checker: fix generic fn inferring multi paras type (fix #10623) (#10626)

vlib/v/checker/check_types.v

@@ -550,7 +550,7 @@ pub fn (mut c Checker) infer_fn_generic_types(f ast.Fn, mut call_expr ast.CallEx
 				if to_set.has_flag(.generic) {
 					to_set = c.unwrap_generic(to_set)
 				}
-			} else {
+			} else if param.typ.has_flag(.generic) {
 				arg_sym := c.table.get_type_symbol(arg.typ)
 				if arg_sym.kind == .array && param_type_sym.kind == .array {
 					mut arg_elem_info := arg_sym.info as ast.Array
@@ -588,7 +588,7 @@ pub fn (mut c Checker) infer_fn_generic_types(f ast.Fn, mut call_expr ast.CallEx
 					}
 				} else if param.typ.has_flag(.variadic) {
 					to_set = c.table.mktyp(arg.typ)
-				} else if arg_sym.kind == .struct_ && param.typ.has_flag(.generic) {
+				} else if arg_sym.kind == .struct_ {
 					info := arg_sym.info as ast.Struct
 					generic_names := info.generic_types.map(c.table.get_type_symbol(it).name)
 					if gt_name in generic_names && info.generic_types.len == info.concrete_types.len {

vlib/v/tests/generic_fn_infer_multi_paras_test.v

@@ -0,0 +1,36 @@
+pub struct Page {
+pub mut:
+	lang    string
+	page    string
+	var_one string
+	var_two string
+}
+
+fn get_keys_and_values<T>(mut keys []string, mut values []string, mut data T) {
+	$for field in T.fields {
+		$if field.typ is string {
+			keys << field.name
+			values << data.$(field.name)
+		}
+	}
+}
+
+fn awesome<T>(mut data T) {
+	mut keys := []string{}
+	mut values := []string{}
+	get_keys_and_values(mut keys, mut values, mut data)
+	println(keys)
+	assert keys == ['lang', 'page', 'var_one', 'var_two']
+	println(values)
+	assert values == ['vlang', 'one', 'variable one', 'variable two']
+}
+
+fn test_generic_fn_infer_multi_paras() {
+	mut page := Page{
+		lang: 'vlang'
+		page: 'one'
+		var_one: 'variable one'
+		var_two: 'variable two'
+	}
+	awesome(mut page)
+}