Limit the identity_op lint to integral operands.

If operands are being applied to non-integers, then the lint is likely
wrong.

Author: alex-ozdemir

clippy_lints/src/identity_op.rs

@@ -61,10 +61,13 @@ impl<'tcx> LateLintPass<'tcx> for IdentityOp {
 }
 
 fn is_allowed(cx: &LateContext<'_>, cmp: BinOp, left: &Expr<'_>, right: &Expr<'_>) -> bool {
-    // `1 << 0` is a common pattern in bit manipulation code
-    cmp.node == BinOpKind::Shl
-        && constant_simple(cx, cx.typeck_results(), right) == Some(Constant::Int(0))
-        && constant_simple(cx, cx.typeck_results(), left) == Some(Constant::Int(1))
+    // This lint applies to integers
+    !cx.typeck_results().expr_ty(left).is_integral()
+        || !cx.typeck_results().expr_ty(right).is_integral()
+        // `1 << 0` is a common pattern in bit manipulation code
+        || (cmp.node == BinOpKind::Shl
+            && constant_simple(cx, cx.typeck_results(), right) == Some(Constant::Int(0))
+            && constant_simple(cx, cx.typeck_results(), left) == Some(Constant::Int(1)))
 }
 
 fn check(cx: &LateContext<'_>, e: &Expr<'_>, m: i8, span: Span, arg: Span) {