checker: add check for call expr in map/filter (#9559)

main.v

@@ -0,0 +1,7 @@
+fn main() {
+	list := [1,2,3].filter(stringsss(it))
+}
+
+fn stringsss(arg int) string {
+	return ''
+}

vlib/v/checker/checker.v

@@ -1409,6 +1409,13 @@ fn (mut c Checker) check_map_and_filter(is_map bool, elem_typ ast.Type, call_exp
 				}
 			}
 		}
+		ast.CallExpr {
+			if is_map && arg_expr.return_type == table.void_type {
+				c.error('type mismatch, `$arg_expr.name` does not return anything', arg_expr.pos)
+			} else if !is_map && arg_expr.return_type != table.bool_type {
+				c.error('type mismatch, `$arg_expr.name` must return a bool', arg_expr.pos)
+			}
+		}
 		else {}
 	}
 }

vlib/v/checker/tests/filter_func_return_nonbool_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/filter_func_return_nonbool_err.vv:2:25: error: type mismatch, `stringsss` must return a bool
+    1 | fn main() {
+    2 |     list := [1,2,3].filter(stringsss(it))
+      |                            ~~~~~~~~~~~~~
+    3 | }
+    4 |

vlib/v/checker/tests/filter_func_return_nonbool_err.vv

@@ -0,0 +1,7 @@
+fn main() {
+	list := [1,2,3].filter(stringsss(it))
+}
+
+fn stringsss(arg int) string {
+	return ''
+}

vlib/v/checker/tests/map_func_void_return_err.out

@@ -0,0 +1,6 @@
+vlib/v/checker/tests/map_func_void_return_err.vv:2:22: error: type mismatch, `voids` does not return anything
+    1 | fn main() {
+    2 |     list := [1,2,3].map(voids(it))
+      |                         ~~~~~~~~~
+    3 | }
+    4 |

vlib/v/checker/tests/map_func_void_return_err.vv

@@ -0,0 +1,7 @@
+fn main() {
+	list := [1,2,3].map(voids(it))
+}
+
+fn voids(arg int) {
+	println(arg)
+}