diff options
| -rw-r--r-- | clippy_lints/src/unused_unit.rs | 21 | ||||
| -rw-r--r-- | tests/ui/unused_unit.edition2021.fixed | 27 | ||||
| -rw-r--r-- | tests/ui/unused_unit.edition2021.stderr | 6 | ||||
| -rw-r--r-- | tests/ui/unused_unit.edition2024.fixed | 29 | ||||
| -rw-r--r-- | tests/ui/unused_unit.rs | 29 |
5 files changed, 83 insertions, 29 deletions
diff --git a/clippy_lints/src/unused_unit.rs b/clippy_lints/src/unused_unit.rs index 3652bb68dea..d503bd3379b 100644 --- a/clippy_lints/src/unused_unit.rs +++ b/clippy_lints/src/unused_unit.rs @@ -6,8 +6,8 @@ use rustc_errors::Applicability; use rustc_hir::def_id::LocalDefId; use rustc_hir::intravisit::FnKind; use rustc_hir::{ - AssocItemConstraintKind, Body, Expr, ExprKind, FnDecl, FnRetTy, GenericArgsParentheses, Node, PolyTraitRef, Term, - Ty, TyKind, + AssocItemConstraintKind, Body, Expr, ExprKind, FnDecl, FnRetTy, GenericArgsParentheses, PolyTraitRef, Term, Ty, + TyKind, }; use rustc_lint::{EarlyContext, EarlyLintPass, LateContext, LateLintPass}; use rustc_session::declare_lint_pass; @@ -49,19 +49,22 @@ impl<'tcx> LateLintPass<'tcx> for UnusedUnit { decl: &'tcx FnDecl<'tcx>, body: &'tcx Body<'tcx>, span: Span, - def_id: LocalDefId, + _def_id: LocalDefId, ) { if let FnRetTy::Return(hir_ty) = decl.output && is_unit_ty(hir_ty) && !hir_ty.span.from_expansion() && get_def(span) == get_def(hir_ty.span) { - // implicit types in closure signatures are forbidden when `for<...>` is present - if let FnKind::Closure = kind - && let Node::Expr(expr) = cx.tcx.hir_node_by_def_id(def_id) - && let ExprKind::Closure(closure) = expr.kind - && !closure.bound_generic_params.is_empty() - { + // The explicit `-> ()` in the closure signature might be necessary for multiple reasons: + // - Implicit types in closure signatures are forbidden when `for<...>` is present + // - If the closure body ends with a function call, and that function's return type is generic, the + // `-> ()` could be required for it to be inferred + // + // There could be more reasons to have it, and, in general, we shouldn't discourage the users from + // writing more type annotations than strictly necessary, because it can help readability and + // maintainability + if let FnKind::Closure = kind { return; } diff --git a/tests/ui/unused_unit.edition2021.fixed b/tests/ui/unused_unit.edition2021.fixed index def8ef86e3c..8e12bd2c8c7 100644 --- a/tests/ui/unused_unit.edition2021.fixed +++ b/tests/ui/unused_unit.edition2021.fixed @@ -127,14 +127,10 @@ mod issue14577 { trait Unit {} impl Unit for () {} - fn run<R: Unit>(f: impl FnOnce() -> R) { - f(); - } - #[allow(dependency_on_unit_never_type_fallback)] fn bar() { - run(|| { todo!() }); //~[edition2021]^ unused_unit + panic!() } struct UnitStruct; @@ -150,3 +146,24 @@ mod pr14962 { type UnusedParensButNoUnit = Box<dyn (Fn())>; } + +mod issue15035 { + + trait Convert<T> { + fn from(value: T) -> Self; + } + + impl Convert<u64> for () { + fn from(_value: u64) -> Self {} + } + + fn handle<T: Convert<u64>>(value: u64) -> T { + Convert::from(value) + } + + pub fn f() -> Option<bool> { + let result: Result<bool, u64> = Err(42); + // the `-> ()` is required for the inference of `handle`'s return type + result.map_err(|err| -> () { handle(err) }).ok() + } +} diff --git a/tests/ui/unused_unit.edition2021.stderr b/tests/ui/unused_unit.edition2021.stderr index 13cc20d4d7a..9ad3c2df915 100644 --- a/tests/ui/unused_unit.edition2021.stderr +++ b/tests/ui/unused_unit.edition2021.stderr @@ -119,10 +119,10 @@ LL | fn test3()-> (){} | ^^^^^ help: remove the `-> ()` error: unneeded unit return type - --> tests/ui/unused_unit.rs:136:15 + --> tests/ui/unused_unit.rs:131:13 | -LL | run(|| -> () { todo!() }); - | ^^^^^^ help: remove the `-> ()` +LL | fn bar() -> () { + | ^^^^^^ help: remove the `-> ()` error: aborting due to 20 previous errors diff --git a/tests/ui/unused_unit.edition2024.fixed b/tests/ui/unused_unit.edition2024.fixed index f908b958b19..688d2fe9afa 100644 --- a/tests/ui/unused_unit.edition2024.fixed +++ b/tests/ui/unused_unit.edition2024.fixed @@ -127,14 +127,10 @@ mod issue14577 { trait Unit {} impl Unit for () {} - fn run<R: Unit>(f: impl FnOnce() -> R) { - f(); - } - #[allow(dependency_on_unit_never_type_fallback)] - fn bar() { - run(|| -> () { todo!() }); + fn bar() -> () { //~[edition2021]^ unused_unit + panic!() } struct UnitStruct; @@ -150,3 +146,24 @@ mod pr14962 { type UnusedParensButNoUnit = Box<dyn (Fn())>; } + +mod issue15035 { + + trait Convert<T> { + fn from(value: T) -> Self; + } + + impl Convert<u64> for () { + fn from(_value: u64) -> Self {} + } + + fn handle<T: Convert<u64>>(value: u64) -> T { + Convert::from(value) + } + + pub fn f() -> Option<bool> { + let result: Result<bool, u64> = Err(42); + // the `-> ()` is required for the inference of `handle`'s return type + result.map_err(|err| -> () { handle(err) }).ok() + } +} diff --git a/tests/ui/unused_unit.rs b/tests/ui/unused_unit.rs index 7298ec40cc2..31e980f2655 100644 --- a/tests/ui/unused_unit.rs +++ b/tests/ui/unused_unit.rs @@ -127,14 +127,10 @@ mod issue14577 { trait Unit {} impl Unit for () {} - fn run<R: Unit>(f: impl FnOnce() -> R) { - f(); - } - #[allow(dependency_on_unit_never_type_fallback)] - fn bar() { - run(|| -> () { todo!() }); + fn bar() -> () { //~[edition2021]^ unused_unit + panic!() } struct UnitStruct; @@ -150,3 +146,24 @@ mod pr14962 { type UnusedParensButNoUnit = Box<dyn (Fn())>; } + +mod issue15035 { + + trait Convert<T> { + fn from(value: T) -> Self; + } + + impl Convert<u64> for () { + fn from(_value: u64) -> Self {} + } + + fn handle<T: Convert<u64>>(value: u64) -> T { + Convert::from(value) + } + + pub fn f() -> Option<bool> { + let result: Result<bool, u64> = Err(42); + // the `-> ()` is required for the inference of `handle`'s return type + result.map_err(|err| -> () { handle(err) }).ok() + } +} |