integer_arithmetic: detect integer arithmetic on references.

changelog: integer_arithmetic fix false negatives with references on integers

Fixes #5328

Author: matthiaskrgr

clippy_lints/src/arithmetic.rs

@@ -82,7 +82,8 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
                     _ => (),
                 }
                 let (l_ty, r_ty) = (cx.tables.expr_ty(l), cx.tables.expr_ty(r));
-                if l_ty.is_integral() && r_ty.is_integral() {
+                // warn on integers as well as references to integers
+                if l_ty.is_integral() || l_ty.is_any_ptr() && r_ty.is_integral() || r_ty.is_any_ptr() {
                     span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
                     self.expr_span = Some(expr.span);
                 } else if l_ty.is_floating_point() && r_ty.is_floating_point() {

tests/ui/arithmetic.rs

@@ -4,7 +4,9 @@
     clippy::shadow_reuse,
     clippy::shadow_unrelated,
     clippy::no_effect,
-    clippy::unnecessary_operation
+    clippy::unnecessary_operation,
+    clippy::op_ref,
+    clippy::trivially_copy_pass_by_ref
 )]
 
 #[rustfmt::skip]
@@ -90,4 +92,26 @@ fn main() {
             1 + 1
         };
     }
+
+    // warn on references as well! (#5328)
+    3 + &1;
+    &3 + 1;
+    &3 + &1;
+}
+
+pub fn foo(x: &i32) -> i32 {
+    let a = 5;
+    a + x
+}
+
+pub fn bar(x: &i32, y: &i32) -> i32 {
+    x + y
+}
+
+pub fn baz(x: i32, y: &i32) -> i32 {
+    x + y
+}
+
+pub fn qux(x: i32, y: i32) -> i32 {
+    (&x + &y)
 }

tests/ui/arithmetic.stderr

@@ -1,127 +1,169 @@
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:13:5
+  --> $DIR/arithmetic.rs:15:5
    |
 LL |     1 + i;
    |     ^^^^^
    |
    = note: `-D clippy::integer-arithmetic` implied by `-D warnings`
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:14:5
+  --> $DIR/arithmetic.rs:16:5
    |
 LL |     i * 2;
    |     ^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:15:5
+  --> $DIR/arithmetic.rs:17:5
    |
 LL | /     1 %
 LL | |     i / 2; // no error, this is part of the expression in the preceding line
    | |_________^
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:17:5
+  --> $DIR/arithmetic.rs:19:5
    |
 LL |     i - 2 + 2 - i;
    |     ^^^^^^^^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:18:5
+  --> $DIR/arithmetic.rs:20:5
    |
 LL |     -i;
    |     ^^
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:30:5
+  --> $DIR/arithmetic.rs:32:5
    |
 LL |     i += 1;
    |     ^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:31:5
+  --> $DIR/arithmetic.rs:33:5
    |
 LL |     i -= 1;
    |     ^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:32:5
+  --> $DIR/arithmetic.rs:34:5
    |
 LL |     i *= 2;
    |     ^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:33:5
+  --> $DIR/arithmetic.rs:35:5
    |
 LL |     i /= 2;
    |     ^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/arithmetic.rs:34:5
+  --> $DIR/arithmetic.rs:36:5
    |
 LL |     i %= 2;
    |     ^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:45:5
+  --> $DIR/arithmetic.rs:47:5
    |
 LL |     f * 2.0;
    |     ^^^^^^^
    |
    = note: `-D clippy::float-arithmetic` implied by `-D warnings`
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:47:5
+  --> $DIR/arithmetic.rs:49:5
    |
 LL |     1.0 + f;
    |     ^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:48:5
+  --> $DIR/arithmetic.rs:50:5
    |
 LL |     f * 2.0;
    |     ^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:49:5
+  --> $DIR/arithmetic.rs:51:5
    |
 LL |     f / 2.0;
    |     ^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:50:5
+  --> $DIR/arithmetic.rs:52:5
    |
 LL |     f - 2.0 * 4.2;
    |     ^^^^^^^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:51:5
+  --> $DIR/arithmetic.rs:53:5
    |
 LL |     -f;
    |     ^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:53:5
+  --> $DIR/arithmetic.rs:55:5
    |
 LL |     f += 1.0;
    |     ^^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:54:5
+  --> $DIR/arithmetic.rs:56:5
    |
 LL |     f -= 1.0;
    |     ^^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:55:5
+  --> $DIR/arithmetic.rs:57:5
    |
 LL |     f *= 2.0;
    |     ^^^^^^^^
 
 error: floating-point arithmetic detected
-  --> $DIR/arithmetic.rs:56:5
+  --> $DIR/arithmetic.rs:58:5
    |
 LL |     f /= 2.0;
    |     ^^^^^^^^
 
-error: aborting due to 20 previous errors
+error: integer arithmetic detected
+  --> $DIR/arithmetic.rs:97:5
+   |
+LL |     3 + &1;
+   |     ^^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/arithmetic.rs:98:5
+   |
+LL |     &3 + 1;
+   |     ^^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/arithmetic.rs:99:5
+   |
+LL |     &3 + &1;
+   |     ^^^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/arithmetic.rs:104:5
+   |
+LL |     a + x
+   |     ^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/arithmetic.rs:108:5
+   |
+LL |     x + y
+   |     ^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/arithmetic.rs:112:5
+   |
+LL |     x + y
+   |     ^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/arithmetic.rs:116:5
+   |
+LL |     (&x + &y)
+   |     ^^^^^^^^^
+
+error: aborting due to 27 previous errors