Fixed edge case of iXX compared with 0

Author: pmk21

clippy_lints/src/implicit_saturating_sub.rs

@@ -88,7 +88,11 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ImplicitSaturatingSub {
                     ExprKind::Lit(ref cond_lit) => {
                         // Check if the constant is zero
                         if let LitKind::Int(0, _) = cond_lit.node {
-                            print_lint_and_sugg(cx, &var_name, expr);
+                            if cx.tables.expr_ty(cond_left).is_signed() {
+                                return;
+                            } else {
+                                print_lint_and_sugg(cx, &var_name, expr);
+                            }
                         } else {
                             return;
                         }

tests/ui/implicit_saturating_sub.rs

@@ -146,4 +146,9 @@ fn main() {
     if i_64 > i64::min_value() {
         i_64 -= 1;
     }
+
+    // No Lint
+    if i_64 > 0 {
+        i_64 -= 1;
+    }
 }