f.write_str(&llvm::build_string(|s| unsafe {
llvm::LLVMRustWriteValueToString(self, s);
}).expect("non-UTF8 value description from LLVM"))
f.write_str(&llvm::build_string(|s| unsafe {
llvm::LLVMRustWriteValueToString(self, s);
}).expect("non-UTF8 value description from LLVM"))