[clang] [clang] fix lack comparison of declRefExpr in ASTStructuralEquivalence (PR #66041)

[via cfe-commits]

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@@ -214,6 +214,16 @@ class StmtComparer {
     return E1->size() == E2->size();
   }
 
+  bool IsStmtEquivalent(const DeclRefExpr *DRE1, const DeclRefExpr *DRE2) {
+    auto *Decl1 = DRE1->getDecl();
+    auto *Decl2 = DRE2->getDecl();
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cor3ntin wrote:

actually you can make these `const`, and then you won't need the `const_cast`s

https://github.com/llvm/llvm-project/pull/66041