[Error] Add non-consuming toString (#95375)

There are some places that want to convert an Error to string, but still
retain the original Error object, for example to emit a non-fatal
warning.

This currently isn't possible, because the entire Error infra is
move-based. And what people end up doing in this case is to move the
Error... twice.

This patch introduces a toStringWithoutConsuming() function to
accommodate this use case. This also requires some infrastructure that
allows visiting Errors without consuming them.

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Support/Error.cpp b/llvm/lib/Support/Error.cpp
index 34ec31e..93481ca 100644
--- a/llvm/lib/Support/Error.cpp
+++ b/llvm/lib/Support/Error.cpp
@@ -82,6 +82,14 @@ std::string toString(Error E) {
   return join(Errors.begin(), Errors.end(), "\n");
 }
 
+std::string toStringWithoutConsuming(const Error &E) {
+  SmallVector<std::string, 2> Errors;
+  visitErrors(E, [&Errors](const ErrorInfoBase &EI) {
+    Errors.push_back(EI.message());
+  });
+  return join(Errors.begin(), Errors.end(), "\n");
+}
+
 std::error_code ErrorList::convertToErrorCode() const {
   return std::error_code(static_cast<int>(ErrorErrorCode::MultipleErrors),
                          getErrorErrorCat());