diff options
| -rw-r--r-- | compiler/rustc_passes/src/check_attr.rs | 47 | ||||
| -rw-r--r-- | tests/ui/lint/unused/unused_attributes-must_use.rs | 5 | ||||
| -rw-r--r-- | tests/ui/lint/unused/unused_attributes-must_use.stderr | 36 |
3 files changed, 55 insertions, 33 deletions
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs index f578708b40c..939637d0e29 100644 --- a/compiler/rustc_passes/src/check_attr.rs +++ b/compiler/rustc_passes/src/check_attr.rs @@ -1431,37 +1431,48 @@ impl<'tcx> CheckAttrVisitor<'tcx> { /// Warns against some misuses of `#[must_use]` fn check_must_use(&self, hir_id: HirId, attr: &Attribute, target: Target) { - if !matches!( + if matches!( target, Target::Fn | Target::Enum | Target::Struct | Target::Union - | Target::Method(_) + | Target::Method(MethodKind::Trait { body: false } | MethodKind::Inherent) | Target::ForeignFn // `impl Trait` in return position can trip // `unused_must_use` if `Trait` is marked as // `#[must_use]` | Target::Trait ) { - let article = match target { - Target::ExternCrate - | Target::Enum - | Target::Impl - | Target::Expression - | Target::Arm - | Target::AssocConst - | Target::AssocTy => "an", - _ => "a", - }; + return; + } - self.tcx.emit_node_span_lint( - UNUSED_ATTRIBUTES, - hir_id, - attr.span, - errors::MustUseNoEffect { article, target }, - ); + // `#[must_use]` can be applied to a trait method definition with a default body + if let Target::Method(MethodKind::Trait { body: true }) = target + && let parent_def_id = self.tcx.hir().get_parent_item(hir_id).def_id + && let containing_item = self.tcx.hir().expect_item(parent_def_id) + && let hir::ItemKind::Trait(..) = containing_item.kind + { + return; } + + let article = match target { + Target::ExternCrate + | Target::Enum + | Target::Impl + | Target::Expression + | Target::Arm + | Target::AssocConst + | Target::AssocTy => "an", + _ => "a", + }; + + self.tcx.emit_node_span_lint( + UNUSED_ATTRIBUTES, + hir_id, + attr.span, + errors::MustUseNoEffect { article, target }, + ); } /// Checks if `#[must_not_suspend]` is applied to a struct, enum, union, or trait. diff --git a/tests/ui/lint/unused/unused_attributes-must_use.rs b/tests/ui/lint/unused/unused_attributes-must_use.rs index 51f868706b6..860fc5046d1 100644 --- a/tests/ui/lint/unused/unused_attributes-must_use.rs +++ b/tests/ui/lint/unused/unused_attributes-must_use.rs @@ -79,6 +79,11 @@ trait Use { #[must_use] //~ ERROR `#[must_use]` has no effect impl Use for () { type AssocTy = (); + + #[must_use] //~ ERROR `#[must_use]` has no effect + fn get_four(&self) -> usize { + 4 + } } #[must_use] //~ ERROR `#[must_use]` has no effect diff --git a/tests/ui/lint/unused/unused_attributes-must_use.stderr b/tests/ui/lint/unused/unused_attributes-must_use.stderr index 9633767c442..28fd8eeb8cb 100644 --- a/tests/ui/lint/unused/unused_attributes-must_use.stderr +++ b/tests/ui/lint/unused/unused_attributes-must_use.stderr @@ -76,43 +76,43 @@ LL | #[must_use] | ^^^^^^^^^^^ error: `#[must_use]` has no effect when applied to a trait alias - --> $DIR/unused_attributes-must_use.rs:84:1 + --> $DIR/unused_attributes-must_use.rs:89:1 | LL | #[must_use] | ^^^^^^^^^^^ error: `#[must_use]` has no effect when applied to a macro def - --> $DIR/unused_attributes-must_use.rs:87:1 + --> $DIR/unused_attributes-must_use.rs:92:1 | LL | #[must_use] | ^^^^^^^^^^^ error: `#[must_use]` has no effect when applied to a statement - --> $DIR/unused_attributes-must_use.rs:95:5 + --> $DIR/unused_attributes-must_use.rs:100:5 | LL | #[must_use] | ^^^^^^^^^^^ error: `#[must_use]` has no effect when applied to a closure - --> $DIR/unused_attributes-must_use.rs:99:13 + --> $DIR/unused_attributes-must_use.rs:104:13 | LL | let x = #[must_use] | ^^^^^^^^^^^ error: `#[must_use]` has no effect when applied to an match arm - --> $DIR/unused_attributes-must_use.rs:121:9 + --> $DIR/unused_attributes-must_use.rs:126:9 | LL | #[must_use] | ^^^^^^^^^^^ error: `#[must_use]` has no effect when applied to a struct field - --> $DIR/unused_attributes-must_use.rs:129:28 + --> $DIR/unused_attributes-must_use.rs:134:28 | LL | let s = PatternField { #[must_use] foo: 123 }; | ^^^^^^^^^^^ error: `#[must_use]` has no effect when applied to a pattern field - --> $DIR/unused_attributes-must_use.rs:130:24 + --> $DIR/unused_attributes-must_use.rs:135:24 | LL | let PatternField { #[must_use] foo } = s; | ^^^^^^^^^^^ @@ -129,6 +129,12 @@ error: `#[must_use]` has no effect when applied to an associated type LL | #[must_use] | ^^^^^^^^^^^ +error: `#[must_use]` has no effect when applied to a provided trait method + --> $DIR/unused_attributes-must_use.rs:83:5 + | +LL | #[must_use] + | ^^^^^^^^^^^ + error: `#[must_use]` has no effect when applied to a foreign static item --> $DIR/unused_attributes-must_use.rs:50:5 | @@ -136,7 +142,7 @@ LL | #[must_use] | ^^^^^^^^^^^ error: unused `X` that must be used - --> $DIR/unused_attributes-must_use.rs:103:5 + --> $DIR/unused_attributes-must_use.rs:108:5 | LL | X; | ^ @@ -152,7 +158,7 @@ LL | let _ = X; | +++++++ error: unused `Y` that must be used - --> $DIR/unused_attributes-must_use.rs:104:5 + --> $DIR/unused_attributes-must_use.rs:109:5 | LL | Y::Z; | ^^^^ @@ -163,7 +169,7 @@ LL | let _ = Y::Z; | +++++++ error: unused `U` that must be used - --> $DIR/unused_attributes-must_use.rs:105:5 + --> $DIR/unused_attributes-must_use.rs:110:5 | LL | U { unit: () }; | ^^^^^^^^^^^^^^ @@ -174,7 +180,7 @@ LL | let _ = U { unit: () }; | +++++++ error: unused return value of `U::method` that must be used - --> $DIR/unused_attributes-must_use.rs:106:5 + --> $DIR/unused_attributes-must_use.rs:111:5 | LL | U::method(); | ^^^^^^^^^^^ @@ -185,7 +191,7 @@ LL | let _ = U::method(); | +++++++ error: unused return value of `foo` that must be used - --> $DIR/unused_attributes-must_use.rs:107:5 + --> $DIR/unused_attributes-must_use.rs:112:5 | LL | foo(); | ^^^^^ @@ -196,7 +202,7 @@ LL | let _ = foo(); | +++++++ error: unused return value of `foreign_foo` that must be used - --> $DIR/unused_attributes-must_use.rs:110:9 + --> $DIR/unused_attributes-must_use.rs:115:9 | LL | foreign_foo(); | ^^^^^^^^^^^^^ @@ -207,7 +213,7 @@ LL | let _ = foreign_foo(); | +++++++ error: unused return value of `Use::get_four` that must be used - --> $DIR/unused_attributes-must_use.rs:118:5 + --> $DIR/unused_attributes-must_use.rs:123:5 | LL | ().get_four(); | ^^^^^^^^^^^^^ @@ -217,5 +223,5 @@ help: use `let _ = ...` to ignore the resulting value LL | let _ = ().get_four(); | +++++++ -error: aborting due to 28 previous errors +error: aborting due to 29 previous errors |