From f3036799888e637d66f76e14887325bb7d0973d4 Mon Sep 17 00:00:00 2001
From: shove <shove@163.com>
Date: Thu, 14 Dec 2023 20:15:45 +0800
Subject: [PATCH] cgen: fix smartcast for struct fields in the match
 branches(fix #20167) (#20171)

---
 vlib/v/gen/c/cgen.v                 |  6 ++++--
 vlib/v/tests/match_smartcast_test.v | 20 ++++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 5c5820db927eb1..3bca8a2f9814c7 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -2479,8 +2479,10 @@ fn (mut g Gen) expr_with_cast(expr ast.Expr, got_type_raw ast.Type, expected_typ
 					}
 				}
 			} else if expr is ast.SelectorExpr {
-				if _ := scope.find_struct_field(expr.expr.str(), expr.expr_type, expr.field_name) {
-					is_already_sum_type = true
+				if v := scope.find_struct_field(expr.expr.str(), expr.expr_type, expr.field_name) {
+					if v.smartcasts.len > 0 && unwrapped_expected_type == v.orig_type {
+						is_already_sum_type = true
+					}
 				}
 			}
 			if is_already_sum_type && !g.inside_return {
diff --git a/vlib/v/tests/match_smartcast_test.v b/vlib/v/tests/match_smartcast_test.v
index 23d66334af1615..5e4ecdd711a0e2 100644
--- a/vlib/v/tests/match_smartcast_test.v
+++ b/vlib/v/tests/match_smartcast_test.v
@@ -97,3 +97,23 @@ fn test_match_mut_selector() {
 		}
 	}
 }
+
+// for issue 20167
+type Any_1 = f64 | int | string
+type Any_2 = int | string
+
+struct Struct {
+	field Any_2
+}
+
+fn test_branches_return_struct_field() {
+	any_2 := Struct{Any_2(42)}
+	m := {
+		'item1': Any_1('')
+		'item2': match any_2.field {
+			string { any_2.field }
+			int { any_2.field }
+		}
+	}
+	assert m['item2']! == Any_1(42)
+}