diff options
| -rw-r--r-- | clippy_lints/src/no_effect.rs | 14 | ||||
| -rw-r--r-- | tests/ui/no_effect.rs | 53 | ||||
| -rw-r--r-- | tests/ui/single_range_in_vec_init.rs | 2 |
3 files changed, 64 insertions, 5 deletions
diff --git a/clippy_lints/src/no_effect.rs b/clippy_lints/src/no_effect.rs index 7ab7976d569..02c48166131 100644 --- a/clippy_lints/src/no_effect.rs +++ b/clippy_lints/src/no_effect.rs @@ -221,10 +221,16 @@ fn is_operator_overridden(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { } } +/// Checks if dropping `expr` might have a visible side effect. +fn expr_ty_has_significant_drop(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { + let ty = cx.typeck_results().expr_ty(expr); + ty.has_significant_drop(cx.tcx, cx.typing_env()) +} + fn has_no_effect(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { match expr.kind { ExprKind::Lit(..) | ExprKind::Closure { .. } => true, - ExprKind::Path(..) => !has_drop(cx, cx.typeck_results().expr_ty(expr)), + ExprKind::Path(..) => !expr_ty_has_significant_drop(cx, expr), ExprKind::Index(a, b, _) | ExprKind::Binary(_, a, b) => has_no_effect(cx, a) && has_no_effect(cx, b), ExprKind::Array(v) | ExprKind::Tup(v) => v.iter().all(|val| has_no_effect(cx, val)), ExprKind::Repeat(inner, _) @@ -233,8 +239,8 @@ fn has_no_effect(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { | ExprKind::Unary(_, inner) | ExprKind::Field(inner, _) | ExprKind::AddrOf(_, _, inner) => has_no_effect(cx, inner), - ExprKind::Struct(_, fields, ref base) => { - !has_drop(cx, cx.typeck_results().expr_ty(expr)) + ExprKind::Struct(_, fields, base) => { + !expr_ty_has_significant_drop(cx, expr) && fields.iter().all(|field| has_no_effect(cx, field.expr)) && match &base { StructTailExpr::None | StructTailExpr::DefaultFields(_) => true, @@ -252,7 +258,7 @@ fn has_no_effect(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { Res::Def(DefKind::Struct | DefKind::Variant | DefKind::Ctor(..), ..) ); if def_matched || is_range_literal(expr) { - !has_drop(cx, cx.typeck_results().expr_ty(expr)) && args.iter().all(|arg| has_no_effect(cx, arg)) + !expr_ty_has_significant_drop(cx, expr) && args.iter().all(|arg| has_no_effect(cx, arg)) } else { false } diff --git a/tests/ui/no_effect.rs b/tests/ui/no_effect.rs index 703c2a3d984..4ab5bc9acde 100644 --- a/tests/ui/no_effect.rs +++ b/tests/ui/no_effect.rs @@ -221,3 +221,56 @@ fn main() { Cout << 142; -Cout; } + +fn issue14592() { + struct MyStruct { + _inner: MyInner, + } + struct MyInner {} + + impl Drop for MyInner { + fn drop(&mut self) { + println!("dropping"); + } + } + + let x = MyStruct { _inner: MyInner {} }; + + let closure = || { + // Do not lint: dropping the assignment or assigning to `_` would + // change the output. + let _x = x; + }; + + println!("1"); + closure(); + println!("2"); + + struct Innocuous { + a: i32, + } + + // Do not lint: one of the fields has a side effect. + let x = MyInner {}; + let closure = || { + let _x = Innocuous { + a: { + x; + 10 + }, + }; + }; + + // Do not lint: the base has a side effect. + let x = MyInner {}; + let closure = || { + let _x = Innocuous { + ..Innocuous { + a: { + x; + 10 + }, + } + }; + }; +} diff --git a/tests/ui/single_range_in_vec_init.rs b/tests/ui/single_range_in_vec_init.rs index c6c0cb347dc..25884450b08 100644 --- a/tests/ui/single_range_in_vec_init.rs +++ b/tests/ui/single_range_in_vec_init.rs @@ -1,6 +1,6 @@ //@aux-build:proc_macros.rs //@no-rustfix: overlapping suggestions -#![allow(clippy::no_effect, clippy::useless_vec, unused)] +#![allow(clippy::no_effect, clippy::unnecessary_operation, clippy::useless_vec, unused)] #![warn(clippy::single_range_in_vec_init)] #![feature(generic_arg_infer)] |