C++: Fix named qualifier dataset check error with decltypes

[jketema]

No description provided.

[Copilot]

Pull Request Overview

This PR fixes an issue with decltype in C++ code by allowing decltype to act as a name qualifier in addition to being a type. The change addresses a problem where decltype couldn't be used in qualified name contexts (e.g., decltype(expr)::member).

Key changes:

• Updated the database schema to include @decltype in the @namequalifyingelement union
• Made Decltype, TypeofType, and IntrinsicTransformedType classes extend NameQualifyingElement
• Added getName() implementations that return descriptive strings like "decltype(...)" instead of none()
• Updated test expectations to reflect new parameter type signatures containing decltype(...)

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
cpp/ql/lib/semmlecode.cpp.dbscheme	Added @decltype to @namequalifyingelement union to allow decltype as a name qualifier
cpp/ql/lib/semmle/code/cpp/Type.qll	Made Decltype extend NameQualifyingElement and added getName() implementation returning "decltype(...)"
cpp/ql/lib/semmle/code/cpp/Type.qll	Updated TypeofType and IntrinsicTransformedType to return descriptive names instead of none()
cpp/ql/lib/semmle/code/cpp/NameQualifiers.qll	Updated documentation to mention decltype as a valid name qualifying element
cpp/ql/test/library-tests/dataflow/taint-tests/test_mad-signatures.expected	Updated test expectations with new decltype(...) parameter type entries
cpp/ql/lib/upgrades/c16b29b27f71247023321cc0d0360998b318837c/upgrade.properties	Added upgrade metadata for the schema change
cpp/downgrades/2121ffec11fac265524955fee1775217364d4ca4/upgrade.properties	Added downgrade metadata for schema compatibility

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[IdrissRio]

LGTM 👍
There’s a small typo in the first commit message. Please consider fixing it.