[clang] WIP: fix assert in hasInitWithSideEffects (PR #146468)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Henrik G. Olsson (hnrklssn)

<details>
<summary>Changes</summary>

This fixes another instance of `Assertion failed: (NumCurrentElementsDeserializing == 0 && "should not be called while already deserializing")`. I ran into it while importing clang modules from Swift, but I haven't been able to reproduce it in a test case yet. The error seems to be that an initializer expression can be deserialized and contain a call to a function whose function body is not yet deserialized. When `evaluateValue()` is called the constexpr evaluation triggers deserialization of the function body.

rdar://154717930

---
Full diff: https://github.com/llvm/llvm-project/pull/146468.diff


1 Files Affected:

- (modified) clang/lib/AST/Decl.cpp (+3-9) 


``````````diff
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 5cdf75d71e4d7..5e91566e87f74 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -2444,20 +2444,14 @@ bool VarDecl::hasInitWithSideEffects() const {
   if (!hasInit())
     return false;
 
-  // Check if we can get the initializer without deserializing
-  const Expr *E = nullptr;
+  // Check if we can get the initializer directly without an external source
   if (auto *S = dyn_cast<Stmt *>(Init)) {
-    E = cast<Expr>(S);
-  } else {
-    E = cast_or_null<Expr>(getEvaluatedStmt()->Value.getWithoutDeserializing());
-  }
-
-  if (E)
+    const Expr *E = cast<Expr>(S);
     return E->HasSideEffects(getASTContext()) &&
            // We can get a value-dependent initializer during error recovery.
            (E->isValueDependent() || !evaluateValue());
+  }
 
-  assert(getEvaluatedStmt()->Value.isOffset());
   // ASTReader tracks this without having to deserialize the initializer
   if (auto Source = getASTContext().getExternalSource())
     return Source->hasInitializerWithSideEffects(this);

``````````

</details>


https://github.com/llvm/llvm-project/pull/146468