[LLVMbugs] [Bug 13331] New: diagnostic when throwing exceptions from constexpr

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=13331

             Bug #: 13331
           Summary: diagnostic when throwing exceptions from constexpr
           Product: clang
           Version: 3.1
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: C++11
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: tomasz at grobelny.net
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Consider this code:
#include <stdexcept>

constexpr int isvalidid(const char* str)
{
        return (*str)==0 ? true : 'a'<=str[0] && str[0]<='z' &&
isvalidid(str+1);
}

constexpr const char* operator "" _id(const char* str, size_t /*length*/)
{
    return isvalidid(str) ? str : throw std::logic_error("identifier must
contain only small latin letters");
}

int main()
{
        auto myId="qwWe"_id;
}

Compilation produces:
terminate called after throwing an instance of 'std::logic_error'
  what():  identifier must contain only small latin letters
Aborted

Line number (of the last but one line) would be a welcome addition.

BTW, is there a better way to achieve compile-time string validation?

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