BUG #18422: Assert in expandTupleDesc() fails on row mismatch with additional SRF

The following bug has been logged on the website:

Bug reference: 18422
Logged by: Alexander Lakhin
Email address: exclusion(at)gmail(dot)com
PostgreSQL version: 16.2
Operating system: Ubuntu 22.04
Description:

The following query:
SELECT * FROM generate_series(1, 1),
COALESCE(row(1)) AS (a int, b int);
triggers an assertion failure:
TRAP: failed Assert("count <= tupdesc->natts"), File: "parse_relation.c",
Line: 3054, PID: 151361

with the following stack trace:
...
#5 0x000055b935579366 in ExceptionalCondition
(conditionName=conditionName(at)entry=0x55b93569420d "count <= tupdesc->natts",
fileName=fileName(at)entry=0x55b9356941e6 "parse_relation.c",
lineNumber=lineNumber(at)entry=3054) at assert.c:66
#6 0x000055b9351841b5 in expandTupleDesc (tupdesc=0x55b9378c7660,
eref=0x55b9378c7358, count=2, offset=offset(at)entry=0,
rtindex=rtindex(at)entry=2, sublevels_up=sublevels_up(at)entry=0, location=-1,
include_dropped=true, colnames=0x0,
colvars=0x7fffaccae3e0) at parse_relation.c:3054
#7 0x000055b93518713a in expandRTE (rte=rte(at)entry=0x55b9377fc360,
rtindex=rtindex(at)entry=2, sublevels_up=sublevels_up(at)entry=0,
location=location(at)entry=-1, include_dropped=include_dropped(at)entry=true,
colnames=colnames(at)entry=0x0,
colvars=0x7fffaccae3e0) at parse_relation.c:2758
#8 0x000055b9353649b6 in build_physical_tlist
(root=root(at)entry=0x55b9378c8108, rel=rel(at)entry=0x55b9378c8cf0) at
plancat.c:1792
#9 0x000055b935330653 in create_scan_plan (root=root(at)entry=0x55b9378c8108,
best_path=best_path(at)entry=0x55b9378c9340, flags=<optimized out>,
flags(at)entry=0) at createplan.c:637
#10 0x000055b93532dd65 in create_plan_recurse
(root=root(at)entry=0x55b9378c8108, best_path=0x55b9378c9340,
flags=flags(at)entry=0) at createplan.c:411
#11 0x000055b93532f585 in create_nestloop_plan (root=0x55b9378c8108,
best_path=0x55b9377fc470) at createplan.c:4342
#12 0x000055b93532f6be in create_join_plan (root=root(at)entry=0x55b9378c8108,
best_path=best_path(at)entry=0x55b9377fc470) at createplan.c:1076
#13 0x000055b93532dd75 in create_plan_recurse
(root=root(at)entry=0x55b9378c8108, best_path=0x55b9377fc470,
flags=flags(at)entry=1) at createplan.c:416
#14 0x000055b93532e575 in create_plan (root=root(at)entry=0x55b9378c8108,
best_path=<optimized out>) at createplan.c:347
#15 0x000055b93533ff5b in standard_planner (parse=0x55b9377fbf78,
query_string=<optimized out>, cursorOptions=2048, boundParams=<optimized
out>) at planner.c:420
#16 0x000055b9353404f8 in planner (parse=parse(at)entry=0x55b9377fbf78,
query_string=query_string(at)entry=0x55b9377fa888 "SELECT * FROM
generate_series(1, 1),\n COALESCE(row(1)) AS (a int, b int);",
cursorOptions=cursorOptions(at)entry=2048,
boundParams=boundParams(at)entry=0x0) at planner.c:281
#17 0x000055b93542c257 in pg_plan_query
(querytree=querytree(at)entry=0x55b9377fbf78,
query_string=query_string(at)entry=0x55b9377fa888 "SELECT * FROM
generate_series(1, 1),\n COALESCE(row(1)) AS (a int, b int);",
cursorOptions=cursorOptions(at)entry=2048,
boundParams=boundParams(at)entry=0x0) at postgres.c:904
#18 0x000055b93542c30d in pg_plan_queries (querytrees=0x55b9378c80b8,
query_string=query_string(at)entry=0x55b9377fa888 "SELECT * FROM
generate_series(1, 1),\n COALESCE(row(1)) AS (a int, b int);",
cursorOptions=cursorOptions(at)entry=2048,
boundParams=boundParams(at)entry=0x0) at postgres.c:996
#19 0x000055b93542c7f0 in exec_simple_query
(query_string=query_string(at)entry=0x55b9377fa888 "SELECT * FROM
generate_series(1, 1),\n COALESCE(row(1)) AS (a int, b int);") at
postgres.c:1193

(gdb) frame 6

(gdb) p tupdesc->natts
$1 = 1

Reproduced on REL_12_STABLE .. master.

`git bisect` blames d57534740 (8a15b4178 on REL_12_STABLE).
(Thanks to Amit Langote for correcting my initial report where this issue
was hastily attributed to JSON_TABLE().)