Auto merge of #9559 - c410-f3r:arith, r=Alexendoo

Fix #9544

Fix #9544

r? `@Alexendoo`

changelog: [`arithmetic_side_effects`]: Fix false negative for `CustomType / usize`, `CustomType * float` and similar

3 files changed, 270 insertions, 60 deletions

diff --git a/clippy_lints/src/operators/arithmetic_side_effects.rs b/clippy_lints/src/operators/arithmetic_side_effects.rs
index 1f22fbd5387..9ba9cc1c517 100644
--- a/clippy_lints/src/operators/arithmetic_side_effects.rs
+++ b/clippy_lints/src/operators/arithmetic_side_effects.rs
@@ -9,6 +9,7 @@ use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
 use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::ty::Ty;
 use rustc_session::impl_lint_pass;
 use rustc_span::source_map::{Span, Spanned};
 
@@ -16,8 +17,9 @@ const HARD_CODED_ALLOWED: &[&str] = &[
     "f32",
     "f64",
     "std::num::Saturating",
-    "std::string::String",
     "std::num::Wrapping",
+    "std::string::String",
+    "&str",
 ];
 
 #[derive(Debug)]
@@ -60,15 +62,14 @@ impl ArithmeticSideEffects {
     }
 
     /// Checks if the given `expr` has any of the inner `allowed` elements.
-    fn is_allowed_ty(&self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
-        self.allowed.contains(
-            cx.typeck_results()
-                .expr_ty(expr)
-                .to_string()
-                .split('<')
-                .next()
-                .unwrap_or_default(),
-        )
+    fn is_allowed_ty(&self, ty: Ty<'_>) -> bool {
+        self.allowed
+            .contains(ty.to_string().split('<').next().unwrap_or_default())
+    }
+
+    // For example, 8i32 or &i64::MAX.
+    fn is_integral(ty: Ty<'_>) -> bool {
+        ty.peel_refs().is_integral()
     }
 
     // Common entry-point to avoid code duplication.
@@ -82,24 +83,13 @@ impl ArithmeticSideEffects {
     /// * 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>(
-        cx: &LateContext<'tcx>,
-        expr: &'expr hir::Expr<'tcx>,
-    ) -> Option<&'expr hir::Expr<'tcx>> {
-        let expr_refs = cx.typeck_results().expr_ty(expr).peel_refs();
-
-        if !expr_refs.is_integral() {
-            return None;
-        }
-
+    fn literal_integer<'expr, 'tcx>(expr: &'expr hir::Expr<'tcx>) -> Option<&'expr hir::Expr<'tcx>> {
         if matches!(expr.kind, hir::ExprKind::Lit(_)) {
             return Some(expr);
         }
-
         if let hir::ExprKind::AddrOf(.., inn) = expr.kind && let hir::ExprKind::Lit(_) = inn.kind {
             return Some(inn)
         }
-
         None
     }
 
@@ -128,14 +118,21 @@ impl ArithmeticSideEffects {
         ) {
             return;
         };
-        if self.is_allowed_ty(cx, lhs) || self.is_allowed_ty(cx, rhs) {
+        let lhs_ty = cx.typeck_results().expr_ty(lhs);
+        let rhs_ty = cx.typeck_results().expr_ty(rhs);
+        let lhs_and_rhs_have_the_same_ty = lhs_ty == rhs_ty;
+        if lhs_and_rhs_have_the_same_ty && self.is_allowed_ty(lhs_ty) && self.is_allowed_ty(rhs_ty) {
             return;
         }
-        let has_valid_op = match (Self::literal_integer(cx, lhs), Self::literal_integer(cx, 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,
+        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,
+            }
+        } else {
+            false
         };
         if !has_valid_op {
             self.issue_lint(cx, expr);
diff --git a/tests/ui/arithmetic_side_effects.rs b/tests/ui/arithmetic_side_effects.rs
index 6741e148547..c9c0f8be653 100644
--- a/tests/ui/arithmetic_side_effects.rs
+++ b/tests/ui/arithmetic_side_effects.rs
@@ -12,6 +12,31 @@
 
 use core::num::{Saturating, Wrapping};
 
+pub struct Custom;
+
+macro_rules! impl_arith {
+    ( $( $_trait:ident, $ty:ty, $method:ident; )* ) => {
+        $(
+            impl core::ops::$_trait<$ty> for Custom {
+                type Output = Self;
+                fn $method(self, _: $ty) -> Self::Output { Self }
+            }
+        )*
+    }
+}
+
+impl_arith!(
+    Add, i32, add;
+    Div, i32, div;
+    Mul, i32, mul;
+    Sub, i32, sub;
+
+    Add, f64, add;
+    Div, f64, div;
+    Mul, f64, mul;
+    Sub, f64, sub;
+);
+
 pub fn association_with_structures_should_not_trigger_the_lint() {
     enum Foo {
         Bar = -2,
@@ -130,7 +155,7 @@ pub fn non_overflowing_ops_or_ops_already_handled_by_the_compiler_should_not_tri
     _n = -(-1);
 }
 
-pub fn overflowing_runtime_ops() {
+pub fn runtime_ops() {
     let mut _n = i32::MAX;
 
     // Assign
@@ -163,6 +188,32 @@ pub fn overflowing_runtime_ops() {
     _n = 2 * _n;
     _n = &2 * _n;
 
