Avoid linting for closures with inferred return types

Author: GnomedDev

clippy_lints/src/question_mark.rs

@@ -16,7 +16,7 @@ use rustc_hir::LangItem::{self, OptionNone, OptionSome, ResultErr, ResultOk};
 use rustc_hir::def::Res;
 use rustc_hir::{
     Arm, BindingMode, Block, Body, ByRef, Expr, ExprKind, FnRetTy, HirId, LetStmt, MatchSource, Mutability, Node, Pat,
-    PatKind, PathSegment, QPath, Stmt, StmtKind, TyKind,
+    PatKind, PathSegment, QPath, Stmt, StmtKind,
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::{self, Ty};
@@ -478,7 +478,7 @@ fn is_inferred_ret_closure(expr: &Expr<'_>) -> bool {
     };
 
     match closure.fn_decl.output {
-        FnRetTy::Return(ret_ty) => matches!(ret_ty.kind, TyKind::Infer),
+        FnRetTy::Return(ret_ty) => ret_ty.is_suggestable_infer_ty(),
         FnRetTy::DefaultReturn(_) => true,
     }
 }

tests/ui/question_mark.fixed

@@ -201,6 +201,16 @@ fn infer_check() {
 
         Ok(())
     };
+
+    let closure = |x: Result<u8, ()>| -> Result<(), _> {
+        // `?` would fail here, as it expands to `Err(val.into())` which is not constrained.
+        let _val = match x {
+            Ok(val) => val,
+            Err(val) => return Err(val),
+        };
+
+        Ok(())
+    };
 }
 
 // see issue #8019

tests/ui/question_mark.rs

@@ -248,6 +248,16 @@ fn infer_check() {
 
         Ok(())
     };
+
+    let closure = |x: Result<u8, ()>| -> Result<(), _> {
+        // `?` would fail here, as it expands to `Err(val.into())` which is not constrained.
+        let _val = match x {
+            Ok(val) => val,
+            Err(val) => return Err(val),
+        };
+
+        Ok(())
+    };
 }
 
 // see issue #8019

tests/ui/question_mark.stderr

@@ -163,23 +163,23 @@ LL | |     };
    | |_____^ help: try instead: `func_returning_result()?`
 
 error: this block may be rewritten with the `?` operator
-  --> tests/ui/question_mark.rs:274:5
+  --> tests/ui/question_mark.rs:284:5
    |
 LL | /     if let Err(err) = func_returning_result() {
 LL | |         return Err(err);
 LL | |     }
    | |_____^ help: replace it with: `func_returning_result()?;`
 
 error: this block may be rewritten with the `?` operator
-  --> tests/ui/question_mark.rs:281:5
+  --> tests/ui/question_mark.rs:291:5
    |
 LL | /     if let Err(err) = func_returning_result() {
 LL | |         return Err(err);
 LL | |     }
    | |_____^ help: replace it with: `func_returning_result()?;`
 
 error: this block may be rewritten with the `?` operator
-  --> tests/ui/question_mark.rs:358:13
+  --> tests/ui/question_mark.rs:368:13
    |
 LL | /             if a.is_none() {
 LL | |                 return None;
@@ -189,7 +189,7 @@ LL | |             }
    | |_____________^ help: replace it with: `a?;`
 
 error: this `let...else` may be rewritten with the `?` operator
-  --> tests/ui/question_mark.rs:418:5
+  --> tests/ui/question_mark.rs:428:5
    |
 LL | /     let Some(v) = bar.foo.owned.clone() else {
 LL | |         return None;