checker: fix panic when calling generic function with too few args (#8416)

vlib/v/checker/check_types.v

@@ -421,14 +421,11 @@ pub fn (mut c Checker) infer_fn_types(f table.Fn, mut call_expr ast.CallExpr) {
 		}
 		mut typ := table.void_type
 		for i, param in f.params {
-			if call_expr.args.len == 0 {
+			arg_i := if i != 0 && call_expr.is_method { i - 1 } else { i }
+			if call_expr.args.len <= arg_i {
 				break
 			}
-			arg := if i != 0 && call_expr.is_method {
-				call_expr.args[i - 1]
-			} else {
-				call_expr.args[i]
-			}
+			arg := call_expr.args[arg_i]
 			param_type_sym := c.table.get_type_symbol(param.typ)
 			if param.typ.has_flag(.generic) && param_type_sym.name == gt_name {
 				typ = arg.typ

vlib/v/checker/tests/function_count_of_args_mismatch_err.out

@@ -0,0 +1,27 @@
+vlib/v/checker/tests/function_count_of_args_mismatch_err.vv:8:13: error: expected 1 arguments, but got 3
+    6 | 
+    7 | fn main() {
+    8 |     test(true, false, 1)
+      |                ~~~~~~~~
+    9 |     test()
+   10 |     test2(true, false, 1)
+vlib/v/checker/tests/function_count_of_args_mismatch_err.vv:9:2: error: expected 1 arguments, but got 0
+    7 | fn main() {
+    8 |     test(true, false, 1)
+    9 |     test()
+      |     ~~~~~~
+   10 |     test2(true, false, 1)
+   11 |     test2(true)
+vlib/v/checker/tests/function_count_of_args_mismatch_err.vv:10:21: error: expected 2 arguments, but got 3
+    8 |     test(true, false, 1)
+    9 |     test()
+   10 |     test2(true, false, 1)
+      |                        ^
+   11 |     test2(true)
+   12 | }
+vlib/v/checker/tests/function_count_of_args_mismatch_err.vv:11:2: error: expected 2 arguments, but got 1
+    9 |     test()
+   10 |     test2(true, false, 1)
+   11 |     test2(true)
+      |     ~~~~~~~~~~~
+   12 | }

vlib/v/checker/tests/function_count_of_args_mismatch_err.vv

@@ -0,0 +1,12 @@
+fn test(b bool) {
+}
+
+fn test2<T>(b bool, v T) {
+}
+
+fn main() {
+	test(true, false, 1)
+	test()
+	test2(true, false, 1)
+	test2(true)
+}

vlib/v/checker/tests/function_too_many_args_err.out

@@ -1,6 +0,0 @@
-vlib/v/checker/tests/function_too_many_args_err.vv:5:16: error: expected 1 arguments, but got 3
-    3 |
-    4 | fn main() {
-    5 |     test(true, false, 1)
-      |                ~~~~~~~~
-    6 | }

vlib/v/checker/tests/function_too_many_args_err.vv

@@ -1,6 +0,0 @@
-fn test(b bool) {
-}
-
-fn main() {
-    test(true, false, 1)
-}