Rewrite logic of has_nontrivial_oprand.
Check whether operator is overrided with a `struct` operand. The struct here refers to `struct`, `enum`, `union`. Add and fix test for `no_effect` lint.
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cocodery
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6d40b105ed
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89774234be
@ -10,6 +10,7 @@ use rustc_hir::{
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use rustc_infer::infer::TyCtxtInferExt as _;
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use rustc_lint::{LateContext, LateLintPass, LintContext};
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use rustc_middle::lint::in_external_macro;
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use rustc_middle::ty;
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use rustc_session::declare_lint_pass;
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use std::ops::Deref;
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@ -87,8 +88,13 @@ impl<'tcx> LateLintPass<'tcx> for NoEffect {
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fn check_no_effect(cx: &LateContext<'_>, stmt: &Stmt<'_>) -> bool {
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if let StmtKind::Semi(expr) = stmt.kind {
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// move `expr.span.from_expansion()` ahead
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if expr.span.from_expansion() {
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return false;
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}
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let expr = peel_blocks(expr);
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// assume nontrivial oprand of `Binary` Expr can skip `check_unnecessary_operation`
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if has_nontrivial_oprand(expr) {
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if has_nontrivial_oprand(cx, expr) {
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return true;
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}
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if has_no_effect(cx, expr) {
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@ -157,66 +163,38 @@ fn check_no_effect(cx: &LateContext<'_>, stmt: &Stmt<'_>) -> bool {
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false
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}
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fn has_nontrivial_oprand(expr: &Expr<'_>) -> bool {
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if expr.span.from_expansion() {
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return false;
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}
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return match peel_blocks(expr).kind {
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ExprKind::Binary(_, lhs, rhs) => !check_nontrivial_operand(lhs, rhs),
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fn has_nontrivial_oprand(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
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// It's very hard or impossable to check whether overrided operator have side-effect this lint.
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// So, this function assume user-defined binary operator is overrided with an side-effect.
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// The definition of user-defined structure here is `struct`, `enum`, `uniom`,
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// Althrough this will weaken the ability of this lint, less error lint-fix happen.
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match expr.kind {
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ExprKind::Binary(_, lhs, rhs) => {
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// get type of lhs and rhs
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let tyck_result = cx.typeck_results();
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let ty_lhs = tyck_result.expr_ty(lhs).kind();
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let ty_rhs = tyck_result.expr_ty(rhs).kind();
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// check whether lhs is a user-defined structure
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// only need to check lhs in fact
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let ud_lhs = match ty_lhs {
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ty::Adt(adt_def, _) => adt_def.is_struct() || adt_def.is_enum() || adt_def.is_union(),
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_ => false,
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};
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let ud_rhs = match ty_rhs {
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ty::Adt(adt_def, _) => adt_def.is_struct() || adt_def.is_enum() || adt_def.is_union(),
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_ => false,
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};
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// reference: rust/compiler/rustc_middle/src/ty/typeck_results.rs: `is_method_call`.
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// use this function to check whether operator is overrided in `ExprKind::Binary`.
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(ud_lhs || ud_rhs) && tyck_result.is_method_call(expr)
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},
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_ => false,
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};
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}
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fn check_nontrivial_operand(lhs: &Expr<'_>, rhs: &Expr<'_>) -> bool {
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// It's seem that impossable to check whether operator is overrided through context of this lint,
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// so, this function assume user-defined binary operator is overrided with an side-effect.
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// The definition of user-defined structure here is `tuple`, `array`, `struct`,
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// it looks like a little bit simple, but useful.
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// Althrough this will weaken the ability of this lint,
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// less miss lint-fix happen.
