Improve cpp intersphinx support

Now types called out in function declarations will be searched for in
the intersphinx inventory as well

tests/roots/test-ext-intersphinx-cppdomain/index.rst

@@ -4,3 +4,5 @@ test-ext-intersphinx-cppdomain
 .. cpp:namespace:: foo
 
 :cpp:class:`Bar`
+
+.. cpp:function:: std::uint8_t FooBarBaz()

tests/test_ext_intersphinx.py

@@ -232,6 +232,12 @@ def test_missing_reference_cppdomain(tempdir, app, status, warning):
             ' href="https://docs.python.org/index.html#cpp_foo_bar"'
             ' title="(in foo v2.0)"><code class="xref cpp cpp-class docutils literal">'
             '<span class="pre">Bar</span></code></a>' in html)
+    assert ('<a class="reference external"'
+            ' href="https://docs.python.org/index.html#std"'
+            ' title="(in foo v2.0)">std</a>' in html)
+    assert ('<a class="reference external"'
+            ' href="https://docs.python.org/index.html#std_uint8_t"'
+            ' title="(in foo v2.0)">uint8_t</a>' in html)
 
 
 def test_missing_reference_jsdomain(tempdir, app, status, warning):

tests/test_util_inventory.py

@@ -34,6 +34,8 @@ module1 py:module 0 foo.html#module-module1 Long Module desc
 module2 py:module 0 foo.html#module-$ -
 module1.func py:function 1 sub/foo.html#$ -
 CFunc c:function 2 cfunc.html#CFunc -
+std cpp:type 1 index.html#std -
+std::uint8_t cpp:type 1 index.html#std_uint8_t -
 foo::Bar cpp:class 1 index.html#cpp_foo_bar -
 foo::Bar::baz cpp:function 1 index.html#cpp_foo_bar_baz -
 a term std:term -1 glossary.html#term-a-term -