[clang] [LifetimeSafety] Add suggestion and inference for implicit this (PR #176703)

[Utkarsh Saxena via cfe-commits]

================
@@ -172,6 +183,7 @@ class OriginManager {
   llvm::BumpPtrAllocator ListAllocator;
   llvm::DenseMap<const clang::ValueDecl *, OriginList *> DeclToList;
   llvm::DenseMap<const clang::Expr *, OriginList *> ExprToList;
+  const Decl *CurrentDecl;
----------------
usx95 wrote:

nit: rename to 

FWIW it could be

```cpp
if (isa<CXXThisExpr>(E)) {
  assert(ThisObjOrigins && "origins for 'this' should be set for a method decl" );
  return *ThisObjOrigins;
}  
```

because `CXXThisExpr` can only occur in a method decl.

https://github.com/llvm/llvm-project/pull/176703