fix: return_and_then FP when return type is not Option or Result

Author: profetia

clippy_lints/src/methods/return_and_then.rs

@@ -9,7 +9,7 @@ use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::{indent_of, reindent_multiline, snippet_with_applicability};
 use clippy_utils::ty::get_type_diagnostic_name;
 use clippy_utils::visitors::for_each_unconsumed_temporary;
-use clippy_utils::{get_parent_expr, peel_blocks};
+use clippy_utils::{get_parent_expr, peel_blocks, return_ty};
 
 use super::RETURN_AND_THEN;
 
@@ -21,12 +21,29 @@ pub(super) fn check<'tcx>(
     recv: &'tcx hir::Expr<'tcx>,
     arg: &'tcx hir::Expr<'_>,
 ) {
-    if cx.tcx.hir_get_fn_id_for_return_block(expr.hir_id).is_none() {
+    let Some(fn_def_id) = cx.tcx.hir_get_fn_id_for_return_block(expr.hir_id) else {
         return;
-    }
+    };
 
+    let fn_return_type = if let hir::Node::Expr(expr) = cx.tcx.hir_node(fn_def_id)
+        && let hir::ExprKind::Closure(..) = expr.kind
+        && let expr_ty = cx.typeck_results().expr_ty(expr)
+        && let ty::Closure(_, args) = expr_ty.kind()
+    {
+        let fn_sig = args.as_closure().sig();
+        cx.tcx.instantiate_bound_regions_with_erased(fn_sig.output())
+    } else if let Some(fn_owner_id) = fn_def_id.as_owner() {
+        return_ty(cx, fn_owner_id)
+    } else {
+        return;
+    };
     let recv_type = cx.typeck_results().expr_ty(recv);
-    if !matches!(get_type_diagnostic_name(cx, recv_type), Some(sym::Option | sym::Result)) {
+
+    let fn_return_symbol = get_type_diagnostic_name(cx, fn_return_type);
+    let recv_symbol = get_type_diagnostic_name(cx, recv_type);
+    if fn_return_symbol != recv_symbol
+        || !matches!(get_type_diagnostic_name(cx, recv_type), Some(sym::Option | sym::Result))
+    {
         return;
     }
 

tests/ui/return_and_then.fixed

@@ -124,3 +124,29 @@ mod issue14781 {
         Ok(())
     }
 }
+
+mod issue14927 {
+    use std::path::Path;
+
+    struct A {
+        pub func: fn(check: bool, a: &Path, b: Option<&Path>),
+    }
+
+    const MY_A: A = A {
+        func: |check, a, b| {
+            if check {
+                let _ = ();
+            } else if let Some(parent) = b.and_then(|p| p.parent()) {
+                let _ = ();
+            }
+        },
+    };
+
+    fn foo(check: bool, a: &Path, b: Option<&Path>) {
+        if check {
+            let _ = ();
+        } else if let Some(parent) = b.and_then(|p| p.parent()) {
+            let _ = ();
+        }
+    }
+}

tests/ui/return_and_then.rs

@@ -115,3 +115,29 @@ mod issue14781 {
         Ok(())
     }
 }
+
+mod issue14927 {
+    use std::path::Path;
+
+    struct A {
+        pub func: fn(check: bool, a: &Path, b: Option<&Path>),
+    }
+
+    const MY_A: A = A {
+        func: |check, a, b| {
+            if check {
+                let _ = ();
+            } else if let Some(parent) = b.and_then(|p| p.parent()) {
+                let _ = ();
+            }
+        },
+    };
+
+    fn foo(check: bool, a: &Path, b: Option<&Path>) {
+        if check {
+            let _ = ();
+        } else if let Some(parent) = b.and_then(|p| p.parent()) {
+            let _ = ();
+        }
+    }
+}