checker: fix panic in generic methods (#7944)

vlib/v/checker/check_types.v

@@ -426,6 +426,9 @@ pub fn (mut c Checker) infer_fn_types(f table.Fn, mut call_expr ast.CallExpr) {
 	gt_name := 'T'
 	mut typ := table.void_type
 	for i, param in f.params {
+		if call_expr.args.len == 0 {
+			break
+		}
 		arg := if i != 0 && call_expr.is_method { call_expr.args[i - 1] } else { call_expr.args[i] }
 		if param.typ.has_flag(.generic) {
 			typ = arg.typ

vlib/v/checker/tests/method_generic_infer_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/method_generic_infer_err.vv:9:7: error: could not infer generic type `T` in call to `func`
+    7 | fn main() {
+    8 |     data := Data{}
+    9 |     data.func()
+      |          ~~~~~~
+   10 | }

vlib/v/checker/tests/method_generic_infer_err.vv

@@ -0,0 +1,10 @@
+struct Data {}
+
+fn (_ Data) func<T>() T {
+	return T{}
+}
+
+fn main() {
+	data := Data{}
+	data.func()
+}