arithmetic_side_effects: check adjusted expression types (rust-lang#14062)

Fix rust-lang#14054

changelog: [`arithmetic_side_effects`]: warn about more cases when
`Deref` is involved

Author: Manishearth

clippy_lints/src/operators/arithmetic_side_effects.rs

@@ -220,7 +220,7 @@ impl ArithmeticSideEffects {
         actual_lhs = expr_or_init(cx, actual_lhs);
         actual_rhs = expr_or_init(cx, actual_rhs);
         let lhs_ty = cx.typeck_results().expr_ty(actual_lhs).peel_refs();
-        let rhs_ty = cx.typeck_results().expr_ty(actual_rhs).peel_refs();
+        let rhs_ty = cx.typeck_results().expr_ty_adjusted(actual_rhs).peel_refs();
         if self.has_allowed_binary(lhs_ty, rhs_ty) {
             return;
         }
@@ -283,7 +283,7 @@ impl ArithmeticSideEffects {
         if ConstEvalCtxt::new(cx).eval_simple(receiver).is_some() {
             return;
         }
-        let instance_ty = cx.typeck_results().expr_ty(receiver);
+        let instance_ty = cx.typeck_results().expr_ty_adjusted(receiver);
         if !Self::is_integral(instance_ty) {
             return;
         }
@@ -311,7 +311,7 @@ impl ArithmeticSideEffects {
         if ConstEvalCtxt::new(cx).eval(un_expr).is_some() {
             return;
         }
-        let ty = cx.typeck_results().expr_ty(expr).peel_refs();
+        let ty = cx.typeck_results().expr_ty_adjusted(expr).peel_refs();
         if self.has_allowed_unary(ty) {
             return;
         }

tests/ui/arithmetic_side_effects.rs

@@ -170,6 +170,7 @@ pub fn hard_coded_allowed() {
 
     let _ = Saturating(0u32) + Saturating(0u32);
     let _ = String::new() + "";
+    let _ = String::new() + &String::new();
     let _ = Wrapping(0u32) + Wrapping(0u32);
 
     let saturating: Saturating<u32> = Saturating(0u32);
@@ -408,11 +409,14 @@ pub fn unknown_ops_or_runtime_ops_that_can_overflow() {
     _n.wrapping_rem(_n);
     _n.wrapping_rem_euclid(_n);
 
+    _n.saturating_div(*Box::new(_n));
+
     // Unary
     _n = -_n;
     _n = -&_n;
     _custom = -_custom;
     _custom = -&_custom;
+    _ = -*Box::new(_n);
 }
 
 // Copied and pasted from the `integer_arithmetic` lint for comparison.
@@ -534,4 +538,11 @@ pub fn issue_12318() {
     one.sub_assign(1);
 }
 
+pub fn explicit_methods() {
+    use core::ops::Add;
+    let one: i32 = 1;
+    one.add(&one);
+    Box::new(one).add(one);
+}
+
 fn main() {}