cgen: fix error when using anon generics fn that have generics struct arg (#10751)

vlib/v/ast/table.v

@@ -192,7 +192,7 @@ pub fn (t &Table) fn_type_signature(f &Fn) string {
 		typ := arg.typ.set_nr_muls(0)
 		arg_type_sym := t.get_type_symbol(typ)
 		sig += arg_type_sym.str().to_lower().replace_each(['.', '__', '&', '', '[]', 'arr_', 'chan ',
-			'chan_', 'map[', 'map_of_', ']', '_to_'])
+			'chan_', 'map[', 'map_of_', ']', '_to_', '<', '_T_', ',', '_', '>', ''])
 		if i < f.params.len - 1 {
 			sig += '_'
 		}

vlib/v/checker/checker.v

@@ -7466,7 +7466,7 @@ fn (mut c Checker) fn_decl(mut node ast.FnDecl) {
 				node.pos)
 		}
 	}
-	if node.language == .v && !c.is_builtin_mod {
+	if node.language == .v && !c.is_builtin_mod && !node.is_anon {
 		c.check_valid_snake_case(node.name, 'function name', node.pos)
 	}
 	if node.name == 'main.main' {

vlib/v/tests/generics_with_anon_generics_fn_test.v

@@ -32,6 +32,11 @@ fn call<T>(f fn (T) T, v T) T {
 	return f(v)
 }
 
+struct Pair<T, U> {
+	a T
+	b U
+}
+
 fn test_generics_with_anon_generics_fn() {
 	mut s := MyStruct<int>{
 		arr: [1, 2, 3, 4, 5]
@@ -44,4 +49,9 @@ fn test_generics_with_anon_generics_fn() {
 	assert call<string>(consume_str, '1') == '1'
 	assert call(consume, 1) == 1
 	assert call(consume_str, '1') == '1'
+
+	pair := Pair<int,string>{1, 's'}
+	assert call(fn (v Pair<int, string>) Pair<int, string> {
+		return v
+	}, pair) == pair
 }