[clang] [alpha.webkit.UncountedLocalVarsChecker] Don't treat a call through a raw pointer/reference guardian argument as a mutation (PR #225309)

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@llvm/pr-subscribers-clang-static-analyzer-1

Author: Fady Farag (iidmsa)

<details>
<summary>Changes</summary>

Previously, when a function parameter was used as the guardian of a raw pointer/reference local, `GuardianVisitor` treated any non-const member function call on the parameter, or passing it to a non-const parameter, as a mutation. That is correct for a `RefPtr<T>&` parameter but not for a raw pointer/reference parameter, where such a call operates on the pointee and cannot change the parameter, which caused an unnecessary warning whenever the parameter was used at all. This only treats a raw pointer/reference guardian argument as mutated when it is assigned to, or when the callee can reseat it by receiving it as `Bar*&` or `Bar**`.

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Full diff: https://github.com/llvm/llvm-project/pull/225309.diff


2 Files Affected:

- (modified) clang/lib/StaticAnalyzer/Checkers/WebKit/RawPtrRefLocalVarsChecker.cpp (+32-10) 
- (modified) clang/test/Analysis/Checkers/WebKit/uncounted-local-vars.cpp (+84) 


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https://github.com/llvm/llvm-project/pull/225309