+    // Custom
+    let _ = Custom + 0;
+    let _ = Custom + 1;
+    let _ = Custom + 2;
+    let _ = Custom + 0.0;
+    let _ = Custom + 1.0;
+    let _ = Custom + 2.0;
+    let _ = Custom - 0;
+    let _ = Custom - 1;
+    let _ = Custom - 2;
+    let _ = Custom - 0.0;
+    let _ = Custom - 1.0;
+    let _ = Custom - 2.0;
+    let _ = Custom / 0;
+    let _ = Custom / 1;
+    let _ = Custom / 2;
+    let _ = Custom / 0.0;
+    let _ = Custom / 1.0;
+    let _ = Custom / 2.0;
+    let _ = Custom * 0;
+    let _ = Custom * 1;
+    let _ = Custom * 2;
+    let _ = Custom * 0.0;
+    let _ = Custom * 1.0;
+    let _ = Custom * 2.0;
+
     // Unary
     _n = -_n;
     _n = -&_n;
diff --git a/tests/ui/arithmetic_side_effects.stderr b/tests/ui/arithmetic_side_effects.stderr
index 4dce13b624b..8cabd05c2f9 100644
--- a/tests/ui/arithmetic_side_effects.stderr
+++ b/tests/ui/arithmetic_side_effects.stderr
@@ -1,172 +1,334 @@
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:137:5
+  --> $DIR/arithmetic_side_effects.rs:78:13
    |
-LL |     _n += 1;
-   |     ^^^^^^^
+LL |     let _ = String::new() + "";
+   |             ^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::arithmetic-side-effects` implied by `-D warnings`
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:138:5
+  --> $DIR/arithmetic_side_effects.rs:86:27
+   |
+LL |     let inferred_string = string + "";
+   |                           ^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:90:13
+   |
+LL |     let _ = inferred_string + "";
+   |             ^^^^^^^^^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $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:163:5
    |
 LL |     _n += &1;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:139:5
+  --> $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:140:5
+  --> $DIR/arithmetic_side_effects.rs:165:5
    |
 LL |     _n -= &1;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:141:5
+  --> $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:142:5
+  --> $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:143:5
+  --> $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:144:5
+  --> $DIR/arithmetic_side_effects.rs:169:5
    |
 LL |     _n %= &0;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:145:5
+  --> $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:146:5
+  --> $DIR/arithmetic_side_effects.rs:171:5
    |
 LL |     _n *= &2;
    |     ^^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:149:10
+  --> $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:150:10
+  --> $DIR/arithmetic_side_effects.rs:175:10
    |
 LL |     _n = _n + &1;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:151:10
+  --> $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:152:10
+  --> $DIR/arithmetic_side_effects.rs:177:10
    |
 LL |     _n = &1 + _n;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:153:10
+  --> $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:154:10
+  --> $DIR/arithmetic_side_effects.rs:179:10
    |
 LL |     _n = _n - &1;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:155:10
+  --> $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:156:10
+  --> $DIR/arithmetic_side_effects.rs:181:10
    |
 LL |     _n = &1 - _n;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:157:10
+  --> $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:158:10
+  --> $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:159:10
+  --> $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:160:10
+  --> $DIR/arithmetic_side_effects.rs:185:10
    |
 LL |     _n = _n % &0;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:161:10
+  --> $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:162:10
+  --> $DIR/arithmetic_side_effects.rs:187:10
    |
 LL |     _n = _n * &2;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:163:10
+  --> $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:164:10
+  --> $DIR/arithmetic_side_effects.rs:189:10
    |
 LL |     _n = &2 * _n;
    |          ^^^^^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:167:10
+  --> $DIR/arithmetic_side_effects.rs:192:13
+   |
+LL |     let _ = Custom + 0;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:193:13
+   |
+LL |     let _ = Custom + 1;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:194:13
+   |
+LL |     let _ = Custom + 2;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:195:13
+   |
+LL |     let _ = Custom + 0.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:196:13
+   |
+LL |     let _ = Custom + 1.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:197:13
+   |
+LL |     let _ = Custom + 2.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:198:13
+   |
+LL |     let _ = Custom - 0;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:199:13
+   |
+LL |     let _ = Custom - 1;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:200:13
+   |
+LL |     let _ = Custom - 2;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:201:13
+   |
+LL |     let _ = Custom - 0.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:202:13
+   |
+LL |     let _ = Custom - 1.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:203:13
+   |
+LL |     let _ = Custom - 2.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:204:13
+   |
+LL |     let _ = Custom / 0;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:205:13
+   |
+LL |     let _ = Custom / 1;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:206:13
+   |
+LL |     let _ = Custom / 2;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:207:13
+   |
+LL |     let _ = Custom / 0.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:208:13
+   |
+LL |     let _ = Custom / 1.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:209:13
+   |
+LL |     let _ = Custom / 2.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:210:13
+   |
+LL |     let _ = Custom * 0;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:211:13
+   |
+LL |     let _ = Custom * 1;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:212:13
+   |
+LL |     let _ = Custom * 2;
+   |             ^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:213:13
+   |
+LL |     let _ = Custom * 0.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:214:13
+   |
+LL |     let _ = Custom * 1.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:215:13
+   |
+LL |     let _ = Custom * 2.0;
+   |             ^^^^^^^^^^^^
+
+error: arithmetic operation that can potentially result in unexpected side-effects
+  --> $DIR/arithmetic_side_effects.rs:218:10
    |
 LL |     _n = -_n;
    |          ^^^
 
 error: arithmetic operation that can potentially result in unexpected side-effects
-  --> $DIR/arithmetic_side_effects.rs:168:10
+  --> $DIR/arithmetic_side_effects.rs:219:10
    |
 LL |     _n = -&_n;
    |          ^^^^
 
-error: aborting due to 28 previous errors
+error: aborting due to 55 previous errors