RFC 1940) + // allow `#[must_use]` on functions and comparison operators (RFC 1940) (active, fn_must_use, "1.21.0", Some(43302)), // allow '|' at beginning of match arms (RFC 1925) diff --git a/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.rs b/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.rs index 7eb4c32972a2..3741ba4f3ae7 100644 --- a/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.rs +++ b/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.rs @@ -11,6 +11,7 @@ #![feature(fn_must_use)] #![warn(unused_must_use)] +#[derive(PartialEq, Eq)] struct MyStruct { n: usize, } @@ -58,13 +59,18 @@ fn main() { need_to_use_this_value(); let mut m = MyStruct { n: 2 }; + let n = MyStruct { n: 3 }; + m.need_to_use_this_method_value(); m.is_even(); // trait method! - m.replace(3); + m.replace(3); // won't warn (annotation needs to be in trait definition) + // comparison methods are `must_use` 2.eq(&3); + m.eq(&n); - // FIXME: operators should probably be `must_use` if underlying method is + // lint includes comparison operators 2 == 3; + m == n; } diff --git a/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.stderr b/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.stderr index 69755c89b484..fdd0a591bc78 100644 --- a/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.stderr +++ b/src/test/ui/rfc_1940-must_use_on_functions/fn_must_use.stderr @@ -1,7 +1,7 @@ warning: unused return value of `need_to_use_this_value` which must be used: it's important - --> $DIR/fn_must_use.rs:58:5 + --> $DIR/fn_must_use.rs:59:5 | -58 | need_to_use_this_value(); +59 | need_to_use_this_value(); | ^^^^^^^^^^^^^^^^^^^^^^^^^ | note: lint level defined here @@ -11,20 +11,38 @@ note: lint level defined here | ^^^^^^^^^^^^^^^ warning: unused return value of `MyStruct::need_to_use_this_method_value` which must be used - --> $DIR/fn_must_use.rs:61:5 + --> $DIR/fn_must_use.rs:64:5 | -61 | m.need_to_use_this_method_value(); +64 | m.need_to_use_this_method_value(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ warning: unused return value of `EvenNature::is_even` which must be used: no side effects - --> $DIR/fn_must_use.rs:62:5 + --> $DIR/fn_must_use.rs:65:5 | -62 | m.is_even(); // trait method! +65 | m.is_even(); // trait method! | ^^^^^^^^^^^^ warning: unused return value of `std::cmp::PartialEq::eq` which must be used - --> $DIR/fn_must_use.rs:66:5 + --> $DIR/fn_must_use.rs:70:5 | -66 | 2.eq(&3); +70 | 2.eq(&3); | ^^^^^^^^^ +warning: unused return value of `std::cmp::PartialEq::eq` which must be used + --> $DIR/fn_must_use.rs:71:5 + | +71 | m.eq(&n); + | ^^^^^^^^^ + +warning: unused comparison which must be used + --> $DIR/fn_must_use.rs:74:5 + | +74 | 2 == 3; + | ^^^^^^ + +warning: unused comparison which must be used + --> $DIR/fn_must_use.rs:75:5 + | +75 | m == n; + | ^^^^^^ +