Auto merge of #9587 - c410-f3r:arith, r=Alexendoo

[arithmetic-side-effects] Do not ignore literal references

To my utter surprise, `rustc` does does not warn stuff like `let n: u8 = &255 + &1` or `let n: u8 = 255 + &1`.

changelog: [arithmetic-side-effects] Do not ignore literal references

3 files changed, 104 insertions, 74 deletions

diff --git a/clippy_lints/src/operators/arithmetic_side_effects.rs b/clippy_lints/src/operators/arithmetic_side_effects.rs
index 9ba9cc1c517..8827daaa3ee 100644
--- a/clippy_lints/src/operators/arithmetic_side_effects.rs
+++ b/clippy_lints/src/operators/arithmetic_side_effects.rs
@@ -1,8 +1,3 @@
-#![allow(
-    // False positive
-    clippy::match_same_arms
-)]
-
 use super::ARITHMETIC_SIDE_EFFECTS;
 use clippy_utils::{consts::constant_simple, diagnostics::span_lint};
 use rustc_ast as ast;
@@ -14,12 +9,12 @@ use rustc_session::impl_lint_pass;
 use rustc_span::source_map::{Span, Spanned};
 
 const HARD_CODED_ALLOWED: &[&str] = &[
+    "&str",
     "f32",
     "f64",
     "std::num::Saturating",
     "std::num::Wrapping",
     "std::string::String",
-    "&str",
 ];
 
 #[derive(Debug)]
@@ -50,10 +45,10 @@ impl ArithmeticSideEffects {
             let ast::LitKind::Int(value, _) = lit.node
         {
             match (&op.node, value) {
-                (hir::BinOpKind::Add | hir::BinOpKind::Sub, 0) |
-                (hir::BinOpKind::Mul, 0 | 1) => true,
                 (hir::BinOpKind::Div | hir::BinOpKind::Rem, 0) => false,
-                (hir::BinOpKind::Div | hir::BinOpKind::Rem, _) => true,
+                (hir::BinOpKind::Add | hir::BinOpKind::Sub, 0)
+                    | (hir::BinOpKind::Div | hir::BinOpKind::Rem, _)
+                    | (hir::BinOpKind::Mul, 0 | 1) => true,
                 _ => false,
             }
         } else {
@@ -79,16 +74,13 @@ impl ArithmeticSideEffects {
         self.expr_span = Some(expr.span);
     }
 
-    /// * If `expr` is a literal integer like `1` or `i32::MAX`, returns itself.
-    /// * Is `expr` is a literal integer reference like `&199`, returns the literal integer without
-    ///   references.
-    /// * If `expr` is anything else, returns `None`.
-    fn literal_integer<'expr, 'tcx>(expr: &'expr hir::Expr<'tcx>) -> Option<&'expr hir::Expr<'tcx>> {
+    /// If `expr` does not match any variant of `LiteralIntegerTy`, returns `None`.
+    fn literal_integer<'expr, 'tcx>(expr: &'expr hir::Expr<'tcx>) -> Option<LiteralIntegerTy<'expr, 'tcx>> {
         if matches!(expr.kind, hir::ExprKind::Lit(_)) {
-            return Some(expr);
+            return Some(LiteralIntegerTy::Value(expr));
         }
         if let hir::ExprKind::AddrOf(.., inn) = expr.kind && let hir::ExprKind::Lit(_) = inn.kind {
-            return Some(inn)
+            return Some(LiteralIntegerTy::Ref(inn));
         }
         None
     }
@@ -126,10 +118,9 @@ impl ArithmeticSideEffects {
         }
         let has_valid_op = if Self::is_integral(lhs_ty) && Self::is_integral(rhs_ty) {
             match (Self::literal_integer(lhs), Self::literal_integer(rhs)) {
-                (None, None) => false,
-                (None, Some(local_expr)) => Self::has_valid_op(op, local_expr),
-                (Some(local_expr), None) => Self::has_valid_op(op, local_expr),
-                (Some(_), Some(_)) => true,
+                (None, Some(lit_int_ty)) | (Some(lit_int_ty), None) => Self::has_valid_op(op, lit_int_ty.into()),
+                (Some(LiteralIntegerTy::Value(_)), Some(LiteralIntegerTy::Value(_))) => true,
+                (None, None) | (Some(_), Some(_)) => false,
             }
         } else {
             false
@@ -186,3 +177,22 @@ impl<'tcx> LateLintPass<'tcx> for ArithmeticSideEffects {
         }
     }
 }
+
+/// Tells if an expression is a integer declared by value or by reference.
+///
+/// If `LiteralIntegerTy::Ref`, then the contained value will be `hir::ExprKind::Lit` rather
+/// than `hirExprKind::Addr`.
+enum LiteralIntegerTy<'expr, 'tcx> {
+    /// For example, `&199`
+    Ref(&'expr hir::Expr<'tcx>),
+    /// For example, `1` or `i32::MAX`
+    Value(&'expr hir::Expr<'tcx>),
+}
+
+impl<'expr, 'tcx> From<LiteralIntegerTy<'expr, 'tcx>> for &'expr hir::Expr<'tcx> {
+    fn from(from: LiteralIntegerTy<'expr, 'tcx>) -> Self {
+        match from {
+            LiteralIntegerTy::Ref(elem) | LiteralIntegerTy::Value(elem) => elem,
+        }
+    }
+}
diff --git a/tests/ui/arithmetic_side_effects.rs b/tests/ui/arithmetic_side_effects.rs
index c9c0f8be653..b25e68f1306 100644
--- a/tests/ui/arithmetic_side_effects.rs
+++ b/tests/ui/arithmetic_side_effects.rs
@@ -148,7 +148,6 @@ pub fn non_overflowing_ops_or_ops_already_handled_by_the_compiler_should_not_tri
     _n = 1 * _n;
     _n = &1 * _n;
     _n = 23 + 85;
-    _n = &23 + &85;
 
