Created attachment 370208 [details]
source code that triggers the error

When trying to compile the attached source code with valac 0.40.0 I get the following error message:

test.vala.c: In function ‘_vala_main’:
test.vala.c:24:14: warning: implicit declaration of function ‘gtk_border_init’; did you mean ‘gtk_border_new’? [-Wimplicit-function-declaration]
  (GtkBorder) gtk_border_init (&border);
              ^~~~~~~~~~~~~~~
              gtk_border_new
test.vala.c:24:2: error: conversion to non-scalar type requested
  (GtkBorder) gtk_border_init (&border);
  ^
error: cc exited with status 256
Compilation failed: 1 error(s), 0 warning(s)