[clang] [clang-tools-extra] [clang] Heuristic resolution for explicit object parameter (PR #155143)

[Mythreya Kuricheti via cfe-commits]

================
@@ -301,9 +302,34 @@ std::vector<const NamedDecl *> HeuristicResolverImpl::resolveMemberExpr(
     return {};
   }
 
+  // check if member expr is in the context of an explicit object method
+  // If so, it's safe to assume the templated arg is of type of the record
+  const auto ExplicitMemberHeuristic =
+      [&](const Expr *Base) -> std::optional<QualType> {
+    if (auto *DeclRef = dyn_cast_if_present<DeclRefExpr>(Base)) {
+      auto *PrDecl = dyn_cast_if_present<ParmVarDecl>(DeclRef->getDecl());
+
----------------
MythreyaK wrote:

`PrDecl` is null [here](https://github.com/llvm/llvm-project/blob/93c96849c89507579a77980ff03adbeabb413573/clang/unittests/Sema/HeuristicResolverTest.cpp#L213), for example.

```
DeclRefExpr 0x2e63d268 'auto' lvalue Var 0x2e63d150 'b' 'auto'
```

https://github.com/llvm/llvm-project/pull/155143