     // Unary
     _n = -1;
@@ -187,6 +186,9 @@ pub fn runtime_ops() {
     _n = _n * &2;
     _n = 2 * _n;
     _n = &2 * _n;
+    _n = 23 + &85;
+    _n = &23 + 85;
+    _n = &23 + &85;
 
     // Custom
     let _ = Custom + 0;
diff --git a/tests/ui/arithmetic_side_effects.stderr b/tests/ui/arithmetic_side_effects.stderr
index 8cabd05c2f9..0f06e22bae9 100644
--- a/tests/ui/arithmetic_side_effects.stderr
+++ b/tests/ui/arithmetic_side_effects.stderr
@@ -19,316 +19,334 @@ LL |     let _ = inferred_string + "";
    |             ^^^^^^^^^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:162:5
+  --> $DIR/arithmetic_side_effects.rs:161:5
    |
 LL |     _n += 1;
    |     ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:163:5
+  --> $DIR/arithmetic_side_effects.rs:162:5
    |
 LL |     _n += &1;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:164:5
+  --> $DIR/arithmetic_side_effects.rs:163:5
    |
 LL |     _n -= 1;
    |     ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:165:5
+  --> $DIR/arithmetic_side_effects.rs:164:5
    |
 LL |     _n -= &1;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:166:5
+  --> $DIR/arithmetic_side_effects.rs:165:5
    |
 LL |     _n /= 0;
    |     ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:167:5
+  --> $DIR/arithmetic_side_effects.rs:166:5
    |
 LL |     _n /= &0;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:168:5
+  --> $DIR/arithmetic_side_effects.rs:167:5
    |
 LL |     _n %= 0;
    |     ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:169:5
+  --> $DIR/arithmetic_side_effects.rs:168:5
    |
 LL |     _n %= &0;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:170:5
+  --> $DIR/arithmetic_side_effects.rs:169:5
    |
 LL |     _n *= 2;
    |     ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:171:5
+  --> $DIR/arithmetic_side_effects.rs:170:5
    |
 LL |     _n *= &2;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:174:10
+  --> $DIR/arithmetic_side_effects.rs:173:10
    |
 LL |     _n = _n + 1;
    |          ^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:175:10
+  --> $DIR/arithmetic_side_effects.rs:174:10
    |
 LL |     _n = _n + &1;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:176:10
+  --> $DIR/arithmetic_side_effects.rs:175:10
    |
 LL |     _n = 1 + _n;
    |          ^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:177:10
+  --> $DIR/arithmetic_side_effects.rs:176:10
    |
 LL |     _n = &1 + _n;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:178:10
+  --> $DIR/arithmetic_side_effects.rs:177:10
    |
 LL |     _n = _n - 1;
    |          ^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:179:10
+  --> $DIR/arithmetic_side_effects.rs:178:10
    |
 LL |     _n = _n - &1;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:180:10
+  --> $DIR/arithmetic_side_effects.rs:179:10
    |
 LL |     _n = 1 - _n;
    |          ^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:181:10
+  --> $DIR/arithmetic_side_effects.rs:180:10
    |
 LL |     _n = &1 - _n;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:182:10
+  --> $DIR/arithmetic_side_effects.rs:181:10
    |
 LL |     _n = _n / 0;
    |          ^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:183:10
+  --> $DIR/arithmetic_side_effects.rs:182:10
    |
 LL |     _n = _n / &0;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:184:10
+  --> $DIR/arithmetic_side_effects.rs:183:10
    |
 LL |     _n = _n % 0;
    |          ^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:185:10
+  --> $DIR/arithmetic_side_effects.rs:184:10
    |
 LL |     _n = _n % &0;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:186:10
+  --> $DIR/arithmetic_side_effects.rs:185:10
    |
 LL |     _n = _n * 2;
    |          ^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:187:10
+  --> $DIR/arithmetic_side_effects.rs:186:10
    |
 LL |     _n = _n * &2;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:188:10
+  --> $DIR/arithmetic_side_effects.rs:187:10
    |
 LL |     _n = 2 * _n;
    |          ^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:189:10
+  --> $DIR/arithmetic_side_effects.rs:188:10
    |
