change the applicability of obfuscated_if_else depending on whether…

… the original code can have side effects

clippy_lints/src/methods/obfuscated_if_else.rs

@@ -1,5 +1,6 @@
 use super::OBFUSCATED_IF_ELSE;
 use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::eager_or_lazy::switch_to_eager_eval;
 use clippy_utils::source::snippet_with_applicability;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
@@ -19,7 +20,12 @@ pub(super) fn check<'tcx>(
     let recv_ty = cx.typeck_results().expr_ty(then_recv);
 
     if recv_ty.is_bool() {
-        let mut applicability = Applicability::MachineApplicable;
+        let mut applicability = if switch_to_eager_eval(cx, then_arg) && switch_to_eager_eval(cx, unwrap_arg) {
+            Applicability::MachineApplicable
+        } else {
+            Applicability::MaybeIncorrect
+        };
+
         let sugg = format!(
             "if {} {{ {} }} else {{ {} }}",
             snippet_with_applicability(cx, then_recv.span, "..", &mut applicability),

tests/ui/obfuscated_if_else.fixed

@@ -1,5 +1,10 @@
 #![warn(clippy::obfuscated_if_else)]
+#![allow(clippy::unit_arg, clippy::unused_unit)]
 
 fn main() {
     if true { "a" } else { "b" };
+
+    let mut a = 0;
+    if true { a += 1 } else { () };
+    if true { () } else { a += 2 };
 }

tests/ui/obfuscated_if_else.rs

@@ -1,5 +1,10 @@
 #![warn(clippy::obfuscated_if_else)]
+#![allow(clippy::unit_arg, clippy::unused_unit)]
 
 fn main() {
     true.then_some("a").unwrap_or("b");
+
+    let mut a = 0;
+    true.then_some(a += 1).unwrap_or(());
+    true.then_some(()).unwrap_or(a += 2);
 }

tests/ui/obfuscated_if_else.stderr

@@ -1,11 +1,23 @@
 error: use of `.then_some(..).unwrap_or(..)` can be written more clearly with `if .. else ..`
-  --> tests/ui/obfuscated_if_else.rs:4:5
+  --> tests/ui/obfuscated_if_else.rs:5:5
    |
 LL |     true.then_some("a").unwrap_or("b");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `if true { "a" } else { "b" }`
    |
    = note: `-D clippy::obfuscated-if-else` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::obfuscated_if_else)]`
 
-error: aborting due to 1 previous error
+error: use of `.then_some(..).unwrap_or(..)` can be written more clearly with `if .. else ..`
+  --> tests/ui/obfuscated_if_else.rs:8:5
+   |
+LL |     true.then_some(a += 1).unwrap_or(());
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `if true { a += 1 } else { () }`
+
+error: use of `.then_some(..).unwrap_or(..)` can be written more clearly with `if .. else ..`
+  --> tests/ui/obfuscated_if_else.rs:9:5
+   |
+LL |     true.then_some(()).unwrap_or(a += 2);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `if true { () } else { a += 2 }`
+
+error: aborting due to 3 previous errors