fmt: AnonFn with body is not single line (#7659)

vlib/v/fmt/fmt.v

@@ -1723,6 +1723,11 @@ fn stmt_is_single_line(stmt ast.Stmt) bool {
 
 fn expr_is_single_line(expr ast.Expr) bool {
 	match expr {
+		ast.AnonFn {
+			if !expr.decl.no_body {
+				return false
+			}
+		}
 		ast.IfExpr {
 			return false
 		}

vlib/v/fmt/tests/fn_trailing_arg_syntax_keep.vv

@@ -35,6 +35,12 @@ fn main() {
 			f: 'here'
 		}
 	)
+	ui.button(
+		width: 70
+		onclick: fn (a voidptr, b voidptr) {
+			webview.new_window(url: 'https://vlang.io', title: 'The V programming language')
+		}
+	)
 }
 
 fn bar_func(bar Bar) {