fix(bind): convert named string map keys before insertion

bind.go

@@ -241,14 +241,15 @@ func bindData(destination any, data map[string][]string, tag string, dataFiles m
 			val.Set(reflect.MakeMap(typ))
 		}
 		for k, v := range data {
+			key := reflect.ValueOf(k).Convert(typ.Key())
 			if isElemString {
-				val.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(v[0]))
+				val.SetMapIndex(key, reflect.ValueOf(v[0]))
 			} else if isElemInterface {
 				// To maintain backward compatibility, we always bind to the first string value
 				// and not the slice of strings when dealing with map[string]any{}
-				val.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(v[0]))
+				val.SetMapIndex(key, reflect.ValueOf(v[0]))
 			} else {
-				val.SetMapIndex(reflect.ValueOf(k), reflect.ValueOf(v))
+				val.SetMapIndex(key, reflect.ValueOf(v))
 			}
 		}
 		return nil

bind_test.go

@@ -542,6 +542,26 @@ func TestDefaultBinder_bindDataToMap(t *testing.T) {
 	})
 }
 
+func TestBindDataToMapWithNamedStringKey(t *testing.T) {
+	type key string
+	data := map[string][]string{"name": {"first", "second"}}
+	t.Run("string values", func(t *testing.T) {
+		var dest map[key]string
+		assert.NoError(t, bindData(&dest, data, "query", nil))
+		assert.Equal(t, map[key]string{"name": "first"}, dest)
+	})
+	t.Run("slice values", func(t *testing.T) {
+		var dest map[key][]string
+		assert.NoError(t, bindData(&dest, data, "query", nil))
+		assert.Equal(t, map[key][]string{"name": {"first", "second"}}, dest)
+	})
+	t.Run("interface values", func(t *testing.T) {
+		var dest map[key]any
+		assert.NoError(t, bindData(&dest, data, "query", nil))
+		assert.Equal(t, map[key]any{"name": "first"}, dest)
+	})
+}
+
 func TestBindbindData(t *testing.T) {
 	ts := new(bindTestStruct)
 	err := bindData(ts, values, "form", nil)