[PATCH] PR15677 - Crash in template diffing.

[Nikola Smiljanić]

Hi rtrieu,

In addition to having and integral type the expression needs to be evaluatable.

I'm not too happy with how GetInt function looks but, one idea would be to return a bool and take APInt as an output parameter, in that case the function would something like this:

  bool GetInt(const TSTiterator &Iter, Expr *ArgExpr, llvm::APInt &Int) {
    // Default, value-depenedent expressions require fetching
    // from the desugared TemplateArgument
    if (Iter.isEnd() && ArgExpr->isValueDependent()) {
      switch (Iter.getDesugar().getKind()) {
      case TemplateArgument::Integral:
        Int = Iter.getDesugar().getAsIntegral();
      case TemplateArgument::Expression:
        ArgExpr = Iter.getDesugar().getAsExpr();
        Int = ArgExpr->EvaluateKnownConstInt(Context);
      default:
        llvm_unreachable("Unexpected template argument kind");
      }
      return true;
    } else if (ArgExpr->isEvaluatable(Context)) {
      Int = ArgExpr->EvaluateKnownConstInt(Context);
      return true;
    }

    return false;
  }

http://reviews.llvm.org/D4226

Files:
  lib/AST/ASTDiagnostic.cpp
  test/Misc/diag-template-diffing.cpp
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