Auto merge of rust-lang#10309 - c410-f3r:arith, r=giraffate

[arithmetic_side_effects] Fix rust-lang#10252 Fix rust-lang#10252 At least for integers, shifts are already handled by the compiler. ---- changelog: [`arithmetic_side_effects`]: No longer lints on right or left shifts with constant integers, as the compiler warns about them. [rust-lang#10309](rust-lang/rust-clippy#10309) <!-- changelog_checked-->

Author: bors

clippy_lints/src/operators/arithmetic_side_effects.rs

@@ -143,6 +143,10 @@ impl ArithmeticSideEffects {
  return;
  }
  let has_valid_op = if Self::is_integral(lhs_ty) && Self::is_integral(rhs_ty) {
+ if let hir::BinOpKind::Shl | hir::BinOpKind::Shr = op.node {
+ // At least for integers, shifts are already handled by the CTFE
+ return;
+ }
  let (actual_lhs, lhs_ref_counter) = peel_hir_expr_refs(lhs);
  let (actual_rhs, rhs_ref_counter) = peel_hir_expr_refs(rhs);
  match (
@@ -151,10 +155,13 @@ impl ArithmeticSideEffects {
  ) {
  (None, None) => false,
  (None, Some(n)) | (Some(n), None) => match (&op.node, n) {
- (hir::BinOpKind::Div | hir::BinOpKind::Rem, 0) => false,
+ // Division and module are always valid if applied to non-zero integers
+ (hir::BinOpKind::Div | hir::BinOpKind::Rem, local_n) if local_n != 0 => true,
+ // Addition or subtracting zeros is always a no-op
  (hir::BinOpKind::Add | hir::BinOpKind::Sub, 0)
- | (hir::BinOpKind::Div | hir::BinOpKind::Rem, _)
- | (hir::BinOpKind::Mul, 0 | 1) => true,
+ // Multiplication by 1 or 0 will never overflow
+ | (hir::BinOpKind::Mul, 0 | 1)
+ => true,
  _ => false,
  },
  (Some(_), Some(_)) => {

tests/ui/arithmetic_side_effects.rs

@@ -45,24 +45,32 @@ impl_arith!(
  Div, Custom, Custom, div;
  Mul, Custom, Custom, mul;
  Rem, Custom, Custom, rem;
+ Shl, Custom, Custom, shl;
+ Shr, Custom, Custom, shr;
  Sub, Custom, Custom, sub;
 
  Add, Custom, &Custom, add;
  Div, Custom, &Custom, div;
  Mul, Custom, &Custom, mul;
  Rem, Custom, &Custom, rem;
+ Shl, Custom, &Custom, shl;
+ Shr, Custom, &Custom, shr;
  Sub, Custom, &Custom, sub;
 
  Add, &Custom, Custom, add;
  Div, &Custom, Custom, div;
  Mul, &Custom, Custom, mul;
  Rem, &Custom, Custom, rem;
+ Shl, &Custom, Custom, shl;
+ Shr, &Custom, Custom, shr;
  Sub, &Custom, Custom, sub;
 
  Add, &Custom, &Custom, add;
  Div, &Custom, &Custom, div;
  Mul, &Custom, &Custom, mul;
  Rem, &Custom, &Custom, rem;
+ Shl, &Custom, &Custom, shl;
+ Shr, &Custom, &Custom, shr;
  Sub, &Custom, &Custom, sub;
 );
 
@@ -71,24 +79,32 @@ impl_assign_arith!(
  DivAssign, Custom, Custom, div_assign;
  MulAssign, Custom, Custom, mul_assign;
  RemAssign, Custom, Custom, rem_assign;
+ ShlAssign, Custom, Custom, shl_assign;
+ ShrAssign, Custom, Custom, shr_assign;
  SubAssign, Custom, Custom, sub_assign;
 
  AddAssign, Custom, &Custom, add_assign;
  DivAssign, Custom, &Custom, div_assign;
  MulAssign, Custom, &Custom, mul_assign;
  RemAssign, Custom, &Custom, rem_assign;
+ ShlAssign, Custom, &Custom, shl_assign;
+ ShrAssign, Custom, &Custom, shr_assign;
  SubAssign, Custom, &Custom, sub_assign;
 
  AddAssign, &Custom, Custom, add_assign;
  DivAssign, &Custom, Custom, div_assign;
  MulAssign, &Custom, Custom, mul_assign;
  RemAssign, &Custom, Custom, rem_assign;
+ ShlAssign, &Custom, Custom, shl_assign;
+ ShrAssign, &Custom, Custom, shr_assign;
  SubAssign, &Custom, Custom, sub_assign;
 
  AddAssign, &Custom, &Custom, add_assign;
  DivAssign, &Custom, &Custom, div_assign;
  MulAssign, &Custom, &Custom, mul_assign;
  RemAssign, &Custom, &Custom, rem_assign;
+ ShlAssign, &Custom, &Custom, shl_assign;
+ ShrAssign, &Custom, &Custom, shr_assign;
  SubAssign, &Custom, &Custom, sub_assign;
 );
 
@@ -297,6 +313,10 @@ pub fn unknown_ops_or_runtime_ops_that_can_overflow() {
  _custom %= &Custom;
  _custom *= Custom;
  _custom *= &Custom;
+ _custom >>= Custom;
+ _custom >>= &Custom;
+ _custom <<= Custom;
+ _custom <<= &Custom;
  _custom += -Custom;
  _custom += &-Custom;
  _custom -= -Custom;
@@ -307,6 +327,10 @@ pub fn unknown_ops_or_runtime_ops_that_can_overflow() {
  _custom %= &-Custom;
  _custom *= -Custom;
  _custom *= &-Custom;
+ _custom >>= -Custom;
+ _custom >>= &-Custom;
+ _custom <<= -Custom;
+ _custom <<= &-Custom;
 
  // Binary
  _n = _n + 1;
@@ -347,6 +371,10 @@ pub fn unknown_ops_or_runtime_ops_that_can_overflow() {
  _custom = Custom + &Custom;
  _custom = &Custom + Custom;
  _custom = &Custom + &Custom;
+ _custom = _custom >> _custom;
+ _custom = _custom >> &_custom;
+ _custom = Custom << _custom;
+ _custom = &Custom << _custom;
 
  // Unary
  _n = -_n;