Bug 1455217 - Part 1: Add an explicit Promise type to xpidl, r=mccr8

This type is fairly simple on the idl parsing side of things. I handle it in the
same way that special types such as ns[C]String, nsid, and jsval are handled, by
using a special native type.

The logic for converting the value between C++ and JS follows the existing logic
from the nsISupports <=> JS Promise conversions.

xpcom/base/nsrootidl.idl

@@ -17,7 +17,16 @@ typedef int64_t PRTime;
  */
 #include "nsStringFwd.h"
 
-/* 
+/*
+ * Forward declaration of mozilla::dom::Promise
+ */
+namespace mozilla {
+namespace dom {
+class Promise;
+} // namespace dom
+} // namespace mozilla
+
+/*
  * Start commenting out the C++ versions of the below in the output header
  */
 #if 0
@@ -88,6 +97,8 @@ typedef unsigned long       size_t;
 [ref, jsval]  native jsval(jsval);
               native jsid(jsid);
 
+[ptr, promise] native Promise(ignored);
+
 %{C++
 /* 
  * End commenting out the C++ versions of the above in the output header

xpcom/idl-parser/xpidl/jsonxpt.py

@@ -45,6 +45,7 @@ TypeMap = {
     'utf8string':         'TD_UTF8STRING',
     'cstring':            'TD_CSTRING',
     'jsval':              'TD_JSVAL',
+    'promise':            'TD_PROMISE',
 }
 
 

xpcom/idl-parser/xpidl/xpidl.py

@@ -455,8 +455,9 @@ class Native(object):
         'utf8string': 'nsACString',
         'cstring': 'nsACString',
         'astring': 'nsAString',
-        'jsval': 'JS::Value'
-        }
+        'jsval': 'JS::Value',
+        'promise': '::mozilla::dom::Promise',
+    }
 
     # Mappings from C++ native name types to rust native names. Types which
     # aren't listed here are incompatible with rust code.
@@ -505,6 +506,9 @@ class Native(object):
         if self.specialtype is None:
             return False
 
+        if self.specialtype == 'promise':
+            return self.modifier == 'ptr'
+
         if self.specialtype == 'nsid':
             return self.modifier is not None
 
@@ -522,7 +526,7 @@ class Native(object):
                 raise IDLError("[shared] only applies to out parameters.")
             const = True
 
-        if self.specialtype is not None and calltype == 'in':
+        if self.specialtype not in [None, 'promise'] and calltype == 'in':
             const = True
 
         if self.specialtype == 'jsval':

xpcom/reflect/xptcall/xptcall.h

@@ -134,6 +134,7 @@ struct nsXPTCVariant : public nsXPTCMiniVariant
               case nsXPTType::T_INTERFACE:         /* fall through */
               case nsXPTType::T_INTERFACE_IS:      /* fall through */
               case nsXPTType::T_DOMOBJECT:         /* fall through */
+              case nsXPTType::T_PROMISE:           /* fall through */
               case nsXPTType::T_ARRAY:             /* fall through */
               case nsXPTType::T_PSTRING_SIZE_IS:   /* fall through */
               case nsXPTType::T_PWSTRING_SIZE_IS:  /* fall through */

xpcom/reflect/xptinfo/xptinfo.h

@@ -190,7 +190,8 @@ enum nsXPTTypeTag : uint8_t
   TD_CSTRING           = 24,
   TD_ASTRING           = 25,
   TD_JSVAL             = 26,
-  TD_DOMOBJECT         = 27
+  TD_DOMOBJECT         = 27,
+  TD_PROMISE           = 28
 };
 
 
@@ -306,7 +307,8 @@ public:
     T_CSTRING           = TD_CSTRING          ,
     T_ASTRING           = TD_ASTRING          ,
     T_JSVAL             = TD_JSVAL            ,
-    T_DOMOBJECT         = TD_DOMOBJECT
+    T_DOMOBJECT         = TD_DOMOBJECT        ,
+    T_PROMISE           = TD_PROMISE
   };
 
   ////////////////////////////////////////////////////////////////