 LL |     _n = &2 * _n;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:192:13
+  --> $DIR/arithmetic_side_effects.rs:189:10
+   |
+LL |     _n = 23 + &85;
+   |          ^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:190:10
+   |
+LL |     _n = &23 + 85;
+   |          ^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:191:10
+   |
+LL |     _n = &23 + &85;
+   |          ^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:194:13
    |
 LL |     let _ = Custom + 0;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:193:13
+  --> $DIR/arithmetic_side_effects.rs:195:13
    |
 LL |     let _ = Custom + 1;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:194:13
+  --> $DIR/arithmetic_side_effects.rs:196:13
    |
 LL |     let _ = Custom + 2;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:195:13
+  --> $DIR/arithmetic_side_effects.rs:197:13
    |
 LL |     let _ = Custom + 0.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:196:13
+  --> $DIR/arithmetic_side_effects.rs:198:13
    |
 LL |     let _ = Custom + 1.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:197:13
+  --> $DIR/arithmetic_side_effects.rs:199:13
    |
 LL |     let _ = Custom + 2.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:198:13
+  --> $DIR/arithmetic_side_effects.rs:200:13
    |
 LL |     let _ = Custom - 0;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:199:13
+  --> $DIR/arithmetic_side_effects.rs:201:13
    |
 LL |     let _ = Custom - 1;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:200:13
+  --> $DIR/arithmetic_side_effects.rs:202:13
    |
 LL |     let _ = Custom - 2;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:201:13
+  --> $DIR/arithmetic_side_effects.rs:203:13
    |
 LL |     let _ = Custom - 0.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:202:13
+  --> $DIR/arithmetic_side_effects.rs:204:13
    |
 LL |     let _ = Custom - 1.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:203:13
+  --> $DIR/arithmetic_side_effects.rs:205:13
    |
 LL |     let _ = Custom - 2.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:204:13
+  --> $DIR/arithmetic_side_effects.rs:206:13
    |
 LL |     let _ = Custom / 0;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:205:13
+  --> $DIR/arithmetic_side_effects.rs:207:13
    |
 LL |     let _ = Custom / 1;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:206:13
+  --> $DIR/arithmetic_side_effects.rs:208:13
    |
 LL |     let _ = Custom / 2;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:207:13
+  --> $DIR/arithmetic_side_effects.rs:209:13
    |
 LL |     let _ = Custom / 0.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:208:13
+  --> $DIR/arithmetic_side_effects.rs:210:13
    |
 LL |     let _ = Custom / 1.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:209:13
+  --> $DIR/arithmetic_side_effects.rs:211:13
    |
 LL |     let _ = Custom / 2.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:210:13
+  --> $DIR/arithmetic_side_effects.rs:212:13
    |
 LL |     let _ = Custom * 0;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:211:13
+  --> $DIR/arithmetic_side_effects.rs:213:13
    |
 LL |     let _ = Custom * 1;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:212:13
+  --> $DIR/arithmetic_side_effects.rs:214:13
    |
 LL |     let _ = Custom * 2;
    |             ^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:213:13
+  --> $DIR/arithmetic_side_effects.rs:215:13
    |
 LL |     let _ = Custom * 0.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:214:13
+  --> $DIR/arithmetic_side_effects.rs:216:13
    |
 LL |     let _ = Custom * 1.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:215:13
+  --> $DIR/arithmetic_side_effects.rs:217:13
    |
 LL |     let _ = Custom * 2.0;
    |             ^^^^^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:218:10
+  --> $DIR/arithmetic_side_effects.rs:220:10
    |
 LL |     _n = -_n;
    |          ^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:219:10
+  --> $DIR/arithmetic_side_effects.rs:221:10
    |
 LL |     _n = -&_n;
    |          ^^^^
 
-error: aborting due to 55 previous errors
+error: aborting due to 58 previous errors