Instead of using the info object for the doc block as a whole (which
always points to the very first line of the block), update the info
pointer for each call to ensure_untagged_section when the existing
section is otherwise empty. This way, Sphinx error information will
match precisely to where the text actually starts.

For example, this patch will move the info pointer for the "Hello!"
untagged section ...

> ##       <-- from here ...
> # Hello! <-- ... to here.
> ##

Signed-off-by: John Snow <jsnow@redhat.com>
---
 scripts/qapi/parser.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py
index adc85b5b394..36cb64a677a 100644
--- a/scripts/qapi/parser.py
+++ b/scripts/qapi/parser.py
@@ -687,7 +687,11 @@ def end(self) -> None:
     def ensure_untagged_section(self, info: QAPISourceInfo) -> None:
         if self.all_sections and not self.all_sections[-1].tag:
             # extend current section
-            self.all_sections[-1].text += '\n'
+            section = self.all_sections[-1]
+            if not section.text:
+                # Section is empty so far; update info to start *here*.
+                section.info = info
+            section.text += '\n'
             return
         # start new section
         section = self.Section(info)
-- 
2.47.1