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// a closure to check whether expr belongs to user-defined structure
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let closure = |expr: &Expr<'_>| -> bool {
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match &expr.kind {
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// check whether expr is a user-defined sturcture
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ExprKind::Tup(..) | ExprKind::Array(..) | ExprKind::Struct(..) => true,
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// resolve expr's path
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ExprKind::Path(rustc_hir::QPath::Resolved(
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_,
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rustc_hir::Path {
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span: _,
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res,
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segments: _,
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},
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)) => {
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match res {
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Res::Def(defkind, _) => match defkind {
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// user-defined
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DefKind::Struct | DefKind::Ctor(_, _) => true,
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_ => false,
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},
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_ => false,
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};
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false
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},
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_ => false,
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}
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};
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let lhs_ud = closure(lhs);
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let rhs_ud = closure(rhs);
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// one of lhs or rhs is user-defined structure
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if lhs_ud || rhs_ud {
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return false;
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}
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true
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}
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fn has_no_effect(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
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if expr.span.from_expansion() {
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return false;
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}
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match peel_blocks(expr).kind {
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match expr.kind {
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ExprKind::Lit(..) | ExprKind::Closure { .. } => true,
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ExprKind::Path(..) => !has_drop(cx, cx.typeck_results().expr_ty(expr)),
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ExprKind::Index(a, b, _) | ExprKind::Binary(_, a, b) => has_no_effect(cx, a) && has_no_effect(cx, b),
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@ -9,6 +9,22 @@
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clippy::useless_vec
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)]
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use std::fmt::Display;
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use std::ops::Shl;
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struct Cout;
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impl<T> Shl<T> for Cout
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where
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T: Display,
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{
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type Output = Self;
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fn shl(self, rhs: T) -> Self::Output {
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println!("{}", rhs);
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self
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}
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}
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struct Unit;
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struct Tuple(i32);
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struct Struct {
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@ -174,4 +190,11 @@ fn main() {
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GreetStruct1("world");
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GreetStruct2()("world");
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GreetStruct3 {}("world");
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fn n() -> i32 {
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42
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}
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Cout << 142;
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Cout << n();
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}
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@ -1,5 +1,5 @@
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error: statement with no effect
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--> $DIR/no_effect.rs:98:5
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--> $DIR/no_effect.rs:114:5
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LL | 0;
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| ^^
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@ -8,151 +8,151 @@ LL | 0;
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= help: to override `-D warnings` add `#[allow(clippy::no_effect)]`
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error: statement with no effect
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--> $DIR/no_effect.rs:101:5
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--> $DIR/no_effect.rs:117:5
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LL | s2;
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| ^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:103:5
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--> $DIR/no_effect.rs:119:5
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LL | Unit;
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| ^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:105:5
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--> $DIR/no_effect.rs:121:5
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LL | Tuple(0);
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| ^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:107:5
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--> $DIR/no_effect.rs:123:5
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LL | Struct { field: 0 };
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| ^^^^^^^^^^^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:109:5
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--> $DIR/no_effect.rs:125:5
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LL | Struct { ..s };
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| ^^^^^^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:111:5
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--> $DIR/no_effect.rs:127:5
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LL | Union { a: 0 };
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| ^^^^^^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:113:5
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--> $DIR/no_effect.rs:129:5
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LL | Enum::Tuple(0);
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| ^^^^^^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:115:5
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--> $DIR/no_effect.rs:131:5
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LL | Enum::Struct { field: 0 };
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:117:5
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--> $DIR/no_effect.rs:133:5
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LL | 5 + 6;
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| ^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:119:5
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--> $DIR/no_effect.rs:135:5
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LL | *&42;
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| ^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:121:5
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--> $DIR/no_effect.rs:137:5
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LL | &6;
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| ^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:123:5
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--> $DIR/no_effect.rs:139:5
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LL | (5, 6, 7);
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| ^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:125:5
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--> $DIR/no_effect.rs:141:5
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LL | ..;
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| ^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:127:5
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--> $DIR/no_effect.rs:143:5
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LL | 5..;
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| ^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:129:5
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--> $DIR/no_effect.rs:145:5
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LL | ..5;
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| ^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:131:5
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--> $DIR/no_effect.rs:147:5
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LL | 5..6;
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| ^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:133:5
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--> $DIR/no_effect.rs:149:5
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LL | 5..=6;
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| ^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:135:5
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--> $DIR/no_effect.rs:151:5
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LL | [42, 55];
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| ^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:137:5
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--> $DIR/no_effect.rs:153:5
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LL | [42, 55][1];
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| ^^^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:139:5
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--> $DIR/no_effect.rs:155:5
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LL | (42, 55).1;
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| ^^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:141:5
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--> $DIR/no_effect.rs:157:5
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LL | [42; 55];
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| ^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:143:5
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--> $DIR/no_effect.rs:159:5
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LL | [42; 55][13];
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| ^^^^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:146:5
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--> $DIR/no_effect.rs:162:5
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LL | || x += 5;
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| ^^^^^^^^^^
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error: statement with no effect
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--> $DIR/no_effect.rs:149:5
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--> $DIR/no_effect.rs:165:5
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LL | FooString { s: s };
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| ^^^^^^^^^^^^^^^^^^^
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error: binding to `_` prefixed variable with no side-effect
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--> $DIR/no_effect.rs:151:5
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--> $DIR/no_effect.rs:167:5
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LL | let _unused = 1;
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| ^^^^^^^^^^^^^^^^
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@ -161,19 +161,19 @@ LL | let _unused = 1;
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= help: to override `-D warnings` add `#[allow(clippy::no_effect_underscore_binding)]`
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error: binding to `_` prefixed variable with no side-effect
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--> $DIR/no_effect.rs:154:5
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--> $DIR/no_effect.rs:170:5
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LL | let _penguin = || println!("Some helpful closure");
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: binding to `_` prefixed variable with no side-effect
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--> $DIR/no_effect.rs:156:5
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--> $DIR/no_effect.rs:172:5
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LL | let _duck = Struct { field: 0 };
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error: binding to `_` prefixed variable with no side-effect
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--> $DIR/no_effect.rs:158:5
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--> $DIR/no_effect.rs:174:5
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LL | let _cat = [2, 4, 6, 8][2];
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^
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