[PATCH] D153296: [AST] Stop evaluate constant expression if the condition expression which in switch statement contains errors

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added a comment.

Making the `return ESR_Failed;` unconditional looks to be the correct change here. We can't continue evaluation past that point because we don't know what would be executed next. Unconditionally returning `ESR_Failed` in that situation is what the other similar paths through `EvaluateStmt` do.



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Comment at: clang/lib/AST/ExprConstant.cpp:4914
 
 static bool EvaluateDependentExpr(const Expr *E, EvalInfo &Info) {
   assert(E->isValueDependent());
----------------
I don't think the changes to this function are appropriate, because:

1) The special-casing of `RecoveryExpr` doesn't seem like it can be correct. There's no guarantee that we get a `RecoveryExpr` any time we encounter an expression that contains errors; error-dependence can be propagated from other places, such as types.
2) For other error-dependent expressions, we also can't necessarily compute a value.
3) It's not the responsibility of this function to deal with the situation where a value is needed and can't be produced -- the responsibility to handle that lies with the caller of this function instead. Eg, look at the handling of `ReturnStmt` or `DoStmt`.

So I think we should undo all the changes in this function, and only fix `SwitchStmt` to properly handle a value-dependent condition.


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  https://reviews.llvm.org/D153296/new/

https://reviews.llvm.org/D153296