checker: check generic struct field fn args type mismatch (#12379)

vlib/v/checker/checker.v

@@ -2280,15 +2280,27 @@ pub fn (mut c Checker) method_call(mut node ast.CallExpr) ast.Type {
 			node.is_method = false
 			node.is_field = true
 			info := field_type_sym.info as ast.FnType
+
+			c.check_expected_arg_count(mut node, info.func) or { return info.func.return_type }
 			node.return_type = info.func.return_type
 			mut earg_types := []ast.Type{}
-			for mut arg in node.args {
+
+			for i, mut arg in node.args {
 				targ := c.check_expr_opt_call(arg.expr, c.expr(arg.expr))
 				arg.typ = targ
 				earg_types << targ
+
+				if i < info.func.params.len {
+					exp_arg_typ := info.func.params[i].typ
+					c.check_expected_call_arg(targ, c.unwrap_generic(exp_arg_typ), node.language) or {
+						if targ != ast.void_type {
+							c.error('$err.msg in argument ${i + 1} to `${left_type_sym.name}.$method_name`',
+								arg.pos)
+						}
+					}
+				}
 			}
 			node.expected_arg_types = earg_types
-			c.check_expected_arg_count(mut node, info.func) or { return info.func.return_type }
 			node.is_method = true
 			return info.func.return_type
 		}

vlib/v/checker/tests/generics_struct_field_fn_args_err.out

@@ -18,10 +18,31 @@ vlib/v/checker/tests/generics_struct_field_fn_args_err.vv:29:15: error: expected
    29 |     println(fun1.call())
       |                  ~~~~~~
    30 |     println(fun1.call(42, 43))
-   31 | }
+   31 |
 vlib/v/checker/tests/generics_struct_field_fn_args_err.vv:30:24: error: expected 1 arguments, but got 2
    28 |     println(fun1.call(42))
    29 |     println(fun1.call())
    30 |     println(fun1.call(42, 43))
       |                           ~~
-   31 | }
+   31 |
+   32 |     println(fun1.call(true))
+vlib/v/checker/tests/generics_struct_field_fn_args_err.vv:32:20: error: cannot use `bool` as `int` in argument 1 to `Fun<fn (int) int>.call`
+   30 |     println(fun1.call(42, 43))
+   31 |
+   32 |     println(fun1.call(true))
+      |                       ~~~~
+   33 |     println(fun1.call('text'))
+   34 |     println(fun1.call(22.2))
+vlib/v/checker/tests/generics_struct_field_fn_args_err.vv:33:20: error: cannot use `string` as `int` in argument 1 to `Fun<fn (int) int>.call`
+   31 |
+   32 |     println(fun1.call(true))
+   33 |     println(fun1.call('text'))
+      |                       ~~~~~~
+   34 |     println(fun1.call(22.2))
+   35 | }
+vlib/v/checker/tests/generics_struct_field_fn_args_err.vv:34:20: error: cannot use `float literal` as `int` in argument 1 to `Fun<fn (int) int>.call`
+   32 |     println(fun1.call(true))
+   33 |     println(fun1.call('text'))
+   34 |     println(fun1.call(22.2))
+      |                       ~~~~
+   35 | }

vlib/v/checker/tests/generics_struct_field_fn_args_err.vv

@@ -28,4 +28,8 @@ fn main() {
 	println(fun1.call(42))
 	println(fun1.call())
 	println(fun1.call(42, 43))
+
+	println(fun1.call(true))
+	println(fun1.call('text'))
+	println(fun1.call(22.2))
 }