[gjs/wip/ptomato/mozjs38: 7/14] js: Adapt to new mozilla::Maybe API

[Philip Chimento <pchimento src gnome org>]

commit 9978df860b121b214747f0d09769174a01c08587
Author: Philip Chimento <philip chimento gmail com>
Date:   Wed Jan 11 23:18:42 2017 -0800

    js: Adapt to new mozilla::Maybe API
    
    mozilla::Maybe now has a bool operator so we don't have to compare against
    .empty(), and we can construct values with mozilla::Some(). The API is
    still fairly verbose and will be improved even further in later
    SpiderMonkey releases.

 gi/function.cpp |   15 +++++++--------
 gi/gerror.cpp   |    7 +++----
 gjs/stack.cpp   |   12 ++++++------
 3 files changed, 16 insertions(+), 18 deletions(-)
---
diff --git a/gi/function.cpp b/gi/function.cpp
index 0529309..ba5214f 100644
--- a/gi/function.cpp
+++ b/gi/function.cpp
@@ -1018,7 +1018,7 @@ gjs_invoke_c_function(JSContext                              *context,
         did_throw_gerror = false;
     }
 
-    if (!js_rval.empty())
+    if (js_rval)
         js_rval.ref().setUndefined();
 
     /* Only process return values if the function didn't throw */
@@ -1048,7 +1048,7 @@ gjs_invoke_c_function(JSContext                              *context,
                                                         &arg_type_info,
                                                         &out_arg_cvalues[array_length_pos],
                                                         true);
-                if (!arg_failed && !js_rval.empty()) {
+                if (!arg_failed && js_rval) {
                     arg_failed = !gjs_value_from_explicit_array(context,
                                                                 return_values[next_rval],
                                                                 &return_info,
@@ -1064,7 +1064,7 @@ gjs_invoke_c_function(JSContext                              *context,
                                                       &return_gargument))
                     failed = true;
             } else {
-                if (!js_rval.empty())
+                if (js_rval)
                     arg_failed = !gjs_value_from_g_argument(context,
                                                             return_values[next_rval],
                                                             &return_info, &return_gargument,
@@ -1181,7 +1181,7 @@ release:
 
             array_length_pos = g_type_info_get_array_length(&arg_type_info);
 
-            if (!js_rval.empty()) {
+            if (js_rval) {
                 if (array_length_pos >= 0) {
                     GIArgInfo array_length_arg;
                     GITypeInfo array_length_type_info;
@@ -1275,7 +1275,7 @@ release:
          * on its own, otherwise return a JavaScript array with
          * [return value, out arg 1, out arg 2, ...]
          */
-        if (!js_rval.empty()) {
+        if (js_rval) {
             if (function->js_out_argc == 1) {
                 js_rval.ref().set(return_values[0]);
             } else {
@@ -1325,8 +1325,7 @@ function_call(JSContext *context,
         return true; /* we are the prototype, or have the wrong class */
 
     /* COMPAT: mozilla::Maybe gains a much more usable API in future versions */
-    mozilla::Maybe<JS::MutableHandleValue> m_retval;
-    m_retval.construct(&retval);
+    auto m_retval = mozilla::Some<JS::MutableHandleValue>(&retval);
     success = gjs_invoke_c_function(context, priv, object, js_argv, m_retval,
                                     NULL);
     if (success)
@@ -1777,7 +1776,7 @@ gjs_invoke_c_function_uncached(JSContext                  *context,
 
   /* COMPAT: mozilla::Maybe gains a much more usable API in future versions */
   mozilla::Maybe<JS::MutableHandleValue> m_rval;
-  m_rval.construct(rval);
+  m_rval.emplace(rval);
   result = gjs_invoke_c_function(context, &function, obj, args, m_rval, NULL);
   uninit_cached_function_data (&function);
   return result;
diff --git a/gi/gerror.cpp b/gi/gerror.cpp
index f395547..1f6e22e 100644
--- a/gi/gerror.cpp
+++ b/gi/gerror.cpp
@@ -401,10 +401,9 @@ define_error_properties(JSContext       *context,
 {
     JS::RootedValue stack(context), fileName(context), lineNumber(context);
     /* COMPAT: mozilla::Maybe gains a much more usable API in future versions */
-    mozilla::Maybe<JS::MutableHandleValue> m_stack, m_file, m_line;
-    m_stack.construct(&stack);
-    m_file.construct(&fileName);
-    m_line.construct(&lineNumber);
+    auto m_stack = mozilla::Some<JS::MutableHandleValue>(&stack);
+    auto m_file = mozilla::Some<JS::MutableHandleValue>(&fileName);
+    auto m_line = mozilla::Some<JS::MutableHandleValue>(&lineNumber);
 
     if (!gjs_context_get_frame_info(context, m_stack, m_file, m_line))
         return;
diff --git a/gjs/stack.cpp b/gjs/stack.cpp
index 7dba9b1..6b0be38 100644
--- a/gjs/stack.cpp
+++ b/gjs/stack.cpp
@@ -66,17 +66,17 @@ gjs_context_get_frame_info(JSContext                              *context,
     JS::RootedObject err_obj(context, JS_New(context, constructor,
                                              JS::HandleValueArray::empty()));
 
-    if (!stack.empty() &&
+    if (stack &&
         !gjs_object_get_property_const(context, err_obj, GJS_STRING_STACK,
                                        stack.ref()))
         return false;
 
-    if (!fileName.empty() &&
+    if (fileName &&
         !gjs_object_get_property_const(context, err_obj, GJS_STRING_FILENAME,
                                        fileName.ref()))
         return false;
 
-    if (!lineNumber.empty() &&
+    if (lineNumber &&
         !gjs_object_get_property_const(context, err_obj, GJS_STRING_LINE_NUMBER,
                                        lineNumber.ref()))
         return false;
@@ -95,9 +95,9 @@ gjs_context_print_stack_stderr(GjsContext *context)
 
     /* Stderr is locale encoding, so we use string_to_filename here */
     /* COMPAT: mozilla::Maybe gains a much more usable API in future versions */
-    mozilla::Maybe<JS::MutableHandleValue> m_stack, m_file, m_line;
-    m_stack.construct(&v_stack);
-    if (!gjs_context_get_frame_info(cx, m_stack, m_file, m_line) ||
+    mozilla::Maybe<JS::MutableHandleValue> none,
+        m_stack = mozilla::Some<JS::MutableHandleValue>(&v_stack);
+    if (!gjs_context_get_frame_info(cx, m_stack, none, none) ||
         !gjs_string_to_filename(cx, v_stack, &stack)) {
         g_printerr("No stack trace available\n");
         return;