[clang] [clang][ExprConst] Don't try to evaluate value-dependent DeclRefExprs (PR #67778)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

<details>
<summary>Changes</summary>

The Expression here migth be value dependent, which makes us run into an assertion later on. Just bail out early.

Fixes #<!-- -->67690

---
Full diff: https://github.com/llvm/llvm-project/pull/67778.diff


2 Files Affected:

- (modified) clang/lib/AST/ExprConstant.cpp (+3) 
- (modified) clang/test/SemaCXX/constant-expression-cxx1z.cpp (+13) 


``````````diff
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index fea06b97259fe31..8372d81234669fd 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -3357,6 +3357,9 @@ static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
     return false;
   }
 
+  if (E->isValueDependent())
+    return false;
+
   // Dig out the initializer, and use the declaration which it's attached to.
   // FIXME: We should eventually check whether the variable has a reachable
   // initializing declaration.
diff --git a/clang/test/SemaCXX/constant-expression-cxx1z.cpp b/clang/test/SemaCXX/constant-expression-cxx1z.cpp
index 9335626a5c90a4f..a36b8f15f826f41 100644
--- a/clang/test/SemaCXX/constant-expression-cxx1z.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx1z.cpp
@@ -177,3 +177,16 @@ namespace LambdaCallOp {
     p();
   }
 }
+
+/// This used to crash due to an assertion failure,
+/// see gh#67690
+namespace {
+  struct C {
+    int x;
+  };
+
+  template <const C *p> void f() {
+    const auto &[c] = *p;
+    &c;
+  }
+}

``````````

</details>


https://github.com/llvm/llvm-project/pull/67778