fix: option_if_let_else suggests wrongly when coersion requires explicit cast

Author: profetia

clippy_lints/src/option_if_let_else.rs

@@ -92,6 +92,7 @@ declare_lint_pass!(OptionIfLetElse => [OPTION_IF_LET_ELSE]);
 struct OptionOccurrence {
     option: String,
     method_sugg: String,
+    method_generics: Option<String>,
     some_expr: String,
     none_expr: String,
 }
@@ -184,6 +185,11 @@ fn try_get_option_occurrence<'tcx>(
             }
         }
 
+        let none_ty_adj = cx.typeck_results().expr_ty_adjusted(none_body);
+        let method_generics = (method_sugg == "map_or_else"
+            && !cx.typeck_results().expr_adjustments(none_body).is_empty())
+        .then(|| format!("::<{none_ty_adj}, _, _>"));
+
         let mut app = Applicability::Unspecified;
 
         let (none_body, is_argless_call) = match none_body.kind {
@@ -198,6 +204,7 @@ fn try_get_option_occurrence<'tcx>(
                 as_mut,
             ),
             method_sugg: method_sugg.to_string(),
+            method_generics,
             some_expr: format!(
                 "|{capture_mut}{capture_name}| {}",
                 Sugg::hir_with_context(cx, some_body, ctxt, "..", &mut app),
@@ -313,8 +320,12 @@ impl<'tcx> LateLintPass<'tcx> for OptionIfLetElse {
                 format!("use Option::{} instead of an if let/else", det.method_sugg),
                 "try",
                 format!(
-                    "{}.{}({}, {})",
-                    det.option, det.method_sugg, det.none_expr, det.some_expr
+                    "{}.{}{}({}, {})",
+                    det.option,
+                    det.method_sugg,
+                    det.method_generics.unwrap_or_default(),
+                    det.none_expr,
+                    det.some_expr
                 ),
                 Applicability::MaybeIncorrect,
             );

tests/ui/option_if_let_else.fixed

@@ -268,3 +268,19 @@ fn issue11893() {
         panic!("Haven't thought about this condition.");
     }
 }
+
+mod issue11059 {
+    use std::fmt::Debug;
+
+    fn box_coercion_unsize(o: Option<i32>) -> Box<dyn Debug> {
+        o.map_or_else::<std::boxed::Box<dyn std::fmt::Debug>, _, _>(|| Box::new("foo"), |o| Box::new(o))
+        //~^ option_if_let_else
+    }
+
+    static S: String = String::new();
+
+    fn deref_with_overload(o: Option<&str>) -> &str {
+        o.map_or_else::<&str, _, _>(|| &S, |o| o)
+        //~^ option_if_let_else
+    }
+}

tests/ui/option_if_let_else.rs

@@ -331,3 +331,19 @@ fn issue11893() {
         panic!("Haven't thought about this condition.");
     }
 }
+
+mod issue11059 {
+    use std::fmt::Debug;
+
+    fn box_coercion_unsize(o: Option<i32>) -> Box<dyn Debug> {
+        if let Some(o) = o { Box::new(o) } else { Box::new("foo") }
+        //~^ option_if_let_else
+    }
+
+    static S: String = String::new();
+
+    fn deref_with_overload(o: Option<&str>) -> &str {
+        if let Some(o) = o { o } else { &S }
+        //~^ option_if_let_else
+    }
+}

tests/ui/option_if_let_else.stderr

@@ -334,5 +334,17 @@ error: use Option::map_or_else instead of an if let/else
 LL |     let mut _hm = if let Some(hm) = &opt { hm.clone() } else { new_map!() };
    |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `opt.as_ref().map_or_else(|| new_map!(), |hm| hm.clone())`
 
-error: aborting due to 25 previous errors
+error: use Option::map_or_else instead of an if let/else
+  --> tests/ui/option_if_let_else.rs:339:9
+   |
+LL |         if let Some(o) = o { Box::new(o) } else { Box::new("foo") }
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `o.map_or_else::<std::boxed::Box<dyn std::fmt::Debug>, _, _>(|| Box::new("foo"), |o| Box::new(o))`
+
+error: use Option::map_or_else instead of an if let/else
+  --> tests/ui/option_if_let_else.rs:346:9
+   |
+LL |         if let Some(o) = o { o } else { &S }
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `o.map_or_else::<&str, _, _>(|| &S, |o| o)`
+
+error: aborting due to 27 previous errors