fix collision between needless_match

Author: J-ZhengLi

clippy_lints/src/question_mark.rs

@@ -120,6 +120,11 @@ fn check_if_let_some_or_err_and_early_return(cx: &LateContext<'_>, expr: &Expr<'
         if (is_early_return(sym::Option, cx, &if_block) && path_to_local_id(peel_blocks(if_then), bind_id))
             || is_early_return(sym::Result, cx, &if_block);
         then {
+            if let Some(else_expr) = if_else {
+                if eq_expr_value(cx, let_expr, peel_blocks(else_expr)) {
+                    return;
+                }
+            }
             let mut applicability = Applicability::MachineApplicable;
             let receiver_str = snippet_with_applicability(cx, let_expr.span, "..", &mut applicability);
             let by_ref = matches!(annot, BindingAnnotation::Ref | BindingAnnotation::RefMut);

tests/ui/needless_match.fixed

@@ -63,7 +63,13 @@ fn result_match() {
 fn if_let_option() {
     let _ = Some(1);
 
-    fn do_something() {}
+fn if_let_result(x: Result<(), i32>) {
+    let _: Result<(), i32> = x;
+    let _: Result<(), i32> = x;
+    // Input type mismatch, don't trigger
+    #[allow(clippy::question_mark)]
+    let _: Result<(), i32> = if let Err(e) = Ok(1) { Err(e) } else { x };
+}
 
     // Don't trigger
     let _ = if let Some(a) = Some(1) {

tests/ui/needless_match.rs

@@ -75,11 +75,29 @@ fn result_match() {
         Err(err) => Err(err),
         Ok(a) => Ok(a),
     };
-    // as ref, don't trigger
-    let res = &func_ret_err(0_i32);
-    let _: Result<&i32, &i32> = match *res {
-        Ok(ref x) => Ok(x),
-        Err(ref x) => Err(x),
+}
+
+fn if_let_option() -> Option<i32> {
+    if let Some(a) = Some(1) { Some(a) } else { None }
+}
+
+fn if_let_result(x: Result<(), i32>) {
+    let _: Result<(), i32> = if let Err(e) = x { Err(e) } else { x };
+    let _: Result<(), i32> = if let Ok(val) = x { Ok(val) } else { x };
+    // Input type mismatch, don't trigger
+    #[allow(clippy::question_mark)]
+    let _: Result<(), i32> = if let Err(e) = Ok(1) { Err(e) } else { x };
+}
+
+fn if_let_custom_enum(x: Choice) {
+    let _: Choice = if let Choice::A = x {
+        Choice::A
+    } else if let Choice::B = x {
+        Choice::B
+    } else if let Choice::C = x {
+        Choice::C
+    } else {
+        x
     };
 }
 

tests/ui/needless_match.stderr

@@ -84,7 +84,7 @@ LL |     let _: Result<i32, i32> = if let Ok(val) = x { Ok(val) } else { x };
    |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace it with: `x`
 
 error: this if-let expression is unnecessary
-  --> $DIR/needless_match.rs:129:21
+  --> $DIR/needless_match.rs:104:21
    |
 LL |       let _: Simple = if let Simple::A = x {
    |  _____________________^