fix: guard is_abstract against decorators without qname

[SAY-5]

Closes #3086.

FunctionDef.is_abstract calls inferred.qname() unconditionally on each inferred decorator, but PEP 695 TypeVar nodes don't expose qname. Decorating a method with a class-scoped type variable (e.g. class C[T]: @T def m(): ...) crashes is_abstract with AttributeError: 'TypeVar' object has no attribute 'qname', propagating up through pylint's class_is_abstract check. Skip decorators that don't expose qname so unrelated decorator shapes don't kill the abstract check.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.58%. Comparing base (1f3b8fa) to head (15ee061).
⚠️ Report is 22 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3089      +/-   ##
==========================================
- Coverage   93.60%   93.58%   -0.02%     
==========================================
  Files          92       92              
  Lines       11364    11365       +1     
==========================================
- Hits        10637    10636       -1     
- Misses        727      729       +2     

Flag	Coverage Δ
linux	93.45% <100.00%> (-0.02%)	⬇️
pypy	93.58% <100.00%> (-0.02%)	⬇️
windows	93.55% <100.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
astroid/nodes/scoped_nodes/scoped_nodes.py	93.20% <100.00%> (-0.08%)	⬇️

... and 3 files with indirect coverage changes

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[gaoflow]

Thanks for fixing this. Heads-up that the same unguarded qname() call exists at a second site this PR doesn't cover, so #3086's crash still reproduces through plain inference after this lands. FunctionDef.decoratornames() (scoped_nodes.py:1463) does result.add(infnode.qname()) for each inferred decorator:

import astroid
astroid.extract_node("class C[T]:\n    @T\n    def m(self): ...  #@").inferred()
# AttributeError: 'TypeVar' object has no attribute 'qname'
# FunctionDef._infer -> bases._is_property -> decoratornames() (scoped_nodes.py:1463)

(Verified on HEAD, 4.2.0b3.) The same guard you applied to is_abstract would work there too. Might be worth covering both sites in this PR so #3086 is fully closed; otherwise I'm happy to send a follow-up PR scoped to decoratornames once this merges.

[SAY-5]

Good catch, thanks. Added the same guard to decoratornames (the result.add(infnode.qname()) loop) plus a regression test for the @T-decorated method case, so #3086 is fully covered now. Confirmed the test fails with AttributeError before the guard and passes after.

[gaoflow]

Nice, that's the site I had in mind. With both is_abstract and the decoratornames loop guarded, #3086 should be fully covered now. Thanks for the quick turnaround.

[codspeed-hq]

Merging this PR will not alter performance

✅ 3 untouched benchmarks
⏩ 1 skipped benchmark¹

---

_{Comparing SAY-5:fix/is-abstract-typevar-qname (15ee061) with main (1d38251)}

Footnotes

1. 1 benchmark was skipped, so the baseline result was used instead. If it was deleted from the codebase, click here and archive it to remove it from the performance reports. ↩