If I do this:

typedef int hb_language_t;

then my API:

hb_language_t 
hb_language_get_default (void);

is correctly introspected.  However, if I do this:

typedef intptr_t hb_language_t;

then the same API generates this warning:

/home/behdad/src/freedesktop/harfbuzz/src/hb-common.h:149: Warning: HarfBuzz: hb_language_get_default: return value: Missing (transfer) annotation

moreover, the generate GIR is invalid and generates this error during typelib compilation:

error parsing file HarfBuzz-0.0.gir: Line 52, character 32: The attribute 'name' on the element 'type' must be specified

Here's the relevant lines from the gir:

    <alias name="language_t" c:type="hb_language_t" introspectable="0"> 
      <type c:type="intptr_t"/> 
    </alias>